Occlusion - UW School of Dentistry

 RD 517 FUNCTIONAL ANALYSIS & OCCLUSION Course Director: S. Dogan Assistant Director: T. Mitchell University of Washington Department of Restorative Dentistry Spring 2010 ResD 517 Occlusion, 2010 Manual Page 1
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Total Clock Hours: 54 (Clinic and/or Laboratory: 36; Lecture: 18) 3 credits
Course Time and Location: 9:30 to 11:20 AM, T‐733 Lecture: Clinic – D2: 12:30 to 4:00 PM, April 2, 09 & 23 only Lab – D‐165: 12:30 to 4:30 PM RESD 517 Session Information: 2010 SPRING Date Time Lecture Topic Laboratory Topic Lecturer 04/02/10 09:30 Analysis of Occlusion Clinic Dogan 04/09/10 09:30 Centric Relation Record Clinic McCoy 04/16/10 09:30 Muscles of Mandibular Movement Wax #19 Abolofia 04/23/10 09:30 Occlusal Assessment Clinic McCoy 04/30/10 09:30 Temporomandibular Joint Occlusal Adjustment Mitchell 05/07/10 09:30 Midterm Exam Occlusal Adjustment Dogan 05/14/10 09:30 Clinical Adjustment Occlusal Adjustment Howard 05/21/10 09:30 Primary Dentition Lab Exam #1 Berg 05/28/10 09:30 Splints/Parafunctional Habits Lab Exam #2 Dogan 06/04/10 09:30 Final Written Exam No laboratory Dogan NOTE: Completion of the dentoform adjustment is mandatory for a course grade. There will be sufficient time for you to adjust these while your projects are being graded. An instructor needs to check and approve the adjustment. If not completed by May 28 2010, 20 points will be deducted from your final exam grade. ResD 517 Occlusion, 2010 Manual Page 2
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APPLICATION OF PRINCIPLES AND CONCEPTS TO SKILLS REQUIRED FOR PATIENT CARE 1. 2. 3. Given a patient, the student should be able to complete the following procedures to meet stated criteria of acceptability for a "functional analysis of occlusion." a. b. c. d. e. f. g. h. I. j. k. Obtain maxillary and mandibular alginate impressions. Pour alginate impressions in a suitable hard dental stone, trim the casts to required form for mounting on an articulator. Obtain a facebow transfer record clinically. Obtain three centric relation records from a patient. Mount the maxillary cast on a semi‐adjustable articulator utilizing the facebow transfer record. Mount mandibular cast on the articulator utilizing the centric relation record. Verify accuracy of the centric relation records. Remount mandibular casts with new records if necessary to achieve accuracy. Identify and record signs, symptoms and history of conditions that may be related to the occlusion. Utilizing prescribed examination and marking techniques, identify and record important factors concerning occlusal relationships that may be contributing to a patient's problems. Identify and record other factors concerning occlusal relationships of the accurately articulated clinical casts. Given articulated casts for a series of patients representing problems of occlusion of increasing complexity, the student should be able to complete the following: a. Identify and chart occlusal discrepancies and tooth contacts in centric relation, lateral and protrusive on an "occlusal assessment" form. b. Given the objectives and techniques of occlusal adjustment, adjust the occlusion of the articulated casts to meet the stated objectives. c. Demonstrate an ability to select the tooth surfaces to be reduced during occlusal adjustment and substantiate selections with sound reasons. d. Given a check list of criteria for a well‐adjusted occlusion, the student should be able to evaluate the accuracy of her/his performance. e. Given articulated casts representing a problem of occlusion, diagnose the occlusal discrepancies, formulate a treatment plan and adjust the occlusion to meet stated objectives. Given a teaching model ("Dentoform") that will be used for preclinical Fixed Prosthodontic procedures, the student would be able to complete the following: a. b. Recognize undesirable occlusal contact relationships. Given the objectives and technique of clinical occlusal adjustment, perform a simulated clinical adjustment to meet the stated objectives. ResD 517 Occlusion, 2010 Manual Page 3
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COURSE EVALUATION Method of Evaluation: Students will be evaluated on written exams, laboratory occlusal adjustments, and a waxing exercise. 70% is the minimum needed to pass the course. In addition, all students must complete the occlusal assessment exercise and the adjustment of the dentoform. Failure to do so results in an incomplete grade until the requirements are met. Examination/Grading Policies: The cognitive portion of the course is worth 50% of the grade. The other 50% is earned via laboratory effort. The breakdown is as follows: All students are required to complete all laboratory exercises in order to pass the course! Functional analysis of clinical case must be completed! Alginate impressions, diagnostic casts, clinical examination and charting of occlusion, clinical mounting records, articulated casts in centric relation, and occlusal adjustment of own articulated casts. This project will be done on each other. The completed form must be signed by an instructor and turned in. Although not graded, no grade can be given until this exercise is completed. Mounting of Occlusal Adjustment Cases (Must Complete) Occlusal Adjustment (Dentoform) ‐ Must Complete Each student will complete a comprehensive occlusal adjustment on his/her dentoform in order to be prepared for the Fixed Prosthetics laboratory exercises. This must be completed and the form initialed by an instructor by May 29th 2009. Failure to complete this requirement will result in a loss of 20 points on your final written exam. In addition, an incomplete will be given as a grade until the adjustment has been completed. Waxing #19: 10% ‐ in conjunction with Dental Materials. You can wax this anytime after Dental Materials has given you permission to start. Occlusal Adjustment of Articulated Casts (Mesmer Case): 15% Midterm Lecture Examination: 25% ‐ Covers all lectures, syllabus, and laboratory information through Week #5. Occlusal Adjustment Laboratory Examination #1: 12.5% Occlusal Adjustment Laboratory Examination #2: 12.5% Final Lecture Examination: 25% ‐ Covers all lectures and laboratory information as well as syllabus information. NOTE: Neatness and cleanliness is a requirement. 5% will be deducted from your grade for every session where you have not properly cleaned up your bench area. ResD 517 Occlusion, 2010 Manual Page 4
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WEEK 1 FUNCTIONAL ANALYSIS OF OCCLUSION LECTURE 1. Preparing the unit 2. Centric Relation 3. Centric Occlusion (CO) and Maximal Intercuspal Position (MIP) 4. Significance of Centric 5. Facebow Transfer CLINIC/LABORATORY 1. Alginate Impressions 2. Facebow Transfer 3. Mount Maxillary Cast ResD 517 Occlusion, 2010 Manual Page 5
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CHANGE of DEFINITIONS NEW OLD Centric Occlusion (CO) Centric Relation Occlusion (CRO) Maximal Intercuspal Position (MIP) Centric Occlusion (CO) Interocclusal Rest Space Freeway Space OLD: CRO = CO or CRO ≠ CO NEW: CO = MIP or CO ≠ MIP ResD 517 Occlusion, 2010 Manual Page 6
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FUNCTIONAL ANALYSIS OF OCCLUSION Centric relation: The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior‐superior position against the shapes of the articular eminencies. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superior and anteriorly. It is restricted to a purely rotary movement about the transverse horizontal axis. The reason for advocating the anterior‐superior position of the condyle disk assembly is that it is the physiologic position of the condyles when the mandible is elevated firmly by normal muscle function. Tooth interferences prevent “normal muscle function” by preventing either condyle from going into its uppermost hinge position. This change of position of the condyle in the glenoid fossa is accomplished to protect the interfering tooth or teeth from absorbing the entire force of the closing musculature. Deviations are initiated by the exquisitely sensitive periodontal receptors around the roots of the interfering teeth. Because of constant repetition of the proprioceptive trigger the muscles become patterned to the devious closure. These memorized patterns of activity are called “engrams.” Centric occlusion (CO): The occlusion of opposing teeth when the mandible is in centric relation. This may or may not coincide with the maximal intercuspal position. Maximal intercuspal position (MIP): The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position—called also maximal intercuspation. MIP may be defined as the complete intercuspation of the opposing teeth independent of condylar position. In other words, this is the vertical and horizontal position of the mandible in which the cusps of the mandibular and maxillary teeth interdigitate maximally. This position is a tooth‐to‐tooth determined relationship. The position is subject to change by alteration of the occlusal surfaces. There is often a short movement path between centric occlusion and MIP which involves a change in vertical dimension. This movement is termed a “slide in centric.” ResD 517 Occlusion, 2010 Manual Page 7
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A “slide in centric” is often a combination of forward and lateral movements. Measurements referring to this slide are not directly comparable since different landmarks have been used to obtain the measurements. However, the average distance for the centric slide in adults and in children seems to be around 1 mm, with greater variance in adults than in children. Note that if, the movement between CO and MIP occurs at the same vertical dimension, the patient is not exhibiting a slide, but is exhibiting “freedom in centric.” This movement is called a “long or wide centric” depending on whether the patient is moving their mandible in an anterior direction or lateral direction. If a patient is asked to tap his/her teeth together, they will hit somewhere close to MIP but the initial contact will depend on posture. This initial contact from rest position is to some extent dependent on muscle balance. Posselt (1952) showed that border movements of the mandible were reproducible, and all other movements take place within the framework of the border movements. It appears, therefore, logical to start the description of mandibular movements with border movements. If the mandible is held back either by the patient or by the operator, a hinge movement can be traced for the lower incisors from centric relation occlusion to the maximum opening possible when the hinge axis is rotating. This movement is called the TERMINAL HINGE MOVEMENT of the mandible and is characterized by the stationary rotation of the horizontal axis through the two temporomandibular joints. Since this position is limited by the ligaments and structures of the temporomandibular joints it has been called the ligamentous position. This position denotes the posterior functional range of the mandible. Under normal physiologic conditions of the masticatory system, this center of rotation and the path of mandibular movements are constant and reproducible. However, for this to be constant and reproducible the condyles must be seated against the meniscus (disk) in the glenoid (mandibular) fossa. SIGNIFICANCE OF CENTRIC 1. The teeth commonly make contact during chewing and during swallowing in MIP 2. Centric relation is a functional border position which is reached chiefly during swallowing, but also occasionally during chewing. 3. CO and MIP do not coincide in the average healthy human dentition. 4. Lateral and protrusive excursions are part of normal masticatory function and chewing strokes converge to MIP. 5. Occlusal interferences between CO and MIP are more apt to create neuromuscular disharmony associated with swallowing than during mastication. ResD 517 Occlusion, 2010 Manual Page 8
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6. Occlusal interferences laterally and protrusively to MIP are more apt to interfere with the muscle harmony in mastication than during swallowing. 7. Centric relation is stable and reproducible when the temporomandibular joint is normal in the absence of unbalanced muscle activity. 8. A lateral slide from CO to MIP is apt to create more neuromuscular disharmony than a straight forward slide. 9. A completely well balanced, straight forward slide from CO is tolerated well, but such a slide would be extremely difficult to produce. 10. A “flat” area (freedom in centric) between CO and MIP (long and/or wide centric) is compatible with occlusal, temporomandibular joint, and muscle harmony. 11. After adjusting an occlusion so that CO is at the same vertical dimension as MIP, some amount of “freedom‐in‐centric” has been automatically established. 12. There is no way to predetermine the ideal length of a “long centric.” 0.3 to 0.8 mm appears to be the adaptive range in which the overwhelming majority of patients function. 13. Centric relation is extremely important as a functional border position of the mandible in swallowing. 14. The patient’s adaptive capacity or tolerance level to occlusal imperfections is of extreme clinical significance. 15. Centric relation is the only “centric” which is reproducible and stable with or without teeth present. However, although this position may vary slightly from year to year, it still remains in the range of acceptability for dental treatment. 16. Centric relation is the only reference position that assures simultaneous, harmonious alignment of both temporomandibular joints. ResD 517 Occlusion, 2010 Manual Page 9
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NORMAL OCCLUSION: requires physiologic adaptability and the absence of recognizable pathologic manifestations. Emphasis is on the functional aspect of occlusion and the capability of the masticatory system to adapt to or compensate for some deviations within the range of tolerance. The adaptive capacity of the neuromuscular system depends to a great extent upon the irritability threshold of the central nervous system, which is influenced by emotional, psychic tension. IDEAL OCCLUSION: is a state in which there are no occlusal interferences present. Ideal occlusion indicates a completely harmonious relationship of the masticatory system for mastication, swallowing and speech. This concept is primarily concerned with function, health, and comfort. The required TMJ and occlusion guidelines for ideal occlusion are: 1. Stable jaw relationship when the teeth make contact in the maximum intercuspal position (MIP). 2. MIP is generally slightly anterior to centric occlusion (CO). 3. An unrestricted movement between CO and MIP without a change in vertical dimension. 4. Complete freedom for smooth gliding occlusal contact movements in the various excursions both from centric occlusion and MIP. 5. The occlusal guidance in various excursions should be on the working (functioning) side rather than the balancing (nonworking) side. FUNCTIONAL STABILITY 1. The impact force of full intercuspation closure must be in the long axis of all posterior teeth and against the central part of the meniscus of the temporomandibular joints. 2. An even degree of wear resistance is necessary. 3. The cutting effectiveness of all functionally alike teeth should be the same. 4. No displacing impact should be present on anterior teeth in MIP closure. 5. There must be no soft tissue contact in functional occlusion. 6. There should be an acceptable interocclusal rest space.
Interocclusal rest space: The difference between the vertical dimension of rest and the vertical dimension while in occlusion.
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CLINIC/LABORATORY ‐ WEEK 1 DENTAL IMPRESSIONS AND CASTS 1. ALGINATE IMPRESSION TECHNIQUE Armamentarium 1. Disposable impression trays or “Rim‐Lock” impression trays (previously sterilized) 2. lab knife 3. rubber bowl and spatula 4. *alginate impression material 5. *mouth mirror 6. chain (for patient bib or napkin) 7. *water measuring cylinder 8. Vaseline 9. *beeswax strips 10. *air/water syringe tip 11. *Biocide 12. *ziploc baggy *to be supplied Procedure a. Tray Selection 1. The patient’s mouth should be clean and free of calculus and debris. If it is not, the teeth should be brushed or scaled. 2. Excess saliva should be removed by thorough rinsing with mouth wash. 3. The patient should be positioned in the dental chair so that the mandibular teeth are approximately parallel to the floor when the mouth is open for the mandibular impression and the maxillary teeth parallel to the floor for the upper impression. 4. Lightly lubricate the patient’s lips with vaseline to make insertion and removal of trays easier and prevent alginate from adhering to the skin. ResD 517 Occlusion, 2010 Manual Page 11
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5. Select Rim‐lock trays that might appear to fit the size of the patient’s upper and lower arches. The “Rim‐lock” trays are available in five sizes, No. 15, 14, 13, 12, and 11 with No. 15 the smallest, increasing in size to No. 11. 6. The tray should be inserted at an angle with one heel of the tray inserted and the tray rotated while reflecting the opposite corner of the mouth. The lips should be reflected over anterior flanges of the tray. After the tray is seated to its desired position. NOTE: Always seat the posterior portion of a maxillary impression first, before seating the anterior part. For the lower arch, the patient is asked to raise the tongue to allow lingual flanges to seat and then to relax it. 7. There should be approximately 3‐6 mm of space between the flanges of the tray and the facial aspect of the teeth. While this cannot be measured, lateral movement of the tray can determine adequacy of space. Occasionally, arch form may require that tray flanges be bent out slightly in the posterior to eliminate interferences. 8. A correctly selected tray should cover all the teeth and not cause patient discomfort upon insertion due to tissue impingement. In the maxillary arch, the tray should not impinge upon the anterior and posterior facial tissue or bony prominences. In the mandibular arch, it should not impinge upon facial or lingual tissues nor bony prominences. 9. In order to further protect soft tissues, extend flanges and provide a post dam to prevent the impression material from going down the patient’s throat. Use beeswax strips (beading wax) to completely line the periphery of the trays (this can be demonstrated by the faculty). The tray must be dry while adapting the wax. 10. As a last step in tray try‐in, note the position on the tray flanges in the vestibular fold when positioned to contact the teeth compared to the position of the flanges when no teeth contact. When the tray is fully seated, the flange border of the tray usually extends to the vestibular fold. During insertion of the loaded impression tray, it should be seated so the border terminates approximately one‐half the distance from the free gingival margin to the vestibular fold. During the impression procedure, cusp or incisal contact with the tray may subsequently result in fuzzy, distorted cusp tips and an inaccurate cast. ResD 517 Occlusion, 2010 Manual Page 12
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11. Also note the position of the anterior notch of the tray relative to the labial frenum and the effect of rotating the tray which will cause tissue impingement. This anterior guide will be important during insertion of the loaded tray. A. ERRORS RELATED TO ALGINATE TECHNIQUE Alginate Impression Procedure 1. Impression distorted due to loss of “rim‐lock” retention. Solution: ‐ force mixed alginate into all rim retention areas before fully loading tray. 2. Impression distorted due to loss of posterior “rim‐lock” retention. Solution: ‐ taper or thin alginate off the posterior third of the tray to avoid excess palatal or pharyngeal alginate which can break the seal upon removal of tray. 3. Impression distorted due to tray movement. Solution: ‐ have patient lift, then relax the tongue after insertion of the lower tray. Hold tray correctly on each side during the initial set of alginate. 4. Mandibular impression badly distorted due to flexure of mandible. Solution: ‐ immediately after proper seating of the lower tray, have the patient close slightly to relax the internal pterygoid muscles. 5. Impression exhibits large occlusal voids. Solution: ‐ mix alginate against the side of the rubber bowl; wipe alginate onto occlusal morphology of the teeth with a finger to minimize air entrapment. 6. Impression distorted due to thin alginate. Solution: ‐ do not overseat the loaded tray to tooth contact. Thin occlusal alginate may pull away from the tray upon removal of the impression from the mouth. ResD 517 Occlusion, 2010 Manual Page 13
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7. Impression cuspal detail distorted due to perforation. Solution: ‐ avoid seating the tray to cusp or incisal edge contact. Perforation of the alginate results in a fuzzy distorted morphology. B. ALGINATE IMPRESSION POUR‐UP 1. Impression distortion due to pour‐up delay or desiccation. Solution: ‐ pour up as soon after removal from the mouth as possible. Wrap impressions in a wet paper towel until pour‐up. If a delay is anticipated, place the wrapped impression in a plastic “zip‐lock” bag. 2. Impression distortion due to posterior excess. Solution: ‐ using a sharp knife or scalpel, trim off excess posterior alginate so the tray can lie flat on the lab bench. 3. Impression distortion due to inversion of pour‐up. Solution: ‐ do not invert poured‐up impression. The weight of the stone may result in slumping cusps. In addition, water may rise to the surface causing a weak porous surface and fuzzy detail. C. MANDIBULAR IMPRESSION 1. Take the mandibular impression first because there is less tendency for the patient to gag than when taking the maxillary impression. 2. Use the manufacturer’s directions as a guide in determining proportions of water and powder and the temperature of the water. Measure the volume of water to give the desired consistency to the mix. (Jeltrate ‐ 1 package to 1 measuring cylinder of water). (Use water slightly on the cool side but not cold, to allow slightly more working time.) 3. Add the powder to the water in the plaster bowl and spatulate until the mix is smooth and creamy. Spatulation time is 45 seconds. During mixing, the bowl should be rotated and the alginate flattened against the side of the bowl to minimize air bubbles. 4. Load the alginate into the lower tray, making sure that it is forced into the peripheral rim‐lock tray. Taper the excess alginate off in the molar region to minimize the flow of excess down the throat. ResD 517 Occlusion, 2010 Manual Page 14
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5. Quickly wipe some alginate over the occlusal surfaces of the teeth with an index finger forcing the alginate into the grooves and sulci to minimize bubbles in the finished impression. 6. Insert the loaded lower tray into the mouth with the aid of the index finger retracting the corner of the mouth. Insert one side of the tray first, at the corner of the mouth opposite the retracting finger and rotate the tray into place. Have the patient lift the tongue as it is being positioned and then relax the tongue. The tray should be inserted downward in the molar region first and then rotated onto the anterior teeth. 7. Retract the lower lip to make sure that it is not being trapped, that the vestibule is being filled and that the tray is correctly positioned. Retract the cheek on both sides with an index finger to make sure that it is not being trapped under the tray posteriorly and that the vestibule is being filled with alginate. Make sure the anterior notch of the tray is lined up with the labial frenum. If the patient shows discomfort during the insertion, a flange is probably impinging on a facial or lingual bony prominence. The loaded tray should be quickly moved anteroposteriorly, laterally, or rotated as required. 8. Settle the tray in place by placing an index finger on each side in the second bicuspid, first molar region and with the thumbs under the lower border of the mandible on each side to support it. Be careful not to depress the anterior portion of the tray into contact with the lower anterior teeth. Monitor position of the flanges of the tray. The excess alginate may extend or flow to the vestibular fold; however, the metal flange border should be short of it to avoid tray contact. 9. Instruct the patient to close to a comfortable position after correct tray insertion, since it has been shown that the medial (internal) pterygoid muscles can distort the mandible slightly in a wide open position, thus resulting in an inaccurate cast. 10.Hold the tray steady in the mouth until the initial set of the alginate. Have the patient stabilize the tray for the remaining two minutes with an index finger on each side on top of the tray and the thumbs under the lower border of the mandible. Clean up the plaster bowl and spatula while waiting for alginate to set. 11.After the alginate has set, remove the lower tray by placing an index finger under the periphery of the tray on one side then grasp the handle with other hand. Have the patient place his/her tongue under the tray anteriorly and lift, at the same time, “snap” the tray free from the teeth. If the impression is rocked or teased free from the teeth, it may distort or tear. ResD 517 Occlusion, 2010 Manual Page 15
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12.Gently rotate the tray from the patient’s mouth, rinse under the tap and examine the impression. It is acceptable if there has been no tooth contact with the tray and there are no tears or bubbles in critical areas. 13.Using a sharp knife, trim posterior excess alginate away to permit the tray to lay flat on the bench without distortion in the posterior region. In order to obtain a neater mandibular cast, additional alginate may be mixed and the open lingual area filled in. This should not be necessary for this exercise. 14. Disinfect the impression as per Dental Materials instructions as follows: Rinse off debris (blood and saliva) with water, but do not dry. Spray tray and impression thoroughly with iodophor disinfectant. Then place and seal the impression in a Ziploc bag. Allow the impression to remain in the bag for ten (10) minutes. When ready to pour up the impression, rinse the impression with water and remove excess. The impression can then be poured according to instructions from your dental materials class. D. Maxillary Impression 1. Mix the alginate as previously described, load the tray and taper the alginate off in the posterior area. Quickly wipe alginate onto occlusal surfaces. 2. Carefully rotate the tray into the mouth while retracting the corner of the lip. When the anterior notch of tray is lined up with labial frenum, seat posterior of loaded tray upward first, then rotate onto anterior teeth letting excess flow into facial vestibule. Quickly retract the lip to ensure that it is not being trapped by the tray. Avoid overseating the tray to tooth contact. 3. If there is a tendency to gag, instruct patient to breathe hard through the nose. Then bend the patient’s head forward, support it, and hold napkin under the chin in case of drooling. It has also been shown that salt sprinkled on the tongue of a patient before making the impression helps to control the gag reflex. NOTE: Avoid removing tray prematurely in the event of gagging. This will result in a mess of alginate intraorally. 4. Hold the tray steady until initial set of the alginate. Have the patient support the tray for the remaining two minutes by placing a thumb under each side of the tray and fingers the against the side of the face for stabilization. Clean the plaster bowl and spatula. ResD 517 Occlusion, 2010 Manual Page 16
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5. After complete set of the alginate, place one thumb at the periphery of the tray in the premolar region, grasp the tray handle and snap the impression free by pulling downward and slightly forward, allowing for anterior teeth inclination. 6. Carefully rotate tray from patient’s mouth, rinse under tap water and examine impression for acceptability. 7. Using a sharp knife, carefully trim away any excess alginate in the tuberosity area to allow tray to lay flat on the bench without distorting the posterior peripheral alginate. Wrap the impression in a wet paper towel and pour up as soon as possible. 8. Disinfect the impression in a similar manner to the mandibular impression. 9. Pour up the impression after the ten minute disinfection procedure. 2. POURING ALGINATE IMPRESSIONS Pouring and trimming your study casts will be done as stipulated in Chapter 2 or your RD 511P “Applied Dental Materials” syllabus. ResD 517 Occlusion, 2010 Manual Page 17
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FACEBOW APPLICATION As mentioned in lecture, the facebow is a relatively simple method of relating the maxillary teeth to the axis‐orbital plane with an accuracy acceptable for diagnosis of occlusal problems and routine restorative procedures. The external auditory meatus is used for the posterior and horizontal reference points as a means of relating the maxillary cast to an arbitrary hinge or opening axis location. The nasion is used as the anterior or vertical reference point. Armamentarium Panadent articulator Rubber bowl Lab knife Facebow Spatula Trimmed casts Fast‐set plaster Pink baseplate wax (regular) D‐5 carver Procedure 1. Preparation of Facebow Bite Fork Various materials or combinations may be applied to the facebow bite‐fork preparatory to the clinical registration. Red compound has been shown to be an accurate material by itself or in combination with a zinc oxide‐eugenol paste; however, this can be very messy. Therefore, pink baseplate wax will be the material of choice even though it is less accurate. a. It may be necessary to modify the bite‐fork with pliers. This will change the anteroposterior curvature from flat to curved which will more closely correspond to the occlusal plane and facilitate obtaining shallow cusp imprints. b. Warm a sheet of regular pink wax in hot water. Starting at one of the ends, roll the sheet of wax into a cylinder, stretch it slightly, bend it into a horseshoe shape, and apply the wax to the bite‐fork. c. Mold the wax to fit on the upper surface of the bite‐fork so that it fits the patient’s mouth (arch size and form, plane of occlusion). d. Soften the wax and position the bite‐fork against the cast of the patient’s maxillary teeth so that the stem is on the patient’s right side, pointing straight forward. Position bite‐fork with the midline mark on the fork aligned with the mid‐saggital plane. Obtain shallow imprints of the cusps and incisal edges. Chill wax with the air syringe, then remove and chill in water. e. If the imprints are too deep, wax should be trimmed away or the procedure repeated after filling in the imprints. ResD 517 Occlusion, 2010 Manual Page 18
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f. g. h. Support the bite‐fork in place with the thumb and fingers of both hands in the premolar region. Remove the bite‐fork without distorting the wax and chill the wax again in cold water. Try the cast of the upper teeth to place in the imprints on the bite‐fork. If the soft tissue areas are touching, reduce either the cast or wax in this area with a sharp blade. The cast should fit the imprints without any rocking or skidding. If the cast is not stable, then either the cast or imprints in bite‐fork are not accurate and the cast or the bite‐fork registration must be remade. NOTE: the stem of the biteplane must extend approximately parallel to the sagittal plane and be on the right side of the patient, Figure 1‐1. Figure 1‐1 1. FACEBOW APPLICATION Seat bite‐fork registration against patient’s maxillary teeth and have patient close mandibular teeth firmly into original indentations using lower jaw to support fork, (Figure 1‐1). 2. ATTACH FACEBOW a. Lock nasion relator saddle with thumb screw forward against nasion relator bracket (top arrow). Slide nasion relator bracket completely onto facebow cross‐bar and lock in place with thumb screw (bottom arrow) (Figure 1‐2). Figure 1‐2 ResD 517 Occlusion, 2010 Manual Page 19
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b. Position bite‐fork attachment post assembly with horizontal slide bar on patient’s right side (arrow 1) and set‐screw facing forward (arrow 2). Insert “short end” of attachment post into cross bar of facebow completely to ring stop (upper end of post should be flush with upper surface of cross bar). Rotate attachment pos until flat area on upper end faces forward to meet flat‐ended set screw. Tighten set screw with hex wrench, to lock attachment post to cross bar (Figure 1‐3). Figure 1‐3 c. Loosen double‐toggle clamp with hex wrench until both members of clamp are completely free to slide and/or rotate respectively, (Figure 1‐4). Figure 1‐ 4 d. Loosen single goggle clamp with hex wrench until clamp slides freely up and down vertical attachment post (Figure 1‐5). Figure 1‐5 e. Slightly loosen (1/2 turn only) large thumb screw at anterior end of facebow (arrow) (Figure 1‐6). Figure 1‐6 ResD 517 Occlusion, 2010 Manual Page 20
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f. While operator holds anterior end of facebow, have patient grasp side arms of bow with his/her fingers near distal ends and extend bow to maximum width bilateral to face (arrows) (Figure1‐7). Figure 1‐7 g. Instruct patient to contract side arms and place ear pieces firmly in auditory meatuses (bilateral horizontal arrows). While patient keeps side arms firmly in contact with ears, tighten large thumb screw (vertical arrow) to lock facebow width (Figure 1‐8). Note: Attachment post clamp is not joined to protruding stem of bite‐fork, at this time. Figure 1‐8 h. Loosen nasion relator shaft thumb screw slightly. While patient continues to support side arms, raise or lower anterior end of facebow until nasion‐
relator saddle can be made to contact patient’s nasion area. Push firmly back with finger of one hand on end of nasion relator shaft while concurrently pulling forward with fingers on nasion relator saddle in firm contact against bridge of patient’s nose (nasion) (Figure 1‐9). Figure 1‐9 i. Have patient sit upright with head held perfectly erect looking straight forward. While patient continues to support both side arms firmly, slide double‐toggle clamp over protruding stem of bite‐
fork. (It may be desirableto slide the clamp close to the patient’s mouth to reduce as much flexion of the components as possible.) Grasp double clamp (to offset torque) and tighten clamp securely to stem of bite‐fork with hex wrench (Figure 1‐10). Figure 1‐10 ResD 517 Occlusion, 2010 Manual Page 21
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j. While patient continues to hold head erect and facebow level, grasp single‐toggle clamp tightly (to offset torque) and tighten clamp securely to vertical attachment post with hex wrench (Figure 1‐11). Figure 1‐11 k. Loosen nasion relator thumb screw slightly and retract nasion relator away from patient’s face. Lock nasion relator in contact with support bracket (arrow) (Figure 1‐12). Figure 1‐12 l. Slightly loosen (1/2 turn only) large thumb screw. Have patient open mouth and retract side arms completely away from ears (arrows) (Figure 1‐13). Figure 1‐13 ResD 517 Occlusion, 2010 Manual Page 22
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m. Instruct patient to remove their hands from facebow. Remove facebow downward and forward from patient’s face (arrow) (Figure 1‐14). Figure 1‐14 n. Loosen hex head screw (1/2 turn only) on facebow cross bar in preparation for removing bite‐fork assembly (Figure 1‐15). Figure 1‐15 o. Remove bite‐fork assembly straight downward (arrow). Transport bite‐fork assembly to laboratory for cast mounting procedure (Figure 1‐
16). Figure 1‐16 ResD 517 Occlusion, 2010 Manual Page 23
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USING YOUR PANADENT ARTICULATOR When centric latch is engaged and articulator is closed, extending arm of latch automatically depresses centric (arrow) and places lower end of centric pin in centric channel of mandibular frame, see Figure 1‐18 (Figure 1‐17). Figure 1‐17 Centric pin engaged in centric channel (arrow). Eccentric movements (lateral &protrusive) should never be attempted when centric latch is engaged or when centric pin is in centric channel (Figure 1‐18). Figure 1‐18 To occlude casts in centric relation, raise and lock incisal pin and support post both about 5 mm above incisal table. Hinge maxillary frame by lifting up on lower end of incisal pin (Figure 1‐19). Figure 1‐19 ResD 517 Occlusion, 2010 Manual Page 24
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To execute protrusive and lateral movements, release centric latch by pushing distally on protruding end of latch (arrow). Be sure centric pin springs upward to disengage centric channel on mandibular frame (Figure 1‐
20). Figure 1‐20 Centric pin out of centric channel (arrow). Lateral and protrusive movements can now be made (‘Figure 1‐21). Figure 1‐21 If centric pin does not spring upward when latch is released, rotate centric pin cap (arrow) to release it (Figure 1‐22). Figure 1‐22 Depress centric pin cap with finger (arrow) to temporarily locate centric relation during use of instrument. (Hinging movement can be made with centric pin depressed but lateral movements should never be attempted with centric locator pin in depressed position) (Figure 1‐23).
Figure 1‐23 ResD 517 Occlusion, 2010 Manual Page 25
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To make protrusive‐retrusive movement, grasp vertical frame of articulator with one hand. Separate casts by pushing down on incisal table (lifting up on incisal pin) (arrows) until incisor teeth are edge to edge. Slowly release finger pressure and allow mandibular frame to retrude to centric relation (Figure 1‐24). Figure 1‐24 To occlude teeth in right lateral chewing motion, grasp end of incisal pin with thumb and index finger and left max‐
illary frame (depress mandibular) to separate teeth. Then move mandibular frame right (incisal pin left) approximately 3 mm (cuspid to cuspid). Bring casts slowly into cuspid contact. Keep slight forward pressure on incisal pin to assure condylar border movement while occluding cast slowly back to centric relation (Figure 1‐25). Figure 1‐25 For left lateral movement, use same basic procedure as for right lateral movement (Figure 1‐26). Figure 1‐26 To reconnect centric latch when articulator is closed, rotate latch upward and forward with fingers (curved arrow) until cradles of latch engage analog axis shafts. (This procedure will automatically depress centric pin into centric channel of mandibular frame of articulator.) (Figure 1‐27). Figure 1‐27 ResD 517 Occlusion, 2010 Manual Page 26
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Centric latch can also be engaged when articulator is in open position by exerting distal pressure on latch bar with fingers (arrow) (Figure 1‐28) Figure 1‐28 To lock centric locator pin in down position when centric latch is disengaged, place finger on flange of pin cap (arrow) (Figure 1‐29). Figure 1‐29 Then depress centric cap and rotate clockwise (arrows) (Figure 1‐30). Figure 1‐30 Lingual approach to teeth is accomplished through lingual access area of articulator (Figure 1‐31). Figure 1‐31 ResD 517 Occlusion, 2010 Manual Page 27
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When articulator is not in use, it is recommended that incisal pin be locked in contact with incisal table. (arrow) slightly separating the teeth to prevent tooth breaking from casts (Figure 1‐32). Figure 1‐32 CAST MOUNTING PROCEDURE (MAXILLARY) Slightly loosen right and left axis shaft screws with hex wrench (Figure 1‐33). Figure 1‐33 Slightly loosen right and left axis shaft thumb screws. Be sure motion analogs contact calibrated sides of articulator (arrow). Rotate motion analogs until #6 horizontal line coincides with superior surface of analogs, then tighten axis shaft thumb screws to maintain positions temporarily (Figure 1‐34). Figure 1‐34 ResD 517 Occlusion, 2010 Manual Page 28
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After analogs have been set at average angulation of “6”, re‐tighten right and left axis shaft lock screws with hex wrench (Figure 1‐35). Figure 1‐35 Set incisal pin at heavy center engraved ring (arrow). This will make the maxillary and mandibular articulator frames parallel to each other. Note: If curved pin articulator is being used, set incisal pin at “0” degrees (Figure 1‐36). Figure 1‐36 Open articulator by hinging maxillary frame back (Figure 1‐
37). Figure 1‐37 ResD 517 Occlusion, 2010 Manual Page 29
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Spray entire articulator, including mounting plates and analogs, lightly with silicone release agent each time before mounting casts to prevent mounting from sticking to articulator. (The lubricant will cause residual mounting stone on articulator to be easily wiped off without scratching finished surface of instrument.) Note: A Vaseline or silicone gel on a cotton swab should be used each time to lubricate the analog paths and reduce wear on the analogs and condylar axis elements (Figure 1‐
38). Figure 1‐38 Rotate maxillary frame back 180°. Extend and lock support post with thumb screw (Figure 1‐39). Figure 1‐39 Slightly loosen incisal table thumb screw and remove table forward (arrow) (Figure 1‐40). Figure 1‐40 ResD 517 Occlusion, 2010 Manual Page 30
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Place mounting fixture in incisal table slot and lock in rear most position (arrow) with thumb screw (Figure 1‐41). Figure 1‐41 Hold upper end of bite‐fork attachment post with thumb and index finger of one hand. Place lower end of attachment post into hole in mounting fixture. Be sure bite‐fork attachment post is completely down to retaining ring stop. Tighten set screw with hex wench (or fingers if “T” head screw is being used) (Figure 1‐42). Figure 1‐42 With model trimmer, grind maxillary surface of cast parallel to occlusal plane of teeth. Grind perimeter of cast with approximately 10‐15° bevel to depth of buccal and labial vestibules. Avoid touching teeth or buccal and labial vestibules. Avoid touching teeth or buccal and labial gingival areas with trimmer wheel (Figure 1‐43). Figure 1‐43 Score superior mounting surface and beveled areas of cast with laboratory knife or carborundum disc for retention in mounting stone (Figure 1‐44). Figure 1‐44 ResD 517 Occlusion, 2010 Manual Page 31
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Remove all bubbles or impression defects from occlusal and incisal areas of casts (Figure 1‐45). Figure 1‐45 Seat cast carefully into bite fork registration and verify fit of cast to registration (Figure 1‐46). Figure1‐46 Hinge maxillary frame upward and forward over cast and bite‐fork assembly (curved arrow) (Figure 1‐47). Figure 1‐47 Close maxillary frame of articulator over cast until end of incisal pin contacts upper surface of mounting fixture (arrow). Determine quantity of mounting stone needed. Grind cast if necessary so there is at least 5 mm space between cast and mounting plate in area indicated by spatula. Make sure base of cast is moist. This will aid in retention to mounting stone (Figure 1‐48). Figure 1‐48 ResD 517 Occlusion, 2010 Manual Page 32
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Hinge maxillary frame back 180°. Mix mounting stone to the consistency of whipped cream. Place stone first in retention areas of mounting plate (Figure 1‐49). Figure 1‐49 Place sufficient amount of soft stone on mounting surface of maxillary cast. (The amount of mounting stone should be only enough to make a “solid” connection with the mounting plate stone. Reinforcement stone can be added later after the initial stone has hardened.) (Figure 1‐50). Figure 1‐50 Hinge maxillary frame forward to joint two pads of soft stone (curved arrow) (Figure 1‐51). Figure 1‐51 Close articulator until incisal pin contacts surface of mounting fixture (arrow) (Figure 1‐52). Figure 1‐52 ResD 517 Occlusion, 2010 Manual Page 33
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Remove any overhanging soft stone with spatula of finger carefully to avoid disturbing cast in bite‐fork registration. (Mounting stone should not extend beyond perimeter of mounting plate and vestibule of cast.) Leave cast undisturbed until mounting stone has completely hardened (Figure 1‐53). Figure 1‐53 After mounting stone has hardened, release centric latch and rotate maxillary frame backward with cast attached (arrow) (Figure 1‐54). Figure 1‐54 Remove mounting fixture, bite‐fork assembly and bite‐fork support. Replace incisal table (Figure 1‐55). Figure 1‐55 Remove maxillary cast from articulator. Cut back excess stone (if any) projecting beyond perimeter of mounting plate and vestibule of cast (Figure 1‐56). Figure 1‐56 ResD 517 Occlusion, 2010 Manual Page 34
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For more secure and esthetic mounting, mix quick‐set plaster to the consistency of whipped cream. Add reinforcement layer of plaster to cast using trimmed edge of cast and perimeter of mounting plate as guides for plaster spatula. While plaster is still soft, use fingers under running tap water to smooth plaster surfaces (Figure 1‐57). Figure 1‐57 Remove any residual plaster from mounting plate and articulator and replace cast on articulator. When standard mounting plates are being used, be sure to rotate mounted cast in the direction the mounting plate screw is being turned (arrows). Tighten mounting plate screw securely (Figure 1‐
58). Figure 1‐58 ResD 517 Occlusion, 2010 Manual Page 35
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FUNCTIONAL ANALYSIS OF OCCLUSION STUDENT BENCH # _______ PROCEDURE ALGINATE IMPRESSIONS CRITERIA No voids, tears, perforations in critical areas; adequate coverage; excesses trimmed DIAGNOSTIC CASTS No excesses, nodules or large voids; properly trimmed casts FACEBOW RECORD AND Bitefork ‐ properly prepared; MOUNTING indentations shallow Facebow ‐ properly related clinically Maxillary cast ‐ stable and fits on bitefork MOUNTING MAXILLARY Maxillary cast ‐ properly, neatly mounted CENTRIC OCCLUSION RECORDS Centric Records (3) properly constructed accurate and trimmed Clinic conduct ‐ proper attire; clean work area PROTRUSIVE RECORD Protrusive Record ‐ Correctly taken and articulator set MOUNTING MANDIBULAR CAST Mandibular cast ‐ neatly mounted correctly VERIFICATION OF CENTRIC Mounted casts have comparable contacts as evidenced by clinical findings. Two out of three CRO records fit articulated casts the same OCCLUSAL ASSESSMENT FORM Clinical examination COMPLETED BY PARTNER Occlusion charted correctly Clinic conduct ‐ proper attire; clean work area PROJECT COMPLETED Instructor initials ______ COMMENTS NOTE: This form is a guide only. No signatures or initials are necessary until all steps are completed. Then turn in your signed form with your bench number as verification of completion. ResD 517 Occlusion, 2010 Manual Page 36
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WEEK 2 LECTURE 1. Fabrication of Centric Relation Records 2. Centric Relation Interocclusal Records, Use, and Verification CLINIC/LABORATORY 1. Centric Relation Records 2. Mount Mandibular Cast 3. Verification of Centric Mounting Accuracy 4. Determining the Angle of Eminence ResD 517 Occlusion, 2010 Manual Page 37
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LECTURE CENTRIC RELATION INTEROCCLUSAL RECORDS Week 1 was dedicated to making accurate impressions, pouring up the impressions and mounting the maxillary cast on the articulator. As illustrated in the Facebow transfer section, we now have the maxillary cast closely oriented to the horizontal axis of the patient in three dimensions. This week we will carry on the process by obtaining the record we need to accurately position the mandibular cast against the maxillary cast. After this is accomplished, we will have the orientation we need to perform restorative treatment requiring occlusal surfaces as well as the "ballpark" orientation to perform meaningful, diagnostic occlusal adjustments, if deemed necessary. The purpose of a centric relation interocclusal record is to serve as the mechanism to accurately mount the lower cast onto the articulator in the same relationship to the upper cast as the mandibular arch is to the maxillary arch in the patient's mouth. Since centric relation represents the posterior border or limit of movement and since it is the only repeatable relationship of the mandible to the maxilla, it seems logical that this is the position we should record. It is well known that centric relation (CR) can often “migrate” over time, so this position is commonly considered an area versus point. Remember that once casts are mounted onto the articulator, that position represents the posterior border position or posterior limit of movement of the articulator, regardless of what that position may actually represent. Therefore, it is mandatory that this relationship represent the true CR terminal hinge relationship of the patient's mandible to his/her maxilla. The centric interocclusal record relates the lower cast to the condylar axis by means of its relationship to the maxillary cast. If a centric relation record is made at an opened vertical position, the relationship will be accurate only if the closing axis is the same on the articulator as it is on the patient. The verification procedure of centric interocclusal recording is so important to the mounting process that it is reason enough to do all mountings with conscientious attention to detail. Given that centric relation is the only repeatable mandibular/maxillary position it stands to reason that fabrication of a second interocclusal record done at a different vertical dimension will verify the accuracy of the original centric record made at the terminal hinge position of the horizontal axis. If a discrepancy exists it will become evident when you position the second record between the arches, then check to see if the teeth close into the record exactly the same as for the first record. Any discrepancy dictates that a third record be done to verify which of the previous two were correct. ResD 517 Occlusion, 2010 Manual Page 38
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The actual step‐by‐step procedure for making centric relation records is given following this explanatory section so will not be dealt with here. As you would expect, the occlusal record should be taken in a "Centric Relation" (CR) position. Therefore, it is important to have the patient reclined as well as to ensure that the head of the condyle is seated against the thinnest avascular portion of the disc in a superior position. Since Centric Relation is a repeatable position, once you have correctly identified the arc of closure, centric records taken at any vertical dimension on that centric relation arc will fit perfectly into the previous record. This is one way of verifying the accuracy of your centric relation recording. Note that in the above illustration the centric relation position is achieved by exerting firm pressure in a downward manner on the chin while "seating" the condyles into the glenoid fossa with pressure at the "angle of the mandible." ResD 517 Occlusion, 2010 Manual Page 39
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CENTRIC RELATION RECORD TECHNIQUE There are many methods for relating the lower model to the upper model on an articulator in centric relation. The following technique is simple and accurate if properly used. It will be the one you will use in the clinic so pay careful attention to its preparation. With modification, it can be used where teeth are missing, malaligned, mobile or have been prepared for restorations. Armamentarium Aluwax wafers Stick wax Ash #7 soft metal Wax spatula Regular pink baseplate wax Sharp knife or scalpel Bunsen burner Aluwax Technique A. Preclinical Preparation of Centric Wafers 1. Carefully examine the diagnostic casts to ensure that all occlusal nodules have been removed. 2. Wet the maxillary cast. Soften an "Aluwax" wafer under hot tap water and press it to place on the upper cast to obtain slight indentations of the cusp tips and incisal edges (gauze impregnated side of the wafer away from the cast). 3. Trim the wafer with a pair of scissors approximately 1 mm outside the outline of the cusp imprints. 4. Warm a piece of pink baseplate wax (regular) over the flame and place it on the lower side of the wafer covering the entire surface. Trim the surplus and seal the edges to the wafer with a hot spatula. This will reinforce the pliable Aluwax wafer. 5. Add an additional layer of pink baseplate wax to the anterior area of the wafer. This will provide the extra thickness needed to allow simultaneous anterior and posterior tooth imprints. 6. Cut a rectangular piece of Ash #7 soft metal to reinforce both sides of the wafer. The metal should be trimmed to an oval shape conforming to the arch curvature and extend to approximately 4 mm from lingual cusps and incisal edge imprints. ResD 517 Occlusion, 2010 Manual Page 40
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7.
After trimming, double the metal over the posterior end of the wafer so that the wax is sandwiched between it. Seal the edges of the metal reinforcement with sticky wax. NOTE: Before sealing the metal, use both the trimmed wafer and the metal as a pattern for trimming two additional Aluwax wafers and metal strips. 8. If the patient has a moderately deep overbite, an additional strip of pink wax may have to be added in the posterior region. This is necessary to gain contact of posterior teeth without warping the record excessively in the anterior region during record taking. 9. B. 1. After preparation of three wafers, warm the wax of the first wafer slightly and readapt it to the wet maxillary cast. 2. Adjust the dental chair so that the patient is placed in a reclined position, the head properly supported and tipped back so that the patient's neck muscles are stretched slightly. 3. Warm the wax wafer in hot tap water (not a water bath) and place it in the patient's mouth, fitting the imprints in the wax over the patient's upper teeth and adapt areas that are not contacting. Remove the wafer and cool under cold water. 4. Replace the wafer and have the patient close until just touching. Check to make sure that the posteriors and anteriors will close into the pink wax at about the same time. If not, modify the wafer by adding or subtracting wax until this can be achieved. 5. Explain the procedure to the patient and practice the hinge movement of the mandible without wax in the mouth. During this "practice" period, identify the location of the "Point of Initial contact" (PIC). Document this on the Occlusal Assessment form to be completed later. Mark the PIC with articulating film, then confirm it by use of a mylar strip. For a severe overbite, it is necessary to cut off the anterior portion of the wafer so that the anterior teeth do not touch the wafer and cause severe distortion. The alternative would be to build up the posterior so thick that an inaccurate centric record would result due to translation of mandible. Taking the Centric Record ResD 517 Occlusion, 2010 Manual Page 41
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The method of manipulation of the mandible is a key element in a successful centric record procedure. The operator's arm should be extended straight to the patient’s face. The first fingers should be spread in a “V” under the inferior borders of the mandible and the extended thumb on the labial of the lower anterior teeth and tissue at the midline. A common alternate technique is to position a bent thumb at the midline of the chin with the same finger support. 6. Tell the patient that you will be guiding them into repeated light contact with the wax and never to close fully into wax. Perforation due to tooth contact will necessitate discarding the wax record. 7. Warm the pink wax side of the first wafer under hot water. DO NOT use a water bath to soften this wax. 8. 9. Place the wafer against the maxillary teeth and hold it in place with the left thumb and second finger against the buccal of the premolars. Using light thumb pressure on the labial midline, tell the patient to open, then touch or "tap, tap" into the wax as you concurrently help the mandible move up and down from a slightly open position, until light imprints (tips of cusps, incisal edges) are made on the underside of the wafer. 10. One technique to assist the mandible into the hinge position is to have the patient move their mandible into extreme protrusive and then quickly “snap” back as far as she/he can before hinge closure. 11. When it is apparent that the patient is repeatedly contacting into the cusp imprints, have him/her hold his/her mandibular teeth in contact with the wax record, then chill the record with an air syringe. 12. To remove the record without distorting it, gently push the record down with the left thumb and finger as you ask the patient to open slowly. This allows you to use the mandibular teeth as a platform. 13. Remove the record from the patient's mouth and chill it with cool water. 14. Examine the record for adequacy of cuspal and incisal imprints. Although a full compliment of imprints ensures maximum stability of the mandibular cast during the mounting procedure, tripodized contact in the anterior and both posterior quadrants is sufficient. ResD 517 Occlusion, 2010 Manual Page 42
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15. If cusp imprints are minimal in one quadrant and adequate in others, do not warm the entire wafer and have patient close deeper into the wax. Instead, drip hot Aluwax on the inadequate areas, return the record to the mouth and guide the mandibular teeth into the original imprints to pick up the additional contact. 16. If cusp imprints are too deep, carefully trim the wax with a sharp knife or scalpel before rechecking in the mouth. 17. Store the record in the same manner as you did the alginate impressions being careful not to distort it. (Aluwax is soft enough so that it is easily warped by rough handling or by changes in temperature). 18. Obtain a second and third record in the manner described above, and mark the records 1, 2, and 3 on the soft support metal. 19. If a posterior edentulous area exists with no posterior stop, the centric record technique may be modified as follows: a. Add a pillar of pink wax to the posterior of the wafer on the edentulous side so that it is centered over the crest of the ridge. b. Obtain a centric record of the existing teeth as previously described. If properly positioned, the wax pillar will be indented by the crest of the edentulous ridge. c. Remove the centric record and relieve the indented pillar wax to allow placement of a layer of zinc oxide eugenol bite registration paste. d. Mix and add a small amount of the “bite registration paste” to the tip of the pillar. Insert it into the mouth and lightly guide the mandible into the Aluwax centric indentations. Hold this position until the paste has set. e. The ZOE paste will have related the soft tissue of the edentulous ridge to the centric record without the tissue displacement that using wax alone would cause. 20. If there are mobile teeth present, the Aluwax wafer may be used as a matrix for the bite registration paste as follows: a. Obtain the centric record as previously described. ResD 517 Occlusion, 2010 Manual Page 43
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b. Lightly lubricate the occlusal surfaces and incisal edges of the teeth with Vaseline or silicone lubricant. c. Mix bite registration paste and apply a thin layer onto the maxillary imprints or indentations. d. Carefully insert and fit the record against the maxillary teeth without pressure. Hold until complete set of the registration paste has occurred, then remove. e. Apply registration paste to the mandibular cuspal imprints and insert the record against the maxillary teeth. Guide the mandible lightly into the registration paste and hold until set. f. After removal of the record, carefully trim any excess registration paste with a sharp scalpel to leave only shallow imprints of the cusp tips and incisal edges. g. If carefully executed, this technique will record the maxillo‐mandibular relation in centric without displacement of mobile teeth. 21. An alternate technique for mobile teeth involves the use of "Ash" metal as a matrix for the bite registration paste as follows: a. Cut a piece of Ash No. 7 soft metal to arch form and mold it to the occlusal plane of the maxillary cast. b. Roughen the peripheral areas of the wafer with a bur and apply cyanoarcylate adhesive to these areas. c. Apply registration paste to the maxillary and mandibular areas and make the centric record as previously described. A. CONFIRMATION OF FIT OF CENTRIC RECORDS ON CASTS 1. Before dismissing the patient, each centric record should be fitted to both casts individually to confirm accuracy of fit. 2. Gently fit the record on one cast. If the impression material contacts soft tissue e.g. retromolar area, tuberosity, interproximal tissue, then either the wax should be carefully trimmed or the stone trimmed with a sharp knife or scalpel. 3. If there is a slight lack of fit in one area, re‐examine the cast for nodules or other occlusal imperfections due to impression technique. ResD 517 Occlusion, 2010 Manual Page 44
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B. 4. Rocking of the wafer or complete lack of fit in one region is usually indicative of a distorted alginate impression and subsequent inaccurate cast. 5. Repeat the above procedures to confirm fit of record on the second cast. MOUNTING THE MANDIBULAR CAST Although centric relation record determination may have been carefully executed clinically, there are a number of possible sources of error that frequently occur during the mounting of the mandibular cast. The following check‐list should be utilized before mounting the cast to minimize errors. a. Casts should be re‐examined and all occlusal or incisal nodules or irregularities removed. b. The centric wafer should not contact stone anywhere except on the occlusal surfaces of the stone cast, i.e., interdental papilla, palate, retromolar pad, tuberosity (trim wax or stone if problem is present). c. The centric wafer fits maxillary and mandibular teeth accurately. (Occasionally the wax wafer warps and may be warmed slightly and readapted in a non‐
contacting area). d. The centric wafer fits both maxillary and mandibular teeth when casts are held together. e. The mandibular cast must not dislodge from the record during the application and set of the mounting plaster. ResD 517 Occlusion, 2010 Manual Page 45
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CAST MOUNTING PROCEDURE (MANDIBULAR) Grind mandibular mounting surface of cast parallel to occlusal plane of teeth with model trimmer. Grind perimeter of cast with approximately 10‐15° bevel to depth of buccal and labial vestibules. Avoid touching teeth or buccal and labial gingival areas with trimmer (Figure 2‐1). Lab knife shows approximate amount of bevel on mounting area of cast (Figure 2‐2). Cut retention grooves in trimmed cast with laboratory knife or carborundum disc (Figure 2‐3). ResD 517 Occlusion, 2010 Manual Page 46
Figure 2‐1 Figure 2‐2 Figure 2‐3 2-11
Score mounting surface of cast with laboratory knife or carborundum disc (Figure 2‐4). Raise and lock maxillary frame against incisal pin about 5 mm above the heavy “O” ring depending on thickness of centric record. (If vertical dimension is not being changed by thickness of centric record, i.e., closed‐bite interocclusal record, leave incisal pin set at “0”). Note: The raising of the maxillary frame on the incisal pin is an arbitrary procedure and does not change the relationship of the occlusal surfaces of the maxillary teeth to the protrusive path which will be set in the articulator at a later time (Figure 2‐5). Figure 2‐4 Figure 2‐5 Rotate centric latch forward to engage latch with axis shaft and depress centric pin into centric channel of lower frame of articulator (Figure 2‐6). Figure 2‐6 ResD 517 Occlusion, 2010 Manual Page 47
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Place centric record carefully on maxillary cast and verify fit. Pay particular attention to see that there are no contacts of centric record material with soft tissue unless it is a designated area to support a distal edentulous ridge (Figure 2‐7). Figure 2‐7 Remove any occlusal bubbles or artifacts if present in tooth area of mandibular cast. Place mandibular cast carefully into cusp tip impressions in centric record and verify fit (Figure 2‐8). Figure 2‐8 Close mandibular frame of articulator over cast until incisal pin touches incisal table to determine amount of plaster needed for mounting (Figure 2‐9). Figure 2‐9 ResD 517 Occlusion, 2010 Manual Page 48
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Grind mounting surface as necessary so there will be at least a 5 mm space between mounting plate and cast (area indicated by spatula (Figure 2‐10). Figure 2‐10 Spray entire mandibular frame, including condylar element and analogs with silicone spray. Also spray the mounting stand for protection of stand and easy removal of any residual mounting stone (Figure 2‐11). Figure 2‐11 Mix quick set mounting stone to consistency of whipped cream. Place amount of soft stone first on mounting plate, being sure to get stone into retention areas of plate. Make sure base of stone cast is moist (Figure 2‐12). Figure 2‐12 ResD 517 Occlusion, 2010 Manual Page 49
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Place minimum amount of soft stone on mounting surface of cast to make connection with stone on mounting plate. Note: do not add more stone than required to make a small to moderate sized connection. If the mounting space is large it is best to build up on the cast and mounting plate and allow this stone to harden. Then make the final connection with a small amount of stone to keep the expansion errors to a minimum (Figure 2‐13). Figure 2‐13 Rotate mandibular frame over casts to join two pads of soft mounting stone (Figure 2‐14). Figure 2‐14 Close articulator frame until end of incisal pin rests on incisal table (arrow). Press cast tightly into centric record with thumb and fingers at premolar areas (arrows) while palm of hand rests on frame of articulator. Hold in this manner until quick‐set stone reaches initial set. Then remove hand and leave articulator undisturbed until mounting stone has completely hardened (Figure 2‐15). Note: As an alternative, heavy duty rubber bands may be used to hold the cast in place during setting of the stone. Figure 2‐15 ResD 517 Occlusion, 2010 Manual Page 50
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Release centric hatch to allow for easy removal of centric record (Figure 2‐16). Figure 2‐16 Lift upper frame of articulator and carefully remove centric record from casts (Figure 2‐17. Figure 2‐17 When mounting stone has hardened, loosen mounting plate screw and remove cast from lower frame (Figure 2‐
18). Figure 2‐18 ResD 517 Occlusion, 2010 Manual Page 51
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For added strength and esthetics, add soft mix of quick‐
set plaster using edge of mounting plate and cut edge of buccal and labial vestibules of cast as guides for spatula. Allow plaster to reach final set (Figure 2‐19). Figure 2‐19 Remove any residual plaster on mounting plate and articulator mounting surface and replace mandibular cast on articulator. Always rotate cast in direction the mounting screw is being tightened to maintain highest accuracy (Figure 2‐20). Figure 2‐20 ResD 517 Occlusion, 2010 Manual Page 52
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C. VERIFICATION OF CENTRIC ACCURACY Verification of a credible or reasonably accurate CO mounting is an important step in the functional analysis procedure. While a small degree of error can be accepted for a diagnostic procedure, such as the one underway, an error in the mounted CO relationship of casts for cast crown or bridge procedures can be time consuming to correct clinically. While various precautions or sources of error have been previously mentioned during the technique outlined for the various steps, a review at the end of this section is appropriate, in particular, if a CO mounting does not closely replicate the patient's CO contact relationship. Two methods of verifying credibility or accuracy of the CO mounting will be described. ResD 517 Occlusion, 2010 Manual Page 53
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1. COMPARISON OF CLINICAL AND ARTICULATOR CO TO MIP CONTACT RELATIONSHIPS a. Comparison of P.I.C. (Point of Initial Contact) If diagnostic casts are available during the clinical examination and charting appointment, mark or circle the clinical CO point of initial contact (P.I.C.) determined previously, on the casts with a pencil. After mounting the mandibular cast, use red ribbon to mark where the mandibular cast first contacts the maxillary cast. Use red ribbon to mark the articulator P.I.C. The marks should be superimposed on one another. Also use a mylar strip to confirm P.I.C. contact if several spots mark at one time. The marks should be superimposed on one another if several spots mark at one time. Marking between the same two teeth as noted clinically and an approximate overlap of red over the penciled P.I.C. indicates a replication of the CRO position. This method of comparison consists of three aspects or criteria for verification: b. Comparison of CO to MIP Slide After mounting the casts, draw vertical lines from the maxillary second premolar to the mandibular second premolar and from the maxillary central to the mandibular central incisor region, with the casts in the CO position. Slide or shift the casts from CO to MIP. Mark second vertical lines in the premolar and central incisor areas. The direction (anterior and lateral) and amount (mm.) of shift should be similar to the clinical findings. c. Credibility of MIP (Maximal Intercuspal position) After checking the slide from CO to MIP, check for a credible interdigitation of teeth in MIP. Visual confirmation that the anteriors and posteriors contact in similar fashion to that found clinically will indicate an accurate mounting. ResD 517 Occlusion, 2010 Manual Page 54
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2. ACCURACY OF FIT OF A SECOND OR THIRD CO RECORD a. Assuming that a second &/or third CO record has been obtained, they may be used to confirm the CO record taking and mounting accuracy. b. To compensate for minor distortions of the CO record, warm it under water and readapt to each cast individually. c. Lock the articulator into centric relation. d. Place CO record No. 2 onto the mandibular teeth to fit the cusp tips. Close the maxillary arm of the articulator to allow maxillary cusps and incisal edges to seat into the CO record. e. If the maxillary teeth fit well with no visible space in posterior or anterior areas and no vertical "play" of the record occurs when pushed with an instrument, then the CO mounted relationship can be considered accurate. In other words, since centric relation is the only reproducible mandibular position, the two records have been replicated and, in addition, no impression or mounting errors were made. NOTE: Deep indentations may prevent proper seating because of the arcing movement. Lightly remove the edge of the indentation if this occurs. f. If the CO record No. 2 does not fit, it is probably inaccurate if the CO contact and slide into MIP are acceptable. g. If the CO record No. 2 does not fit and the CO contact and slide into MIP is in error beyond the limit of acceptability, then the mandibular cast should be remounted to record No. 2. If there seems to be no discernible error, check the mounting using the third CO record. If this does not fit, the casts should be remounted using record No. 2 or 3. A REVIEW OF SOURCES OF ERROR AFFECTING CRO MOUNTING ACCURACY The sources of error can be categorized as follows: a. Clinical Centric Record Procedures b. CO Record and Cast Mounting Interim c. Mandibular Cast Mounting Procedure d. Alginate Impression Procedures‐ described in Week 1 e. Alginate Impression Pour‐up‐ described in Week 1 ResD 517 Occlusion, 2010 Manual Page 55
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A. Clinical Centric Record Procedures 1. Record not obtained in centric relation. Solution: ‐ use proper jaw support and manipulation then practice movement with the patient before obtaining records. 2. Record perforated tooth contact causing slide. Solution: ‐ increase anterior thickness and do not oversoften the wax. 3. Record not obtained in centric relation due to wax thickness. Solution: ‐ use a wafer of one aluwax and one thin pink, rather than two aluwax; excessive thickness may result in anterior translation of the condyles. 4. Record distortion upon removal. Solution: ‐ cool with air and remove by pushing down on the record as patient opens using mandible as a platform. 5. Record distortion due to minimal rigidity. Solution: ‐ do not use single thickness aluwax; Ash metal support should be extended as wide and as anterior as possible without occlusal interference on the metal. B. CO Record and Cast Mounting Interim 1. Record distortion due to improper storage. Solution: ‐ Keep CO record on maxillary or mandibular cast if available or wrap in a wet tissue or paper towel and seal in "zip‐ lock" plastic bag after the disinfection procedure. C. Mandibular Cast Mounting Procedure 1. Record does not fit casts due to wax distortion. Solution: ‐ on the assumption that casts and the CO record procedure were accurate, a slightly distorted CO record presents no problem. Warm the record under water and readapt to each cast individually before mounting the mandibular cast. ResD 517 Occlusion, 2010 Manual Page 56
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2. Record does not fit casts due to stone nodules. Solution: ‐ recheck occlusal morphology of both casts and eliminate any remaining nodules or suspicious irregularities. 3. Record does not fit casts due to stone tissue interference. Solution: ‐ check for wax contact with stone tuberosity, retromolar pad, palatal or interdental papilla contact. Scrape interfering stone or carefully trim wax with a scalpel. 4. Articulator condylar heads not in posterior position during mounting. Solution: ‐ reconfirm that both centric latches are locked in centric. 5. Casts and CO record not secure during mounting. Solution: ‐ criss‐cross two heavy rubber bands around casts and maxillary arm of articulator so that casts are secure in the record, make sure even pressure exists. The tendency is to have excessive pressure over the posterior region which would cause the anteriors to not fully seat. 6. Mandibular cast position distortion due to expanding mounting plaster. Solution: ‐ cast should be trimmed so there is minimal peripheral excess, thus less mounting plaster will be required. A low expansion mounting plaster or stone should be used, e.g. Kerr No. 2 Impression plaster or Whip‐Mix mounting stone. D. A. Protrusive Condylar Determination 1. Fabricate a double thickness of baseplate and position it over all the maxillary teeth. 2. Warm slightly, then press on it firmly enough to develop cuspal indentations. 3. Have your patient protrude her/his mandible about 5 to 7 mm from the CR position, then close into the wax, developing small imprints of the mandibular cusp tips. ADJUSTMENT OF CONDYLAR GUIDANCE MECHANISMS ResD 517 Occlusion, 2010 Manual Page 57
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4. Remove, chill, disinfect, then set aside on a damp paper towel for use in determining the angle of eminence for the articulator. NOTE: This procedure is a “one‐time procedure” which is not repeatable. Think about why this action is only a one‐time, not repeated procedure. 5. Although the angle of eminence you have determined is relatively accurate for your patient it may be a smaller angle than the anatomical boney angle because there are tissues, a disk, and restrictive ligaments affecting the protrusive movement of the condyles. ResD 517 Occlusion, 2010 Manual Page 58
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SETTING YOUR ARTICULATOR FOR PROTRUSIVE Raise and lock incisal pin and support pin (arrow) at least 5 mm above incisal table (Figure 2‐21). Figure 2‐21 Loosen thumb screws and retract right and left Dyna‐Link pins (arrow) (Figure 2‐22). Figure 2‐22 Place Dyna‐Link pins in storage holes in articulator legs (arrow) (Figure 2‐23). Figure 2‐23 ResD 517 Occlusion, 2010 Manual Page 59
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Release centric latch (arrow) to allow centric pin to spring upward and lift lower end of pin out of centric channel in mandibular frame. (If centric pin does not spring upward when latch is retracted, rotate centric pin cap to release it) (Figure 2‐24). Figure 2‐24 Separate maxillary frame from mandibular frame of articulator (Figure 2‐25). Figure 2‐25 Stretch elastic band on lower surface of mandibular frame over extending latch arm to keep latch retracted back and down out of the way (Figure 2‐26). Figure 2‐26 ResD 517 Occlusion, 2010 Manual Page 60
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Loosen right and left analog shaft lock screws with hex wrench (Figure 2‐27). Figure 2‐27 Rotate and lock both motion analogs in their “0” positions using only thumb screws to maintain position. The “0” line should be equal to the upper surface of the analogs. The analogs should be in contact with the calibrated sides of the articulator (Figure 2‐28). Figure 2‐28 Place protrusive interocclusal record on mandibular cast. Fit maxillary cast vertically into protrusive record. (Be sure centric and incisal pins have been raised.) (Figure 2‐29). Figure 2‐29 ResD 517 Occlusion, 2010 Manual Page 61
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While placing straight downward pressure on maxillary cast (vertical arrows) to keep maximum contact with protrusive record, loosen incisal pin screw and allow incisal pin to drop down to make contact with incisal table (horizontal arrow). Lock incisal pin firmly before proceeding (Figure 2‐30). Figure 2‐30 While holding downward pressure on the casts with one hand, move the other hand to grasp the right analog thumb screw (Figure 2‐31). Figure 2‐31 While continuing downward pressure above cast, loosen thumb screw and allow right side analog to “fall” (rotate) downward to contact superior surface of condylar element (curved arrow). Tighten axis shaft thumb screw to hold the analog angular position (Figure 2‐32). Figure 2‐32 ResD 517 Occlusion, 2010 Manual Page 62
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While maintaining downward pressure on casts (large arrow), loosen left side axis shaft thumb screw to obtain angular inclination for left side. If analog does not rotate freely downward into contact with condylar element, tap lightly on upper anterior surface of analog. Note: If the patient’s condyles did not protrude symmetrically, it may be necessary to move the analogs slightly laterally away from the calibrated side of the articulator to make contact with condyle element (Figure 2‐33). Angular setting is read where upper surface of analog corresponds to a calibration line on side of articulate or (arrow) (Figure 2‐34). Figure 2‐33 Figure 2‐34 After analog angulations have been obtained, make sure analogs are in contact with calibrated sides of articulator. Tighten both analog axis shaft lock screws with hex wrench to retain analog angulation (Figure 2‐35). Figure 2‐35 Reinsert right and left Dyna‐Link pins (arrow) and lock in place with retaining thumb screws. Release elastic centric latch hold down and engage centric latch over centric pin cap (Figure 2‐36). Figure 2‐36 ResD 517 Occlusion, 2010 Manual Page 63
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WEEK 3 LECTURE MUSCLES OF MASTICATION NEUROMUSCULAR INFLUENCES LABORATORY WAX #19 FOR DENTAL MATERIALS ResD 517 Occlusion, 2010 Manual Page 64
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LECTURE NEUROMUSCULAR INFLUENCE ON MASTICATION The function of the masticatory system is controlled by neuromuscular activity. For the most part, this activity is learned. This ensures that there will be continual adaptation as the components of the masticatory system modify during growth and jaw development. The learned rhythmic pattern of mastication is regulated by a centrally programmed neural pattern generator. It responds to impulses from about the mouth, the temporomandibular joint, and the masticatory and postural muscles. Therefore, this system ensures modification of the chewing movement and force necessary during chewing of various foods. As opposed to the act of swallowing, which is governed mainly by a complex system of innate reflex neuromuscular activity, mastication is a learned activity that finally resembles the adult pattern at about age 10 to 12. The cerebral cortex can initiate mastication directly or indirectly. Feedback to the cortex from periodontal mechanoreceptors has been shown to induce changes in the excitability of jaw muscle motor neurons. Stress and emotion are believed to have a regulatory effect. The peripheral element involves the activity of periodontal ligament mechanoreceptors, the TMJ receptors, the Golgi tendon organs, neuromuscular spindles, pain receptors, the depressor muscles of the mandible, and the muscle spindles of the muscles of mastication. Feedback from these areas are combined with directions from higher cortical centers to provide appropriate muscular activity. When a muscle is stretched, it contracts. The simple reflex affecting this is known as the myotactic or stretch reflex. The impulses initiating this reflex arise in the muscle spindles, which are specialized receptors, sensitive to changes in stretch in the muscles alongside them. The impulses travel via afferent (sensory) neurons to their cell bodies in the central nervous system and are transmitted by motor synapses to affect muscle contraction. The monosynaptic stretch reflex, together with reflexes involving TMJ receptors, appear to actively maintain the mandibular postural rest position. NOTE: Airway protective reflexes can override this postural rest activity as can patient age, pain, loss of teeth, and emotional tension. ResD 517 Occlusion, 2010 Manual Page 65
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Various degrees of tooth contact occur during function. These contacts are felt to be responsible for sending impulses from the proprioceptors to the brain which causes appropriate patterns of mandibular movement to ensure muscle synchrony. Occlusal contacts during function help guide the mandible to centric occlusion. Successful adaptation to most types of tooth contact is the rule rather than the exception, thereby making occlusally related stomatognathic breakdown rare. However, it has been postulated that if the avoidance mechanism necessary to avoid occlusal interferences is too great, thereby preventing the mandible from easily reaching centric occlusion, mandibular dysfunction may result. Iatrogrenic induced occlusal interferences may be more important than developmental ones. Whatever the case, great care should always be given to the total evaluation of each case before irreversible occlusal adjustment is performed. It should also be remembered that the effects of treatment may be behavioral rather than physical. Whatever the cause of the mandibular dysfunction, it involves muscle tenderness (myospasm) in the vast majority of patients. Muscles can be stimulated into spasm by either prolonged contraction or prolonged stretching. When a muscle contracts, its antagonist is stretched so that the same affect on one muscle affects the other. Muscles are always in some degree of contraction, even at rest. A light contraction of opposing muscles is responsible for the resting posture and is called normal tonicity. Muscles that are not in a normal state of tonicity are either hypotonic or hypertonic. In this resting state, the muscle in its entirety never fatigues. Individual muscle fibers have an optimum length of time that they can contract without fatigue. When it comes time for them to rest and restore their electrochemical balance, other fiber bundles take over. Because only a small part of the total number of fibers are contracting at a given time, a resting muscle can maintain at all times the degree of contraction required for maintaining the postural position. As you would expect, an increased demand on the muscle for activity causes an increase in the number of fiber bundles contracting. If the duration and intensity become greater than the muscle can handle by alteration of working and resting fibers, the entire muscle fatigues, leading to muscle spasm. Fatigue often produces pain, possibly because of ischemia resulting from tight contraction of the spastic muscle around its own blood supply, but more likely because of the build‐up of toxins resulting from the chemical activity associated with prolonged contraction. If an occlusal interference causes prolonged contraction that requires the muscles to hold the mandible in a position not in harmony with the integrated normal muscle function, myospasm can occur. Although other causes are known to elicit discomfort in the muscles of mastication, when the pain is related to muscle, there will often be a corresponding deviation that requires abnormal activity of the specific painful muscles. Regardless of the cause, elimination of the interference is the key to removing the stimulus to the muscle. Symptomatic relief may be within minutes, or require more time for the adaptation of the muscle(s) to return to normal. Note that a “normal patient” does not maintain occlusal contact for long periods of time unless he/she is a clencher or bruxer. The emotional makeup of a patient and the stress he/she is undergoing are powerful etiological factors. Many experts in the field of “temporomandibular joint dysfunction” treatment feel that occlusal disharmony is secondary to stress in TMD treatment. ResD 517 Occlusion, 2010 Manual Page 66
MUSCLES CONTROLLING MASTICATION 3-4
OBJECTIVES: At the completion of this lesson, the student will be able to: a. Discuss the muscles involved in the masticatory apparatus. b. Discuss the motion created by a given muscle of mastication and what movement that motion will initiate c. Discuss the relationship of the muscles and mandibular movement to the TMJ condylar disc system for various movements of the mandible d. Understand and discuss the muscle activity required for speech, deglutition, yawning, and other mandibular movements. MUSCLES OF MASTICATION Temporalis Masseter Lateral Ptergoid Medial Pterygoid SUPRAHYOIDS Geniohyoid Mylohyoid Digastric Stylohyoid INFRAHYOIDS Thyrohyoid Sternohyoid Sternothyroid Omohyoid ResD 517 Occlusion, 2010 Manual Page 67
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MASSETER Origin: Superficial portion ‐ anterior 2/3 of the lower border of the zygomatic arch. Deep portion ‐ medial surface of the zygomatic arch. Insertion: Lateral surface of the ramus, coronoid process and the angle of the mandible. The masseter's principal function is to elevate the jaw and clench the teeth. It is the most powerful elevator muscle and provides the primary force for chewing a normal bolus of food. The superficial portion aids to a minor degree in the protrusion of the mandible. When the mandible is protruded and a biting force is applied, like biting off a piece of thread with your incisors, the deep portion stabilizes the condyle against the articular eminence thus keeping the condyle from sliding around at a given location. ResD 517 Occlusion, 2010 Manual Page 68
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TEMPORALIS Origin: Temporal Fossa and Temporal Fascia Insertion: Coronoid Process and anterior border of the ramus. The temporalis is the principal elevator of the jaw. It also aids in retracting and positioning the mandible and allows clenching of the teeth. Because of this, it is very sensitive to occlusal interferences. The temporalis can contract in its entirety or can contract its individual sections depending on the movement desired. When the entire muscle contracts, the mandible is elevated and the teeth are brought into contact. Contraction of only the middle portion (MP) elevates and slightly retrudes the mandible. Contraction of the posterior portion (PP) will provide a retrusive component of movement. The anterior fibers (AP) are almost vertical and contract shortly before the rest of the fibers during elevation of the mandible. The muscle is variable between patients and, therefore, the amount of influence is variable. Regardless, it is a significant positioning muscle of the mandible. ResD 517 Occlusion, 2010 Manual Page 69
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LATERAL PTERYGOID Origin: Superior Head ‐ infratemporal surface of the sphenoid greater wing. Inferior Head ‐ outer portion of lateral pterygoid plate. Insertion: Anterior portion of the condylar neck and the TMJ capsule. The Inferior Head from its attachment on the outer portion of the lateral pterygoid plate, extends posteriorly, superiorly, and laterally to insert on the condylar neck. When both the right and left inferior heads contract simultaneously, the mandible is protruded by the condyles and discs being pulled down the articular eminences. When this muscle works with the mandibular depressors, the active side becomes the nonworking (translating or balancing) side in mandibular movements. Therefore, when you stop to think about it, the working side movement is initiated by the inferior head of the lateral pterygoid on the contralateral side. The Superior Head is roughly 1/3 the cross‐sectional area of the inferior head, it extends almost horizontally distally and laterally and inserts primarily on the articular capsule and disc with a small connection on the condylar neck. This muscle is inactive during opening but is highly active during closure of the mandible against resistance, such as chewing. Therefore, this head is contracting while it lengthens as the condyle translates back up into the fossa. Because it is in the active state while lengthening it is capable of producing high tensions and is more susceptible to injury than the inferior head. ResD 517 Occlusion, 2010 Manual Page 70
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MEDIAL PTERYGOID Origin: Medial surface of the lateral pterygoid plate; pyramidal process of the palatine bone, maxillary tuberosity. Insertion: Posterior and lower part of the medial surface of the ramus and the angle of the mandible. The medial pterygoid is primarily an elevator of the mandible. It acts with the masseter and temporalis to close the mandible into occlusion. Also, when the lateral pterygoid muscle is active, the medial pterygoid supports the condylar movement by keeping the head of the condyle in the right relationship to the articular eminence. Therefore, it is active during protrusive movements even though it does not cause the actual movement. ResD 517 Occlusion, 2010 Manual Page 71
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SUPRAHYOIDS GENIOHYOID Origin: Inferior genial tubercle on the inner surface of the mandibular symphysis. Insertion: Anterior surface of the body of the hyoid bone. Action: Elevates the hyoid bone and tongue. Acts as a depressor‐retractor of the mandible. MYLOHYOID Origin: A line from the last molar root to the mandibular symphysis. Insertion: Median raphe from chin to hyoid bone. Action: Elevates the hyoid bone and base of the tongue and raises the floor of the mouth. DIGASTRIC Origin: Posterior Belly ‐ mastoid notch of the temporal bone. Anterior Belly ‐ digastric fossa of the mandible. Insertion: Intermediate tendon attached to the hyoid bone by a fibrous sling. Action: Raises the hyoid bone and base of the tongue and the hyoid bone. Acts as a depressor‐retractor of the mandible. STYLOHOID Origin: Posterior border of the styloid process. Insertion: Body of the hyoid bone at the junction with greater horn. Action: Elevates the hyoid bone and the base of the tongue. Suprahyoids as a group function to elevate the hyoid bone and depress the mandible. The digastric and geniohyoid muscles are depressor retractors of the mandible which is dependent on the position of the hyoid bone. They exert a fairly balanced combination of depression and retraction if the hyoid bone is fixed by the infrahyoid, mylohyoid, and stylohyoid muscles. INFRAHYOIDS (AS A GROUP) THYROHYOID STERNOTHYROID OMOHYOID STERNOHYOID ResD 517 Occlusion, 2010 Manual Page 72
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COMBINED MUSCLE ACTIVITY There are several features of muscle function which may help occlusal function. Firstly, muscles of mastication are in function (either contracting or relaxing to various degrees) during all movements of the mandible. Secondly, innumerable variations in range of mandibular movements are made possible by the wide area of origin of some of the muscles compared to insertions and the ability of numerous groups of muscle fibers within a muscle to act independently. Thirdly, the muscles conform to reproducible patterns of movement when healthy. Fourthly, muscle activity is limited by ligaments but is not guided by them. Mandibular muscles demonstrate standard patterns of activity in healthy subjects during vertical and horizontal movements of the mandible. The masseter and temporalis muscles usually act as "on‐off" muscles. These muscles produce power or crushing force (≥320 psi in adults with natural dentitions) when the teeth are clenched in intercuspal position (centric occlusion) or when a hard bolus of food is interposed between the teeth. When the mouth is open, the masseter and temporalis show minimal activity. MANDIBULAR OPENING: The inferior head of the lateral pterygoid muscle shows initial and sustained activity after initial rotation. The depressor‐retractors (digastric and geniohyoid muscles) initiate and follow the movement to completion. If this occurs without resistance, the depressor‐retractors act without great force. In a normal opening the depressor function is more apparent than the retractor action. In forced opening (isometric exercises) the digastric is activated almost as soon as the lateral pterygoid muscle. COMBINED PROTRUSION AND OPENING: There is activity in the medial and lateral pterygoid muscles and sometimes the anterior fibers of the temporalis, as well as the digastric and geniohyoid muscles. The temporalis and masseter muscles, become very active during the final stage of wide opening of the mandible, stopping the opening. UNRESTRICTED MANDIBULAR CLOSING: The medial pterygoid, anterior temporalis, and masseter muscles are all active during the elevation of the mandible. The suprahyoids relax. The inferior heads of the lateral pterygoids relax allowing the articular disc to glide back into the fossa and temporalis (posterior and middle fibers) contract. FORWARD DISPLACEMENT OF THE MANDIBLE DURING CLOSURE: The lateral pterygoids must protrude the mandible to bypass the closure interference. The temporalis posterior and medial fibers cannot complete retraction of the mandible; these muscles maintained under continuous function and not allowed to rest, can become dysfunctional to the point of tenderness. Although the elevator muscles play the main part in closure, the final adjustment to precise closure or to the avoidance of occlusion in the chewing cycle is left to the postural muscles (temporalis and superior head of the lateral pterygoid). ResD 517 Occlusion, 2010 Manual Page 73
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The activity of the medial pterygoid is increased first, then the masseter muscles follow. Opening and closing movements of the mandible all take place within a space limited by the ligaments and by the shape of the bones. MANDIBULAR RETRUSION: In retrusion, the deep portion of the masseter and the posterior fibers of the temporalis combine forces with the depressors (the geniohyoid and digastric muscles) while the elevators are slightly contracted to maintain the mandibular position in the horizontal plane. The superior head of the lateral pterygoid also contracts to stabilize the movement. The opening components of the suprahyoids and the inferior heads of the lateral pterygoids are "relaxed" during this movement. CHEWING MOVEMENTS Both chewing movements, cutting (incising) and grinding, can be divided into three phases: (1) is a free movement of the lower jaw (2) second phase continues until contact of certain teeth or the patient’s chewing force has been reached (3) this phase is a truly articulatory or mastication movement, for it occurs under contact of teeth or force of mastication until the food is sufficiently “mashed” to swallow. The first phase requires no force; force is applied only during the second and third phases ‐ the masticatory stroke. However, remember that during "chewing" the teeth often do not contact. The bolus of food is "mashed" by the posterior teeth. In fact, under normal conditions, teeth only touch at the end and at the beginning of the chewing stroke. Muscle balance is of greatest importance during the second phase because the closing movement may occur under great force while the teeth cannot stabilize the position of the mandible to the disc and disc to the posterior slope of the articular eminence. The powerful holding force of the lateral pterygoid muscle is necessary to prevent displacement of the mandible during this precarious phase. CENTRIC RELATION: This is the position of the mandible from which rotation only occurs around the horizontal axis. This may require assistance from the dentist but can often be practiced voluntarily by the patient if the muscles are healthy. The backward pull is achieved by the posterior temporalis fibers, superior head of the lateral pterygoid, and deep belly of the masseter with assistance from the digastrics and geniohyoids. The latter two muscles then continue the opening arcing movement for about 15 to 25 mm before a combination of rotation and translation occur. Closing from this position involves the elevator muscles but the posterior temporalis, superior head of the lateral pterygoid, and deep fibers of the masseter continue to contract in order to "hold" the condyles in a rotational position. With healthy muscles involved, this position/movement is reproducible and very valuable in diagnosis, treatment planning, and in the actual treatment of the patient. ResD 517 Occlusion, 2010 Manual Page 74
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LATERAL MANDIBULAR MOVEMENTS: Lateral movements are brought about by ipsilateral (same side) contraction of the posterior and middle fibers of the temporalis muscle and contralateral contractions of the lateral and medial pterygoid muscles and, to a lesser degree, the anterior fibers of the temporalis muscle. During horizontal movements with tooth contact, the masseter and/or temporalis muscles are also active. Lateral movements are initiated by the lateral and medial pterygoid muscles. The action of the temporalis muscles are considered to be secondary. The temporalis muscle is less active during protrusive lateral movements than when lateral movements are made with the jaw retruded. BENNETT MOVEMENT takes place when stronger contraction of ipsilateral medial pterygoid and the contralateral masseter occurs along with ipsilateral lateral pterygoid contraction. This is in addition to the contralateral contraction of the lateral and medial pterygoid muscles. The rotating condyle is allowed only a small rotary movement because its lateral pole is limited by the temporomandibular ligament and cannot move backwards for more than about 1 mm. If it does move laterally, then it must move slightly forward and downward in order to facilitate movement of the nonworking or translating condyle. The amount of Bennett movement is limited by the temporomandibular ligament. MUSCLE SPLINTING OF THE MANDIBLE is the reaction of the muscles that flex and extend the mandible through contracting simultaneously in response to a painful or unpleasant stimulus when moving the mandible. This causes the joint to become fixed. These muscles are called splinting muscles and tend to serve as a protective reflex by limiting the movement of the painful joint. With prolonged "splinting" the muscles may become the source of primary pain. Limited mouth opening often results from splinting of the muscles of mastication. The lateral pterygoid is usually painful along with its medial pterygoid, because they function in harmony to position the mandible in the horizontal plane. In patients with pain associated with malocclusion, the pterygoids are usually tender to palpation when the acquired bite requires excessive contraction of them to position the mandible in an eccentric position. ResD 517 Occlusion, 2010 Manual Page 75
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If the anterior and posterior digastric bellies as well as the posterior temporalis are painful, the upper anterior teeth are examined for lingual overcontouring and/or abraded lingual surfaces of anterior maxillary full crowns. The lower anterior incisal edges also are often abraded to fit the upper lingual surfaces precisely. An example of a muscular disability originating in the dental arch is a patient who reports that artificial crowns on maxillary anterior teeth have never been comfortable. In addition, the patient has a history of temporal and occipital headaches. This condition developed because the patient learned to hold the mandible in retrusion during final closure to avoid striking the overcontoured lingual surface of the upper teeth. The digastric and posterior temporalis muscles contracting simultaneously retrude the mandible so they could become tender to palpation with excessive function. If the patient is unable to avoid occluding against the upper anterior teeth, the incisors may tip labially, with visible diastemata as the teeth flair anteriorly or become actively mobile without periodontal pocket defects forming. The masseter, medial pterygoid, and temporalis muscles are called the power muscles and can generate considerable force when the need or abuses of function arise. ResD 517 Occlusion, 2010 Manual Page 76
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WEEK 3 LABORATORY EXERCISE WAXING #19 You should all have your dies trimmed and ready to wax from your dental materials laboratory course. So we have arranged to oversee the waxing of these crowns this week so they will be ready to invest and cast next week in your dental materials lab. You will have until 3:00 PM to complete the waxups using the same criteria as was required in Winter quarter. You can start waxing when the dies have been sectioned and trimmed, casts mounted on the apex articulator, and die relief and hardener has been successfully applied to the working dies (#19). All of these steps must have been evaluated and signed off by your Dental Materials Lab instructor. No starting check is necessary. At 3:00 PM, your apex articulators with name and/or bench number on it should be in the instructor’s room and ready for grading. After grading, your articulator will be placed in your mail box, as will your grade sheet after the grade has been entered on the master sheet. Next Monday, the dental materials faculty will be evaluating your waxups to make sure they are still acceptable for casting after storage. Therefore, it is in your best interest to correct the deficiencies identified in this course before having your waxups checked by them. As a precursor to the waxing exercise, application of die relief and die hardener is required. This was carefully explained in your Dental Materials course. However, as a reminder, the same information is being included in this week’s instructions. A. Application of Die Relief and Die Hardener Introduction: The application of die relief to the stone model is recommended only for extra‐coronal restorations. In view of the fact that this material is applied to provide a space for the luting cement and thus allow for seating of the restoration, a 25 micrometer die relief thickness is required. The recommendation of the school is that two thin coats be applied to the die. In the instructions below, it is suggested that the die relief be applied first, then the die hardener. This procedure will allow the die hardener to form a mechanical (not chemical) link to the stone die and thus reduce the possibility of having the die relief removed with the wax restoration. CAUTION: Do not apply either die relief or die hardener to a newly separated stone die. Let the stone die dry for 8 hours minimum before applying these products. ResD 517 Occlusion, 2010 Manual Page 77
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B. Application of Die Relief NOTE: DO NOT apply any die lubricant until die relief and die hardener have been applied. 1. Outline the finish line on the stone die with the edge of a red pencil. This will delineate the region to be clear of when placing the die relief. 2. The die relief material must be painted on the axial and occlusal surfaces of the prep BEFORE the application of die hardener or separating medium. 3. Check the consistency of the die relief material. It is very important that the “new” consistency be maintained at all times. To accomplish this, the thinner must be added when this consistency is obviously too viscous. If the proper die relief consistency is not maintained, a thicker than desired die relief layer will result. ResD 517 Occlusion, 2010 Manual Page 78
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4. Unscrew the cap and brush from the blue bottle. Draw the brush across the internal lip of the bottle to eliminate excess die relief from the brush. Apply the brush to the prep beginning 1 mm occlusal to the line and lightly draw the brush in an occlusal direction. Continue this action until all axial surfaces have been covered with die relief. NOTE 1: The brush supplied with the PDQ is acceptable. You may use a fine brush and clean immediately after placing the die relief. NOTE 2: This 1 mm dimension is an absolute must. NOTE 3: Die relief application must be done rapidly. Remember, the solvent dries quickly. If applied slowly, the brush will stick to the die, and, the die relief will not adhere strongly to the die. 5. Finally, apply the die relief over the entire occlusal surface. CAUTION: When approaching a line angle with this painting action, reduce the pressure on the brush. This avoids an excess of material at this point, as shown in the figure above. 6. Allow time (at least 10 minutes) for the die relief coat to dry before applying the second coat. Adequate dryness can be determined by touch. 7. The requirements for adequate die relief are that a layer 25 micrometers be created. Thus, it is recommended that two coats be applied to achieve this die relief thickness. 8. For the second coat, use the grey colored material and repeat as described above. Two different colors are used so you can tell when the first coat is covered. ResD 517 Occlusion, 2010 Manual Page 79
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C. Application of Die Hardener NOTE 1: Do not apply die lubricant to the prep until the die hardener has been applied and allowed to dry for at least three minutes. NOTE 2: The die hardener, when applied, should have a thin consistency much like that of WATER. THE FIRST TWO DROPS FROM THE TUBE SHOULD BE DISCARDED, they are generally very viscous. 1. Use a cotton pellet in a pair of cotton pliers. Soak the cotton pellet with die hardener by applying two drops directly from the tube. 2. Lightly apply the die hardener to the stone die. This should be applied from the die relief margin (1 mm above the finish line) to a line 2 mm gingival to the preparation finish line. The entire periphery of the finish line can be coated in one step. NOTE: BE SURE that when the cotton pellet has been discarded, to clean the tips of the cotton pliers thoroughly. 3. Using the air syringe, lightly blow any excess die hardener away from the finish line in a gingival direction. NOT occlusally and not parallel to the finish line. This action will thin and dry the die hardener. The die hardener helps prevent loss of marginal integrity through abrasion and provides a protective cover for the red penciled margin. D. Application of Die Lubricant 1. Apply a thin coat of Gator Lube die lubricant to all surfaces which will have wax applied. This lubricant should be applied with the #2 Dixon brush. Extend the lubricant at least 3‐
4 mm below the finish line. 2. IMPORTANT: Place another layer of lubricant on your dies just before turning them in for grading. This is important for the wax may shrink enough over the weekend that you will have trouble removing them next Monday when you invest and cast the crowns. 3. Your waxups will be graded in RD 517, then taken to your RD 511 class for refinalizing margins, investing and casting. Although we expect your margins to be perfect, letting your waxups sit over the weekend may result in some marginal shrinkage. Therefore, you need to “remarginate” just before investing your masterpiece next week. NOW YOU ARE READY TO WAX THE MASTERPIECES FOR DENTAL MATERIALS!! ResD 517 Occlusion, 2010 Manual Page 80
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Student Secret ID # _________________
Waxing Grade Sheet, Tooth #19
Course: RESD 517 – 2010
This waxup is worth 100 points. Each criteria will be graded according to the value indicated. Each minor error is worth one point. A major error will result in loss of all points for that criteria. More than two or three minor errors indicated in specific categories will be equivalent to a major error and all category points will be lost. Major Minor FACULTY COMMENTS 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 1. FINISH & EXTERNAL SURFACES (10 points) Margins (3 pts) Occlusal grooves & pits (3 pts) Ridges (2 pts) Cusps (2pts) 2. OCCLUSAL – OUTLINE FORM (20 points) External crown outline (5 pts) Cusps – position, size, contour (3 pts) Marginal ridges – position size, contour (3 pts) Cusp ridges – position, size, and contour (4 pts) Occlusal table outline (5 pts) 3. OCCLUSAL – ANATOMY (20 points) Occlusal anatomy does not resemble a maxillary first molar (loss of all 20 points) Grooves – developmental/supplemental (10 pts) Fossae (pits) (5 pts) Ridges (oblique/triangular) (5 pts) 4. FACIAL VIEW (10 points) Occlusal outline formed (3 pts) Mesial/distal contours (3 pts) Alignment with adjacent teeth (4) 5. MESIAL/DISTAL VIEW (20 points) Cusp heights, shape & location (6 pts) Buccal & lingual contours (including HOCs) (8 pts) Alignment with adjacent teeth (6 pts) 6. LINGUAL VIEW (10 points) Outline form (5 pts) Cusps (5 pts) 7. CONTACTS AND EMBRASURES (10 points) Proximal contacts (position, size) (5 pts) Embrasures (position, size) (5 pts) 8 8 8 8 TOTAL = ________________ ResD 517 Occlusion, 2010 Manual Page 81
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WEEK 4 LECTURE OCCLUSAL ASSESSMENT CLINIC OCCLUSAL ASSESSMENT EXERCISES LABORATORY MOUNT FOUR SETS OF CASTS ResD 517 Occlusion, 2010 Manual Page 82
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INDICATIONS FOR OCCLUSAL EXAMINATION An occlusal examination is a basic part of any dental examination. It is as basic and significant as caries identification or the periodontal examination. 1. OBJECTIVES OF OCCLUSAL EXAMINATION Identify and record symptoms and history of conditions that may be related to occlusion, e.g.: a. Tooth mobility, migration, excessive or abnormal wear, thermal or percussion sensitivity. b. Temporomandibular joint symptoms or dysfunction, including joint or muscle pain, joint sounds, or deviation or limitation in opening or closing movements, muscle trismus or hypertrophy, facial asymmetry. c. Other occlusal complaints, habits, or pertinent physical or psychological findings. Identify and record the following factors concerning occlusal relationships: a. Angle’s classification of posterior and anterior malocclusion and the amount of horizontal and vertical anterior overlap, open bite areas, asymmetries, irregularities in occlusal plane, extruded teeth, marginal ridge irregularities, crossbites, freeway space. etc. b. Which teeth contact in centric relation and where does the contact occur? c. Direction and amount of shift from the first tooth contact in centric relation to centric occlusion. d. Which teeth contact in working, nonworking and protrusive relationships? ResD 517 Occlusion, 2010 Manual Page 83
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OCCLUSAL ASSESSMENT 1. PAIN For this section, we are mostly interested in facial pain related to the muscles of mastication. However, there are occasions when facial pain exists with other etiologic factors involved. As you will learn in this course and others that follow, the classification of pain into acute (less than 6 months duration) and chronic (more than 6 months duration) is a valuable tool to help differentiate the causative factors and the correct treatment. Question the patient for any known facial pain. Then palpate the muscles of mastication as described in class. Of particular interest will be the “superficial” palpation of the lateral pterygoid muscle because this muscle is most likely to be involved with muscle pain caused by occlusal interferences. Besides the duration of the pain, it will be helpful to find out the degree of pain (sharp, dull, etc.), location of the pain and the time of day that the pain occurs. All of these factors will greatly aid you in arriving at a diagnosis and treatment plan for the patient. This course will not study in depth, temporomandibular disorders. That will come through subsequent dental courses. Our goal will be to build a framework for you to understand the relationship between the muscles of mastication, mandibular movement, and dental occlusion. 2. PARAFUNCTIONAL HABITS We want you to determine by communication with the patient and through visual investigation any parafunctional habits that the patient knowingly and/or unknowingly has established. Some common ones which are seen most frequently include, but are not limited to, bruxing (nocturnal and/or diurnal), clenching, nail biting, and tongue thrusting. Most of the time, there is intraoral evidence of parafunctional habits. 3. LOCALIZED OCCLUSAL IRREGULARITIES In addition to functional occlusal interferences, (i.e. CO to MIP, lateral and protrusive), localized occlusal irregularities may also be present. It is important to identify these and plan correction during occlusal adjustment preparatory to restorative treatment. ResD 517 Occlusion, 2010 Manual Page 84
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a. Extruded teeth ‐ An opposing tooth may extrude due to massive tooth breakdown or more frequently, into an edentulous area. This may be corrected by grinding or placement of an onlay or crown depending on the severity of extrusion. Reduction of an extruded tooth opposing a broken down tooth provides: 1. increased length of crown preparation 2. elimination of possible working, nonworking and/or protrusive interferences b. Hanging or plunging maxillary lingual cusps Reduction of a lingual cusp tipped down into a broken down carious area or over carved amalgam decreases the possibility of balancing (nonworking) interferences. c. Gross marginal ridge discrepancies ‐ Correction of uneven marginal ridges by recontouring decreases the possibility of food impaction or wedging between contacts. d. Flat or non‐anatomic opposing restoration ‐ Opposing restorations, whether amalgam or gold, can readily be modified to form fossae and cusps to improve centric contact. e. Grasping cusps ‐ The length of the grasping cusps contact with the opposing tooth should be decreased to eliminate excessive contact time when going into excursions. This is very often related to supraerupted lingual cusps of maxillary molars. 4. TYPES OF OCCLUSAL RELATIONSHIPS a. Angle’s Classification of Malocclusion: The three classifications are listed in the Glossary of Terms under “malocclusion.” To refresh your memory, this is a first molar relationship only. As you will see in lecture, the anterior relationship of the teeth may or may not reflect the molar relationship. As you were taught in RSD 516, in a “normal” occlusion, the distobuccal cusp of the mandibular first molar fits into the central fossa of the maxillary first permanent molar. This is considered Angle’s class I or “neutrocclusion.” Angles’ Class II is “distocclusion” and Class III is “mesiocclusion” which describes the position of the distobuccal cusp for each of these classifications. It is NOT uncommon for this relationship to be different on the two sides of a patient’s mouth. ResD 517 Occlusion, 2010 Manual Page 85
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b. Also important, as explained in RD 516, is the interocclusal relationship of the posterior teeth. Note and indicate whether the patient has “one‐on‐one” occlusion or “one‐on‐two” occlusion. As you will see, one side may be different from the other side. Also, premolars and first molars often have “one‐on‐two” occlusal relationships while the second molars often are “one‐on‐one.” c. You learned the importance in RD 516 of the type of disclusion a patient exhibits. Therefore, identify and enter on the form which type of excursive relationship (i.e., group function, canine protected, or mutual protected occlusion) the patient exhibits. d. As you remember from RD 516, the degree of vertical and horizontal overlap of the anterior teeth affects the shape and form of posterior teeth. Identifying and entering these factors in the assessment form is important. 5. HEAVY WEAR FACETS Mark on the illustration areas where you feel “abnormal” wear is occurring on the teeth. Since you are looking at each other’s mouths, wear areas should not be much larger than 1.0 to 1.5 mm. Anything larger than this should be so noted. Some wear on the canines and anterior teeth is permissible. However, use your own good judgment to determine if excessive wear is occurring. 6. PATHS OF OCCLUSION DIRECTION OF CO‐MIP SLIDE RULE Look at the maxillary inclines from the direction to which the mandible slides. CENTRIC OCCLUSION ASSESSMENT a. With the patient in a reclined position, practice moving the mandible in the arc of centric relation until this movement can be reproduced consistently. Within this arc, at the position of first tooth contact (in centric relation occlusion), observe the relationship of the upper and lower teeth and determine the degree and direction of mandibular slide. Document this information in writing on your occlusal assessment form. ResD 517 Occlusion, 2010 Manual Page 86
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b. Document the maxillary inclines which could possibly cause the identified slide. Then identify the side on which the first contact(s) in centric relation occurs (the patient can usually identify this for you), dry the teeth on this side, and mark the first tooth contact with red ribbon. (Drying of the teeth must be repeated each time articulating ribbon is used in order to obtain good markings.) Do not let the mandible slip into centric occlusion. Verify that the initial contact is on an incline that satisfies the CO‐
MIP rule. Refer back to the possible inclines documented after the degree and direction of slide were determined. Assuming a “normal” occlusal relationship: “A” contacts = lingual inclines of buccal cusps of maxillary posterior teeth and buccal inclines of mandibular buccal cusps “B” contacts = buccal inclines of maxillary lingual cusps and lingual inclines of mandibular buccal cusps “C” contacts = lingual inclines of maxillary lingual cusps and buccal of mandibular lingual cusps c. Using ribbon and articulating forceps, have the patient tap in centric relation occlusion and mark the point of initial contact (PIC) in CO. Verify that the interfering incline will cause the direction of mandibular slide. d. Clinically, usually one set of opposing teeth will mark with one or more other sets of teeth being very close to contacting. One, two, three, or even four sets of CO markings may be visible which may or may not indicate actual CO contact. i. Horizontal‐Anterior shift ‐ identify a point on the maxillary first or second premolar on the sagittal plane and relate it to a lower premolar mark. Have the patient close into MIP and note the approximate amount. ii. Horizontal‐Lateral shift ‐ do the same sequence again but from a frontal view, documenting the lateral shift. ResD 517 Occlusion, 2010 Manual Page 87
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iii. Vertical closure ‐ view the anteriors or premolars in CO from the front position. Allow the mandible to slide into MIP and note the vertical closure. The difference indicates the vertical closure in the anterior region. A 0.3 mm vertical slide in the anterior region is equivalent to approximately a 0.1 mm slide in the second molar area. e. Confirm true contacts by placing micro‐thin mylar strip (.0005 inch thick) between each set of marks in succession. Actual contacts will not permit the strip to be pulled out when the teeth are closed in CO. f. Indicate initial contact areas on the examination form. g. The degree of shift or discrepancy between the CO terminal hinge position and MIP should be measured approximately and recorded on the examination form. h. Record amount and direction of slide on examination form. i. Repeat procedure for right lateral, left lateral and protrusive. Have the patient start from MIP position even though there may be a detectable shift from CO to MIP. Use a different colored ribbon in excursive movements to keep them distinct from centric relation markings. 7. FREMITUS (FUNCTIONAL MOBILITY) This term is also defined for you in the “Glossary of Terms” in the back of the syllabus. It’s importance, however, should be emphasized. The dentist can quite often detect “heavy” contact of teeth when the mandible moves in excursive directions. This is most easily determined by placing your finger on the facial aspect of a tooth and have the patient “grind” around in excursive movements with his/her teeth in contact. Fremitus occurs if you feel the tooth “moving” during any of the functional movements. This situation quite often occurs on upper premolars and patients will complain of a “sore” tooth. In cases like this, maintain your centric contact but “lighten” the excursive contact on the tooth. Successful treatment of this type of problem is a REAL practice builder!! 8. NON‐FUNCTIONAL MOBILITY Since excessive tooth mobility is often a sign of occlusal traumatism, it is important to estimate and chart individual tooth mobility. A useful clinical technique is to apply buccal or lingual force with the butt ends of two dental instruments and estimate the amount of movement. (The use of fingers for this procedure is very inaccurate due to the resiliency of finger tissue.) ResD 517 Occlusion, 2010 Manual Page 88
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The degree of tooth movement is estimated and charted from 0 to III with increments of one‐half marked as (‐), as follows: 0 (‐) I II III = Mobility within normal limits (not necessary to chart) = Mobility greater than normal but less than 1 mm buccolingually = Mobility approximately 1 mm buccolingually = Mobility approximately 2 mm buccolingually but no apical mobility = Mobility greater than 2 mm bucco‐lingually plus apical mobility When the form has been completed, confirm your findings with your instructor. After this, note any recommended occlusal adjustment procedures for your patient. 9. 1. DEVIATION ON OPENING Stand in front of the patient and ask them to open their mouth. Note whether the initial opening (up to 25 mm) is straight or deviated to one side. Measure with a mm ruler how far the patient can open. Indicate on the form how far the patient opens and the amount of left or right deviation. A patient with “normal” opening ability should be able to open 35 to 50 mm. A deviation to the left or right upon opening could indicate an anatomical anomaly in the TMJ ensemble or a CO‐MIP slide which is equal and opposite to the amount and direction of the deviation. Think about why this could happen by understanding the role muscles play in positioning the mandible. DIAGNOSTIC ADJUSTMENT – A PREREQUISITE TO CLINICAL ADJUSTMENT Signs and symptoms that may be related to occlusal trauma in many cases indicate the need for diagnostic mounting procedures followed by adjustment or equilibration of the patient’s articulated casts. In addition, the fabrication and insertion of an acrylic splint may be indicated to, in part, determine if elimination of interfering tooth contacts by reversible means results in a relief of patient symptoms. There are clinical situations where occlusal interferences are minor and as a result, mounting records followed by diagnostic adjustment of articulated casts are not necessary. Some examples are as follows: a. Minor CO or MIP slide or shift, (<=3/4 mm anterior slide). b. Isolated nonworking or balancing interference. c. Isolated heavy or premature posterior lateral working contact. d. Isolated heavy or premature anterior protrusive contact. ResD 517 Occlusion, 2010 Manual Page 89
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2. e. Heavy or deflective posterior protrusive interference. f. Localized morphologic occlusal irregularities. g. Occlusal problems related to a specific recent restorative procedure. For clinical situations where the occlusal interferences are of greater magnitude or the probable end result cannot be visualized with confidence by the operator, diagnostic adjustment of articulated cast is an absolute requirement. THE ADJUSTED DIAGNOSTIC CASTS SHOULD PROVIDE THE OPERATOR WITH THE FOLOWING INFORMATION: a. An indication of the probable end result relative to the objectives of an acceptable occlusion. b. Whether a satisfactory occlusion can be attained by grinding without mutilation of occlusal morphology or undue exposure of dentin. c. Whether some teeth end up out of occlusion and thus necessitate restorative procedures. d. Whether the severity of the interfering occlusal contact relationships necessitates correction, primarily by restorative procedures. e. Whether the occlusal relationships require primarily orthodontic treatment. f. Whether a satisfactory occlusion can be achieved by a combination of occlusal adjustment in conjunction with a restoration and/or orthodontic therapy. 3. THE ADJUSTED DIAGNOSTIC CASTS ALSO PROIVDE THE OPERATOR SEVERAL ADVANTAGES AS FOLLOWS: a. Enables the operator to gain confidence in the adjustment procedures and an efficient sequence preparatory to clinical adjustment. b. Provides a learning process for decision making relative to teeth and surfaces to be altered or adjusted which makes the clinical adjustment more efficient and accurate. c. Enables the operator to view location and approximate amount of clinical alteration necessary by comparing adjusted casts to a set of unadjusted casts. d. Provides the operator with a non‐clinical reversible procedure which can provide important information that may modify the original plan for correction of the occlusion. ResD 517 Occlusion, 2010 Manual Page 90
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e. Enables more accurate identification, correction, and subsequent recording of localized occlusal irregularities that should be corrected during clinical adjustment. These include hanging (plunging) cusps, facets, extruded teeth, wide occlusal tables, gross marginal ridge discrepancies. f. Provides a set of demonstration casts to illustrate to the patient what will be accomplished relative to alteration of occlusal morphology as compared to original conditions. 4. ADDITIONAL USES OF DIAGNOSTIC ARTICULATED CASTS The diagnostic adjustment of an articulated occlusion preparatory to clinical adjustment is only one use of accurately articulated casts. Other uses are: a. One can pre‐wax the occlusion to determine what can be accomplished by restorative treatment. This is particularly useful if teeth are tipped, rotated, extruded, or missing. b. By pre‐waxing occlusion, a guide for the amount of tooth reduction is obtained. This is important when onlays and ¾ crowns are indicated and teeth are extruded, tipped or rotated; also it is an aid when teeth indicated for full coverage are in labio‐ or linguo‐version. c. The operator can utilize the pre‐waxed bridge area for fabrication of an acrylic temporary bridge. d. The articulated casts can provide a visual aid to minimize misunderstanding when presenting the treatment plan to the patient. 5. OBJECTIVES OF OCCLUSAL ADJUSTMENT A. CENTRIC OCCLUSAL POSITION 1. Eliminate CO to MIP lateral slide 2. Eliminate CO to MIP anterior slide. 3. Establish stable centric within the arc of centric relation. 4. The vertical dimension of the new centric relation should be as closed as the original vertical dimension of centric occlusion. 5. Tooth contact in CO should direct forces axially within the root support system. ResD 517 Occlusion, 2010 Manual Page 91
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6. There should be maximum distribution of centric contacts, i.e., supported by as many posterior teeth as possible and several contacts on each tooth. 7. Centric contacts should be centralized buccolingually as much as possible. 8. Centric contacts should be small (/½ – ¾ mm). 9. Centric holding cusps should contact in fossae or at right angles to marginal rides wherever possible rather than occlusal embrasures or inclines. 10. Centric contacts may be cusp tip to flat area in center of fossa or may be reciprocally balanced on two or three inclined planes if necessary. 11. Eliminate interferences and establish free gliding horizontal movement (freedom of centric). B. WORKING RANGE 1. or Establish cuspid guidance with disclusion of posterior teeth during lateral excursions, 2. Establish group function if the cuspid is malposed labially, periodontically weakened or worn and group function is already present, or 3. Establish initial posterior group function and terminal cuspid disclusion if cuspid is not in centric contact. It is important to establish a “progressive” group function which starts with the maxillary first premolar, then progressively adds contacts of the other posterior teeth. For example, start with 1st premolar, then add 2nd premolar, etc. Skipping a tooth is not acceptable. 4. Because of its position relative to muscles of mastication and rotating condyle, maxillary first premolars may aid the cuspid in discluding the remaining posterior teeth. 5. Eliminate cross‐tooth working side contacts, i.e., only lingual cusp contacts of the maxillary posterior teeth are desired on the working side. ResD 517 Occlusion, 2010 Manual Page 92
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C. NONWORKING (BALANCING) RANGE 1. D. Eliminate cross‐arch balancing (nonworking) interferences while maintaining centric contacts. PROTRUSIVE RANGE 1. Distribute contact to as many anterior teeth as possible (at least two central incisors). 2. Eliminate deflective posterior interferences and maintain centric. E. OCCLUSAL MORPHOLOGY 1. Eliminate facets, correct marginal ridge and occlusal plane irregularities, shorten hanging cusps, and narrow wide occlusal tables if necessary. 2. Refine occlusal morphology keeping centric contacts small (1/2 – 3/4 mm) and properly positioned. 6. OCCLUSAL ADJUSTMENT RULES a. A cusp may be repositioned to the buccal, lingual, mesial, or distal by adjusting the opposite slope of the cups in order to make it contact in a stable centric holding position in the opposite arch, and direct the forces axially. Extreme care should be exercised for over‐adjusting cup height. This could result in loss of centric contact. b. Whenever possible repositioned cusps and grooves should be refined and reshaped to avoid undesirable contact in excursions. c. Recontour interferences on noncentric holding cusps when possible. d. Recontour cuspal interferences when the cusp interferes in centric and lateral excursion. e. Reduce interfering centric cusps if they are long, grasping, or plunging. f. Where necessary, a fossa may be repositioned to buccal, lingual, mesial, or distal to accept a cusp in a more stable centric holding position. g. Establish stabilizing fossae for cusp if the occlusion ends to be too flat. h. Reduce a fossa if the centric holding cusp also contacts in lateral group function, if this is desirable. ResD 517 Occlusion, 2010 Manual Page 93
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i. Refine fossae to accept cusps in a stable centric holding position when the cusp interferes in centric only. j. Maintain centric holding cusps when possible. k. The presence of group function or canine guidance occlusion will heavily influence which surface to adjust when cuspids cause interferences in centric relation occlusion. Normally, such interferences involve re‐contouring the lingual of the maxillary canine since this action will increase the amount of canine disclusion. 7. ADJUSTMENT GUIDELINES a. Avoid Confusion of Markings After scraping and repositioning a cusp, lightly remove the opposing marking with the D‐5 instrument. All prominent remaining marking except smudges should be eliminated to avoid confusion before a next‐series of markings with articulating ribbon begins. b. Selection of Fossae Although it is tempting during occlusal adjustment to reposition cusps towards the closest fossae, consideration should be given to the effect of this future contact in the eccentric positions. Excellent centric contacts might be developed, which could cause interferences in the working and/or nonworking positions. In general, direct mandibular centric cusps mesially to the fossae of maxillary premolars and to the mesial, central, and distal fossae of maxillary molars to avoid undesirable contacts in working and nonworking positions. Conversely, direct maxillary lingual centric cusps distally toward the distal fossae of mandibular premolars and into the central and distal fossae of mandibular molars. c. Amount of Stone Adjustment There is no precise measurement. the operator’s experience and the degree of correction necessary generally dictates the amount of reduction at each step. A guide is to approximately achieve a less than or equal to 0.5 mm reduction until one gets the “feel” of the procedure and progress is made. In later stages near completion of the adjustment, the marks are scraped very lightly to bring non‐contacting or lightly contacting teeth into solid contact without losing contact on the adjusted teeth. It is important to remember that during ResD 517 Occlusion, 2010 Manual Page 94
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adjustment of teeth and closure of vertical dimension, the resultant vertical closure is not constant from posterior to anterior. NOTICE: After the correct mounting of your casts (4 sets) have been accomplished and approved by an instructor, it is necessary to paint the occlusal surfaces of the casts yellow. This will give you a reference for where you have and have not done occlusal adjusting. It will also allow you to remove articulating ribbon marks by wiping them off the yellow paint rather than scraping them off. OCCLUSION I CASE “Carson Case” A. CASE DESCRIPTION This occlusal adjustment case represents a typical clinical situation whereby a patient exhibits significant interfering tooth contact relationships and signs or symptoms that may be related to these occlusal interferences. Diagnostic casts of this patient were mounted on an articulator for diagnostic occlusal adjustment to be followed by clinical occlusal adjustment. The patient responded well with diminished symptoms several months after adjustment. B. CASE PERSONAL INFORMATION AND DENTAL HISTORY This case is meant to provide the student with a ”simple” case which can be easily completed in one laboratory session. It is important for you to become comfortable adjusting proper inclines or cusps while moving in various excursions. This case will not be graded. It is intended to introduce you to occlusal adjustment. Instructors will be assigned to sections in order to answer questions and assist in your adjustment. Be sure to ask questions and understand what you are doing. Next week you start the Mesmer case which will count as part of your final grade for this course. C. INCISAL PIN ADJUSTMENT Before proceeding with occlusal adjustment, the incisal pin of the articulator should be set at the vertical dimension of MIP as follows! 1. The adjustable metal incisal guidance mechanism will be required for the occlusal adjustment procedure. 2. Move the articulated casts into the best possible MIP position. 3. While putting hand pressure on top of the articulator, loosen the incisal pin adjustment screw, tap the pin against the metal incisal guidance mechanism and tighten screw. Be sure to have the flat “chisel” end contacting the incisal guide table. ResD 517 Occlusion, 2010 Manual Page 95
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4. The above procedure now establishes the incisal pin vertical dimension of the articulator at the MIP position. There is a zero “0” line on the pin with 0.5 degree marks extending above and below the line. Marks above “0” are plus and those below are minus readings. In the CO position of the articulator, the end of the incisal pin may be 3 to 5 degrees above the incisal plate. Enter this MIP contact position reading in ink of your grade sheet. 5. The purpose of this incisal pin setting is to enable the operator to observe the closure of vertical dimension during diagnostic occlusal adjustment. As previously stated, one important objective during occlusal adjustment is to adjust until the vertical dimension is as closed as the vertical dimension of MIP, i.e., the incisal pin contacts the incisal guidance plate. The above incisal pin contact is only one guide to closure of vertical dimension. The vertical dimension may have to be closed slightly more than MIP to achieve the objectives of occlusal adjustment, but must be adjusted to at least the vertical dimension of MIP. During diagnostic occlusal adjustment of this typical case in the CO position, the vertical dimension will gradually close as interfering tooth contacts are scraped until the incisal pin contacts the incisal guidance plate (the vertical dimension of MIP). Even though the original vertical dimension of MIP has been attained, the important objectives in adjustment of the CO position may not have been attained, i.e., a shift may still be present, many contacts on inclines, contacts not well distributed, etc. Therefore, you may go slightly beyond the MIP position to achieve a better result, but no more than another 0.5 degree. Points will be deducted if you stop prior to reaching the CO vertical dimension or close beyond 0.5 degree past MIP. The main guides regarding a limiting closure of vertical dimension are as follows: a. The progress toward reaching objectives of an acceptable centric relation `
occlusion with compromises as needed. b. Excessive reduction of occlusal morphology. c. Early contact of anterior teeth and excessive reduction necessary. d. Lower incisors close to contacting palatal tissue. ResD 517 Occlusion, 2010 Manual Page 96
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2. DIAGNOSTIC OCCLUSAL ADJUSTMENT TECHNIQUE A. ARMAMENTARIA Articulating film forceps (two) Red and green articulating ribbon (from Dental Materials) D‐5 carver (discoid‐cleoid) Micro‐thin mylar strip B. GENERAL SEQUENCE OF PROCEDURE Set the angle of eminence on your articulator to 25° on both left and right sides. The general sequence of occlusal adjustment will be centric first, followed by working, then nonworking, and lastly, protrusive. Although the CO interferences are adjusted first, due consideration must be given to lateral and protrusive positions and contacts for the following reason: one must direct the adjustment and repositioning of centric cusps not only to meet the stated objectives in the CO position, but also to minimize undesirable contacts or interferences in eccentric positions. It should be pointed out that this sequence of procedure is not universal in the instruction of occlusal adjustment. Another sequence being taught is to adjust lateral working and nonworking and protrusive in this order with the centric adjustment last. This alternate procedure is held to be more difficult to perform clinically, when adjusting lateral excursions from an unstable CO position. Therefore, the recommended sequence will be CO adjustment first to a stable occlusion. During this adjustment sequence, some charted nonworking range contacts or interferences will be minimized as a matter of course. Follow the step by step sequence of performing this exercise as outlined on the "Occlusion I" Evaluation form (page 4‐23). Note the necessity to have the preliminary first three steps checked off before beginning your adjustment. Since this is an ungraded exercise, fill out the steps, then ask your instructor to verify your answers. It is important that you understand these answers!! Fig. 6‐3 pictures the results of doing an occlusal adjustment on the Mesmer case. Note the position and size of remaining contacts. The explanations provided in Week 4 lecture will help you understand the reasons for finding out and entering the required information. ResD 517 Occlusion, 2010 Manual Page 97
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CLINICAL ASSESSMENT AND CHARTING A. ARMAMENTARIUM Articulating ribbon forceps (2) Mylar strips Exacta articulating film Gauze and cotton rolls Mouth mirror Patient bib chain Plastic ruler B. CLINICAL OCCLUSAL ASSESSMENT Using the Clinical Assessment Form provided, complete the required information for the appropriate sections. C. CENTRIC RELATION OCCLUSION ADJUSTMENT 1. First Marking and Adjustment a. Mark the point of initial contact. b. After marking the CO point(s) of initial contact, check to make sure the mark agrees with the CO‐MIP slide rule. The next step is to decide how to adjust the marks. c. Lightly scrape the inner slopes of these cusps to include the red marks to start the adjustment. d. After completing this adjustment and future adjustments, wipe off the extraneous ribbon marks from both casts. This will help keep your casts neat, clean, and ready for the next adjustment sequence. 2. Second Marking and Adjustment a. As a result of the first scraping or adjustment, the vertical dimension will close slightly and three or four sets of teeth may come into contact. This will require successive decisions regarding the angle of scraping and whether one or both contacting teeth should be adjusted. b. After adjusting one or both marks of each set of opposing teeth in a systematic manner, more teeth will come into contact upon marking. ResD 517 Occlusion, 2010 Manual Page 98
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c. As the vertical dimension closes during successive adjustments, six, seven, and hopefully, eight sets of posterior teeth will come into contact. However, some of these contacts may be on unstable positions, i.e, inclines, which can be stabilized by repositioning contacting cusps. The principle and technique of "cusp repositioning," (pp. 4‐20) as described following, will be one of the aspects of the entire adjustment procedure. 3. Principle of Cusp Respositioning "Cusp repositioning" can be an integral part of a successful occlusal adjustment unless the problem is a so called "high spot" due to a recently placed restoration. This slight premature contact can usually be relieved by deepening the fossa of a flat restoration, reducing the marginal ridge, or reducing the cusp tip of the opposing tooth. Since most diagnostic adjustments on the articulator exhibit varying degrees of horizontal and vertical slide, a different problem is encountered with each patient. Since CO to MIP slides are basically initial contacts on inclines or cusp slopes followed by closure into maximum intercuspation, mere shortening of cusp tips results in only shorter cusps contacting on the same slopes, merely compounding the problem. In seeking a more stable position, the patient's mandible will close until occlusal forces are perpendicular to the closed position. The angle of adjustment of cusps can be directed to "reposition” or move cusp tips to the more desirable centric fossae position in the opposing arch. The cusp heights are progressively shortened and closure of vertical occurs during cusp repositioning. This will place them in the most stable position and centralized buccolingually. While this is one important objective, it will not always be possible to achieve throughout the arch and compromises will be necessary, e.g., "moving" to a fossa buccolingually or contacting on a marginal ridge. Care must also be exercised in cases where a group function occlusion is the working side functional relationship. When you stop to think about how much repositioning you can accomplish it is obvious that the greater the vertical slide, the greater the potential for moving cusps, while the greater the horizontal slide, the greater the need may be for cusp repositioning. 4. Rules for "Cusp Repositioning" Cusps may be repositioned by scraping in 4 ways, ‐ buccally, lingually, mesially and distally and also four combinations ‐ mesio‐buccally, distobuccally, mesio‐
lingually and distolingually, depending upon where the desired fossa is located (page 4‐20). a. Decide on the direction(s) you want a centric contact to "move" towards the selected fossa, then shave or scrape the opposite slope(s) of the opposing cusp removing the mark on the cusp if the cusp only interferes in centric. If it also interferes in excursive movements, modify the cusp. ResD 517 Occlusion, 2010 Manual Page 99
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PRINCIPLES OF CUSP REPOSITIONING DURING OCCLUSAL ADJUSTMENT FOUR BASIC DIRECTIONS ResD 517 Occlusion, 2010 Manual Page 100
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5. Summary of an Efficient Adjustment Sequence An orderly step‐by‐step procedure is the key to efficient occlusal adjustment and minimized confusion especially when two or more sets of opposing teeth contact in the CO position. a. Tap articulated casts to define centric marks. b. Assuming that two or more sets of teeth mark in CO the first question is where to start making adjustments. c. Start with the most distal marks of the most posterior set of teeth contacting and systematically proceed mesially to other contacts on that set of teeth. d. Referring to objectives of CO adjustment, contacts ideally should be centralized buccolingually in the center of the fossa. e. The Figure on page 6‐3 shows an example of a completed “Mesmer Case” which will be your next lab project. Note the size and location of the centric contacts and the neatness with which the adjustment has been accomplished. The Occlusion I case will certainly require different adjustments, but should look as neat and clean as the Mesmer case. ResD 517 Occlusion, 2010 Manual Page 101
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GOALS OF ADJUSTMENT 1. CO AT THE SAME VERTICAL DIMENSION AS MIP 2. SIMULTANEOUS CONTACT OF ALL POSTERIORS AT THE SAME TIME IN CENTRIC 3. FORCES DOWN THE LONG AXIS OF THE TEETH 4. NO LATERAL OR PROTRUSIVE INTERFERENCES 5. CANINE DISCLUSION DESIRED 6. FIRST PREMOLAR DISCLUSION ACCEPTABLE 7. GROUP FUNCTION REQUIRES EVEN SIMULTANEOUS CONTACT WITH POSTERIORS STARTING WITH FIRST PREMOLAR AND PROCEEDING POSTERIORLY A. SEQUENTIAL GAPS NOT ALLOWED IN MOST CASES RULES OF ADJUSTMENT 1. REMOVE INTERFERENCES ON NONCENTRIC HOLDING CUSPS WHEN POSSIBLE 2. ADJUST CUSPAL INTERFERENCES WHEN INTERFERING IN CENTRIC AND LATERAL 3. KNOW WHAT TYPE OF OCCLUSION YOU WANT TO HAVE CUSP REPOSITIONING 1. DETERMINE DESIRED LOCATION 2. ADJUST CUSP SLOPE OF DESIRED TOOTH 3. MORE SUCCESSFUL IF LARGER VERTICAL SLIDE INVOLVED ResD 517 Occlusion, 2010 Manual Page 102
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CLINICAL OCCLUSAL ASSESSMENT DATE PATIENT DENTIST PAIN (if none, proceed to Parafunctional Habits). Describe the presence of any muscle tendernes
(degree, location, duration, and time of day): PARAFUNCTIONAL HABITS LOCALIZED OCCLUSAL IRREGULARITIES A. TYPE OF OCCLUSION 1. Molar relationship (Angle’s classification I, II, III ‐ specify side) 2. Functional relationship (group function or mutual protection ‐ specify side and teeth involved) 3. Centric tooth contact relationship (one on one, or one on two) 4. Anterior vertical overlap ____ mm and/or anterior horizontal overlap ____ mm B. MARK AREAS OF “HEAVY WEAR FACETS” (continue on reverse side) ResD 517 Occlusion, 2010 Manual Page 103
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C. PATHS OF OCCLUSION 1. From centric occlusion position to maximal intercuspal position a. Measured at the incisors, from initial contact to maximum contact the mandible moves Horizontally (straight forward) ______ mm; not at all ______ Vertically ______ mm; to the right ______ mm; to the left ______ mm b. Potential maxillary inclines involved: c. The first tooth/teeth to contact is/are #(s): d. Initial contact area: 2. Protrusive movement interfering tooth contact #s 3. Right lateral movement interfering contacts a. Working _____________________________________ b. Nonworking _____________________________________ 4. Left lateral movement interfering contacts a. Working _______________________________________ b. Nonworking ____________________________________ 5. Opening movement (first 5‐10 mm) straight ______ mm deviates to the right ______ mm; to the left ______ mm maximum opening ______ mm D. MISCELLANEOUS 1. Teeth exhibiting fremitus (indicate tooth #) 2. Teeth with detectable mobility Class I ____________________ Class II ____________________ Class III _____________________________ REMARKS (include any recommendation for occlusal adjustment) ResD 517 Occlusion, 2010 Manual Page 104
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WEEK 5 LECTURE TEMPOROMANDIBULAR JOINT (TMJ) LABORATORY ADJUSTMENT OF OCCLUSION I CASE ResD 517 Occlusion, 2010 Manual Page 105
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LECTURE TEMPOROMANDIBULAR JOINT (TMJ) The TMJ is a compound joint with the articular disc serving as the third “bone” in the system. The joint is divided into two separate systems which work co‐jointly to produce the motions associated with the mandible. The first joint system is the system below the articular disc. It is composed of the condylar head and the inferior synovial cavity. Since the disc is tightly bound to the condyle by the lateral and medial discal ligaments, referred to as collateral ligaments, the only movement between the two elements is rotation of the condyle on the disc's inferior surface. Therefore, this portion of the joint is responsible for rotational movements. The second joint system in the compound joint is the superior synovial cavity which consists of the superior surface of the articular disc and the inferior and lateral surface of the squamous portion of the temporal bone called the glenoid or mandibular fossa. The disc is not tightly attached to the articular surface of the glenoid fossa and the free sliding movement can occur between these surfaces. This movement occurs when the condyle(s) move(s) forward or translate(s). Hence, the upper portion of the joint is responsible for translation movements. HC = head of condyle DISC = articular disc MP = medial pole LP = lateral pole ResD 517 Occlusion, 2010 Manual Page 106
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TMJ LATERAL VIEW RT, Retrodiscal tissues; SRL, superior retrodiscal lamina (elastic); IRL, inferior retrodiscal lamina (collagenous); SLP, superior lateral pterygoid muscle; ILP, inferior lateral pterygoid muscle; AS, articular surface; SC, superior joint cavity; IC, inferior joint cavity; DL, distal (collateral) ligament; ACL, anterior capsular ligament; PCL, posterior capsular ligament. (From Okeson, Mosby Co., St. Louis, 1985)
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As the mandible moves anteriorly down the articular eminence (Figure 2) from centric relation the disc is restrained by the attachment of the superior retrodiscal lamina to the posterior border of the disc. This elastic lamina retracts the disc posteriorly on the condylar head (Figure 3). In centric relation or centric occlusion, there is no pull on the disc. When the mandible is opened and pulled down the articular eminence, the superior retrodiscal lamina becomes increasingly stretched, creating increased force to retract the disc (Figure 4). As the disc rotates over the top of the condylar head and in the full forward position, the posterior retroactive force on the disc is maximal (Figure 5). The anterior lip of the donut shaped disc prevents the disc from being overretracted posteriorly (Figures 4, 5). All of the elements of this complex joint when working in harmony, tend to keep the disc centered on the condylar head when under a load. ResD 517 Occlusion, 2010 Manual Page 108
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ARTICULAR DISC The articular disc consists of dense collangenous connective tissue, which in the central area is avascular, hyaline, and without nerve tissue. It has a smooth surface but lacks a definite synovial lining. The posterior aspect of the disc fits into the glenoid fossa and extends for a short distance down the distal surface of the condyle, separated from the condyle by the joint space. Posterior to the disc, towards the postglenoid spine, there is soft vascular connective tissue with abundant nerve endings (Retrodiscal tissues, Page 7‐3). Thus, the condyle cannot be moved up and back, but can be moved down and back, as often happens in dysfunctional disturbances. The disc blends with the connective tissue of the joint capsule and, anteriorly in some areas, rather fine tendons connect the disc to the superior lateral pterygoid muscle. The superior lateral pterygoid also has a broad, strong attachment to the neck of the condyle. Anteriorly, the joint capsule is indefinite and loosely arranged. Posteriorly, it is much thicker but without a definite functional capsular arrangement of fibrous connective tissue. Only in the lateral wall are the fibers arranged in parallel bundles, constituting the temporomandibular ligament. The looseness of the capsule forming the upper compartment allows gliding movements during articulation. ResD 517 Occlusion, 2010 Manual Page 109
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As in all other joint systems, the ligaments serve to limit joint motion and to protect the structures of the joint. Ligaments are made of collagenous connective tissue and have a limited ability to stretch. They do not actively participate in joint function but rather, act passively to restrain movement. The TMJ has three functional ligaments. They are: 1. the collateral ligaments 2. the capsular ligament 3. the temporomandibular ligament Two additional ligaments are associated with the joint. They are: 1. the sphenomandibular ligament 2. the stylomandibular ligament COLLATERAL (DISCAL) LIGAMENTS (MDL AND LDL) There are both Medial and Lateral collateral ligaments. They function to attach their respective capsular surfaces with the same pole of the condyle. For example, the medial collateral (discal) ligament (MDL) attaches the medial surface of the articular disk to the medial pole of the condyle. Conversely, the lateral collateral (discal) ligament (LDL) attaches the lateral border of the articular disk with the lateral pole of the condyle. These ligaments describe a mediolateral division of the joint space into upper and lower or superior and inferior joint cavities. Recognition of these two joint spaces is important since discussions of joint pathology involve locations based on this division. SC (superior cavity), IC (inferior cavity), AD (articular disc), CL (capsular ligament). These ligaments function to keep the disc associated with the condyle. They serve to keep the disc on the condylar head as the condyle moves anteriorly and posteriorly. Because the attachments are on the lateral surfaces, the attachments allow the disc to be rotated anteriorly and posteriorly on the condylar head's articular surface. In combination with the disc, these ligaments are responsible for the hinge movement of the mandible. Hinge movement occurs between the condyle and articular disc. These ligaments are innervated and have a blood supply. Innervation provides proprioceptive information about the joint. Additionally, pain fibers are associated with the ligaments and straining them will illicit pain. ResD 517 Occlusion, 2010 Manual Page 110
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CAPSULAR LIGAMENT The capsular ligament surrounds and contains the entire TMJ. Since we know the boundaries of the TMJ, it is only logical to associate the capsular ligament with those boundaries. The capsular ligament attaches superiorly to the temporal bone along the borders of the articular surfaces of the mandibular fossa and articular eminence. Inferiorly, the fibers of the capsular ligament attach to the neck of the condyle. The capsular ligament resists any medial, lateral, or inferior forces that tend to separate or dislocate the articular surfaces. In other words, it holds the joint together and limits the distance the articular surfaces can move apart. The capsular ligament also provides the casing for the TMJ’s synovial fluid which lubricates the articular surfaces. Lubrication is thought to occur in two ways. First the synovial fluid is absorbed by the articular surfaces. When a surface is placed under load, the surface "weeps" the synovial fluid like a sponge giving up its fluid load when it is squeezed. This provides lubricant at the precise spot it is needed and helps protect the joint under load. Prolonged loading of the joint will exhaust this supply just as prolonged squeezing a sponge will not elicit any further fluid release. The second method of lubrication is by a mechanism similar to an oil dashpot. Synovial fluid is distributed around the joint space. When the joint moves toward one side of the space, the fluid is forced to move through the joint since it was trapped in the joint space by the capsular ligament. This fluid movement through the joint provides fresh lubricant to the articular surfaces as the joint functions. The capsular ligament is well innervated and provides proprioceptive feedback on the TMJ. ResD 517 Occlusion, 2010 Manual Page 111
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TEMPOROMANDIBULAR LIGAMENT The lateral portion of the capsular ligament is reinforced by strong, tight fibers that make up the temporomandibular ligament. This ligament is composed of two distinct parts, an outer oblique part (OOP), and an inner horizontal part (IHP). The outer, posterior inferior directed portion extends from the outer surface of the articular eminence and the beginning of the zygomatic process to the outer surface of the condylar neck. There it joins the capsular ligament attachment. This portion of TM ligament limits the excessive dropping of the condyle and hence acts to limit the extent of mouth opening and the amount of rotational opening of the mandible. As the mandible starts its opening movement, the ligament is not engaged until the opening arc moves the condylar neck far enough posterior to tighten the ligament. At this point, the mandible cannot simply rotate any further and must translate forward down the articular eminence if it is to continue opening. Note that at this point, the TM ligament is engaged at a fixed length and maintains the fixed distance between the condylar neck and the lateral border of the articular eminence even though the condylar head is translating down the eminence. The inner portion extends horizontally from the outer surface of the articular eminence and zygomatic process, posteriorly to the lateral pole of the condyle and the posterior part of the articular disk. This portion of the ligament limits the posterior movement of both the condyle and disk. When force is applied to the mandible to displace the condyle posteriorly, this portion of the ligament becomes tight and prevents the condyle from moving into the posterior region of the mandibular fossa. Therefore, the TM ligament protects the retrodiscal tissues from trauma created by the posterior displacement of the condyle. This inner portion also protects the superior lateral pterygoid muscle from overlengthening.
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SPHENOMANDIBULAR AND STYLOMANDIBULAR LIGAMENTS Both of these ligaments are viewed as accessory ligaments to the TMJ. The sphenomandibular ligament does not have any significant affect on mandibular movement. It arises from the spine of the sphenoid bone and extends downward and laterally to the lingula. You can sometimes feel this ligament when you are giving a mandibular block injection. The stylomandibular ligament arises from the styloid process and extends down and forward to the angle and posterior border of the ramus of the mandible. It becomes tight when the mandible is protruded and is most relaxed when the mandible is opened. It limits excessive protrusive movements. ResD 517 Occlusion, 2010 Manual Page 113
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CONDYLAR POSITIONS AND MOVEMENTS Normally, when the jaws are closed, the condyle contacts the disc and the disc contacts the glenoid fossa. Ideally, if occlusal contact is maintained when gliding movements are performed, the glenoid fossa/disc/condyle relationship should be maintained. Movements in the lower (condyle‐
disc) compartment are mainly hinge‐like. In the upper (glenoid fossa‐disc) compartment the disc glides with the condyle during the opening cycle, and the disc follows the condyle head all the way anteriorly in wide opening movements. When hard food is masticated, the condylar head on the working side may momentarily lose its contact with the anterior slope of the glenoid fossa, but guided by the well integrated neuromuscular system, it is again brought into contact with the disc and the temporal bone. Hinge movement, (rotational movement with contact between the guiding parts of the joint), and bodily or translatory movements are found within the temporomandibular joint during mastication. A hinge axis movement may occur in various degrees of protrusion; but reference is usually made to the stationary hinge axis movement with the mandible in centric relation. This rotational movement can usually be performed for no more than 15 to 25 mm of the initial opening movement. In lateral movements the working side condyle not only rotates but may do so with a slight lateral shift. This lateral shift of the mandible during lateral jaw movement is called the BENNETT MOVEMENT and can have immediate and/or progressive components. The angle formed on the plane by this path of the translating (nonworking) condyle during this movement is called the BENNETT ANGLE. In contrast to viewing the Bennett angle on the horizontal plane, the FISHER angle is the angle formed by the difference of the protrusive and nonworking condylar paths as viewed on the saggital plane. In a normal masticatory system the TMJ is subject to a minimal amount of stress during "empty" movements (e.g., swallowing and eating). Even while chewing hard food, the joint is protected from injurious stresses by a delicate neuromuscular mechanism of control and coordination of the functional forces. However, the greatest stress in function is upon the joint on the balancing (nonworking) side. ResD 517 Occlusion, 2010 Manual Page 114
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LABORATORY Mounting correct ________ Student Secret ID# ____________ Evaluation for Adjusted Occlusion: Case I MAXIMUM TOTAL 6 STUDENT 1. DEGREE & INITIALDIRECTION OF C0/MIP SLIDE ANSWER: ______ (i.e., amount of vertical. lateral, and/or horizontal slide) POSSIBLE INCLINES INVOLVED (“A, B and/or C”) ANSWER: ____________ 2. INITIAL CO CONTACT (Refers to teeth and position) ANSWER: _________ 3. Initial “MIP” mark by STUDENT = INSTRUCTOR COMMENT 6 6 10 Deduct all points if initial and ending MIP marks not correct (beyond 0.5 degree of initial mark) Ending “MIP” mark By FACULTY= ****Instructor to check first three sections before continuing**** 4. CO/MIP ADJUSTMENT 6 REMOVED INTERFERENCES: ‐ 3 for perceptible slide NUMBER OF POSTERIOR CONTACTS 22 Subtract 3 points for each set of missing contacts. You must have one set of centric contacts for each pair of teeth. Subtract 3 points for each set of contacts which are the 14 wrong size or in the wrong location. 5. PROTRUSIVE MOVEMENT 14 Removed interferences (subtract 3 for each remaining interference or uneven anterior contact) 6. LEFT LATERAL MOVEMENT* 12 REMOVED WORKING INTERFERENCES Subtract 3 for each remaining. REMOVED NONWORKING INTERFERENCES 15 Subtract 5 for each remaining. 12 7. RIGHT LATERAL MOVEMENT* REMOVED WORKING INTERFERENCES: Subtract 5 for each remaining. REMOVED NONWORKING INTERFERENCES 15 Subtract 5 for each remaining. 8. TOOTH CONTOUR, ANATOMY & FINISH 12 After occlusal adjustment, subtract 3 points for each unsatisfactory tooth. 9. NEATNESS (subtract 10 points if unacceptable) TOTAL
150 ResD 517 Occlusion, 2010 Manual Page 115
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C. LABORATORY DENTOFORM ADJUSTMENT ARMAMENTARIUM Red and black or green articulating ribbon Articulating forceps Mylar strips Straight L 303 green flame stone or Contra‐angle 303 green flame stone “Brownie” rubber polishing point (for smoothing) Straight #2 or #4 round bur TECHNIQUE The technique to be followed will be consistent with that previously taught that the end result will be short of ideal. except 1. Mark contacting quadrants with red ribbon by firm tapping. 2. Apply principles of “cusp repositioning” to move contacts from inclines to stable positions buccolingually, if necessary. 3. Where initial contacts are already in a reasonable buccolingual position, reduce either cusp or opposing surface or both slightly. 4. Close vertical dimension until most teeth contact, most contacts are in reasonably stable positions and no “rocking” in centric evident. 5. If a deep first molar central fossae exists, it may be difficult to attain stable centric contacts between centric cusps and their fossae. 6. Use a mylar strip to determine contact distribution. If one or two teeth are still out contact but occlusion is stable, accept this as the end result to avoid mutilation of the dentition. 7. If possible, try to attain cuspid contacts to provide disclusion in lateral and to use as centric stops during restorative procedures or during adjustment of replacement teeth. 8. Re‐establish basic morphology if necessary, using a #1 round bur. 9. Smooth the morphology with a “Brownie” polishing point or a small burlew disk. 10. Anterior interferences in CR/CO may be present. If so, adjust the mandibular anteriors. You will be prepping the maxillary anteriors in fixed prosthetics and, therefore, need to conserve the faciolingual tooth structure of these anteriors. Therefore, avoid reducing the lingual surfaces of the maxillary anterior teeth. ResD 517 Occlusion, 2010 Manual Page 116
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RD 517 DENTOFORM OCCLUSAL ADJUSTMENT Sudent Secret ID# ___________ INSTRUCTIONS: Your dentoform needs to be accurately adjusted in MIP so that you will be ready for your dental materials project and your fixed prosthetics preclinic course next Autumn Quarter. Eccentric interferences are not usually a problem with the dentoform during the manufacturing stage. It is also necessary for you to neatly and legibly tattoo your two digit ID number on all sides of your dentoform so that grading can be done in a totally anonymous manner. The number should read correctly from in front of the dentoform. Although you will not be graded on how well you do this, it will make a MAJOR difference in how well you perform in the dental materials and fixed prosthetics courses. Therefore, it is in your best interest to make the necessary adjustments accurately and restore lost anatomy in an accurate manner while making sure you have smooth occlusal surfaces when your are finished. IF you need to reduce anterior interferences on centrals and/or laterals to obtain a good posterior centric, remove the incisal contact of the mandibular anteriors because you will be crowning the upper anteriors and will need all the faciolingual thickness you can get when you prepare the teeth. The canines are thick enough that you can adjust the lingual inclines of the maxillary teeth if you need to adjust them at all. For dental materials, remove tooth #19 before adjusting the occlusion. All adjustments should be made on the mandibular arch. The adjustment will be satisfactory when, at least, #18 & #20 and three out of four posterior contacts on the right side hold mylar firmly and there is no slide from CO to MIP. In preparation for the fixed preclinical course, replace #19, then adjust the occlusion in the same way you did for dental materials. At least six out of eight posterior centric contacts are required for successful completion of this adjustment. PLEASE HAVE A FACULTY MEMBER DOUBLE CHECK YOUR ADJUSTMENTS, AND TURN IT IN WHEN ADJUSTMENTS ARE COMPLETED 1. Centric and eccentric interferences removed. 2. Tooth contour and anatomy adequately restored. VERIFICATION: Adjustments completed for Dental Materials: ___________________ (Instructor initials, signature, or stamp) Total exercise completed: ________________ (Instructor initials, signature, or stamp) ResD 517 Occlusion, 2010 Manual Page 117
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WEEK 6
MIDTERM LECTURE EXAM
LABORATORY
BEGIN MESMER CASE
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MESMER CASE CASE 2 (MESMER) DESCRIPTION A. CASE DESCRIPTION This occlusal adjustment case represents a more difficult clinical situation than the first clinical adjustment case. The patient exhibits significant interfering tooth contact relationships and signs or symptoms that may be related to theses occlusal interferences. Diagnostic casts of this patient were mounted on an articulator for diagnostic occlusal adjustment to be followed by clinical occlusal adjustment. The patient responded well with diminished symptoms several months after adjustment. Identical patient casts have been mounted on articulators to replicate the occlusal relationships. You will have enough time until 3:00 PM next week to complete this adjustment. You have plenty of time to be careful and precise in your adjustment. Contrary to waxing, once you take off tooth structure, you can’t put it back. This project is worth 15% of your final grade. A comparison between reduced stone surfaces and original casts or patient dentition is a guideline for the amount of enamel reduction during the clinical phase, thus speeding up the procedure. The completed adjustment should look similar to the illustration on page 6‐3 . B. CASE PERSONAL INFORMATION AND DENTAL HISTORY This patient is a 28 year old female in good general health. She underwent orthodontic treatment at the age of 12 for a two year duration. The patient states that she is not aware of any parafunctional habits, however, occasionally experiences some soreness in the masseter muscle region, increasing lately in frequency. ResD 517 Occlusion, 2010 Manual Page 119
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DIAGNOSTIC OCCLUSAL ADJUSTMENT “(MESMER” CASE) COMPLETED DIAGNOSTIC OCCLUSAL ADJUSTMENT Maxillary and mandibular views of a completed well adjusted occlusion that meets all objective in CO, lateral ResD 517 Occlusion, 2010 Manual Page 120
and protrusive ranges 6-4
C. DENTAL EXAMINATION a. Tooth and Periodontal Examination The patient exhibits fissure caries in the molar regions and also requires replacement of some failing amalgams. There are moderate wear facets in the canine and molar regions. Periodontal examination indicated normal sulcus depth and tooth mobility. D. CONFIRMATION OF MOUNTING CREDIBULITY Due to the multiple mounting procedure of casts in a short time frame, there may be an occasional major mounting error that will require remounting before proceeding with diagnostic adjustment. 1. 2. 3. 4. 5. To check credibility of mounting, bring the teeth into contact in CO. Move the casts into maximum intercuspation or MIP. The mandibular cast should move anteriorly and slightly to the patient’s left according to previous description of clinical observations. (The incisal pin will shift posteriorly and to the right.) Most posterior teeth should contact in MIP. Slight lack of contact in the 1st or 2nd molar region can be considered normal and acceptable. A major lack of contact on one side or the other will require you to remount. When holding the articulated casts in the MIP, it may be observed that they may “rock” slightly in the anteroposterior direction. This can be considered normal due to multiple duplication of casts. ResD 517 Occlusion, 2010 Manual Page 121
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E. INCISAL PIN ADJUSTMENT Before proceeding with the occlusal adjustment, the incisal pin of the articulator should be set at the vertical dimension of centric occlusion (CO) as was done with the first adjustment case. In other words: 1. Move the articulated casts into the best possible MIP position. 2. While putting hand pressure on top of the articulator, loosen the incisal pin adjustment screw, tap the pin against the metal incisal guidance mechanism and tighten screw. 3. The above procedure now establishes the incisal pin vertical dimension of the articulator at the MIP. In the CO position of the articulator, the end of the incisal pin will be about 3 to 5 degree above the incisal plate. Enter this value in the correct place in Section 3 of your grading form. Use ink to insure that the value doesn’t become illegible. DIAGNOSTIC OCCLUSAL ADJUSTMENT TECHNIQUE A. ARMAMENTARIA Articulating ribbon forceps Exacta‐Film or articulating ribbon D‐5 carver (discoid‐cleoid) Micro‐thin mylar strip B. GENERAL SEQUENCE OF PROCEDURE The general sequence of occlusal adjustment will be similar to that used for the Carson case, including setting the angle of eminence to 25° bilaterally. Note that you have until 3 PM next Friday to complete this case which will be graded at that time. Faculty will be available to help you until 3 PM on that day. ResD 517 Occlusion, 2010 Manual Page 122
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Mounting correct __________ Student Secret ID # _______ Evaluation for Adjusted Occlusion: Case Mesmer STUDENT MAXIMUM TOTAL INSTRUCTOR COMMENT 1. DEGREE & INITIALDIRECTION 6 OF C0/MIP SLIDE ANSWER: ______ (i.e., amount of vertical. lateral, and/or horizontal slide) POSSIBLE INCLINES INVOLVED 6 (“A, B and/or C”) ANSWER: ____________ 2. INITIAL CO CONTACT 6 (Refers to teeth and position) ANSWER: _________ 10 3. Initial “MIP” mark by STUDENT = Deduct all points if initial and ending MIP marks not correct (beyond 0.5 degree of initial mark) Ending “MIP” mark By FACULTY= ****Instructor to check first three sections before continuing**** 4. CO/MIP ADJUSTMENT 6 REMOVED INTERFERENCES: ‐ 2 for perceptible slide NUMBER OF POSTERIOR CONTACTS 22 Subtract 3 points for each set of missing contacts. You must have one set of centric contacts for each pair of teeth. Subtract 3 points for each set of contacts which are the 14 wrong size or in the wrong location. 5. PROTRUSIVE MOVEMENT 14 Removed interferences (subtract 3 for each remaining interference or uneven anterior contact) 6. LEFT LATERAL MOVEMENT* 12 REMOVED WORKING INTERFERENCES Subtract 3 for each remaining. REMOVED NONWORKING INTERFERENCES 15 Subtract 5 for each remaining. 7. RIGHT LATERAL MOVEMENT* 12 REMOVED WORKING INTERFERENCES: Subtract 4 for each remaining. REMOVED NONWORKING INTERFERENCES 15 Subtract 5 for each remaining. 8. TOOTH CONTOUR, ANATOMY & FINISH 12 After occlusal adjustment, subtract 4 points for each unsatisfactory tooth. 9. NEATNESS (subtract 10 points if unacceptable) TOTAL
150 *Nonworking side disclusion will result in loss of all points. ResD 517 Occlusion, 2010 Manual Page 123
WEEK 7 LECTURE TMJ Disorders LABORATORY FINISH MESMER BY 3:30 PM ResD 517 Occlusion, 2010 Manual Page 124
TMJ Disorders - A Biologic Perspective
James A Howard DDS
Learning Objectives
Provide a format to identify key elements of the examination, history
and diagnosis to enable the clinician to arrive at the proper diagnosis.
Outline the available treatment options available for TMJ disorders and facial pain.
Have every course participant be an ambassador for The Orthopedic Orphan The Temporomandibular Joint – the joint complex that few clinicians want to
claim responsibility for in dentistry or medicine.
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Epidemiology
Gender
Hormonal
Ligament laxity
Tx seeking behavior
Gender Distribution of 3,428 TMJ Patients
90
80
85.4 %
70
Sample size
3,428
60
50
40
Male
Female
30
20
10
0
14.6 %
Gender Distribution of
Age
1200
1000
78% of females seek treatment
between the ages of 15–50 years
800
Sample size
3,428
600
85.4% female
400
200
0
age 0-9 yr
age 10-19
age 20-29
age 30-39
age 40-49
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age 50-59
age 60-69
age 70-79
Etiology
The Three P’s
• Predisposing
factors
• Precipitating
factors
• Perpetuating
factors
There is limited knowledge about the predisposing factors for
temporomandibular joint dysfunction. Childhood trauma, connective
tissue disorders such as rheumatoid arthritis, and certain occlusal
variables have been identified.
Precipitating factors are often what trigger the episode that causes the
patient to seek treatment. A careful history is necessary to determine
why the patient is seeking treatment at this time and to help the clinician
determine if the signs and symptoms are likely to be self-limiting.
When identifying the causes of and facial pain it is important to identify
if the suspected etiology will be a perpetuating factor resulting in
recurrence of the patients problems.
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Parafunction – as an Etiology
Parafunction can result in a repetitive use injury to the TMJs, just as occurs with
other joints. Tooth grinding can injure the tissues attaching the disc to the condyle.
Clenching and grinding causes disc deformation, altered bone density, joint pain
(arthralgia), muscle pain (myalgia) and tooth pain (odontalgia). The tooth damage
often has multiple etiologies including chemical attrition and altered salivary flow.
Sleep disorder bruxism is a central nervous system generated rhythm pattern – it is not a habit and it is not caused by malocclusion.
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Parafunction
Abnormal Tooth Wear
Consider the multiple etiologies
in addition to bruxism
ABNORMAL TOOTH WEAR
DIAGNOSIS OF WORN DENTITIONS
Abrasion
Attrition
Erosion
Fracture
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Occlusion - as an Etiology
Angle’s Classification of
Dental Malocclusion
Class I
76 %
Class II
22 %
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Class III
3%
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Trauma - as an Etiology
microtrauma – repetitive stress and strain
The
Three P’s
Macro trauma
• Predisposing
• Precipitating
• Perpetuating
Right TMJ condylar adaptation in 23 year old
professional violinist after 15 years of playing
R
Lateral tomgraphy
Anterior Posterior
Anteroposterior view
Medial
Lateral
R
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Trauma
macrotrauma – external (versus internal)
Macrotrauma may be a predisposing factor, especially during the period of
growth and development. It is a precipitating factor and the most common
reason for males under the age of 30 years seeking treatment for TMJ disorders. It
is not usually a perpetuating factor. A chin scar may indicate prior trauma and the
force to the temporomandibular joint can lead to disc displacement on the side
opposite of the blow. It is important to rule out a fracture with imaging.
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Trauma
facial asymmetry
The evidence for an association between altered craniofacial morphology and TMJ
disorders is supported by two recent articles:
Flores-Mir C, Nebbe B, Heo G, Major PW.
Longitudinal study of temporomandibular joint disc status and craniofacial
growth. Am J Orthod Dentofacial Orthop 2006;130:324-30
Ahn SJ, Baek SH, Kim TW, Nahm DS.
Discrimination of internal derangement of temporomandibular joint by
lateral cephalometric analysis. Am J Orthod Dentofacial Orthop 2006;130:331-9
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Systemic factors- as an Etiology
hypermobility syndrome
Systemic Ligament Laxity
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Systemic factors
connective tissue disorders – rheumatoid arthritis
Anterior openbite
Shortened ramus
Antegonial notching
TMJ Involvement in RA
Anterior openbite
Antegonial notching
ROM often normal
Minimal pain
Crepitus common
Imaging advised
Coordinate care with
medical colleagues
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Central Nervous System
Dystonia is a syndrome of sustained muscle contractions, usually producing
twisting and repetitive movements or abnormal postures.
Myoclonus is a sudden "Shock" like muscular movement.
Tremor is a rhythmical sinusoidal oscillation of a body part.
Tic is a stereotypic or patterned movement that is frequently preceded by an urge
to need to move, transient suppressabbility, and post movement relief.
Tardive dyskinesia is an involuntary, coordinated, patterned, repetitive, rhythmic,
purposeless, but seemingly purposeful or ritualistic, movement or utterance.
Restless leg Syndrome is a condition that results in an irresistible urge to move
the legs. This tends to be noticeable on relaxing or when lying down trying to fall
asleep. It resolves with physical activity. People may find they have to get out of
bed and exercise their legs for a long time before they are able to fall asleep.
This condition is most often due to an inherited trait. It also occurs as the result of
an underlying health problem (e.g. iron deficiency, thyroid dysfunction, vitamin
deficiency). Most, if not all the time there is an associated problem during sleep
and may be accompanied by other parafunctions such as sleep bruxism. "Periodic
Leg Movements of Sleep" is a condition that results in the legs twitching, twisting
or jumping every 20 - 30 second during the night. These movements can be bad
enough to disrupt the deeper stages of sleep, and result in marked daytime fatigue.
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Data Collection
Three Minute TMJ Exam
Range of motion
Arthrokinetic
TMJ auscultation
TMJ palpation
TMJ functional loading
Masticatory musculature
Occlusal examination
Intraoral examination
Head & neck examination
Cranial nerve examination
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Examination for TMJ dysfunction
Range of mandibular motion
Mandibular Range of Motion [ROM]
Range of motion
Vertical mandibular movement
Females 47mm
Males 52mm
M
F
Mandibular
Range of Motion [ROM]
unt/unt/unt
The mandibular range of motion [ROM]:
changes with age
is correlated with changing body stature
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45
46
47
38
35
Millimeter mm
Age – from 4 published studies - Females
10 15 18
30
67
Zawawi, KH, Al-Badawi EA, Lobo SL, Melis, M
J Can Dent Assoc
2003 Dec;69(11):737-741
An index for the measurement of normal maximum mouth opening.
¾ 148 subjects, mean age 27.4 years old
¾ Tested ability to position the 3 middle fingers vertically between
the incisal edges up to the first distal interphalangeal fold
¾All subjects could position 3 fingers
mean width of 48.8mm for the right hand
47.0mm for the left hand
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Extremes of Range of Motion
ANTERIOR
ANTERIOR
23 mm
77 mm
Excessive steepness of the TMJ articular eminence can predispose to disc displacement.
A flat eminence can lead to condylar subluxation.
ANTERIOR
Degenerative joint disease can alter intracapsular bony contours and is usually accompanied by a decreased mandibular range of motion.
ANTERIOR
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Masticatory muscle palpation
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Temporomandibular joint auscultation to determine joint noise
TMJ noise is experienced by 34% - 42% of the population under the age
of 40 years old. The ratio of noise in the population is 4/3 female/male.
The older the person is the more likely crepitus occurs, usually preceded
by a history of clicking and often indicative of degenerative joint disease
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Lateral section of normal TMJ
Lateral section of displaced and deformed disc
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FORCE
AGE RELATED
ARTICULAR
ADAPTABILITY
OF THE
TMJ
FORCE
High
Low
YOUNG
OLD
unt/unt/unt
TMJ Disorders in the Elderly
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Imaging
Imaging
Panoramic
minimal expense widely available
Cone beam volume imaging
less radiation and less expense than
conventional computed tomography
– provides three dimensional analysis
– soft tissue not well visualized
Computerized tomography (CT scan)
readily available – ideal for bone detail
Arthrography
limited availability – dynamic study to document disc
condyle relationship, only method for detecting
perforations or adhesions
Single photon emission computed tomography (SPECT)
ideal for detecting active change in bone or soft tissue
Magnetic resonance imaging (MRI)
ideal soft tissue imaging but no mandibular motion
Imaging should serve as an adjunct to and not a substitute for a thorough history
and examination. The cost benefit ratio must be considered and a screening
panoramic film is often all that is necessary.
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Imaging
MRI
Closed
Open
TMJ internal derangement: anterior
displacement without reduction (T1-weighted
MRI; TR450; TE20). Disk is displaced with
Posterior band (P) lying anterior to condyle (C).
CT
MRI
CT and MRI taken the same day of a 13 year old female with a history
of mandibular trauma four months before the imaging. Note adaptation of
the disc to the bony condylar defect.
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Diagnosis
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Treatment
Treatment
Physiotherapy
Home care
Physical therapy/massage/osteopathic/chiropractic
Modification of oromotor activities
Habits
Clenching/tooth tapping/tongue habits/jaw jutting
Fingernail biting
Activities
Singing/wind instrument/violin/scuba
Intraoral appliances
Diagnostic vs therapeutic vs preventative
Appliance Design
Directive vs permissive
Deprogrammer of occlusion vs deprogrammer joint position
Myalgia vs arthralgia
Attrition prevention – attrition vs abrasion vs abfraction
Occlusal stabilization vs joint stabilization
Occlusal Modification
Surgical intervention
Medical consultations and management
prescription medication
blood studies for sedimentation rate and connective tissue disorders
physical therapy/chiropractic/osteopathic/massage therapy
Neurology/Rheumatology/Gastroenterology/Otolaryngology
Sleep Medicine
Pain Management
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Stress management/relaxation training/meditation/psychotherapy
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Occlusal therapy
It can be very difficult to determine if the occlusal alteration is a result of muscle
and or TMJ involvement versus if the dysfunctional occlusion is triggering a
response of the muscles and adversely loading the joint.
Before irreversible occlusal; therapy is initiated it is advisable to use an intraroral
appliance to deprogram the mandibular position, achieve a reproducible jaw
relationship and be certain there is no active TMJ disease.
There is literature to support that occlusal factors predispose to developing TMJ
disorders but there is no reliable evidence that altering the occlusion will alter an
already existing TMJ disorder.
Role of intraoral appliances
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Self management – home physiotherapy
Anti‐inflammatory Medications
Lips Together
Teeth Apart
Moist Heat
Soft Diet
Educating the patient about the nature of their problem is an important
aspect of treatment, and sometimes the only treatment necessary.
Explaining that the TMJ is like any other joint, and than the joint and
associated muscles will respond to the same precautions they would take
with a sprained ankle of knee:
avoid loading
minimize use
anti-inflammatories
moist heat
lips together teeth apart
soft diet
over the counter NSAID/.aspirin
heat better than cold unless acute TMJ sprain
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Web Resources
www.rad.washington.edu/anatomy/
Temporomandibular Joint Tutorial
Graphic display of CT, MRI and arthrography of the TMJ
www.bartleby.com/107/
Anatomy of the Human Body (Gray's Anatomy)
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www.lib.uiowa.edu/commons/skullvr/gallery/tmj2.htm
Animation showing mandibular movement and occlusion of teeth that can be
utilized to educate patients about this relationship
www.aaop.org/
American Academy of Orofacial Pain
Excellent color illustrations and patient brochures that can be ordered for practice.
Best journal for TMJ Disorders and Orofacial Pain.
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www.ncbi.nlm.nih.gov/sites/entrez/
PubMed is a service of the U.S. National Library of Medicine that includes over 17
million citations from MEDLINE and other life science journals for biomedical
articles back to the 1950s. PubMed includes links to full text articles and other
related resources. This is the best resource available for literature review.
Links to PubMed Central which provides more limited bibliography but with
complete articles available.
www.webmd.com/
This WEB resource provides quick overview of 300 medical conditions and
allows for quick access to information on over 200 prescription medications.
Useful to both the health care provider and patients as the information is carefully
screened by an independent medical review board.
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8-1
WEEK 8 LECTURE PRIMARY DENTITION LABORATORY LAB EXAM #1 FINISH BY 3:30 PM ResD 517 Occlusion, 2010 Manual Page 169
8-2
LECTURE PRIMARY DENTITION 1. OBJECTIVES Upon completing this unit, you should be able to: A. Demonstrate your understanding of all terms listed in the glossary n written and verbal communication. B. Identify all areas of the primary teeth that have names, particularly hose of the primary first molars. C. Identify all primary teeth by name and letter. D. Correlate the eruption of primary and permanent teeth with the proximate age levels and correct sequences of eruption. 2. GLOSSARY A‐T is the letter system used to identify and record the primary teeth. Cervical Ridge (Cervical Deflecting Ridge) ‐ a pronounced elevation of enamel found on the mesial 1/2 of the buccal surface of primary posterior eeth particularly maxillary and mandibular first molars. Primary ‐ preferred term for first set of teeth, also known as the deciduous, baby or milk teeth. Succedaneous Teeth ‐ the permanent teeth that replace the primary teeth. Transverse Ridge ‐ an elevation uniting the ridges of the MB cusp and the ML cusp of the primary first mandibular molar. ResD 517 Occlusion, 2010 Manual Page 170
8-3
3. CHRONOLOGY OF THE HUMAN DENTITION PRIMARY DENTITION a. Hard Tissue Formation Begins from the 3rd to 6th month in utero. Mean initial calcification of the maxillary central incisor is 3 ½ months (Kraus). b. Approximate Amount of Enamel at Birth Tooth Name *1. Maxillary Central 2. Maxillary Lateral 3. Mandibular Centrals/Laterals 4. Cuspids 5. 1st Molars 6. 2nd Molars % Complete 5/6 2/3 3/5 1/3 Occlusal calcified plus part of crown Cusps united *In the primary incisors there is only one center of calcification which spreads laterally in both directions. Enamel formation of primary teeth is usually completed by the end of the first year after birth. c. Roots Completed Root formation is usually completed between age 1½ and 3½. d. Sequence and Time of Exfoliation Tooth Name 1. Centrals 2. Laterals 3. 1st Molars and Mandibular Cuspids 4. 2nd Molars and Maxillary Cuspids ResD 517 Occlusion, 2010 Manual Page 171
Age 6 ‐ 7 years 6 ‐ 8 years 9 ‐ 11 years 10 ‐ 12 years 8-4
4. PERMANENT DENTITION a. Hard Tissue Formation 1. 2. 3. 4. 5. 1st permanent molars begin at birth or slightly before. Maxillary centrals and cuspids; mandibular centrals, laterals and cuspids ‐ hard tissue formation begins 3 ‐ 6 months after birth. Maxillary laterals: 10 ‐ 12 months after birth. Both maxillary and mandibular 1st and 2nd premolars and 2nd molars: 1½ ‐ 3 years. 3rd molars: 7 ‐ 10 years b. Enamel Completed 1. 2. 3. 4. 1st permanent molars: 2½ ‐ 3 years Centrals, laterals, and 1st premolars: 4 ‐ 6 years Cuspids, 2nd premolars and 2nd molars: 6 ‐ 8 years 3rd molars: 12 ‐ 16 years c. Crown formation is completed at least three years before eruption. d. Root formation is usually completed three years after eruption 5. DEVELOPMENTAL ANOMALIES Enamel Dysplasia ‐ refers to abnormal enamel development. With this condition, variation in color or morphology can result. a. Amelogenesis Imperfecta ‐ is a hereditary disorder affecting enamel formation of both dentitions. Yellow to brown pitted crowns may result. Teeth are highly susceptible to decay. b. Fluorosis ‐ results in mottled enamel due to high fluoride intake during tooth development. Permanent teeth are involved. Pitted surfaces occur with white to yellow/brown spots. >1 part/million is enough to cause some evidence of this condition. Evidence of fluorosis can occur only during a narrow window during the development process. For example, the “window of vulnerability” for the important permanent maxillary incisors is between 18 and 24 months of age. High Fever ‐ pitted enamel on permanent teeth due to early childhood high fever. Specific crown formation at the time of fever is affected so one can often determine the general age of the patient. c. ResD 517 Occlusion, 2010 Manual Page 172
8-5
d. Focal Hypomaturation ‐ localized chalky white spot on a tooth due to trauma or other interferences with enamel matrix maturation. Generally, this appears in the middle third of the facial or lingual surface. The area is “soft” and susceptible to decay. e. Hypodontia ‐ less than the normal number of teeth are present. Dentinal Dysplasia ‐ refers to abnormal dentin development. This can be due to hereditary or systemic causes. a. Dentinogenesis Imperfecta ‐ is a hereditary disorder affecting dentin formation of both dentition. Teeth have a light blue‐gray to yellow, somewhat opalescent appearance. There is a total absence of pulp chamber and canal. Teeth are “weak.” This anomaly is twice as common as Amelogenesis Imperfecta. b. 6. Tetracycline Stain ‐ is due to antibiotic tetracyclines taken by a pregnant woman, infant, or child. It is generalized in the deciduous dentition, but permanent teeth may be affected. Teeth appear yellow to grayish‐brown. MISCELLANEOUS COMMENTS Most often, the complete primary dentition is in the mouth from age 2 to about age 5½ without any permanent teeth being present. Shortly after the fourth birthday, as the maxilla and mandible grow larger, spaces develop between the primary teeth to facilitate eruption of the larger permanent teeth. Often, a primate space occurs between erupted primary canines and first molars. As the anterior succedaneous teeth begin to erupt, root resorption occurs on the primary tooth being exfoliated. Usually, the permanent anterior will be visible in the mouth within a few months after the loss of its primary precurser. In certain instances, both teeth may be present in the mouth at the same time. In these cases, the permanent most often erupts lingual to the primary tooth. Normally, mandibular primary and permanent teeth erupt earlier than their maxillary counterparts. The widely flared roots of the primary posterior teeth allow their succedaneous counterpart to fit comfortably within the confines of the roots. This helps the permanent tooth erupt into the specific space of its primary counterpart. Normally, mandibular primary and permanent teeth erupt earlier than their maxillary counterparts. ResD 517 Occlusion, 2010 Manual Page 173
8-6
IDENTIFYING CHARACTERISTICS OF THE PRIMARY TEETH 1. Primary teeth have basically the same identifying characteristics as permanent teeth except for the following: GENERAL DIFFERENCES 1. Size ‐ Primary teeth are considerably smaller than permanent teeth in: a. overall size b. crown dimensions ‐ short compared to permanent teeth Primary teeth crowns are said to be “short and squatty,” being proportionately smaller inciso‐cervically than mesiodistally. 2. Color ‐ Primary teeth are generally whiter than permanent teeth. The enamel color is often called “milk white.” 3. Prominent Cervical Ridges ‐ Primary teeth have markedly more prominent cervical ridges. 4. Root Trunks Generally Absent ‐ If present, very small. 5. Molar Roots Widely Flared ‐ This characteristic is most prominent on maxillary molars. 6. Molar Roots Very Thin and Ribbon‐Shaped ‐ These roots are much wider buccolingually than mesiodistally. 7. Roots Often Partially Resorbed 8. No Mammelons on anterior teeth 9. Crowns Frequently Abraded 10. Enamel is thinner in primary teeth 11. Pulp Chamber is relatively larger in comparison to tooth size The following characteristics are listed to help you differentiate primary teeth from each other. Only differences which vary from the same comparisons of permanent teeth to each other are listed. For comparisons not listed, refer to permanent teeth. ResD 517 Occlusion, 2010 Manual Page 174
8-7
A. PRIMARY ANTERIOR TEETH Incisors 1. The primary maxillary central incisor is the only permanent or primary incisor with a mesiodistal diameter greater than its crown height. a. It’s cingulum is prominent and extends further incisally than permanent centrals, sometimes to the very incisal edge. 2. From the incisal view, the lateral incisor is almost circular while the central incisor is more “diamond” shaped. Canines 1. The maxillary canine has crown margins which bulge proximally. This results in it looking “diamond shaped” from the facial or lingual and the mesial cusp ridge is longer than its distal one. 2. The mandibular canine is proportioned opposite to the maxillary canine which makes it look more ”arrow” shaped. THE MORPHOLOGICAL CHARACTERISTICS OF MAXILLARY AND MANDIBULAR FIRST MOLARS ARE DISCUSSED BELOW: 2. PRIMARY MAXILLARY FIRST MOLAR A. Major Characteristics 1. Three Roots 2. Two Cusps ‐ This molar generally has two (MB & ML) cusps although a tiny third cusp (DB) may occasionally be found. A DL cusp rarely occurs. 3. Prominent Buccal Cervical Ridge ‐ This prominent ridge is generally located along the mesial 1/2 of the buccal surface. 4. Heights of Contour ‐ The buccal height of contour is found on the cervical 1/3 of the crown while the lingual height of contour is found on the middle 1/3. 5. MB Cusp Largest 6. Root Sizes ‐ MB root: wider buccolingually than DB root. Lingual root longest and most divergent. ResD 517 Occlusion, 2010 Manual Page 175
8-8
B. Primary Maxillary First Molar 1. Is the smallest molar except its faciolingual dimension. The mandibular first molar is smallest in this dimension. 2. From the buccal aspect, the lingual root is positioned exactly midway between the two buccal roots. 3. From the proximal views, the buccal roots appear straight with a slight buccal flare. The lingual root is banana shaped with a definite lingual flare, but with a noticeable buccal curvature in its apical third. 4. From the occlusal, it looks trapezoidal (straight mesial and distal converge towards the lingual). Primary Maxillary Second Molar 1. Is almost a model of the first permanent maxillary molar. 2. In fact, even anomalies on this molar will very often occur on the first permanent molar. 3. PRIMARY MANDIBULAR FIRST MOLAR A. Major Characteristics 1. Two Roots 2. Four Cusps ‐ In order of decreasing size: MB, ML, DB, DL 3. A Rectangular Occlusal Outline 4. ML Line Angle More Rounded ‐ The ML line angle is more rounded than the other line angles of this tooth. 5. Very Prominent Buccal Cervical Ridge ‐ As on the maxillary first molar, this prominence is located along the mesial 1/2 of the buccal surface. 6. Heights of Contour ‐ Buccal height of contour on cervical 1/3 of the crown; lingual height of contour on middle 1/3. ResD 517 Occlusion, 2010 Manual Page 176
8-9
B. Other Characteristics 1. Buccal Cusps Close Together ‐ The distance between the MB and DB cusps is shorter than the distance between the ML and DL cusps. 2. Transverse Ridge ‐ A transverse ridge extends between the two mesial cusps of this molar. C. Primary Mandibular First Molar 1. Is the most atypical of all the primary molars. 2. ML cusp projects higher occlusally and the MB occupies 2/3 of the crown. The MB cusp of this tooth has a short mesial cusp ridge and a longer distal cusp ridge. 3. Mesial root is longer and thicker. In fact, it is almost as broad buccolingially as the crown. 4. PRIMARY MANDIBULAR SECOND MOLAR A. Is almost a duplicate of the permanent mandibular first molar except for the crown and root proportions. B. Differences from the permanent molar is similar to the maxillary with one primary difference, the permanent molar is broader buccolingually relative to the crown length than the mandibular primary molar. ResD 517 Occlusion, 2010 Manual Page 177
8-10
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8-11
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8-12
PRIMARY TEETH The first molar figures on the following two (5‐12 and 5‐13) pages can be labeled with the terms below to better identify structures and areas. TERMS 1. Bifurcation 17. Lingual groove 2. Buccal groove 18. Lingual root 3. Central groove 19. Mesial contact area 4. Central pit 20. Mesial marginal ridge 5. Cervical line 21. Mesial pit 6. Cervical ridge 22. Mesial root 7. Distal contact area 23. Mesiobuccal cusp 8. Distal groove 24. Mesiobuccal triangular ridge 9. Distal marginal ridge 25. Mesiobuccal root 10. Distal pit 26. Mesiolingual cusp 11. Distal root 27. Mesiolingual triangular ridge 12. Distobuccal cusp 28. Oblique ridge 13. Distobuccal triangular ridge 29. Transverse ridge 14. Distobuccal root 30. Trifurcation 15. Distolingual cusp 31. Cervical area 16. Distolingual triangular ridge 32. Cervix Illustrations of the other primary teeth are provided on pages 5‐12 through 5‐21. ResD 517 Occlusion, 2010 Manual Page 180
8-13
PRIMARY MAXILLARY FIRST MOLAR B ResD 517 Occlusion, 2010 Manual Page 181
8-14
PRIMARY MANDIBULAR FIRST MOLAR S ResD 517 Occlusion, 2010 Manual Page 182
8-15
PRIMARY MAXILLARY CENTRAL INCISOR E ResD 517 Occlusion, 2010 Manual Page 183
8-16
PRIMARY MAXILLARY LATERAL INCISOR D ResD 517 Occlusion, 2010 Manual Page 184
8-17
PRIMARY MAXILLARY CANINE C ResD 517 Occlusion, 2010 Manual Page 185
8-18
PRIMARY MAXILLARY SECOND MOLAR A ResD 517 Occlusion, 2010 Manual Page 186
8-19
PRIMARY MANDIBULAR CENTRAL INCISOR P ResD 517 Occlusion, 2010 Manual Page 187
8-20
PRIMARY MANDIBULAR LATERAL INCISOR Q ResD 517 Occlusion, 2010 Manual Page 188
8-21
PRIMARY MANDIBULAR CANINE R ResD 517 Occlusion, 2010 Manual Page 189
8-22
PRIMARY MANDIBULAR SECOND MOLAR T ResD 517 Occlusion, 2010 Manual Page 190
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Using numbers 1 through 10 and 1 through 16 in increasing order, mark on the diagrams below the approximate sequence in which the corresponding primary or permanent tooth erupts. Use the eruption charts on page 9‐22 to provide the answers. Note general patterns in the eruption sequence of primary and permanent teeth. ResD 517 Occlusion, 2010 Manual Page 191
8-24
ResD 517 Occlusion, 2010 Manual Page 192
8-25
SELF TEST 1. Which of the following are true concerning primary teeth? 1. generally short and squatty 2. twenty in total number 3. enamel thin and pulp chambers large 4. roots narrow labiolingually and broad mesiodistally 5. prominent cervical ridges a. 2, 3, 4, 5 b. 1, 2, 3, 5 c. all of the above d. none of the above 2. A primary tooth which is similar in anatomy to a permanent maxillary first molar is a: a. maxillary first molar b. maxillary second molar c. mandibular first premolar d. mandibular second molar e. mandibular first molar 3. Which of the following primary teeth are significantly different from the permanent teeth in their crown anatomy? a. mandibular first molars b. mandibular second molars c. maxillary first molars d. maxillary second molars 4. In which primary tooth is the mesial fossa most distinctly separated from the major part of the occlusal table by a transverse ridge? a. maxillary second molar b. mandibular second molar c. mandibular first molar d. maxillary first molar e. none of the above ResD 517 Occlusion, 2010 Manual Page 193
8-26
5. 6. 7. Identify I on the adjacent figure: a. b. c. d. ML cusp of tooth A MB cusp of tooth B DL cusp of tooth A DL cusp of tooth B Identify I on the adjacent figure. a. b. c. d. e. ML cusp on t MB cusp on t ML cusp on S MB cusp on S DL cusp on S Which of the following statements are correct concerning the eruption of the permanent teeth? 1. 2. 3. 4. 5. The first permanent tooth to erupt is always the mandibular central incisor. Eruption charts are a statistical average from which there is normal deviation. With the exception of the bicuspids, mandibular teeth erupt ahead of their maxillary counterparts. There are usually some teeth erupting each year between 6 and 12 years of age. Most thirteen year old children would have 28 permanent teeth. a. b. c. d. e. 1, 2, and 3 1, 4, and 5 2, 3, and 5 3, 4, and 5 2, 3, 4, and 5 ResD 517 Occlusion, 2010 Manual Page 194
8-27
8. 9. 10. Arrange the following primary teeth in their general sequence of eruption: 1. 2. 3. 4. 5. mandibular first molar maxillary canine maxillary central incisor mandibular central incisor maxillary second molar a. b. c. d. 1, 2, 3, 4, 5 3, 4, 2, 1, 5 2, 3, 1, 5, 4 4, 3, 1, 2, 5 Arrange the following permanent teeth in their general sequence of eruption: 1. mandibular first molar 2. maxillary third molar 3. mandibular canine 4. maxillary first premolar 5. maxillary canine a. b. c. d. 1, 3,4, 2, 5 1, 3, 4, 5, 2 1, 2, 3, 4, 5 4, 2, 3, 1, 5 The cervical deflecting ridge on primary molars is most prominent on which surface? a. b. c. d. e. buccal lingual mesiobuccal distal occlusal ResD 517 Occlusion, 2010 Manual Page 195
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LABORATORY EXAMINATION #1 Adjustment must be completed by 3:30 PM. BE SURE TO HAVE AN INSTRUCTOR INITIAL OR STAMP YOUR GRADING FORM IN THE PROPER LOCATION BEFORE YOU START. Set the right and left angle of eminence to 25°. When finished with the case, place your articulator with the adjusted casts and your evaluation form on your bench number in the “grading room.” BE SURE TO HAVE YOUR STUDENT SECRET ID# ON YOUR ARTICULATOR AND ON THE EVALUATION FORM. Your finished case should be turned in with your articulator locked in centric. Part of the evaluation for “finish of adjustment” will be to have a neat and clean articulator and mounted casts. Small articulator markings on the occlusal surfaces are permissible. Your graded form and articulator may be placed in your lab mail box. Working disclusion on first premolar on the working side is acceptable with or without canine support. First premolar disclusion in protrusive is acceptable until anteriors pick up. ResD 517 Occlusion, 2010 Manual Page 196
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Mounting correct __________ Student Secret ID # _______ Evaluation for Adjusted Occlusion: Case Floren STUDENT MAXIMUM TOTAL INSTRUCTOR COMMENT 1. DEGREE & INITIALDIRECTION 5 OF C0/MIP SLIDE ANSWER: ______ (i.e., amount of vertical. lateral, and/or horizontal slide) POSSIBLE INCLINES INVOLVED 5 (“A, B and/or C”) ANSWER: ____________ 2. INITIAL CO CONTACT 5 (Refers to teeth and position) ANSWER: _________ 10 3. Initial “MIP” mark by STUDENT = Deduct all points if initial and ending MIP marks not correct (beyond 0.5 degree of initial mark) Ending “MIP” mark By FACULTY= ****Instructor to check first three sections before continuing**** 4. CO/MIP ADJUSTMENT 5 REMOVED INTERFERENCES: ‐ 2 for perceptible slide NUMBER OF POSTERIOR CONTACTS 15 Subtract 2 points for each set of missing contacts. You must have one set of centric contacts for each pair of teeth. Subtract 2 points for each set of contacts which are the wrong size or in the wrong location. 5. PROTRUSIVE MOVEMENT Removed interferences (subtract 2for each remaining interference or uneven anterior contact) 6. LEFT LATERAL MOVEMENT* REMOVED WORKING INTERFERENCES Subtract 3 for each remaining. REMOVED NONWORKING INTERFERENCES Subtract 5 for each remaining. 7. RIGHT LATERAL MOVEMENT* REMOVED WORKING INTERFERENCES: Subtract 4 for each remaining. REMOVED NONWORKING INTERFERENCES Subtract 5 for each remaining. 8. TOOTH CONTOUR, ANATOMY & FINISH After occlusal adjustment, subtract 4 points for each unsatisfactory tooth. 9. NEATNESS (subtract 10 points if unacceptable) TOTAL
*Nonworking side disclusion will result in loss of all points. ResD 517 Occlusion, 2010 Manual Page 197
10 10 10 15 10 15 10 125 WEEK 9 LECTURE PARAFUNCTIONAL HABITS/SPLINTS LABORATORY EXAM #2 FINISH BY 3:30 PM ResD 517 Occlusion, 2010 Manual Page 198
Major TMD Symptoms
• Muscle pain
• Tooth pain
• Headache
• Poor sleep
• Anxiety
• Bruxing / clenching
ResD 517 Occlusion, 2010 Manual Page 199
Terminology
THE GLOSSARY OF PROSTHODONTIC TERMS (2005)
Parafunction: disordered or perverted function
Bruxism
• 1: the parafunctional grinding of teeth
• 2: an oral habit consisting of involuntary rhythmic or
spasmodic nonfunctional grinding, or clenching of
teeth, in other than chewing movements of the
mandible, which may lead to occlusal trauma
(Clenching: The pressing and clamping of the jaws and teeth together
frequently associated with acute nervous tension or physical effort)
ResD 517 Occlusion, 2010 Manual Page 200
Bruxism
(Teeth grinding and clenching)
• People can clench and grind without being aware of it during both the day
and night (diurnal/nocturnal bruxism)
• Sleep-related bruxism is often the bigger problem because it is harder to
control
• The cause of bruxism is not completely agreed upon
• Daily stress may be the trigger in many people
• Some people probably clench their teeth and never feel symptoms
ResD 517 Occlusion, 2010 Manual Page 201
Bruxism is complicated mix of factors
•
•
•
•
•
•
How much stress you are under
How long and tightly you clench and grind
Whether your teeth are misaligned
Your posture
Your ability to relax
Your sleeping habits
Each person is different!
ResD 517 Occlusion, 2010 Manual Page 202
An examination can rule out other disorders that
may cause similar jaw pain or ear pain, including:
• Dental disorders
• Ear disorders such as ear infections
• Problems with the temporomandibular joint
(TMJ)
You may also have a history of significant stress
and tension.
ResD 517 Occlusion, 2010 Manual Page 203
Biologic Determinants
• Several structural components of the masticatory system:
– alveolar and cranial bone,
– the temporomandibular joint (TMJ) including its disc and associated
ligaments,
– the dentition (both pulp and periodontium), and
– the masticatory muscles (including ligaments and tendons and other
connective tissues).
• These physiologic determinants include
–
–
–
–
–
cardiovascular,
endocrine,
immunologic,
metabolic, and
neural influence(both peripheral [eg, receptors, nerve fibers] and
central nervous system [CNS])
ResD 517 Occlusion, 2010 Manual Page 204
Muscle Pathology / Myalgia
Engrams: Protective neurologic reflexes
Engrams: As deflective contacts increase, engram patterns
increase, which increases muscle activity / fatigue.
Further contraction is painful and leads to Muscle Spasm.
ResD 517 Occlusion, 2010 Manual Page 205
Dysfunction
Disease of the temporomandibular apparatus. 2nd ed. Editors: Morgan, House, Hall, Vamvas
CV Mosby 1982
ResD 517 Occlusion, 2010 Manual Page 206
Adaptive Potential
The masticatory system has a remarkable capacity to adapt to these various influences
• Some examples of such “positive” responses to mechanical loading, infection, or
trauma of craniofacial tissues; they include TMJ remodeling, reparative dentin, and
a host of protective reflexes (eg, nociceptive jaw opening)
– Nociceptors can detect mechanical, thermal or chemical changes, above a set
threshold and transmits signals to the brain. Nociception triggers a variety of
autonomic responses.
•
•
The threshold of the adaptive potential of the tissues may be exceeded and be
associated with a number of “negative” responses.
These negative outcomes would include such pathophysiologic manifestations as
chronic pain (eg, temporomandibular disorders [TMD]) that is thought to reflect
neuroplastic changes manifesting increased nociceptive responses, damage or
disease of TMJ tissues (eg, disc tear or perforation, osteoarthritis) or the teeth (eg,
dental caries, periodontal disease), maladaptive behavior (eg, bruxism), and
neurologic disorders (eg, dyskinesia: involuntary movement).
– All these outcomes can be associated with serious impairment of the function
of the masticatory system and thereby influence the occlusal interface.
ResD 517 Occlusion, 2010 Manual Page 207
Methods to Assess Parafunction
There are several ways to assess parafunctional activity. The reliability of
these methods is questionable.
• Questionnaires are the most commonly used method.
• Clinical examination and observations of tooth wear are also widely used
in clinical settings.
• The wear on occlusal splints and interarch contacts and force are
measured.
Electromyographic recording of the masticatory muscles during sleep is a
method to assess bruxism.
Polysomnography in a sleep laboratory is currently considered the most
specific method of analysis. It is expensive, and the subject’s
parafunctional activity might be affected by the unfamiliar conditions of
the sleep laboratory.
ResD 517 Occlusion, 2010 Manual Page 208
Psychological factors, such as stress, may play important roles in TMD!
Kanehira et al.,2008
• Question 1: Do you sometimes have difficulties
in opening your mouth?
• Question 2: Are you aware of noise during opening and
closing your mouth?
• Question 3: Do you experience pain in or around the
jaw joints during opening and closing your mouth?
• Question 4: Do you clench your teeth in the day-time
or at work?
• Question 5: Do you clench or grind your teeth while
asleep?
• Question 6: Do you generally feel stress?
ResD 517 Occlusion, 2010 Manual Page 209
Parafunction and Tooth Wear
Tooth wear is associated with many factors, and
parafunctional activity can cause tooth wear.
However, the presence of attrition cannot be used as a
criterion to define the bruxer group.
The incidence and severity of tooth wear are thought
to increase with age. The prevalence of nocturnal
grinding decreases with age after 50 years of age.
Seligman DA et al., 1988; Pintado MR et al., 1997; Ekfeldt A et al., 1990.
ResD 517 Occlusion, 2010 Manual Page 210
Tooth Wear
• Attrition: the mechanical wear resulting from mastication or
parafunction, limited to contacting surfaces of the teeth
– wear facet : any wear line or plane on a tooth surface
caused by attrition
• Abrasion: an abnormal wearing away of the tooth substance
by causes other than mastication
• Erosion: in dentistry, the progressive loss of tooth substance
by chemical processes that do not involve bacterial action
producing defects that are sharply defined, wedge-shaped
depressions often in facial and cervical areas
ResD 517 Occlusion, 2010 Manual Page 211
Parafunction and Occlusion
The occlusal force during nocturnal bruxism can easily exceed the
level during normal function such as chewing.
Occlusal interference has historically been regarded as a cause of
bruxism, evidence countering this historic concept has been
reported:
-No significant difference in occlusion is seen in bruxism and
control groups;
-No difference in the effect on bruxism by an occlusal splint
covering the occlusal surface of the dentition or not.
Rugh JD et al., 1984; Ichiki R et al., 1999.
ResD 517 Occlusion, 2010 Manual Page 212
Clinical signs and symptoms
associated with occlusal trauma
• Tooth mobility
• Fremitus
– Periodontal fremitus occurs in either of the alveolar
bones when an individual sustains trauma from
occlusion. It is a result of teeth exhibiting at least
slight mobility rubbing against the adjacent walls of
their sockets.
• Tooth migration
• Pain
• Tooth Wear
ResD 517 Occlusion, 2010 Manual Page 213
Types of occlusal trauma
• There are two types of occlusal trauma, primary and secondary.
Primary occlusal trauma
• Primary occlusal trauma occurs when greater than normal occlusal forces
are placed on teeth, as in the case of parafunctional habits, such as
bruxism or various chewing or biting habits, including but not limited to
those involving fingernails and pencils or pens.
• Primary occlusal trauma will occur when there is a normal periodontal
attachment apparatus and, thus, no periodontal disease.
Secondary occlusal trauma
• Secondary occlusal trauma occurs when normal occlusal forces are placed
on teeth with compromised periodontal attachment, thus contributing
harm to an already damaged system. As stated, secondary occlusal trauma
occurs when there is a compromised periodontal attachment and, thus, a
pre-existing periodontal condition.
ResD 517 Occlusion, 2010 Manual Page 214
Parafunction
and
Myofascial Pain/Temporomandibular Disorders
There is no strong evidence for a cause-and-effect relationship between
bruxism and myofascial pain/TMD. Dao TT et al., 1994; Magnusson T et al.,
2000.
There are many reports on the prevalence of TMD, and most agree that
TMD is more prevalent in women than in men. By contrast, the studies on
gender differences in bruxism do not show a constant result—while some
studies reported no gender difference in the incidence of bruxism (Lavigne
GJ, Montplaisir JY.1994), others reported diverse gender differences (Gross
AJ et al., 1988).
A twin study with a large sample size reported that more women have
bruxism than men, and that the incidence of bruxism increases with age
from 30 to 50 years (Hublin C et al., 1998
ResD 517 Occlusion, 2010 Manual Page 215
Relationship between jaw injury, third molar removal, and
orthodontic treatment and TMD symptoms…Akhter R et al., 2008
• TMD symptoms were significantly associated with
jaw injury.
• Experience of third molar removal was significantly
associated with TMD.
• No association was found between orthodontic
experience and TMD.
ResD 517 Occlusion, 2010 Manual Page 216
Disc Displacement Disorders (DDR)
Disc displacement disorders are now classified into the following
subtypes (Dworkin and LeResche, 1992):
(1) Disc displacement with reduction (DDR): The disc is displaced
from its original position between the condyle and the eminence
to an anterior and medial or lateral position, but reduces on full
opening, usually resulting in a noise.
(2) Disc displacement without reduction (DDWR), with limited opening
(3) Disc displacement without reduction, without limited opening
ResD 517 Occlusion, 2010 Manual Page 217
Disc Displacement Disorders (DDR)
Disc displacement disorders are now classified into the following
subtypes (Dworkin and LeResche, 1992):
(1) Disc displacement with reduction (DDR)
(2) Disc displacement without reduction (DDWR), with limited
opening: a condition in which the disc is displaced from its original
position between the condyle and the eminence to an anterior and
medial or lateral position, associated with limited mandibular
opening.
(3) Disc displacement without reduction, without limited opening:
same as #2 but not associated with limited mandibular opening.
ResD 517 Occlusion, 2010 Manual Page 218
Applications of Oral Splints
•
•
•
•
•
•
•
•
•
•
•
Temporomandibular disorders
Myofascial pain
Disc displacement disorders
Arthritides of the
temporomandibular joints
Headaches/migraine
Motor and sleep disorders
Sleep bruxism
Sleep apnea
Parkinson's disease
Oral tardive dyskinesia
Occlusal rehabilitation
ResD 517 Occlusion, 2010 Manual Page 219
•
•
•
•
•
•
•
•
•
•
•
•
Orthodontics
Periodontics
Prosthodontics
Phantom bite
Others (Prevention of tissue
trauma, habits)
Diurnal bruxism
Sports
Cheek or fingernail biting
Electroconvulsive therapy
Lip commissure burn
Esophageal reflux
Sinusitis
Mechanisms Proposed for Oral Splint Effectiveness
• Myofascial pain
–
–
–
–
–
–
Change in the vertical dimension of occlusion
Repositioning of the temporomandibular joints
Decrease in the level of muscle activity
Reducing bruxism???
Removal of occlusal interferences
Enhancing the patient's cognitive awareness
• Disc displacement disorders
– "Recapturing" the disc
– 'Unloading" the joints
• Arthritis/arthralgia
– "Unloading" the joints
• Sleep bruxism
– Removal of occlusal interferences
– Change in muscle activity
– Modification of patient's habits
ResD 517 Occlusion, 2010 Manual Page 220
Synonyms for Oral Splints Used in the Treatment of
Temporomandibular Disorders and Bruxism
•
•
•
•
•
•
•
•
•
•
•
•
Anterior deprogramming splint
Anterior positioning splint
Anterior repositioning splint
Bite splint
Buccal separator
Disclusion splint
Distal push splint
Flat occlusal splint
Hawley splint
Herbst splint
Hydrostatic splint
Levandoski splint
ResD 517 Occlusion, 2010 Manual Page 221
• Mandibular advancing repositioning
splint
• Mandibular orthopedic repositioning
appliance
• Mandibular repositioning splint
• Michigan occlusal splint
• Muscle deprogramming splint
• Night guard
•
•
•
•
•
•
•
Occlusal correcting splint
Occlusal disengagement splint
Orthopedic interocclusal appliance
Pain release splint
Pivoting appliance
Protrusive positioners
Stabilization splint
All Splints Will:
• Alter Occlusal Condition
• Alter Condyle Position
• Increase Vertical Dimension
• Induce Cognitive Awareness
• Placebo Effect (30% of effect?)
• Increase Peripheral Input to CNS & alter the Engram pattern
• The lateral pteryogoid muscle is what pulls the jaw from side-to-side and
forwards, and is the muscle that experiences relief when splint therapy is
successful!!
ResD 517 Occlusion, 2010 Manual Page 222
splint therapy
Splint therapy may be defined as the art and
science of establishing neuromuscular harmony
in the masticatory system and creating a
mechanical disadvantage for parafunctional
forces with removable appliances.
A properly constructed splint supports a
harmonious relation among the muscles of
mastication, disk assemblies, joints, ligaments,
bones, teeth, and tendons.
ResD 517 Occlusion, 2010 Manual Page 223
SPLINT TYPES AND FUNCTIONS
All splints are classified as either permissive or
nonpermissive.
• A permissive splint allows the teeth to move on
the splint unimpeded, which in turn allows the
condylar head and disk to function anatomically.
• A nonpermissive splint has a ramp or
“indentations” that position the mandible
inferiorly and anteriorly and secure it there.
ResD 517 Occlusion, 2010 Manual Page 224
permissive splints
stabilization splints (flat plane, Tanner,
bite planes (anterior jigs, Lucia jig, anterior
Deprogrammer)
superior repositioning, and centric relation
[CR])
Soft splints and hydrostatic splints could be considered pseudo-permissive splints, as
their functions are extremely different than those of the permissives.
ResD 517 Occlusion, 2010 Manual Page 225
nonpermissive splint
repositioning splint (anterior repositioning appliance [ARA])
ResD 517 Occlusion, 2010 Manual Page 226
Functions of splints
Properly fabricated splints have at least 6 functions:
(1)
(2)
(3)
(4)
(5)
(6)
to relax the muscles,
to allow the condyle to seat in CR,
to provide diagnostic information,
to protect teeth and associated structures from bruxism,
to mitigate periodontal ligament proprioception, and
to reduce cellular hypoxia levels.
Most important: DO NOT HARM!!
ResD 517 Occlusion, 2010 Manual Page 227
1-Relaxing the muscles
• Tooth interferences to the CR arc of closure hyperactivate the
lateral pterygoid muscle (Ramford S, Ash M. 1983);
• Posterior tooth interferences during excursive mandibular
movements cause hyperactivity of the closing muscles (Manns
A et al., 1993);
• The elimination of posterior excursive contacts by anterior
guidance significantly reduces elevator muscle hyperactivity
(Williamson EH, Lundquist DO. 1983).
ResD 517 Occlusion, 2010 Manual Page 228
1-Relaxing the muscles
• A splint with equal-intensity contacts on all of the teeth, with
immediate disclusion of all posterior teeth by the anterior teeth
and condylar guidance in all movements, will relax the elevator and
positioning muscles.
• The more balanced and frictionless the splint, the better the
opportunity for reducing muscle hyperactivity. A muscle that is
fatigued through ongoing muscle hyperactivity can present with
pain. If the hyperactivity is stopped, the pain caused by this activity
usually will disappear (Mao J et al., 1993).
• Occlusal splints alters the occlusion reversibly.
• Acute or chronic symptoms of muscle hyperactivity were lessened
significantly with 24-hour splint wear (Okeson JP et al., 1982).
ResD 517 Occlusion, 2010 Manual Page 229
2-Allowing the condyle to seat in centric relation
•
For the condyle to completely seat under the disk in this anterosuperior position, the
lateral pterygoid must completely relax because of its attachment to the disk through
the superior belly.
•
If this muscle stays contracted after hyperactivity, the disk will be pulled anteromedially
(along the direction of the muscle origin) and will not seat completely over the condyle.
•
When the disk is loaded in a power bite or through parafunctional activities, the disk,
attached muscle, condylar head, condylar ligaments, and retrodiscal tissues can sustain
excess force loads and be damaged if the condyle/disk assembly is not properly related
to the fossa.
•
Chronic and acute overloading of the condyle/disk assembly when it is out of its normal
physiologic position contributes greatly to temporomandibular disorders.
•
Lateral deviation from the CR can lead to bone changes in the condyles and can lead to
cartilage breakdown and arthritis in the condylar heads
ResD 517 Occlusion, 2010 Manual Page 230
2-Allowing the condyle to seat in centric relation
Temporomandibular joints are susceptible to overload.
•
•
•
Centric relation is the optimal arrangement of joint, disk, and muscle.
It is not muscle braced position.
This position is consistently repeatable because of the boney stop for the
condyle/disk assembly as the condyle hinges on its axis through the medial pole.
•
A person can function if the arrangement is anterior to this position, but the
condyle and disk must be allowed by the dentition to return unimpeded to
perform their load-bearing function.
•
Splint therapy must use CR as the ultimate treatment position except in situations
where inflammation of the joint makes this position uncomfortable.
•
The patient may use his/her anteroinferior condylar position until the
inflammation subsides (approximately 7 days) and be reintroduced to the CR
position before permanent changes in the muscle, disk, or supporting tissues take
place.
ResD 517 Occlusion, 2010 Manual Page 231
3-Providing diagnostic information
•
Wear patterns that exist on the splint are reintroduced into the natural dentition
when the splint is not worn. A horizontal “grazing” pattern (COW) would indicate
a different occlusal scheme than a vertical “chopping” bite (RAT).
•
Information gained from wear patterns on splints helps determine occlusal
configurations, material choice, cusp heights and shapes, guidance angulations,
axial loads, and the envelope of function.
ResD 517 Occlusion, 2010 Manual Page 232
3-Providing diagnostic information
If a patient rapidly becomes comfortable with a splint, it may be an indication
that the disorder is muscular.
If symptoms worsen with permissive splint wear, this may indicate an internal
derangement (disk) problem (perhaps caused by free reign of the condylar head
back to the retrodiscal tissues without housing by the disk) or an error in the
initial diagnosis.
ResD 517 Occlusion, 2010 Manual Page 233
4-Protecting teeth and associated structures
from bruxism
•
A CR–balanced nocturnal permissive splint can protect teeth from extensive wear
caused by parafunctional activity (bruxism).
•
A splint not balanced in CR will show increased localized wear (usually in the
posterior of the splint).
•
The sleeper’s attempt to get to CR with the help of the elevator muscles is
interrupted by the splint.
•
Splints do not stop bruxism but do redistribute the load borne by the teeth and
masticatory system.
ResD 517 Occlusion, 2010 Manual Page 234
5-Mitigating periodontal ligament
proprioception
•
Unlike the six exteroceptive senses (sight, taste, smell, touch, hearing, and balance) by which
we perceive the outside world, and interoceptive senses, by which we perceive the pain and
the stretching of internal organs, proprioception is a third distinct sensory modality that
provides feedback solely on the status of the body internally. It is the sense that indicates
whether the body is moving with required effort, as well as where the various parts of the
body are located in relation to each other (Wikipedia).
ResD 517 Occlusion, 2010 Manual Page 235
5-Mitigating periodontal ligament
proprioception
Proprioceptive fibers contained in the periodontal ligaments of each
tooth send nerve messages to the central nervous system. They indicate
the amount of force on individual teeth and can trigger muscle patterns
to protect teeth from overload. A splint can balance proprioception and
even lessen it to mitigate proprioceptive output.
•
Periodontal afferent feedback (proprioception) must be responsible for
this rapid adaptation of the muscles (Hellsing G., 1984).
•
Stimulation of pressure receptors in the periodontal membrane can lead
to a jaw-opening reflex (Hannam AG et al., 1981). This helps clarify why
the teeth must be kept in balance with the condyle/disk assembly to
maintain neuromuscular harmony in the associated muscles.
ResD 517 Occlusion, 2010 Manual Page 236
6-Reducing cellular hypoxia levels
•
Pressure was measured in the superior joint
space of patients with articular disk
displacements. When clenched maximally,
recorded pressures reached up to 200 mm Hg.
•
When a flat plane appliance was placed, no
significant pressure was recorded. This lends
credence to stabilization splint therapy from a
molecular point of view (Nitzan DW 1994).
Anterior displacement of the intra-articular disk without reduction on attempted mouth opening. The displaced disk acts as a barrier and
prevents full translation of the condyle.
McCarty W: Diagnosis and treatment of internal derangements of the articular disc and mandibular condyle. In Solberg WK, Clark GT [eds]:
ResD 517 Occlusion,
Manual Page
237 Diagnosis and Treatment. Chicago, Quintessence, 1980, p 151
Temporomandibular
Joint2010
Problems:
Biologic
The characteristics of a successful splint should include:
•
stability;
•
balance in CR;
•
equal intensity stops on all teeth;
•
immediate posterior disclusion;
•
a “skating rink” surface;
•
smooth transitions in lateral,
•
protrusive, and extended lateral excursions (crossover);
•
comfort during wear;
•
reasonable esthetics.
Patient compliance contributes to splint success.
ResD 517 Occlusion, 2010 Manual Page 238
SPLINT CHARACTERISTICS
•
Immobile surface prepared for heavy forces from all directions provides the stability.
•
A slight undercut to ensure a firm fit.
•
The patient should feel no sense of tightness on any of the teeth; if that is not the case, tooth
hypersensitivity usually will follow. (Think of starting with parafunction!)
•
The length of the splint on the lingual and buccal is dependent on the need for retention as a
result of tooth size and shape.
•
The shorter and thinner the splint is on the lingual, the better the patient compliance, the
more distinct the speech, and the more comfortable the tongue posture will be.
•
The buccal flanges must be thick enough to be strong but not impinge on the neutral zones.
Thinness can create discomfort or lip “trapping.”
ResD 517 Occlusion, 2010 Manual Page 239
SPLINT CHARACTERISTICS
•
Fabrication in a hard, heat-polymerized acrylic resin will facilitate the establishment and
adjustment of contact points.
•
Orthodontic acrylic resin is userf riendly, easy to adjust, and soft enough not to hyperactivate
periodontal ligaments. It also can be polished to a high luster for a low-friction surface.
•
Methyl methacrylates are relatively easy to work with but maintain a strong odor and exhibit
a granular composition that is harder to polish and adjust.
•
The soft rubber resilient materials used for sports guards possess none of the characteristics
important to splint therapy and have no effective use in this arena.
•
What to do with patients who have allergies to different resins materials? .
ResD 517 Occlusion, 2010 Manual Page 240
Methyl Methacrylate
Diethyl Phthalate
SPLINT CHARACTERISTICS
•
Maxillary and mandibular appliances have completely different designs, though
they function the same.
•
All teeth contact in CR on a maxillary appliance.
•
A mandibular appliance often will have cuspid-to-cuspid contact in CR, with the
maxillary anterior teeth not touching.
BECAUSE:
• Many TMD patients have a significant horizontal overlap; to extend the
mandibular acrylic resin to contact the maxillary teeth would be unsightly,
physically uncomfortable, and unnecessary.
ResD 517 Occlusion, 2010 Manual Page 241
SPLINT CHARACTERISTICS
•
Anterior contact area must be balanced by having the patient move in protrusive,
lateral, and mediolateral movements, marking the areas, and establishing anterior
guidance principles.
ResD 517 Occlusion, 2010 Manual Page 242
SPLINT CHARACTERISTICS
•
Mandibular appliances are the popular choice for active patients who wear splints 24 hours
per day, as they do not show or affect speech as much as maxillary appliances.
•
On the other hand, the maxillary appliance is an attractive choice for night wear, as all of the
teeth are in contact with equal intensity, and the 13% of the population that bruxes
isometrically will have these forces more equally balanced.
•
Other reasons for the choice of one arch over the other include arch irregularities, the
patient’s profession, and the potential for gagging.
•
It is appropriate for the patient to have a mandibular appliance for day wear and a maxillary
appliance for the night
ResD 517 Occlusion, 2010 Manual Page 243
Anterior repositioning splints
• Anterior repositioning splints were originally designed to “recapture” the
disks by protruding the mandibular jaw forward until the condyle popped
back on the disk and “locked” it into position.
•
• The clicking that initially stopped with these appliances returned in a large
percentage of the patients, which indicates that the intended function of
anterior repositioning splints was not accomplished (Lundh H and
Westesson PL 1989).
• In patients who did not experience further clicking, the disk may have
been permanently pushed out to the side on the lateral pole instead of
recapturing the disk.
ResD 517 Occlusion, 2010 Manual Page 244
Anterior repositioning splints
Success (???) in alleviating pain with anterior repositioning splints can be impressive.
WHY is it happening with this splint?
EXPLAINATION: If the jaw is brought down and forward, the condyle will not impinge on
the inflamed retrodiscal tissues, which are a major source of pain.
•
Anterior repositioning splints tend to introduce posterior open bites!!!! in long-term
wearers (when the appliance does not cover the anterior teeth).
•
Orthodontics or restorative dentistry is required to close the teeth into their new
anteroinferior musclebraced position.
ResD 517 Occlusion, 2010 Manual Page 245
CHOOSING THE CORRECT SPLINT
Determination of the appropriate type of splint therapy depends on the specific diagnosis of
the temporomandibular disorder and a thorough understanding of the anatomy of the
condyle/disk complex.
Muscle incoordination is determined by muscle palpation, joint loading, range-of-motion measurements,
joint palpation, occlusal evaluation.
Patients present with
•
painful symptoms in the facial muscles,
•
headaches,
•
limited ranges of motion,
•
frequent joint inflammation, and
•
occlusal interferences to CR;
•
infrequent clicking on jaw movement also may be present.
Anatomic asymmetry is reversible if caught in time and treated with bite plane therapy or permissive
splint therapy in Phase I (reversible treatment) and with appropriate Phase II therapy (additive or
subtractive occlusal therapy, restorative dentistry, orthodontics, maxillofacial surgery, and segmental
alveolar surgery) to restore balance from/to the CR position.
ResD 517 Occlusion, 2010 Manual Page 246
CHOOSING THE CORRECT SPLINT
•
Muscle and disk incoordination has the same signs and symptoms as muscle incoordination except
reciprocal clicking or a history of reciprocal clicking that stops.
•
Diagnosis may include sagittally corrected tomograms.
•
Patients often present with the medial pole of the condyle intact under the disk with the lateral pole of
the disk damaged from loading or stretching and subsequent ligament laxity.
•
Most symptoms may be reversible if caught in time, though the reversibility of clicking depends on the
shape of the distorted disk and the fibrosis of the lateral pterygoid muscle.
•
Treatment usually includes permissive splint therapy and Phase II therapy for stabilization because of the
weak ligament structure.
With advanced muscle and disk incoordination, symptoms may be the same as in
previous stages, though jaw locking, painful joint noises, and increases in pain with splint
therapy may be evident.
These patients often have a long history of joint noises without pain that have become
painful. Pain on loading with bimanual manipulation is evident and may be extreme.
Surgical intervention might be necessary depending on the location and degree of
displacement of the disk. These stages are irreversible but may be managed to a painfreeResD
state
with2010appropriate
medications, splint therapy, and Phase II therapy.
517 Occlusion,
Manual Page 247
SPLINT DESIGN WITH FUNCTIONAL CONSIDERATIONS
•
The splint must allow the condyle to achieve the CR position. This can be achieved
with bimanual manipulation.
•
The splint could be considered a set of teeth with occlusal interferences.
Therefore, the splint must be continually monitored and adjusted.
•
When the muscle relaxes and/or inflammation subsides, the position of the teeth
on the splint changes.
•
When readjustment on the splint to the CR position is accomplished, the teeth and
condyle/disk assembly achieve neuromuscular harmony.
•
The majority of splint wearers need to be seen more often than every 2 weeks for
initial adjustments.
•
After 3 months with no changes on the splint, a comfortable musculature, and no
pain on loading, the patient is ready for evaluation of phase II therapy.
ResD 517 Occlusion, 2010 Manual Page 248
What is Phase II therapy?
•
If a bite splint does not relieve pain: Phase II therapy?
•
Many patients do not require Phase 2 treatment.
Phase II therapy includes:
e.g.
• Occlusal equilibration
• Orthodontics
• Crowns
• Jaw surgery - need to have orthodontic treatment before surgery.
ResD 517 Occlusion, 2010 Manual Page 249
SPLINT FABRICATION
•
Laboratories often provide a prosthesis from a maximum intercuspation (MI)
occlusion that presents high on the distal of the splint and ends up having a hole
ground all the way through the acrylic resin in an attempt to balance the occlusal
relation.
•
Without an accurate CR occlusal record, accurate casts of all occluding surfaces,
and a reliable face-bow transfer, seating time will be longer and occasionally
impossible because of excessive or inadequate acrylic resin.
•
With precise laboratory instruction and records, seating and adjusting should take
no longer than 10 minutes.
ResD 517 Occlusion, 2010 Manual Page 250
WHAT SPLINTS CANNOT DO
Splints cannot do 3 basic things:
•
unload the joint,
• prevent bruxism, or
• “heal” the patient
•
Some authors and lecturers have stated that splints function to unload the joints and
therefore take pressure off the disk. This theory has been disproved and cannot be explained
anatomically or physiologically (Kuboki T et al., 1999).
•
The elevator muscles are located behind the most posterior tooth and therefore ensure that
the joint will always be loaded when the elevators contract.
•
Splints do not prevent bruxism; they balance the force distribution to the entire masticatory
system. They can decrease the frequency but not the intensity of bruxing episodes.
•
Splints also do not heal patients; they give patients the opportunity to heal themselves. The
patient pays not for the fabrication of a splint only but also for the care, skill, and judgment of
the practitioner whose goal is to enable healing through appropriate design, monitoring, and
adjustment.
ResD 517 Occlusion, 2010 Manual Page 251
What Do We Not Know?
• Biologic reactions to mechanical stress and trauma
• Immunologic influences and neuroimmune interactions
• Molecular, physiologic, and genetic basis of chronic
pain
• Molecular, physiologic, and genetic basis of the aging
process
• Molecular, physiologic, and genetic basis of gender
differences
• Neural basis of maladaptive behavior and neurologic
dysfunction
• the adaptive capacity of the masticatory system
ResD 517 Occlusion, 2010 Manual Page 252
9-1
LABORATORY EXAMINATION #2 Adjustment must be completed by 3:30 PM. BE SURE TO HAVE AN INSTRUCTOR INITIAL OR STAMP YOUR GRADING FORM IN THE PROPER LOCATION BEFORE YOU START. Set the right and left angle of eminence to 25°. When finished with the case, place your articulator with the adjusted casts and your evaluation form on your bench number in the “grading room.” BE SURE TO HAVE YOUR STUDENT SECRET ID# ON YOUR ARTICULATOR AND ON THE EVALUATION FORM. Your finished case should be turned in with your articulator locked in centric. Part of the evaluation for “finish of adjustment” will be to have a neat and clean articulator and mounted casts. Small articulator markings on the occlusal surfaces are permissible. Your graded form and articulator may be placed in your lab mail box. Working disclusion on first premolar on the working side is acceptable with or without canine support. First premolar disclusion in protrusive is acceptable until anteriors pick up. ResD 517 Occlusion, 2010 Manual Page 253
9-2
Mounting correct __________ Student Secret ID # _______ Evaluation for Adjusted Occlusion: Case Powell STUDENT MAXIMUM TOTAL INSTRUCTOR COMMENT 1. DEGREE & INITIALDIRECTION 5 OF C0/MIP SLIDE ANSWER: ______ (i.e., amount of vertical. lateral, and/or horizontal slide) POSSIBLE INCLINES INVOLVED 5 (“A, B and/or C”) ANSWER: ____________ 2. INITIAL CO CONTACT 5 (Refers to teeth and position) ANSWER: _________ 10 3. Initial “MIP” mark by STUDENT = Deduct all points if initial and ending MIP marks not correct (beyond 0.5 degree of initial mark) Ending “MIP” mark By FACULTY= ****Instructor to check first three sections before continuing**** 4. CO/MIP ADJUSTMENT 5 REMOVED INTERFERENCES: ‐ 2 for perceptible slide NUMBER OF POSTERIOR CONTACTS 15 Subtract 2 points for each set of missing contacts. You must have one set of centric contacts for each pair of teeth. Subtract 2 points for each set of contacts which are the wrong size or in the wrong location. 5. PROTRUSIVE MOVEMENT Removed interferences (subtract 2for each remaining interference or uneven anterior contact) 6. LEFT LATERAL MOVEMENT* REMOVED WORKING INTERFERENCES Subtract 3 for each remaining. REMOVED NONWORKING INTERFERENCES Subtract 5 for each remaining. 7. RIGHT LATERAL MOVEMENT* REMOVED WORKING INTERFERENCES: Subtract 4 for each remaining. REMOVED NONWORKING INTERFERENCES Subtract 5 for each remaining. 8. TOOTH CONTOUR, ANATOMY & FINISH After occlusal adjustment, subtract 4 points for each unsatisfactory tooth. 9. NEATNESS (subtract 10 points if unacceptable) TOTAL
*Nonworking side disclusion will result in loss of all points. ResD 517 Occlusion, 2010 Manual Page 254
10 10 10 15 10 15 10 125 10-1
GLOSSARY OF OCCLUSION TERMS acquired occlusal position ‐ The relationship of teeth in maximum inter‐cuspation regardless of jaw positions. arc of closure ‐ The circular or elliptic area created by closure of the mandible. arcon ‐ A contraction of the words "articulator" and "condyle" used to describe an articulator containing the condylar path elements on its upper member and the condylar elements on the lower member. articulation, temporomandibular ‐ A diarthrodial, sliding hinge (ginglymus) joint. Movement in the upper joint compartments is mostly translational and the lower joint compartment is mostly rotational. The joint connects the mandibular condyle to the articular fossa of the temporal bone with the temporomandibular disk interposed. articulator ‐ A mechanical device that represents the temporomandibular joints and jaw members to which maxillary and mandibular casts may be attached to simulate some or all of the mandibular movements. articulator, arcon ‐ An instrument following anatomic guidelines such that the ball of the condyle analogs are carried on the mandibular element, and the fossa assemblies on the maxillary element. articulator, nonadjustable ‐ An articulator that does not allow adjustment to replicate mandibular movements. articulator, semiadjustable ‐ An articulator that allows adjustment to replicate mandibular movements in the sagittal plane but not in the horizontal plane. axis ‐ A straight line around which a body may rotate. axis, condylar ‐ A hypothetical line through the two mandibular condyles around which the mandible may rotate. axis, hinge (transverse horizontal) ‐ An imaginary line around which the mandible may rotate through the saggital plane. axis, sagittal (longitudinal) ‐ An imaginary anteroposterior line around which the mandible may rotate through the frontal (coronal) plane. ResD 517 Occlusion, 2010 Manual Page 255
10-2
axis, vertical ‐ An imaginary line around which the mandible may rotate through the horizontal plane. Bennett angle ‐ The angle formed on the horizontal by plane the advancing (orbiting) condyle and a straight protrusive movement of the nonworking condyle. Bennett movement – Bennett movement (side shift) – any translatory movement of the working side condyle. bracing position ‐ The position the mandible assumes to facilitate swallowing. This position “braces” the mandible so the muscles can move the bolus of food out of the mouth and down the esophagus in an efficient manner. bruxism ‐ The parafunctional grinding of teeth. canine guidance ‐ Canine‐protected articulation. Arrangement of canine teeth that prevents posterior tooth contact on lateral eccentric mandibular movement. canine protected articulation ‐ A form of mutually protected articulation in which the vertical and horizontal overlap of the canine teeth disengages the posterior teeth in the excursive movements of the mandible. centric occlusion (CO)‐ The occlusion of opposing teeth when the mandible is in centric relation. This may or may not coincide with the maximal intercuspal position. centric relation The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior‐superior position against the shapes of the articular eminencies. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superior and anteriorly. It is restricted to a purely rotary movement about the transverse horizontal axis. clenching ‐ The exertion of force in a static tooth‐to‐tooth relationship. clicking (temporomandibular joint) ‐ A distinct snapping sound or sensation, usually audible and detectable by stethoscope and palpation, that emanates from the temporomandibular joint(s) during jaw movement. It is often associated with internal derangements of the temporomandibular joint. ResD 517 Occlusion, 2010 Manual Page 256
10-3
contacts, tooth: balancing contacts ‐ contacts of the teeth on the side opposite the side toward which the mandible moves in articulation. This is on the opposite side from the rotating condyle. syn. mediotrusive contacts, non‐working contacts working contacts ‐ contacts of teeth made on the side of the occlusion towards which the mandible has moved. This occurs on the same side as the rotating condyle. syn. laterotrusive contacts cross‐tooth contacts ‐ refers to contacts of the lingual cusps (“C” inclines in a normal occlusion) on the working side. If the buccal cusps (“A” inclines) don’t contact when group function occlusion is desired, these cross‐tooth contacts are considered interferences. curve, compensating ‐ The anteroposterior curvature in the median (saggital) plane and the mediolateral curvature in the frontal plane in the alignment of the occluding surfaces and incisal edges of artificial teeth that are used to develop balanced occlusion. cusps: centric holding ‐ the cusps which contact the opposing arch in centric occlusion. syn. supporting cusps, stamp cusps non‐centric holding ‐ the cusps which are not in contact when the mandible closes into centric occlusion. syn. shearing cusps, guiding cusps grasping ‐ cusps which stay in contact with the opposing tooth longer than is desired when the mandible moves in an eccentric movement. plunging ‐ cusps which “hang down” below the normal plane of occlusion. The mesiolingual cusps of maxillary molars are most often found in this position. disk/disc (TMJ) ‐ An avascular interarticular tissue. disocclusion (disclusion) ‐ Separation of opposing teeth during eccentric movements of the mandible. dysfunction ‐ The presence of functional disharmony between the morphological form (occlusion, joints) and function (muscles and neuromuscular function), which may result in pathologic changes in the tissues or produce a functional disturbance. ResD 517 Occlusion, 2010 Manual Page 257
10-4
ear bow ‐ A face bow, that indexes to the external auditory meatus and registers the relation of the maxillary dental structures to the cranial structures and horizontal reference plane. This instrument is used to transfer the maxillary cast to the articulator. The ear bow is engineered to provide for an average anatomic dimension between the external auditory meatus and the horizontal axis of the mandible. eccentric ‐ An adjective denoting any position other than that which is a centric position. equilibration ‐ 1. The act or acts of placing a body in the state of equilibrium. 2. The state or condition of being in equilibrium. excursive movement ‐ Excursion; movement occurring when the mandible moves away from the intercuspal position. facebow ‐ An instrument used to record the spatial relationship of the maxillae to some anatomic reference and transfer this relationship to an articulator. Customarily this reference is a plane established by a transverse horizontal axis and a selected anterior point. Fisher angle ‐ The angle formed by the inclinations of the protrusive and nonworking side condylar paths as viewed in the sagittal plane. freedom in centric ‐ the ability (freedom) of the mandible to move slightly anteroposteriorly or mediolaterally without a change in vertical dimension when in centric occlusion. long centric – the freedom of the mandible to move anteroposteriorly without a change in vertical dimension when in centric occlusion. wide centric – the freedom of the mandible to move mediolaterally without a change in vertical dimension when in centric occlusion. fremitus ‐ movement of a tooth when the teeth are moving in functional (eccentric) contact. This can be determined by palpation. group function ‐ Multiple contact relations between the maxillary and mandibular teeth in lateral movements on the working side, whereby simultaneous contact of several teeth acts as a group to distribute occlusal forces. group function (progressive) – the systematic adding of posterior contacts from 1st premolar posteriorly as the working side moves laterally from CO. incisal guidance ‐ 1. The influence of the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements. 2. The influence of the contacting surfaces of the guide pin and table on articulator movements. ResD 517 Occlusion, 2010 Manual Page 258
10-5
infraocclusion ‐ Malocclusion in which the occluding surfaces of teeth are below the normal occlusal plane. intercondylar ‐ Situated between two condyles. intercuspal contact ‐ The contact between the cusps of opposing teeth. intercuspation, maximum (centric occlusion) ‐ The complete intercuspation of the opposing teeth independent of condylar position. interocclusal ‐ Between the occlusal surfaces of opposing teeth. interocclusal record ‐ A registration of the positional relation of the opposing teeth or arches. interocclusal rest space ‐ The differences between the vertical dimension of rest and the occluding vertical dimension. ischemia ‐ Local and temporary deficiency of blood, chiefly resulting from the contraction of a blood vessel. laterotrusion – Condylar movement on the working side in the horizontal plane. This term may be used in combination with terms describing condylar movement in other planes (e.g. laterodetrusion, lateroprotrusion, lateroretrusion, laterosurtrusion, etc.). malocclusion ‐ 1. Any deviation from a physiologically acceptable contact of opposing dentitions. 2. Any deviation from a normal occlusion. Angle's Class I ‐ (neutrocclusion) The dental relationship in which there is normal anteroposterior relationship of the jaws, as indicated by correct intercuspation of maxillary and mandibular molars. Angle's Class II ‐ (distocclusion) ‐ The dental relationship in which the mandibular dental arch is posterior to the maxillary arch in one or both lateral segments; the mandibular first molar is distal to the maxillary first molar. Often, there is excessive horizontal overlap in the anterior of region. Angle's Class III. (mesiocclusion) ‐ The dental relationship in which the mandibular arch is anterior to the maxillary arch in one or both lateral segments; mandibular first molar is mesial to maxillary first molar. Mandibular incisors may be in anterior reverse occlusion (crossbite). Subdivision. Unilaterally mesial with other characteristics the same. Maximal intercuspal position (MIP): The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position—called also maximal intercuspation. ResD 517 Occlusion, 2010 Manual Page 259
10-6
mastication ‐ The process of chewing food for swallowing and digestion. mediotrusion – A movement of the mandible medially (e.g. non‐working movement). nonworking condyle ‐ The condyle on the nonworking (orbiting) side. nasion – The middle point of the frontonasal suture. nonworking side ‐ The side of the mandible that moves toward the median line in lateral excursion. The condyle on that side is referred to as the nonworking‐side condyle. nonworking‐side interference ‐ Undesirable contacts of the opposing occlusal surfaces on the nonworking side. occlusal adjustment ‐ 1. Any change in the occlusion intended to alter the occluding relationship. 2. Any alteration of the occluding surfaces of the teeth or restorations. occlusal device ‐ Any removable artificial occlusal surface used for diagnosis or therapy regarding the relationship of the mandible to the maxillae. It may be used for stabilization, for TMJ dysfunction therapy, or to prevent wear of the dentition. occlusal prematurity ‐ Any contact of opposing teeth that occurs before the planned intercuspation. occlusal traumatism ‐ Injury to the periodontium resulting from occlusal forces in excess of the reparative capacity of the attachment apparatus. occlusion (articulation) – The contact relationships of maxillary and mandibular teeth (natural or false) as they contact each other. mutually protected occlusion – An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation, the canines protect the incisors and posterior teeth in lateral excursions and the anterior teeth protect the posterior teeth in protrusive movements. canine protected occlusion – A form of mutually protected occlusion in which the vertical and horizontal overlap of the canine teeth disengages (discludes) the posterior teeth in the excursive movements of the mandible. balanced occlusion ‐ An arrangement of the teeth that presents a harmonious relation of the occluding surfaces in all centric and eccentric positions within the functional range of mastication and swallowing. ResD 517 Occlusion, 2010 Manual Page 260
10-7
eccentric occlusion ‐ An occlusion other than centric occlusion. functional occlusion ‐ The contacts of the maxillary and mandibular teeth during mastication and swallowing. group function occlusion – refer to page 9‐15 normal occlusion ‐ Angle’s Class I overlap, horizontal ‐ The projection in a horizontal direction of teeth in one arch beyond their antagonists (overjet). overlap, vertical ‐ 1. The distance teeth lap over their antagonists vertically, especially the distance the maxillary incisal edges extend below those of the mandibular teeth (overbite). The term may also be used to describe the vertical relations of opposing cusps. 2. The vertical relationship of the incisal edges of the maxillary incisors to the mandibular incisors when the teeth are in maximum intercuspation. pain ‐ A subjective unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. pain, masticatory ‐ Discomfort about the face and mouth induced by chewing or other use of the jaws but independent of local disease involving the teeth and mouth. physiologic rest position ‐ The postural position of the mandible when an individual is resting comfortably in an upright position and the associated muscles are in a state of minimal contractual activity. plane, Camper's ‐ A plane extending from the inferior border of the ala of the nose to the superior border of the tragus of the ear. plane, Frankfort ‐ A plane passing through the lowest point in the margin of the orbit and the highest point in the margin of the auditory meatus. plane, frontal ‐ Any plane parallel with the long axis of the body and perpendicular to the median plane. plane, horizontal ‐ Any transverse plane at right angles to the long axis of the body. plane, sagittal ‐ The median plane; a plane that bisects a bilaterally symmetric body. plunger cusp ‐ A cusp that tends to force food interproximally. ResD 517 Occlusion, 2010 Manual Page 261
10-8
posterior overclosure ‐ The loss of occluding vertical dimension as a result of the loss or drifting of posterior teeth. posterior reference points ‐ Two points located one on each side of the face in the area of transverse horizontal axis that, together with an anterior reference point, establish the horizontal reference plane. proprioception ‐ Reception of stimulations of sensory nerve terminals within the tissues of the body that gives information concerning movements and position of the body. protrusion ‐ A position of the mandible anterior to centric relation. record, centric jaw ‐ A record of centric relation position. record, eccentric jaw ‐ A record of the mandible in any position other than centric relation. record, interocclusal ‐ A record of the positional relationship of the teeth or jaws to each other. record, centric (terminal jaw) relation ‐ A registration of the mandible to the maxillae made at the vertical dimension of occlusion in the centric relation position. retrognathic ‐ A retruded position of the mandible in relation to the maxillae. reverse occlusion (crossbite) ‐ An occlusion in which the overlap of the mandibular teeth is facial to the opposing maxillary teeth. rotation ‐ The movement of a rigid body in which the parts move in circular paths with their centers on a fixed straight line that is called the axis of rotation. The planes of the circles in which the particles move are perpendicular to the axis of rotation. rotation center ‐ A point around which all other points in a body move. sagittal ‐ Anterior‐posterior direction, dividing into right and left halves at right angles to coronal sections. silent period ‐ A momentary electromyographically observable decrease in elevator muscle activity on initial tooth contact, presumably the inhibitory effect of stimulated periodontal membrane receptors. splint ‐ 1. Noun. A device that maintains hard and/or soft tissue in a predetermined position. 2. A rigid or flexible material used to protect, immobilize, or restrict motion in a part. 3. Verb. To immobilize, support, or brace. splint, provisional ‐ An interim device to stabilize teeth during diagnosis or therapy. ResD 517 Occlusion, 2010 Manual Page 262
10-9
splinting, muscular ‐ Contraction of a muscle or group of muscles attended by pain and interference with function and producing involuntary movement and distortion; differs from muscle spasm in that the contraction is not sustained when the muscle is at rest. succedaneous teeth are those permanent teeth which succeed (take the place of) primary teeth. supraeruption ‐ Movement of teeth above the normal occlusal plane. supraocclusion ‐ Malocclusion in which the occluding surfaces of teeth extend beyond the normal occlusal plane. Also called overeruption. swallowing threshold ‐ The critical moment of reflex action initiated by sufficient stimulation before the act of deglutition. synovial fluid ‐ A viscid fluid contained in joint cavities and secreted by the synovial membrane. temporomandibular articulation ‐ The articulation of the condyloid process of the mandible and the interarticular disk with the mandibular fossa of the squamous portion of the temporal bone. temporomandibular joint ‐ The articulation between the temporal bone and the mandible. It is a diarthrodial, ginglymus (sliding‐hinge) joint. tinnitis ‐ A noise in the ears, such as ringing and roaring. tongue habit ‐ Conscious or unconscious movements of the tongue that are not related to purposeful functions. Such habits may produce malocclusion or injuries to tissues of the tongue or the attachment apparatus of the teeth. tongue thrusting ‐ The infantile pattern of suckle‐swallow in which the tongue is placed between the incisor teeth or alveolar ridges during the initial stages of deglutition, resulting sometimes in anterior open occlusal relationship, deformation of the jaws, and abnormal function. tooth mobility ‐ Perceptible movement of a tooth not under function. Use of two hard surfaces to determine the degree of movement is mandatory. translation ‐ The motion of a rigid body in which a straight line passing through any two of its particles always remains parallel to its initial position. The motion may be described as a sliding or gliding motion. working side ‐ The side toward which the mandible moves in a lateral excursion. ResD 517 Occlusion, 2010 Manual Page 263