Patients with discolored and malaligned anterior teeth able to obtain

Patients with discolored and malaligned anterior teeth able to
obtain significant esthetic improvement after restoration with
CAD/CAM (Cerec 3D) porcelain veneers ─ case report
CHIA-YUNG LIN BOR-SHIUNN LEE MING-SHU LEE MIN-HUEY CHEN
1
Graduate Institute of Clinical Dentistry and School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan, ROC.
Division of Operative and Esthetic Dentistry, National Taiwan University Hospital, Taipei, Taiwan, ROC.
2
The use of porcelain and other all-ceramic veneers to restore discolored or malformed anterior teeth
has become a significant component of esthetic dentistry over the past decade. CAD/CAM (Cerec 3D) is
a sophisticated clinical restorative method capable of creating complex ceramic restorations including
porcelain veneers and full-coverage crowns. We report a case of discolored and malaligned anterior teeth
in a 26-year-old male patient who obtained significant esthetic improvement in the appearance of the
anterior teeth after restoration with CAD/CAM (CEREC 3D) porcelain veneers. Our patient had
suffered from discolored teeth since childhood and came to the Operative and Esthetic Dentistry
Department of National Taiwan University Hospital (NTUH) seeking treatment. A clinical examination
revealed that the patient had severe brown discoloration with band formation on all teeth, developmental
enamel defects with drug-induced discoloration, and anterior teeth malalignment. The patient’s
discolored and malaligned anterior teeth (#14~#24 and #34~#44) were restored with CAD/CAM
(CEREC 3D) porcelain veneers. This dental work resulted in significant esthetic improvement in the
appearance of the patient’s anterior teeth, and the patient was satisfied with the final prosthetic
restorations. We concluded that patients with discolored and malaligned anterior teeth can obtain
significant esthetic improvement by restoration with CAD/CAM (CEREC 3D) porcelain veneers. （J Dent
Sci, 1(2)：88-93, 2006）
Key words: developmental enamel defect, tooth discoloration, CAD/CAM porcelain veneer.
During the past 20 years, dentists have applied
veneers to teeth using various techniques to correct
esthetic problems. Veneers can be divided into 3
categories: free-hand-placed direct composite resins,
preformed acrylic laminates, and laboratory-fabricated
acrylic resins, composite resins, porcelains, and glass
ceramic veneers1,2. Porcelain and other all-ceramic
veneers are rated as the best veneer restorations3. The
use of porcelain and other all-ceramic veneers to
restore discolored or malformed anterior teeth has
become a significant component of esthetic dentistry
in the past decade3.
Received: March 15, 2006
Accepted: May 28, 2006
Reprint requests to:Dr. Min-Huey Chen, Department of Dentistry,
National Taiwan University Hospital, 1 Chang-Te
Street, Taipei, Taiwan 10048, ROC.
88
The most limiting factor in the choice of
materials for dental restorations is the restricted range
of fabrication technologies. The ability to fabricate a
restoration outside the mouth and subsequently
integrate it with a tooth extends the range of materials
available to dentists4. An indirect approach also
enables the possibility of further optimizing the
physical properties of the restoration by widening the
choice of materials. The CEREC method (Sirona
A.G., Bensheim, Germany) for restoring teeth by
CAD/CAM is now over 10 years old5. It is the
ingenious result of a sophisticated analysis of the
requirements of a dental restorative system and the
application of logical problem-reduction in cavity
design. In its infancy, it was limited to the fabrication
of simple inlays only. From those beginnings, it has
matured into a sophisticated clinical restorative
method, CEREC 3D, capable of creating complex
J Dent Sci 2006‧Vol 1‧No 2
CAD/CAM porcelain veneers
Figure 1. Frontal view of the anterior teeth discoloration before
porcelain veneer treatment.
Figure 2. Ovoid form of the upper arch. There were brownish
linear grooves on the palatal sides of #16 and #26. No attrition
or abrasion was present.
ceramic restorations and full-coverage crowns at the
chair side.
CASE PRESENTATION
A 26-year-old male patient came to the Operative
and Esthetic Dentistry Department of National Taiwan
University Hospital with the chief complaint of
discolored teeth (Figure 1). He asked for full-mouth
veneer restorations. He denied having any systemic
diseases, as well as any food or drug allergies. The
patient had smoked for several years but had no
parafunctional habits like clenching or bruxism
(Figures 2, 3). According to the patient, he had had
frequent illnesses and had taken long-term medication
during his childhood.
The initial clinical impression was a full mouth
of yellowish-brown teeth. Small asymmetrical white
opacities were found on his incisors, and banded
discoloration was found on the incisal 1/3 of the
anterior teeth (Figure 1). There was linear grooving
with discoloration on the middle 1/3 of his first molars
and anterior teeth. The lower left canine (#33) was
fractured above the groove. Enamel wearing and
defects accompanied by brown stains were observed
on the 4 canines (Figures 4, 5). The anterior teeth were
also malaligned, and the marginal gingival lines were
unsymmetrical at the upper central incisors. There was
spacing at the interproximal area from the upper right
central incisor (#11) to the left lateral incisor (#22).
The right molar relationship was a class III
J Dent Sci 2006‧Vol 1‧No 2
Figure 3. Ovoid form of the lower arch. There were brownish
linear grooves on the buccal sides of #36 and #46..
malocclusion. From an esthetic viewpoint, his
upper right central incisor (#11) was too wide and
left central incisor (#21) was too long compared
with the standard width-length ratio of 0.75~0.8,
the incisal curve was too straight, and a crossbite
was evident at teeth #22 and #32.
The patient selected CAD/CAM (CEREC 3D)
porcelain veneers for the upper and lower anterior
region (#14~#24 and #34~#44) to improve the
esthetics and mask the malalignment, after he was
informed about other possible choices, including
veneering with direct light-curing composite resin,
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C.Y. Lin, B.S. Lee, B. S. Lee, M. S. Lee, et al.
Figure 4. Left buccal view before porcelain veneer treatment.
Spacing was observed in the interproximal area between #21 and
#22.
technique described by Christensen6. The labial
enamel was reduced by approximately 0.75 mm in
the incisal 1/3 of the crown, decreasing gradually to
0.3 mm in the cervical region to create space for the
veneer. The initial edge reduction was about 0.7 mm.
No overlap preparation was made in the incisal edge.
If a tooth was worn short incisally, it was veneered
labially and extended palatally with the veneer,
without overlapping onto the palatal surface. The
proximal preparation ended at the contact area,
except teeth #21 and #22 which required an
alignment change (Figure 6).
3. After preparation, impressions were taken, poured
in die stone, and sent to the laboratory for
fabrication of the restorations.
4. The patient was recalled when the veneers were
ready. Before luting, the inner surfaces of the
veneers were treated with 0.4% hydrofluoric acid
for 4 minutes and rinsed with water. After drying in
air, a silane-coupling and bonding agent was applied.
After cleaning, teeth were etched with a 37%
phosphoric acid solution, rinsed with water and
dried with compressed air. Excite DSC (IvoclarVivadent, NY, USA) bonding agent was then
applied to both the etched enamel and dentin
surfaces. The luting composite, Variolink II Esthetic
Cementation System (Ivoclar-Vivadent, NY, USA),
was evenly placed over the veneer’s bonding
surface before it was placed onto the tooth surface.
The veneer was then lightly pressed into place with
finger pressure. Dental floss was used to remove
Figure 5. Right buccal view before porcelain veneer treatment.
The right molar relationship was a class III malocclusion.
indirect composite resin, and bleaching the teeth.
The procedure we followed for fitting the
CAD/CAM (CEREC 3D) porcelain veneers is as
follows.
1. His teeth were cleaned to remove extrinsic stains
and dental calculus at the first appointment. He was
informed about the need for good gingival health
and educated in effective plaque control. Both
preoperative and postoperative photographs were
taken in order to evaluate the change in appearance.
2. The preparation of the teeth was based on a
90
Figure 6. Frontal view of #14~#24 after the preparation. The
contact points of the teeth were preserved, except for #11 and #21
due to the alignment change.
J Dent Sci 2006‧Vol 1‧No 2
CAD/CAM porcelain veneers
Figure 7. Frontal view after porcelain veneer treatment. The
width-length ratios of #11 and #21 were changed.
Figure 9. Right buccal view after porcelain veneer treatment.
between #21 and #22 was closed, and the #22~#32
crossbite was camouflaged. The width-length ratios
of #11 and #21 were changed to 0.81 and 0.74,
which are closer to standard values, and the incisal
curve was more harmonious (Figures 7-9).
After restoration with CAD/CAM (CEREC 3D)
porcelain veneers, the patient’s discolored and
malaligned anterior teeth exhibited significant esthetic
improvement, and the patient was satisfied with the
final prosthetic restorations.
Figure 8. Left buccal view after porcelain veneer treatment.
The space between #21 and #22 was closed.
excess luting material from the veneer’s
interproximal area. After removing the excessive
cement, the veneers were light-cured with a
light-curing unit (L.E.Demetron I, Kerr Corporation,
city?, CA, USA) at an intensity of 1000 MW/cm2
for 20 seconds in both the labial and marginal areas.
5. The margins of the veneers were then finished with
a super-fine polishing diamond bur and checked
with a dental probe to ensure that there was no
excess cement along the veneer’s labial margin. The
occlusion was checked and adjusted.
6. The patient was recalled after 1 week to re-check
the occlusion, proximal contact relationships,
marginal integrity, and gingival health. Teeth
discolorations were covered by veneer, the space
J Dent Sci 2006‧Vol 1‧No 2
DISCUSSION
During enamel formation, ameloblasts are
susceptible to various external factors, like metabolic
injury, which may cause defects in the quantity and
shape of the enamel or in the quality and color of the
enamel7. Quantitatively defective enamel, known as
enamel hypoplasia, produces teeth with insufficient
amounts of enamel, ranging from pits and grooves to a
complete absence (aplasia). Stain engagement can be
found with this type tooth. Qualitatively defective
enamel, known as enamel hypocalcification, means
that the quantity of enamel is normal but it is soft and
friable, so that it easily fractures and wears readily.
The color of this type of tooth varies from white
opaque to yellow to brown. Teeth also tend to darken
with age as a result of exogenous staining. In this
case, a white spot may be the result of enamel
hypomaturation, while easily wearing enamel may be
the result of hypomineralization and linear grooving
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C.Y. Lin, B.S. Lee, B. S. Lee, M. S. Lee, et al.
with discoloration may be the result of hypoplasia.
Factors associated with enamel defects may occur
locally or systemically. Most enamel defects affect the
anterior teeth and first molars, and the affected teeth
may have coronal discoloration or actual pits and
irregularities. The specific causes of systemically
induced enamel defects are often obscure but are
usually attributed to childhood infectious diseases.
The patient stated that he had had several illnesses and
had undergone long-term medical therapy during
childhood. In this case, systemic factors from
infectious illnesses were suspected.
Tetracyclines can cause discoloration and enamel
hypoplasia of both the primary and permanent
dentitions if administered during the period of tooth
development8. The discoloration, which is permanent,
varies from yellow or gray to brown9. The labial
surfaces of yellow-stained anterior teeth darken in
time, while the palatal surfaces and buccal surfaces of
posterior teeth remain yellow10. Calcification of the
permanent teeth begins after birth and is completed at
7~8 years of age, with the exception of the third
molar11. Therefore, administration of tetracycline to
children under 8 years of age should be avoided as it
may result in tooth discoloration and enamel
hypoplasia12. There is a possible association between
staining and enamel hypoplasia as a result of the
high-dosage intake of tetracycline during tooth
calcification13. In our case, the yellow to brownish
discoloration could have been drug-induced, and
extrinsic smoking stains on the canines may have been
a result of enamel hypoplasia. Treatment for this kind
of patient may include vital or nonvital teeth bleaching,
which will lighten the discoloration but may leave a
translucent appearance14. As tetracycline staining is
intrinsic, the bleaching technique is most often only
partially successful. There are 3 other options,
including placing composite resins, porcelain laminate
veneers, or full-coverage porcelain crowns15,16, to
physically cover the teeth. The advantages and
disadvantages of each of these options are described
below.
Patients’ demand for treatment of unesthetic
anterior teeth is steadily growing. Full crowns are the
most predictable and durable but undoubtedly most
invasive, with substantial removal of large amounts of
sound tooth substance and possible adverse effects on
the adjacent pulp and periodontal tissues3. Resin
composite veneers can be used to mask tooth
discolorations and correct unaesthetic tooth forms or
92
positions. However, such restorations suffer from a
limited longevity because resin composites remain
susceptible to discoloration, wear, and marginal
fractures. Glazed porcelain veneers were proposed as
being durable anterior restorations with superior
esthetics. Simonsen and Calamia17 introduced special
acid etching procedures that substantially improved
long-term porcelain veneer retention. They demonstrated that the bond strength of a hydrofluoric
acid-etched and silanated veneer to a luting resin
composite is routinely greater than the bond strength
of the same luting resin to the etched enamel surface18.
Further, porcelain retains less plaque than other
restorative materials or enamel, and the plaque is
removed more rapidly, which causes no or a minimal
periodontal response.
The CEREC method (Sirona, Bensheim, Germany) for restoring teeth by CAD/CAM is now over
10 years old5. Technological improvements have
increased the range of restorations capable of being
milled19, to the extent that virtually any shape can now
be made.
Machinable ceramics as used by the CEREC
system provide a useful restoration with high success
rates4. ProCAD® (Ivoclar-Vivadent, city?, NY, USA)
with leucite-reinforced porcelain blocks was used in
our case. Tooth preparation for CAD/CAM (CEREC
3D) porcelain veneers is the same as that for veneers
fabricated from conventional low-fusing feldspathic
porcelain. ProCAD® 100/I12 was selected according
the shade and shape of this patient’s teeth; a
more-opaque color was needed to cover his severe
tetracycline staining. Standardized data are calculated
for individual cases. The anatomy, occlusal
morphology, and color stability of CAD/CAMgenerated ProCAD® block restorations were
satisfactory in a 3-year clinical performance study20.
CEREC 3D is the name of the software used in the
CEREC 3 system. While a light-cured luting
composite is preferred for bonding conventional
porcelain veneers, a dual-cured or self-curing luting
composite is used for CAD/CAM porcelain veneers.
When the luting space was set to 30 µm, crowns with
a good fit could be fabricated on the Cerec 3 system21.
These restorations are color stable and wear at a
clinically acceptable rate, and they can compete with
the layering technique crowns in aesthetic value22. The
marginal fit of restorations milled by CEREC 3 was
within the ADA specifications of 50 µm23. However,
there are no long-term reports about CEREC 3.
J Dent Sci 2006‧Vol 1‧No 2
CAD/CAM porcelain veneers
Further, caution should be exercised when using this
system for restoring non-vital teeth, as a higher
fracture incidence has been noted4.
13.
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