Literature Review – Feline Tooth Resorption

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Putting Knowledge into Practice
Banfield Applied Research & Knowledge Team
March 2011
Literature Review – Feline Tooth Resorption
By Amy Hille, DVM, MPH; Ashlee Addleman, MPH | Contributing Authors
INTRODUCTION
Tooth resorption (TR) is a common and
important dental condition affecting cats.
Although it is acknowledged to be a common
disease, reported prevalence estimates vary
greatly and the exact impact of the disease on an
otherwise healthy cat population is unknown.
Various factors, such as difficulty in diagnosing
this disease, under-reporting, patient population
characteristics, or other unknown variables may
account for the wide range of prevalence noted
in the literature. In recent years, a great deal
of interest has been devoted to understanding
the disease process more fully and identifying
potential causes of tooth resorption. Changes in
the nomenclature of TR tend to reflect changes
in theories of etiology.1 Tooth resorption has
been referred to as caries, erosions, neck lesions,
feline odontoclastic resorptive lesions (FORLs),
and resorptive lesions. However, since the term
“tooth resorption” currently best reflects the
disease process, this term is now more commonly
used and is the nomenclature recognized by the
American Veterinary Dental College (AVDC).1,2
CLINICAL BOTTOM LINE
•Published literature suggests that tooth
resorption is the most common dental issue
seen in cats, following periodontal disease.
•Staging and typing are considered best
practice for diagnosis of tooth resorption.
•Tooth resorption is most commonly found
on the mandibular molars and premolars;
therefore, it is recommended to examine
these particular teeth thoroughly during
oral examinations.
•Although tooth resorption can be found
anywhere on the tooth surface, the
cementoenamel junction (CEJ) tends to be
the area most affected.
•Once cats have evidence of tooth
resorption, they tend to be prone to future
tooth resorption lesions; therefore, it is
highly recommended that dental
radiographs be performed for every tooth.
•The causes of tooth resorption are
unknown, thus making recommendations
for prevention difficult; lesions are treated
with either extraction or crown amputation
in the majority of cases.
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Table 1: Potential Feline Tooth Resorption Factors
Local Microenvironment Factors
Around Teeth
Details
Mast cells
Increased in the gingival tissue of cats with TR
[3]
Inflammatory cytokines
Expression of IL-1β, IL-6, IL-10, TNF-α and IFN-γ was higher
in tissue from cats with TR
[4]
Nuclear vitamin D receptor (nVDR)
Increased in tissue from teeth with TR
[4]
pH
Acidosis was found to be a major regulator of osteoclast
formation in vitro
[5]
Hypoxia
Induced giant osteoclast formation in vitro
[6]
Systemic Factors
Details
Reference(s)
25-OHD (25-hydroxyvitamin D)
Serum concentration of 25-OHD was higher in cats with TR
[7]
Urine specific gravity
Significantly lower in cats with TR compared to cats without
[7]
Biochemical markers of bone turnover
No significant association
[8]
Age
Literature suggests TR risk increased with age
Structural Characteristics of Teeth
Details
[9,10,11,12]
Reference(s)
Dentin mineralization
Lowest at the cementoenamel junction
[13]
Periodontitis
Lower occurrence of root resorption in teeth when both TR
and periodontitis are present
[14]
Despite an incomplete understanding of
of TR are an enigma.1 Despite the gaps in
therefore needs to be diagnosed early by careful
systemic factors and structural characteristics of
the underlying causes, TR can be a serious
manifestation of periodontal disease and
oral examination and followed with appropriate
and timely treatment.
PATHOGENESIS
In veterinary medicine, the underlying causes
2
Reference(s)
knowledge, studies have identified aspects of
the local microenvironment around the teeth,
teeth that are unique to feline tooth resorption.
Table 1 is a summary of these factors that may
be associated with feline tooth resorption. The
major limitation to these studies, however, is
the temporality of associations, i.e., it is not
Feline Tooth Resorption
known whether these changes precipitate tooth
accurate classification (i.e., staging and typing) of
CLASSIFICATION
treating this disease.9
resorption or are initiated by disease process.
Tooth resorption in domestic cats can be
classified into stages based on amount of
TR lesions offers the best support to the clinical
decision-making process when diagnosing and
CLINICAL FINDINGS AND DIAGNOSIS
tooth destruction caused by TR, and into types
Tooth resorption can present clinically without
important since the treatment and prognosis can
addition, tooth resorption should be suspected
based on the appearance of the root in dental
radiographs. Staging and typing of lesions is
be more accurately determined for patients by
using these classifications.1,14 Different staging
systems are used in clinical practice to classify
tooth destruction resulting from TR, but most
systems use five stages. To further describe
the lesion pathology of the crown and root, the
AVDC endorses a similar classification system
but further subdivides stage 4 (into 4a, b, c) to
capture this detail.2 Table 2, pages 4-5, presents
the AVDC-endorsed classification system.2
A root typing system can also be used to
describe the appearance of the root upon
radiographic presentation. To classify a lesion
as type 1, the root should have a normal
radiographic appearance with evidence of a
normal periodontal ligament. Conversely, type
2 lesions present with an abnormal tooth root
replaced by alveolar bone, and narrowed or
missing periodontal ligament space.14 Until
underlying disease processes are identified,
overt symptoms or may cause signs such as
discomfort, lethargy, dysphagia or halitosis.1,15 In
when cats show jaw movement or chattering
upon probing a suspicious lesion with a dental
instrument. 1,15 Early lesions may not be visible,
but once they have developed, lesions may
appear as obvious pink spots on the crown of the
tooth.15 Lesions are also discovered underneath
plaque or calculus, while others manifest
subgingivally. 15 Diagnosis of TR is performed
by tactile probing and/or dental radiography as
part of an oral exam.1,15 Lesions can be identified
at the cementoenamel junction (CEJ) by visual
inspection, or by feeling for a rough area that has
a sharp margin, using a dental explorer. 1,15
Focusing the dental examination on the teeth
and the areas of the teeth most likely to be
affected can make classification and diagnosis
of TR easier. In a study examining all teeth
from 182 cats, the mandibular third premolars
and mandibular first molars were reported to
comprise 14.6 and 11.3 percent of all affected
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Stage 1
Stage 2
Mild dental
hard tissue loss
(cementum or
cementum and
enamel).
Moderate dental
hard tissue loss
(cementum or
cementum and
enamel with loss of
dentin that does not
extend to the pulp
cavity).
Stage 3
Deep dental
hard tissue loss
(cementum or
cementum and
enamel with
loss of dentin
that extends to
the pulp cavity);
most of the
tooth retains its
integrity.
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Stage 4
Extensive dental hard tissue loss (cementum or
cementum and enamel with loss of dentin that extends to
the pulp cavity); most of the tooth has lost its integrity.
Stage 4a
Stage 4b
Crown and root
are equally
affected.
Crown is more
severely affected than
the root.
Source: Copyright AVDC, used with permission.
Table 2: AVDC’s Classification System (Staging) of Tooth Resorption
Feline Tooth Resorption
Table 2: AVDC’s Classification System (Staging) of Tooth Resorption (cont’d)
Stage 4c
Stage 5
Root is more
severely affected
than the crown.
Remnants of dental
hard tissue are visible
only as irregular
radiopacities, and
gingival covering is
complete.
teeth, respectively.7 A different study also
literature reports TR at the CEJ, studies have
After evaluating 228 clinically healthy cats,
radiographs of the entire dentition when a patient
provides evidence suggesting that TR lesions
mostly occur with mandibular third premolars.11
authors reported that the mandibular third
premolar was affected most.11
Although tooth resorption can be found
anywhere on the tooth surface, the CEJ tends to
be the area most affected. In one study examining
138 teeth from 13 healthy cats and another
examining 22 teeth from 12 cats, between 38
and 95 percent of lesions, respectively, were
found at or near the CEJ.10,16 Another area of
the tooth susceptible to TR is the furcation of
multi-rooted teeth. According to DeLaurier et
al. (2008), 95 percent of multi-rooted teeth
with tooth resorption showed evidence in this
area of the tooth.10 Although the majority of the
found TR lesions on all areas of the tooth.10,16,17
This reinforces recommendations to take intraoral
presents for dental evaluation, because tooth
resorption is not entirely exclusive to the CEJ and
the furcation of multi-rooted teeth.2
In addition to the dental examination, intraoral
dental radiographs under general anesthesia are
highly recommended for accurate diagnosis of
TR.15 Dental radiographs can provide superior
diagnostic information regarding the severity
of the lesions when compared to the clinical
examination alone, and thus enable the most
accurate prognosis and effective treatment.15 It is
essential to radiograph the entire dentition when
a TR is found on a single tooth, as cats rarely have
lesions on a single tooth.15 In addition to using
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dental radiographs to diagnose TRs, Heaton and
replacing the root should be observed.14,19 It is
disease status. The authors suggest using the
periodontitis, stomatitis, tooth mobility or
colleagues advocate using dental radiographs
as a screening method to determine overall TR
tooth resorption status of the radiographic views
for the left and right mandibular third premolars
(two intraoral films and parallel technique) to
predict the overall status of TR in a patient.
Using this technique, the authors reported
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a sensitivity of 78.5 percent and a negative
predictive value of 91.3 percent. A screening
also important that no underlying pathologic
changes in the mouth are present, such as
radiographic evidence of disease.19
Additionally, it is worth noting that restoration
of teeth, such as glass ionomer and/or
composite filling, has been shown to have poor
long-term success rates and is not advisable
as a treatment option.1,15 An alternative option
technique such as that described by Heaton and
currently being investigated is a human
radiation exposure.
proof of concept study and works by inhibiting
colleagues may decrease the amount of time
a patient spends under anesthesia as well as
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TREATMENT
Treatment options for cats with TR are limited,
but choosing an appropriate treatment is critical
for eliminating the pain associated with TR and
preventing further complications. In the majority
of cases, lesions are treated with either extraction
or crown amputation. Complete surgical
extraction of teeth is necessary for patients with
type 1 lesions.19 With type 1 lesions, extraction is
important regardless of the status of the crown,
because leaving the root can provide a nidus
for infection after crown amputation. For type
19
2 lesions, crown amputation may be a viable
treatment option in a select group of patients;
for these patients, signs of the alveolar bone
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osteoporosis drug, called alendronate. This
biphosphonate compound was explored in a
the activity of osteoclasts. When given orally at
a dose of 9 mg/kg biweekly to feline subjects, it
was found to accumulate on the alveolar bone
and subgingival tooth surfaces. Results from this
study suggested that alendronate slowed the
process of resorption in cats already diagnosed
with TR and that it might someday be a viable
treatment option.20 No matter which treatment
option is selected, it is imperative that lesions
be classified and diagnosed accurately, as
the consequences of selecting an unsuitable
treatment for a patient may result in severe
infection, endodontic disease, gingivitis and/or
periodontitis.1,15,19
Feline Tooth Resorption
DISCUSSION
Tooth resorption remains a serious dental
condition that affects cats significantly, but
the pathogenesis remains undefined. Tooth
resorption is diagnosed by visualization and
probing during physical examinations, and
with dental radiographs, an essential tool in
complete diagnosis and staging. It is strongly
recommended that radiographs be taken of every
tooth when TR is suspected. TR is classified
using both staging and typing systems, and
accurate classification of TR helps to support
the clinical decision-making in treating this
disease. Treatment options are currently limited
to surgical extraction or crown amputation.
Features of the local microenvironment around
the tooth as well as systemic and structural
Until definitive causes are confirmed, accurate
diagnosis by means of staging and typing systems
and subsequent selection of an appropriate
treatment are proven to reduce oral pain in
affected cats. Currently, this approach offers the
best strategy for management of the disease.
Since etiology and pathogenesis are yet to be
fully determined and are still widely debated,
veterinarians are only able to provide limited
advice to clients on prevention of feline tooth
resorption. Recommended strategies should
focus on prevention of dental disease in
general; this usually consists of semiannual oral
examinations and professional dental prophylaxis
beginning early in adulthood.2
factors have been identified in association with
abnormal tooth resorption in cats. Additional
research into these associations may provide
further insight into this disease.
ABOUT THE AUTHORS
Amy Hille, DVM, MPH, graduated from Kansas State University with a Bachelor of Science in Animal Science in 1997
and a DVM in 2001. She completed her Master of Public Health from Oregon Health & Science University in 2006 with
an emphasis in biostatistics and epidemiology. Amy joined the Banfield Applied Research & Knowledge (BARK) team
in 2010 as an associate medical advisor.
Ashlee Addleman, MPH, graduated from Portland State University in 2004 with a Bachelor of Science in Community
Health Studies and received her Master of Public Health from Walden University in 2010. Ashlee joined the BARK team
as a research project specialist in 2006 and has been with Banfield Pet Hospital since 2002.
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Banfield Applied Research & Knowledge Team
REFERENCES
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2. American Veterinary Dental College. Classification of tooth
resorption. 2010. Accessed Jan. 27, 2011.
www.avdc.org/nomenclature.html#resorption.
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18. Heaton M, Wilkinson J, Gorrel C, et al. A rapid screening
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26(2):74-81.
For more information, or to contact the Banfield Applied Research & Knowledge Team,
e-mail: [email protected]
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