DEFINITION/OVERVIEW
- Tooth resorption is defined as resorption of dental hard tissue by odontoclasts
- Odontoclasts derive from hematopoietic stem cells, migrate from blood vessels of the periodontal ligament and alveolar bone toward the external root surface (external resorption), or are recruited from blood vessels of the pulp and move toward the dentinal surface facing the pulp tissue (internal resorption)
- Idiopathic resorption: can affect any root surface of a single tooth or of multiple teeth; there is no history of trauma, tooth bleaching, endodontic disease, orthodontic treatment, neoplasia, or systemic conditions
- External resorption
- Cervical root resorption after blunt trauma (which can have occurred years prior to the clinically apparent resorption) or tooth bleaching (mainly a problem in humans)
- Apical root resorption due to the following:
- Periapical disease after pulpal inflammation/infection
- Orthodontic treatment (resorption arrests after discontinuation of tooth movement)
- Periapical disease after pulpal inflammation/infection
- Apical, lateral, and/or cervical root resorption due to neoplasia
- Benign neoplasm with expansive growth cause pressure resorption along the root surface
- Malignant neoplasm with infiltrative growth cause invasive resorption with moth-eaten root appearance
- Benign neoplasm with expansive growth cause pressure resorption along the root surface
- Other reported links with external resorption include (but are not limited to) hypoparathyroidism, drugs (e.g., anticonvulsants), radiation therapy, oxalosis, tumoral calcinosis, and Paget’s disease
- Cervical root resorption after blunt trauma (which can have occurred years prior to the clinically apparent resorption) or tooth bleaching (mainly a problem in humans)
- Internal resorption
- Often described as oval-shaped radiolucency within the pulp cavity of teeth with at least some vital pulp tissue remaining
- May be caused by trauma (e.g., concussion) or vital pulp therapy (e.g., use of calcium hydroxide as pulp capping agent)
- Often described as oval-shaped radiolucency within the pulp cavity of teeth with at least some vital pulp tissue remaining
- The following description of tooth resorption is focused on the progressive disease affecting multiple teeth, as recognized in the domestic cat (feline tooth resorption), but dogs (canine tooth resorption) and other mammals (including man) can occasionally be affected as well
ETIOLOGY/PATHOPHYSIOLOGY
- Synonyms of tooth resorption include feline odontoclastic resorptive lesion (FORL), neck lesion, feline caries, cervical line erosion, and external root resorption
- “Neck lesion” is a topographical distinction only
- The terms “erosion” and “caries” are inappropriate, as the lesion is resorptive in nature and not caused by acidic agents and/or cariogenic bacteria
- “Neck lesion” is a topographical distinction only
- Tooth resorption is an external resorption of unknown cause, affecting any tooth surface of multiple, if not all, teeth
- Reported prevalence rates range between 25% and 75%, and the disease is rarely seen in cats younger than 2 years of age
- Possible reported causes include periodontal disease, anatomical peculiarities, mechanical trauma, immunosuppressive viruses, increased vitamin A intake, and increased vitamin D intake
- Histological examination of clinically and radiographically healthy teeth from cats with tooth resorption on other teeth showed periodontal ligament degeneration, hypercementosis, decreased width of the periodontal space, and dentoalveolar ankylosis, but inflammatory cells did not play a primary role in the initiation of the disease
- Cats with tooth resorption apparently have significantly increased serum levels of 25-hydroxyvitamin D compared with cats without the disease, indicating that cats with tooth resorption must have had a higher dietary intake of vitamin D compared with cats without the disease
- Cats with tooth resorption apparently have significantly decreased urine specific gravity compared with cats without the disease, indicating that there is a trend toward decreased renal function in cats with tooth resorption
- Risk factors may include preexisting periodontal disease, trauma from occlusion, and diets high in vitamin D
SIGNALMENT/HISTORY
- Tooth resorption does usually not become clinically apparent prior to 4–6 years of age
- There is no gender or breed predisposition, but purebred cats may develop the disease at a younger age compared with other breeds
- Most cats do not show obvious clinical signs; owners may report difficulty eating hard food, refusal to drink cold water, and repetitive lower jaw motions (jaw opening reflex)
- Tooth resorption apical to the gingival attachment is asymptomatic, unless associated with endodontic and/or periapical disease
CLINICAL FEATURES
- Oral examination is performed under general anesthesia
- Fractured crowns, “red spots” at the cervical portion of teeth, and missing teeth may readily be noticed
- A fine-pointed dental explorer is run across the crown surfaces of all teeth to detect any irregularities associated with tooth integrity
- Probing of defects may cause bleeding from inflamed granulation tissue
- The gingiva may appear bulgy, inflamed, and friable in areas of missing teeth (suspect root remnants)
- The bone at the alveolar margin may be thickened (“alveolar bone expansion”), and teeth may appear elongated or extruded (“supereruption” of canine and other teeth)
- American Veterinary Dental College (AVDC) Nomenclature “Classification of Tooth Resorption” (see Appendix B) (images courtesy of AVDC: http://avdc.org/nomenclature.html)
- Tooth resorption is classified based on the severity of the resorption (stages 1–5) and on the location of the resorption (types 1–3)
- Stages of tooth resorption (TR): this classification is based on the assumption that tooth resorption is a progressive condition
- Stage 1 (TR 1): mild dental hard tissue loss (cementum or cementum and enamel) (Fig. 49-1)
- Stage 2 (TR 2): moderate dental hard tissue loss (cementum or cementum and enamel with loss of dentin that does extend not into the pulp cavity) (Fig. 49-2)
- Stage 3 (TR 3): deep dental hard tissue loss (cementum or cementum and enamel with loss of dentin that extends into the pulp cavity); most of the tooth retains its integrity (Fig. 49-3)
- Stage 4 (TR 4): extensive dental hard tissue loss (cementum or cementum and enamel with loss of dentin that extends into the pulp cavity); most of the tooth has lost its integrity
- TR 4a: crown and root are equally affected (Fig. 49-4, a)
- TR 4b: crown is more severely affected than the root (Fig. 49-4, b)
- TR 4c: root is more severely affected than the crown (Fig. 49-4, c)
- Stage 5 (TR 5): remnants of dental hard tissue are visible only as irregular radiopacities, and gingival covering is complete (Fig. 49-5)
- Types of resorption, based on radiographic appearance
- On a radiograph of a tooth with type 1 (T1) appearance, a focal or multifocal radiolucency is present in the tooth with otherwise normal opacity and normal periodontal ligament space (Fig. 49-6)
- On a radiograph of a tooth with type 2 (T2) appearance, there is narrowing or disappearance of the periodontal ligament space in at least some areas and decreased radiopacity of part of the tooth (Fig. 49-7)
- On a radiograph of a tooth with type 3 (T3) appearance, features of both types 1 and 2 are present in the same tooth; a tooth with this appearance has areas of normal and narrow or lost periodontal ligament space, and there is focal or multifocal radiolucency in the tooth and decreased radiopacity in other areas of the tooth (Fig. 49-8)
- Tooth resorption is classified based on the severity of the resorption (stages 1–5) and on the location of the resorption (types 1–3)
Figure 49-1 Stage 1 (TR 1): mild dental hard tissue loss (cementum or cementum and enamel).
(Image courtesy of AVDC Nomenclature “Classification of Tooth Resorption”: http://avdc.org/nomenclature.html)
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