Tooth resorption in cats
Oral disease in cats comprises four major conditions: periodontal disease, oral neoplasia (particularly squamous cell carcinoma), feline stomatitis and tooth resorption. Previously referred to by several terms—and recently including cervical line lesions, resorptive lesions and feline odontoclastic resorptive lesions (FORLs)—tooth resorption is likely the most common significant oral condition affecting feline patients.
The combined gross and radiographic occurrence of tooth resorption in random populations of clinically healthy cats ranges from 29 to 38 percent.1-4 The number presenting to veterinary facilities primarily for dental disease is as much as twice as high.5,6
Many gross lesions are small and not readily detectable by awake oral examination alone. Magnification, immobilization and lighting generally provide a thorough gross evaluation but will not uncover tooth resorption below the level of the marginal bone. Therefore, dental radiography is paramount in establishing an adequate diagnosis.
One of the most useful clinical classifications of tooth resorption to date is based on the gross and radiographic description of the lesions by type. Treatment is solely dependent on this type of classification, so, again, dental radiography is essential in making a final determination.
Grossly, Type 1 tooth resorption is characterized by gingivitis and periodontitis generally initiated at the junction between the cementum and the enamel. The origin is thought to be inflammatory. Cavitation defects are seen in the crown, with inflamed gingival tissue often covering the defect (Photo 1). Radiographically, these teeth have variations in density in the crown or root. A distinct periodontal ligament space is generally appreciated (Photo 2). Type 1 and Type 2 tooth resorption may be observed concurrently in individual roots of a single tooth (Photo 3). Therefore, diagnostic evaluation of each root is important to determine how each should be approached therapeutically.
Type 2 (Photos 2 and 3) tooth resorption is generally thought to start at the apical half of the root. Crown involvement is generally not noted until late in the resorption process. The hallmark of Type 2 resorption is the lack of radiographic evidence of a periodontal ligament space surrounding the root.
Tooth roots classified as undergoing Type 1 resorption require the removal of the entire tooth root and crown by using traditional extraction techniques (Photo 4). Tooth roots for which no periodontal ligament space is readily detected and where no periodontal bone destruction or periapical lucencies exist may be treated by crown amputation and intentional root retention. In these cases, a conservative periodontal flap exposes the marginal extent of the tooth (Photo 5), and a round carbide or diamond bur on a water-cooled, high-speed handpiece is used to remove the crown and contour the bone (Photo 6) before closure with 5-0 absorbable suture (Photo 7).
Exceptions exist for these generalizations regarding Type 2 lesions. Some roots may require partial extractions (more significant root remnant removal) if the periodontal ligament space is minimally detectable radiographically or abnormal tissue exists grossly upon exposure (consider biopsy in this instance). This includes friable tooth remnants. If there’s a bleeding pulp, the entire root should be removed.
Research and prevention
Although causes have not been determined for tooth resorption in general, one study suggests that cats with tooth resorption have significantly higher serum concentrations of 25-hydroxyvitamin D than cats do without tooth resorption.7 These researchers also found that 41 percent of canned cat foods have in excess of 30 times the vitamin D requirements of cats.8 Feeding diets that meet but don’t exceed the 250 IU/kg dry weight equivalent may prove to be a key to preventing tooth resorption. It’s also generally thought that Type 1 resorption is of inflammatory origin, so good oral hygiene may be key to preventing this form of resorption.
The importance of dental radiography cannot be overstated but neither can the physical observation of the tooth root upon exposure. Consequently, veterinary practices that don’t have dental radiography and adequate surgical magnification shouldn’t be treating cats with tooth resorption. Either obtaining the proper equipment and training or referring to a specialist are the only feasible options for evaluating and treating these patients. Congratulations if your practice is effectively evaluating and treating these important feline oral defects.
Dr. Beckman is acting president of the American Veterinary Dental Society and owns and operates a companion-animal and referral dentistry and oral surgery practice in Punta Gorda, Fla. He sees referrals at Affiliated Veterinary Specialists in Orlando and at Georgia Veterinary Specialists in Atlanta, lectures internationally and operates the Veterinary Dental Education Center in Punta Gorda.
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2. Ingham KE, Gorrel C, Blackburn J, et al. Prevalence of odontoclastic resorptive lesions in a population of clinically healthy cats. J Small Anim Pract 2001;42(9):439-443.
3. Pettersson A, Mannerfelt T. Prevalence of dental resorptive lesions in Swedish cats. J Vet Dent 2003;20(3):140-142.
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8. Gawor JP, Reiter AM, Jodkowska K, et al. Influence of diet on oral health in cats and dogs. J Nutr 2006;136(7 Suppl):2021S-2023S.