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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com exTernal TooTh resorPTion in caTs Peer reviewed 24 PREVALENCE All permanent teeth are susceptible to resorption. Tooth resorption, however, is rarely diagnosed in cats younger than 2 years of age. Most affected cats develop lesions by 4 to 6 years of age. 5 In addition, purebred cats, such as Abyssinian, Siamese, Russian blue, Scottish fold, and Persian breeds, appear to be affected at an earlier age. A study that evaluated prevalence and risk factors associated with tooth resorption found older age and higher magnesium content of food to be variably associated with tooth resorption. 8 Tooth resorption is also more prevalent in cats that: 1,9,10 • Gulp rather than chew their food • Eat only table food • Are female • Drink municipal (as compared to well) water • Are on a raw-liver diet or low-calcium diet • Live exclusively indoors. DIAGNOSIS Examination of the conscious cat often reveals tooth resorption as an area of missing tooth substance caused by the destruction of enamel and underlying dentin. Any surface of the tooth can be affected, although most areas are apparent at the labial or buccal surfaces at the neck of the tooth near the cementoenamel junction. The teeth most commonly affected are: • Mandibular third premolars (the teeth immediately behind the canines) • Mandibular first molars • Maxillary third and fourth premolars. Often, resorptions affecting the canine teeth occur apical to the cementoenamel junction and, therefore, are not clinically apparent (Figure 11). General anesthesia is necessary to conduct a thorough tooth-by-tooth clinical and radiographic examination. In certain cases, the overlying gingiva is infamed and, in others, there is no infammation to indicate pathology. A dental explorer is helpful to probe for a defect or indentation at the cementoenamel junction and gingival attachment. All surfaces of every tooth should be explored. Normal anatomic appreciation is important, especially of the mandibular frst molar, where furcation involvement or exposure is often misdiagnosed as tooth resorption (Figure 12). FIGURE 7. Stage 5 tooth resorption; clinical appearance in right mandibular third premolar (A) and radiograph confrming Stage 5 tooth resorption (B). A B FIGURE 8. Radiograph demonstrating Type 1 tooth resorption of left mandibular frst molar. Complete tooth extraction is indicated. FIGURE 9. Radiograph of Type 2 tooth resorption demonstrating replacement of the left mandibular third premolar roots by bone. FIGURE 10. Radiographic appearance of Type 3 tooth resorption. Radiograph shows Type 2 tooth resorption in distal root of left mandibular premolar and Type 1 tooth resorption in mesial root.