Tooth resorptions (TRs) are dental lesions associated with progressive loss of tooth substance. A high prevalence of TR is observed in the feline population in general, and especially in the domestic cat. The etiology of TR and the reason for the high prevalence in cats is unknown. This study was conducted to measure the serum vitamin D3 (25-OH-D) concentrations of a colony of domestic cats to determine whether there was a correlation with the prevalence of tooth resorption. Cats included in the study (n = 64) had been fed a variety of nutritionally complete extruded dry premium diets throughout their lives and had never been fed canned food; the dry diets the cats received in the period prior to the study varied in vitamin D3 content from 800 to 1500 IU/kg dry matter (most ranged from 900–1000 IU). The study included a single dental examination, with a complete periodontal examination performed under general anesthesia. A complete set of 10 radiographs was taken for each cat. Lesions were classified (based on radiographic appearance) as type 1 (presence of a normal periodontal ligament and similar radiodensity of affected and adjacent tooth roots) or type 2 (absence of the periodontal ligament space and extensive root replacement by alveolar bone). Cats were fasted overnight and jugular vein blood samples (2 mL) were collected for serum vitamin D measurements. A total of 168 TRs were diagnosed in 40/64 cats; 85 were type 1 and 83 were type 2. Although they were not significantly different, the mean serum 25-OH-D concentrations in these affected cats were lower compared with those in cats without TR. Higher serum 25-OH-D concentrations were not associated with a higher prevalence of TR.

Commentary: This study did not support the potential for varying concentrations of serum vitamin D in the pathogenesis of TRs and provided additional conflicting data regarding the relationship as documented in the literature. Future studies with large sample sizes and varied populations should be performed to better characterize the relationship. It is of note that serum vitamin D3 (25-OH-D) assays are difficult to conduct in veterinary subjects; assay optimization may help to circumvent these difficulties and to identify a causative and potentially preventable cause of TRs in feline populations.—Indu Mani, DVM, DSc

Tooth resorption and vitamin D3 status in cats fed premium dry diets. Girard N, Servet E, Ing F, et al. J VET DENT 27:142-147, 2010.