Dental and Temporomandibular Joint Pathology of the Northern Fur Seal (Callorhinus ursinus).

Skulls from 145 northern fur seals (Callorhinus ursinus) were examined macroscopically according to predefined criteria. The museum specimens were acquired from strandings along the west coast of the USA between 1896 and 2008. Seventy-one skulls (49.0%) were from male animals, 56 (38.6%) from female animals and 18 (12.4%) from animals of unknown sex. Their age varied from juvenile to adult, with 58 adult animals (40.0%) and 87 juvenile animals (60.0%). The majority of teeth were available for examination (95.1%); 3.4% of teeth were artefactually absent, 0.8% were deemed absent due to acquired tooth loss and 0.6% were deemed congenitally absent. Males were no more likely than females to have either acquired tooth loss (P = 0.054) or congenitally absent teeth (P = 0.919). Adults had significantly more acquired tooth loss than juveniles (P = 0.0099). Malformations were seen in 11 teeth (0.2% of all 4,699 teeth available for examination). Two roots, instead of the typical one root, were found on 14 teeth (0.3%). Supernumerary teeth were associated with 14 normal teeth (0.3%) in eight specimens (5.5% of the total number of specimens). A total of 22 persistent deciduous teeth were found, 19 of which were associated with the maxillary canine teeth. Attrition/abrasion was seen on 194 teeth (3.9%); the canine teeth were most often affected, accounting for 39.7% of all abraded teeth. Adults were found to have a greater prevalence of abraded teeth than juveniles (P <0.0001). No significant difference was found in the appearance of attrition/abrasion between males and females (P = 0.072). Tooth fractures were found in 24 specimens (16.6%), affecting a total of 54 teeth (1.1%). Periapical lesions were found in two skulls (1.4%). None of the specimens showed signs of enamel hypoplasia. About a fifth (18.6%) of alveoli, either with or without teeth, showed signs of alveolar bony changes consistent with periodontitis. A total of 108 specimens (74.5%) had at least one tooth associated with mild periodontitis. Lesions consistent with temporomandibular joint osteoarthritis (TMJ-OA) were found in 29 specimens (20.0%). Both periodontal disease and TMJ-OA were significantly more common in adults than in juveniles (P <0.0001). Periodontitis was found to be more common in males than in females (P <0.012). Although the significance of the high incidence of periodontitis and TMJ-OA in the northern fur seal remains unknown, the occurrence and severity of these diseases found in this study may play an important role in this species morbidity and mortality.