Clinical, radiographic and histological findings of seven teeth from two California sea lions (Zalophus californianus) housed under professional care

Abstract

Seven teeth extracted from two adult California sea lions (Zalophus californianus) due to pulp exposure and/or to gain access to the mandibular canine teeth were histologically evaluated, and the findings were compared with clinical and radiographic findings. Three teeth were diagnosed with pulp exposure, and two of these showed no radiographic signs of endodontic disease and were histologically vital with prominent coronal pulpitis and a pulp polyp. Another tooth with pulp exposure was showing clinical and radiographic signs of endodontic disease and was histologically confirmed with pulp necrosis. A discoloured incisor tooth was showing radiographic signs of endodontic disease and was also histologically non-vital. Two clinically and radiographically healthy mandibular first premolar teeth and one second incisor tooth had no evidence of pulpitis or pulp necrosis but had pulp canal obliteration. Regular clinical and radiographic follow-up for 5 months to 3 years after the procedures confirmed uneventful healing of the extraction sites, despite initial flap's dehiscence. Although extractions of affected teeth in California sea lions are considered the most practical and beneficial therapy, these are associated with the risks of extensive trauma and anaesthesia and the need to perform these surgical procedures on-site under variable conditions. As California sea lions can be trained to allow conscious dental radiographic re-checks, monitoring teeth with clinical signs of pulp polyp formation and without radiographic signs of endodontic disease warrant further evaluation/reconsideration from previous recommendations. Endodontic treatment of abscessed teeth in California sea lions is reportedly unsuccessful and is discouraged. However, vital pulpectomy could be an alternative treatment to extraction in teeth with pulp polyps as it was found to be highly successful in humans, but the possibility of endodontic failure and need for further treatments should be weighted in the treatment choice.

Keywords: California sea lion; dental pulp necrosis; dental pulp polyp; endodontic disease; pulpitis.

Figure 1

Animal #1. (A) clinical appearance of the right mandibular canine, premolar, and molar teeth. All teeth are abraded with pulp exposure; pulp tissue is grossly vital and protruding over the crown surface. (B) extraoral radiograph of the right mandible obtained 6 months later. No obvious radiographic signs of endodontic disease are noticed, except for a possibly wider pulp canal of the right mandibular first (apical asterisk) and third premolar (apical full circle) teeth. (C) clinical appearance of the completely healed extraction sites 6 weeks after the surgery. (D) intraoral dental radiograph of the remaining premolar and molar teeth of the right mandible at the time of the second surgery (44 months after radiograph from the 1B image was obtained). Despite dental pulp exposure these teeth appear to continuously develop, close the apices and remain without any obvious radiographic signs of endodontic disease. (E) extraoral radiograph of the right mandible obtained 10 months after the second surgery. All extraction sites are healed and there is evidence of bone formation in all previously vacated alveoli. However, at this point it appears as the remaining premolar and molar teeth developed periapical lucencies. (F) extraoral radiograph of the right mandible obtained 22 months after the second surgery. There is evidence of continuous bone healing of all extraction sites. Periapical disease of the remaining teeth has become even more evident, especially at the molar tooth.

Figure 2

Animal #1. (A) preoperative lateral intraoral dental radiographic view of the left mandibular canine tooth at the time of second surgery. Although the left mandibular second incisor tooth is not entirely visualized, there is visible inflammatory resorption of the tooth apex (asterisk), indicative of endodontic disease of this clinically discolored tooth. (B) preoperative occlusal intraoral dental radiographic view of the left mandibular canine tooth at the time of second surgery. The extraction site of the right mandibular canine tooth has completely healed. There are no obvious radiographic signs of endodontic disease despite pulp exposure of the severely abraded canine tooth. (C) immediate post-operative intraoral dental radiograph of the vacated alveoli of the left mandibular incisor and canine teeth. (D) the extracted teeth (I1: first incisor; I2: second incisor; C: canine; P1: first premolar). (E-G) intraoral radiographs (occlusal view) obtained, respectively, 10, 15, and 22 months after the (second) surgery demonstrate continuous healing and remodeling of the rostral mandibles post dental extractions.

Figure 3

Animal #2. (A,B) intraoral radiographs (occlusal view) obtained 6 months apart reveal severe inflammatory root resorption and periapical lesion of the right mandibular canine tooth (arrows). (C) clinically visible draining tract (arrow) in the area of the right mandibular canine tooth apex corresponds with the radiographic findings on the intraoral radiographs. (D) the draining tract disappeared and the extraction site was completely healed 5 weeks after the surgery. (E) intraoral radiograph (occlusal view) obtained 8 months after the surgery demonstrates healing post extraction of the right mandibular incisor, canine and premolar teeth.

Figure 4

Histological images of the left mandibular canine tooth of the animal #1; H&E stain. (A) low magnification histological image of a section through the crown of the decalcified tooth has uniform dentin (d) except immediately surrounding the pulp chamber (arrows). (B) high magnification histological image of the section in Figure 4A. The vital pulp stroma with many congested blood vessels (v) and moderate numbers of inflammatory cells (small dark foci indicated by arrows). The innermost layer of tertiary dentin resembles bone (bracket). (C) low magnification histological image of a section through the root of the decalcified tooth has normal dentin (d) and uniform pulp stroma in the pulp chamber (p). (D) high magnification histological image of the section in Figure 4C. There is normal organization of dentin (d), predentin layer (arrow), odontoblast layer (double arrow), and pulp stroma (p) without inflammation.