Infection may be introduced into the pulp chamber of the teeth by various routes, eg, hematogenous (anachoretic pulpitis), periodontal, or from direct crown insult. In horses, hypoplasia of the cementum in the enamel lakes (infundibulae) of the upper cheek teeth may predispose to infundibular caries and subsequent pulpitis and apical osteitis. Depending on the site of the infected tooth, there may be accompanying signs of maxillary sinusitis, local cellulitis, periostitis, alveolar periodontitis, and fistula formation. The pathologic features of dental decay are nonspecific. Consequently, the cause of the apical infection in a draining mandibular dental fistula in a horse or llama may be obscure. Many animals are not examined until the infection is advanced, and tooth fractures may well be secondary rather than primary. It has been suggested that, in some species (eg, the horse), the initiating feature of the establishment of apical osteitis and pulpitis is abnormal eruption and dental impaction. The cause of apical osteitis in cattle and New World camelids may be similarly influenced.
When dental decay is advanced, extraction of the affected tooth is recommended. In horses, this usually has been achieved by surgical exposure of the decayed tooth and then repulsion into the mouth. Recent experience has shown that oral extraction is possible, with careful technique, sedation, and nerve blocks, thus avoiding serious complications associated with repulsion and the use of general anesthesia. After exodontia, the socket should be cleaned carefully to remove all fragments of diseased bone and tooth. Dental acrylics, dental waxes, and wound packs should be used to ensure that the socket can heal properly by protecting it from food material. After dental extractions, the adjacent teeth gradually move to close the gap in the dental arcade. However, this process is never complete, and the occluding arcade will form a step elongation opposite the missing teeth and hooks at the ends of the opposing arcades (both rostral and caudal). Such irregularities in horses can be corrected by grinding and realigning the arcades every 6–12 mo.
Because of such complications, surgical techniques that preserve the teeth should be considered, at least for horses. The age of the animal and the specifics of local disease should be considered before contemplating root-end resection and endodontic therapy in large animals.