A histological study of peripheral dental caries of equine cheek teeth.

Peripheral caries of equine cheek teeth is a poorly described disorder and, in particular little is known of its histopathology. Histological examinations of decalcified sections of 21 equine peripheral caries-affected cheek teeth showed two different patterns of cemental lesions; including progressive enlargement of focal, flask-like lesions leading to breakdown of the adjacent cementum, and secondly; a more generalized flaking-off of thin layers of under-run, surface cementum. A thick layer of plaque and food material usually lay on the surface of affected cementum and also within cemental defects. Gram-stained sections showed large numbers of bacteria within the lacunae and canaliculi of affected peripheral cementum and within associated plaque. Pioneer bacteria were also seen within dentinal tubules of adjacent, normal-appearing dentin. Subgingival extension of peripheral caries lesions with localized periodontal destruction was rare. Grading of peripheral caries lesions by gross examination was found to underestimate the severity of the disorder as compared to histological grading.