Studies of the Dentition of Sheep: IV.—Radiological Studies from Investigations into the Shedding of Permanent Incisor Teeth by Hill Sheep

Abstract

SUMMARY This communication reports the results of radiological studies carried out during the course of long-term investigations of the shedding of permanent incisor teeth by Scottish Blackface sheep. These experiments were primarily aimed at explaining why sheep on some hill farms begin to shed their permanent incisor teeth at a much earlier age than is the case on other hill farms. In general these studies confirmed the results of clinical observations which were reported by Duckworth et al. (1962) as Part I in this series and added further information. On ‘poor tooth’ farms the permanent incisor teeth were commonly found to be migrating from their sockets very shortly after they had reached their fully functional position. Migration of permanent incisors from their sockets was often first evident without radiographically apparent erosion of the walls of the sockets and widening of the periodontal membranes, but this was, in general, quickly followed by severe erosion of the periphery of the incisor alveolar bone. Erosion of incisor alveolar bone was invariably severe in flocks where turnip feeding is practised. The incisors were often eventually left with little or no bony support and were thus held mainly or solely in soft tissue. It is considered that this overall deterioration of the alveolar bone structure and the consequent removal of the solid supports for the teeth inevitably leads to the loss of the incisor dentition. Whatever the state of the incisor alveolar bone the indications were that, in general, the skeletons of the hill sheep in these studies were well mineralized.