The pathogenesis of excessive wear in the permanent teeth of sheep.
The two central pairs of permanent incisor teeth (l1P, I2P) were compared post mortem in sheep from two flocks, one of which showed excessive wear. Sheep were usually killed in groups of six. Excessive wear occurred during the winter and spring after the eruption of l1P. When l1P erupted at an early age it was also subject to that season;s wear but when it erupted at a later age, it was subject to less wear according to the amount of time it was in apposition with the dental pad during the high wear season. A small amount of compensatory growth at the root of the tooth occurred in some sheep when cementum was deposited on the apex. Apparent eruption of the crown of the tooth was actually due to gum recession. Normal reparative dentine was laid down in the pulp cavity of the crown of the tooth in anticipation of wear, but where wear was excessive unstructured dentine was deposited. In two cases the rate of wear was so great that the reparative dentine could not keep up and infection was able to gain access to the pulp cavity. There was no evidence of difference in the rate of wear of the molar teeth between the two flocks.
Thurley
D C
DC
Wallaceville Animal Research Centre, Research Division, Ministry of Agriculture and Fisheries, Private Bag, Upper Hutt.