Wear of fluorapatite single crystals. I. A method for quantitative evaluation of wear.

The effect of dentifrices and toothbrushing on the wear of enamel, exposed dentin, and cementum has been the topic of extensive experimental research.1-3 Little attempt has been made, however, to study the mechanisms that control the surface failure of enamel under an applied stress that results primarily from sliding. To identify the wear phenomenon of enamel at the level of slip or cleavage interactions or both requires a simplified system that is not influenced by variable or undetermined effects (for example, dentifrice composition and the rate of brushing). Single crystals have been used in industry for the past decade to study the phenomenon of wear.46 Bowden, Brookes and Hanwell7,8 studied the plowing friction and surface damage of diamond and MgO single crystals. By sliding conical diamonds with various apical angles on known crystallographic surfaces in specified directions, they related frictional anisotropy and surface damage to specific slip and cleavage interactions. The purpose of this study was to evaluate a method for characterizing the surface fail-