Dental arch shape and tooth wear variability.

The rapid rate of tooth wear frequently reported among certain contemporary aboriginal populations has often been attributed to dietary form and abrasives. Several investigators have reported a close correlation between food bulk and the wear planes formed over the dental arches, i.e., steep oblique wear vs. flat horizontal planes. In this investigation we demonstrate that arch shape is an additional and a significant factor influencing the distribution of wear facets and exposed dentin over occlusal surfaces. We examined 64 dental stone casts of Aboriginals from Yuendumu, Central Australia, born between 1900 and 1940. These casts offer a record of the variety of tooth wear and arch forms and their interrelationships. This group of individuals, some subsisting on abrasive and some on soft diets, have dentition which exhibit various wear rates and wear patterns probably due to the diversity of arch shape, size, and occlusal relationships. Hypsiloid or U-shaped maxillas had a more buccally directed wear in contrast to the parabolic or hyperbolic forms, which exhibit a heavier lingual loading. Varying occlusal conditions also contribute to differing wear patterns over the arches. Individuals with alternate intercuspation, for example, have a more horizontally directed wear. These and other conditions of shape, size, and occlusion emphasize the importance of morphological factors in the production of tooth wear rates and patterns in addition to dietary abrasives.