ENAMEL MICROSTRUCTURE AND MOLAR WEAR IN THE GREATER GALAGO, OTOLEMUR-CRASSICAUDATUS (MAMMALIA, PRIMATES)

This study describes the molar enamel microstructure of the greater ga lago, based on SEM study of four individuals. Galago molar enamel cons ists primarily of radially oriented Pattern 1 prisms. However, the mos t superficial enamel is characterized by regions of poorly developed p risms or nonprismatic enamel, and Pattern 3 prisms can be found at dep ths intermediate and deep to the enamel surface. Orientations of prism long axes relative to wear surfaces differ among functionally distinc t regions (cuspal facets, Phase I/II facets, and crushing basins). Con sequently, orientations of enamel crystallites relative to these surfa ces also differ. Because crystallites are the structural unit involved in enamel abrasion, these differences in orientation may have importa nt effects on molar wear patterns. Crystallite orientations differ mos t between cuspal facets and Phase I/II facet surfaces. Cuspal facets a re characterized by near surface-parallel interprismatic and surface-o blique prismatic crystallites. Previous experimental studies suggest t hat this arrangement is most resistant to wear when surface-normal (co mpressive) loads predominate. In contrast, prismatic and interprismati c crystallites intercept Phase I/II facet surfaces obliquely, an arran gement expected to resist abrasion when surface-parallel (shearing) lo ads predominate. Superficial enamel is preserved at most basin surface s, indicating that these regions are subject to comparatively little a brasive wear. These results support the hypothesis that galago occlusa l enamel is organized so as to resist abrasion of different functional regions, a property that may prove important in maintaining functiona l efficiency. However, this largely reflects constraints of occlusal t opography on a microstructure typical of many mammals and thus does no t appear to represent a structural innovation. (C) 1993 Wiley-Liss, In c.