ENAMEL THICKNESS OF HUMAN MAXILLARY MOLARS RECONSIDERED

Forty-four modern human maxillary molars (M1 = 21, M2 = 12, and M3 = 1 1) were sectioned through the mesial cusps in a plane perpendicular to the cervical margin of the crown. Eight measurements of enamel thickn ess as well as bucco-lingual (BL) and mesio-distal (MD) diameters were recorded for each tooth in order to investigate differences in these dimensions between tooth categories. Uni- and multi-variate analyses r evealed first maxillary molars to have generally thinner enamel than s econd or third upper molars, especially with regard to the occlusal ba sin. Furthermore, the decrease of MD diameters from anterior to poster ior is greater than that of BL diameters. Principal Component Analysis using enamel thickness measurements resulted in complete separation o f first molars, while second and third maxillary molars showed a certa in amount of overlap. This finding casts doubt on using an overall mea sure of ''molar enamel thickness'' derived from mixed samples of molar s for taxonomic purposes. There appears to be a relationship between b ite force and enamel thickness such that posterior molars, where masti catory forces are stronger, have thicker enamel than anterior teeth. I t is suggested that the gradient of enamel thickness between (and with in) teeth in extant and extinct species may thus provide further infor mation about relative wear resistance as well as the biomechanical con straints of the orofacial skeleton. (C) 1993 Wiley-Liss, Inc.