Correlates of enamel hypoplasia with human dental reduction

Human dental reduction has been manifested in evolutionary and secular trends, but it is not known to what degree each of these complementary processes contributes to changes in tooth size. Enamel hypoplasia is a marker of developmental stress that is often found to be of greater frequency and severity in populations undergoing dental size reduction. In order to test the developmental association of enamel hypoplasia with tooth size, measurements of bucco-lingual and mesio-distal diameters were taken on teeth of 54 black male skulls from southern Africa. Those dentitions that exhibited incisal enamel hypoplasia were significantly reduced in size as compared to those showing no signs of developmental stress. A distinct pattern of reduction emerged: the bucco-lingual diameters of the I¹ , I² , P³ , P⁴ , M¹ , and M² were significantly reduced, whereas the mesio-distal diameters of only the I² and M² decreased in size. The I² and M² showed the greatest degree of reduction despite the lack of macroscopic enamel hypoplasia on the M² . Application of the data to the variety of dental reduction patterns evinced in modern and ancient populations indicates that factors including tooth shape, developmental timing of stress, and genetic determinants of tooth size must be considered in order to partition evolutionary and secular trends in the dentition.