"Perikymata Counts in Two Modern Human Sample Populations" by Michael Sheng-tien Yuan

Michael Sheng-tien Yuan

Deposited 2000

Abstract
Many studies based on the perikymata, a dental enamel surface microstructure, have attempted to estimate the age-at-death and crown formation times on human and other fossil specimens. However, due to problematic assumptions, the small sample sizes, the wide range of perikymata count estimates, and the limited portions of dentition explored, considerable controversy has resulted. The collection of baseline information on perikymata counts for various hominid and hominoid dentitions represents an important step toward resolving the controversies.

The goal of this study is to establish a database of modern human perikymata counts of the maxillary third premolars for comparative purposes . This study applies the technique of scanning electron microscopy (SEM) to examine the perikymata, counts of the maxillary third premolars (P 3). A total sample size of 92 specimens, including right and left sides from males (n = 45) and females (n = 47), was investigated in two modern human populations, Taiwanese (Chinese) and Japanese.

The results demonstrated: (1) There is sexual dimorphism, though not statistically significant within the two populations: perikymata counts are higher in males. (2) There are no significant differences between right and left sides. (3) There are no significant differences for sex-combined samples between the two ethnic groups. (4) When data are pooled for the East Asian samples, the mean perikymata count for maxillary third premolars is 150 with a standard deviation of 25. (5) The perikymata counts are significantly correlated with their corresponding crown height. (6) Although the data on perikymata counts follow a normal distribution, the variation is high (coefficient of variation = 16%).

Issues of the histology, periodicity, research methodology, and correlations among the enamel microstructures including cross-striations, lines of Retzius, Hunter Schreger bands, and perikymata, were critically reviewed. This study disputes the perikymata count application in anthropology and questions the interpretation of the ape affinity of australopithecines in hominid dental evolution.