Inter- and intrapopulation variability of dental tissue proportions of European and African modern human populations’ permanent canines

Numerous studies have shown that human dentition traits vary both between and within populations. However, there is still little knowledge about how dental tissue proportions differ between modern human groups. In this study, two samples of European and African individuals were compared to assess the possible differences and similarities present in the dental tissue dimensions of their permanent canines. For this purpose, the volumes and surface areas of the coronal dentine and pulp complex and the enamel cap of 127 canines were measured by microcomputed tomography. The results show the existence of interpopulation variability in the dental tissue pattern of both samples, which is mainly due to the presence of a larger enamel component in the African population, while dentine seems to play a less critical role in the differences described between both dental samples. We also observed a similar pattern of sexual dimorphism in the dental tissue proportions of European and African canines, but in this case, the intrapopulation variability was mainly due to the presence of a greater dentine component in males. Therefore, because the dimensions of dental tissues vary at both inter- and intrapopulation levels in modern human groups, our results highlight the importance of selecting comparative samples that are geographically mixed and sex-balanced for future paleoanthropological investigations on dental tissue patterns of extinct and extant species to avoid overestimating or underestimating any possible similarities or differences.

Sexual dimorphism of deciduous canine dental tissues dimensions of modern human populations

The dental tissue proportions of human permanent canines are one of only a few sexually dimorphic features that are present in childhood, and therefore offer the opportunity to estimate the sex of immature individuals. This work aims to evaluate for the first time the degree of sexual dimorphism ‍in the three-dimensional (3D) measurements of deciduous canine dental tissues, to assess their potential in sexual assessment. Computed microtomographic techniques have been employed to anal‍yse the maxillary and mandibular deciduous canines of 65 individuals (36 females and 29 males) of known sex and age. The teeth were scanned and the volumes and 3D surface areas of the enamel cup and the dentine–pulp complex were obtained. Our results did not show statistically significant differences in either the absolute or relative dimensions of the enamel and dentine between female and male teeth. We hence conclude that volumes and 3D surface areas of deciduous canine dental tissues do not allow for sex determination, which contrasts with what has been observed in permanent canines by other authors. The differences in the degree of sexual dimorphism in dental tissue proportions be‍tween permanent and deciduous canines seem to be due to a decrease in the intersexual variability of ‍the dentine component dimensions. Since the dentine component is a tissue capable of responding to ‍changes in sex hormone concentration levels, our results might indicate that hormones play a more important role in the development of sexual dimorphism in the permanent dentition than previously thought.