Sexual Dimorphism in Permanent Human Dentition
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Sexual dimorphism refers to differences between males and females of the same species. A general pattern of sexual dimorphism is displayed in humans. Across mammalian populations, males generally have a larger body than females. Many studies have shown that, as body mass increases, tooth volume increases isometrically (Ungar, 2014). For example, on average, males have larger teeth than females (Schwartz and Dean, 2005). However, despite clear gross dental size differences, some studies have suggested that males and females also exhibit divergent quantities of enamel (Saunders et al., 2007). Females have been shown to have relatively thicker enamel, and a larger enamel cap area than males (Smith et al., 2006). This reveals an ambiguity. Although males possess overall larger teeth, studies suggest that male dental composition contains less relative enamel than would be expected given their tooth size. Similarly, females have been shown to exhibit smaller teeth than males, but a greater relative amount of enamel. This study has developed a methodological protocol for taking volumetric measures on dental microstructure using computed tomography (CT) scans. This protocol will help future studies evaluate the relative quantity of enamel and dentin in teeth. A better understanding of the volumetric differences in the dental microstructure is imperative to the understanding of dental sexual dimorphism. We examined the dental microstructure using 3D modeling from individuals in the Point Hope population. This population has been known to use their teeth as tools in several ways. We understand the microstructure of the dentition within the sample population may be impacted by some wear and use of dentition within this community. The dental microstructure was examined using 3D modelling in 14 individuals from a sample of the Point Hope population including eight adult females and six adult males of unknown age. Three hundred and twelve total teeth were examined. One hundred and eighty-six teeth came from female subjects, and one hundred twenty-six teeth came from males. The 3D models of the dentition and microstructure of enamel and dentin was generated using the software. Due to a small sample size, analysis of gross dental size and enamel volumes were performed using a one-tailed, non-parametric Mann-Whitney U-Test (a=0.10). Volumetric measurements of the total tooth volume, enamel volume, and dentin volume were recorded for each subject. Our results suggest that there are divergent quantities of enamel between males and females within the mandibular teeth. Specifically, the central incisors, lateral incisors, canines, first premolars, second premolars, and second molars within the mandible showed that there are statistical differences between sexes in dental composition. Males possessed a greater amount of enamel in their mandibular central incisors, lateral incisors, canines, first premolars, second premolars, and second molars. Additionally, the maxillary dentition also demonstrated notable statistical difference in enamel quantity within the second premolars between males and females. Males had a larger enamel quantity within their second molars than females. Males also demonstrated larger average total dental volume (345.59 mm3) than females (342.02 mm3). We have successfully generated a protocol in which future studies could quantify dental microstructure and add to the understanding of dental sexual dimorphism. Further research implementing this protocol for segmenting CT scans and utilizing the segmentation to gather volumetric measurements of dental microstructure should use higher resolution micro-CT scans and a larger sample population.