Variation in Dental Tissues: Using Bayesian Multilevel Modelling to Explore Intra- and Inter-Individual Dental Variation

Abstract

ObjectivesDental variation within populations and, even more so, within individuals is far less well understood than variation between populations. This is problematic as a single tooth type is often used as a representative of the whole dentition, despite a lack of understanding of intra-tooth type relationships. This research investigates the variation of dental tissues and proportions within and between individuals. Materials and MethodsUpper and lower first incisor to second premolar tooth rows were obtained from 30 individuals (n=300), from 3 archaeological samples. The teeth were micro-CT scanned and surface area and volumetric measurements were obtained from the surface meshes extracted. Dental variation of these measurements on a tooth and individual level was studied using Bayesian Multilevel Modelling. ResultsThe individual and tooth level variation differed by dental measurement, ranging between 9.5%-47.5% and 52.6-90.5% respectively. Enamel volume had the highest degree of individual-level variation in contrast to coronal dentine volume that had the lowest of individual-level variation. Tooth type, isomere, and position in field all showed a significant effect on the dental measurements examined in this study. DiscussionTooth selection and sampling strategies should consider individual and tooth-level variation, with at least one tooth from each type and isomere included in analyses. This will ensure that any population-level differences are not masked by variability between teeth. The low level of coronal dentine volume individual variation indicates that it is particularly useful in studies with small sample sizes.