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Objectives: Exact symmetry and perfect balance between opposite jaw halves, as well as between antagonistic teeth, is not frequently observed in natural masticatory systems. Research results show that asymmetry in our body, skull, and jaws is often related to genetic, epigenetic, environmental and individual ontogenetic factors. Our study aims to provide evidence for a significant link between masticatory asymmetry and occlusal contact between antagonist teeth by testing the hypothesis that tooth inclination is one of the mechanisms driving distribution of wear in masticatory phases in addition to dietary and cultural habits., Materials and Methods: The present work investigates the relationship between dental macrowear patterns and tooth inclinations on a sample of complete maxillary and mandibular 3D models of dental arches from 19 young and adult Yuendumu Aboriginal individuals. The analysis was carried out on first molars (M1) from all quadrants. Occlusal Fingerprint Analysis was used for the quantification of macrowear patterns, and 2D cross-sectional geometric analysis was carried out to investigate asymmetry in dental arches., Results: The asymmetry is highly variable on both arches, and it is associated with differences in the inclination of upper M1 crowns. Each molar has variable inclination (buccal/lingual) which influence tooth to tooth contact, producing greater or lesser variation in wear pattern. Interindividual variability of morphological variation of the occlusal relationship has to be considered in macrowear analysis., Discussion: Our results suggest that overall asymmetry in the masticatory apparatus in modern humans affects occlusal contact areas between antagonist teeth influencing macrowear and chewing efficiency during ontogeny., (© 2018 The Authors. American Journal of Physical Anthropology Published by Wiley Periodicals, Inc.)

Enamel thickness figures prominently in studies of human evolution, particularly for taxonomy, phylogeny, and paleodietary reconstruction. Attention has focused on molar teeth, through the use of advanced imaging technologies and novel protocols. Despite the important results achieved thus far, further work is needed to investigate all tooth classes. We apply a recent approach developed for anterior teeth to investigate the 3D enamel thickness of Neandertal and modern human (MH) canines. In terms of crown size, the values obtained for both upper and lower unworn/slightly worn canines are significantly greater in Neandertals than in Upper Paleolithic and recent MH. The 3D relative enamel thickness (RET) is significantly lower in Neandertals than in MH. Moreover, differences in 3D RET values between the two groups appear to decrease in worn canines beginning from wear stage 3, suggesting that both the pattern and the stage of wear may have important effects on the 3D RET value. Nevertheless, the 3D average enamel thickness (AET) does not differ between the two groups. In both groups, 3D AET and 3D RET indices are greater in upper canines than in lower canines, and overall the enamel is thicker on the occlusal half of the labial aspect of the crown, particularly in MH. By contrast, the few early modern humans investigated show the highest volumes of enamel while for all other components of 3D enamel, thickness this group holds an intermediate position between Neandertals and recent MH. Overall, our study supports the general findings that Neandertals have relatively thinner enamel than MH (as also observed in molars), indicating that unworn/slightly worn canines can be successfully used to discriminate between the two groups. Further studies, however, are needed to understand whether these differences are functionally related or are the result of pleiotropic or genetic drift effects., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: This study investigates the effect of allometry on the shape of lower dm2 (dm2) and lower M1 (M1) crown outlines and examines whether the trajectory and magnitude of allometric scaling are shared between Neandertals and Homo sapiens., Methods: Our sample included 164 specimens: 57 recent H. sapiens, 44 Upper Paleolithic H. sapiens, 17 early H. sapiens, and 46 Neandertals. Of these, 59 represent dm2/M1 pairs from the same individuals. Occlusal photographs were used to obtain crown shapes of dm2s and M1s. Principal components analysis (PCA) of the matrix of shape coordinates was used to explore the pattern of morphological variation across the dm2 and M1 samples. Allometry was investigated by means of the Pearson product-moment correlation coefficient. Two-block partial least squares (2B-PLS) analysis was used to explore patterns of covariation between dm2 and M1 crown outlines of matched individual pairs., Results: The PCA confirmed significant differences between Neandertal and H. sapiens dm2 and M1 shapes. Allometry accounted for a small but statistically significant proportion of the total morphological variance. The magnitude of the allometric contribution to crown shape was stronger among Neandertals than among H. sapiens. However, we could not reject the null hypothesis that the two species share the same allometric trajectory. The 2B-PLS analysis of the pooled sample of paired individuals revealed a significant correlation in crown shape between dm2 and M1. While Procrustes distances differed significantly between dm2 and M1 in Neandertals, it did not among H. sapiens groups., Conclusions: Our results confirm several of the results obtained by a similar study of upper dm2/M1 (dm(2)/M(1)), but there are differences as well. Neandertal dm2/M1 shapes are less derived than those of the dm(2)/M(1). Such differences may support previous studies, which have suggested that different developmental and/or epigenetic factors affect the upper and lower dentitions., (© 2015 Wiley Periodicals, Inc.)

Despite the general increase in digital techniques for dental morphometric analyses, only a few methods are available to study worn teeth. Moreover, permanent dentitions are studied much more frequently than deciduous teeth. In this study, we address both issues by providing a taxonomic classification of Neanderthal and modern human (MH) lower second deciduous molars (dm(2) s) through the analysis of crown and cervical outlines. Crown and cervical outlines were obtained from a three-dimensional (3D) digital sample of uniformly oriented dm(2) s. Both outlines were centered on the centroid of their area and represented by 16 pseudolandmarks obtained by equiangularly spaced radial vectors out of the centroid. We removed size information from the oriented and centered outlines with a uniform scaling of the pseudolandmark configurations to unit Centroid Size. Group shape variation was evaluated separately for the dm(2) crown and cervical outlines through a shape-space principal component (PC) analysis. Finally, quadratic discriminant analysis of a subset of PCs was used to classify the specimens. Our results demonstrate that both outlines successfully separate the two groups. Neanderthals showed a buccodistal expansion and convex lingual outline shape, whilst MHs have buccodistal reduction and straight lingual outline shape. Therefore, we confirmed that the cervical outline represents an effective parameter for distinguishing between the two taxa when dealing with worn or damaged dm(2) s., (Copyright © 2012 Wiley Periodicals, Inc.)