Cervical and Crown Outline Analysis of Worn Neanderthal and Modern Human Lower Second Deciduous Molars

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 Nean- derthal and modern human (MH) lower second decidu- ous molars (dm 2 s) through the analysis of crown and cer- vical outlines. Crown and cervical outlines were obtained from a three-dimensional (3D) digital sample of uni- formly oriented dm 2 s. Both outlines were centered on the centroid of their area and represented by 16 pseudo- landmarks obtained by equiangularly spaced radial vec- tors 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 sep- arately 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 expan- sion and convex lingual outline shape, whilst MHs have buccodistal reduction and straight lingual outline shape. Therefore, we confirmed that the cervical outline repre- sents an effective parameter for distinguishing between the two taxa when dealing with worn or damaged dm 2 s