Para-masticatory wear facets and their functional significance in hunteregatherer maxillary molars

摘要

The mastication of tough and hard foods combined with the extensive use of teeth as tools, have been considered possible antemortem causes in determining enamel microfractures of the tooth crown. This phenomenon, known as dental chipping, has been found in different fossil hominins and in several pre-historic and historic human populations who adopted different subsistence strategies. However, little is understood of the mechanism, function and the formation of dental chipping. In this study we analyze the maxillary molar wear areas associated with dental chipping (and named para-facets) of several hunteregatherer specimens, using the Occlusal Fingerprint Analysis method. We employ three-dimensional digital models of tooth crowns created by surface scanning of dental replicas, to analyze the dip and dip directions of normal occlusal wear areas and para-facets. This allows us to reconstruct the jaw movements responsible for the creation of para-facets, and investigate whether they are produced during normal mastication or not. Vectors of the para-facets do not show any preferred direction and are distributed randomly as visualized by the occlusal compass, displaying significant differences with the major jaw movements in action during the normal chewing cycle. More importantly, no antagonist contacts in the lower teeth are associated with the para-facets of the upper teeth. This excludes the possibility that the para-facets are created during normal mastication. We therefore suggest that this unusual type of tooth wear is mainly due to attritional and abrasive contacts generated through daily task activities for foods processing and/ or manufacturing of objects.