Original Synthetic Article: The relationships between occlusion and posture in the hominid lineage, implications for the transition between mesolithic and neolithic populations

Abstract

Abstract – Background and Aim: Connecting the occlusion to the posture during growth consists in studying the correlations between the contact of both dental arches and the constraints acting within the skull base, at the level of the sphenoidal synchondroses. They articulate the ethmoid, sphenoid and basi-occipital anlages which are in the same alignment during the first weeks of the embryonic period. The basi-occipital belongs to the metamerised axial skeleton (petrous bones, exo-occipital, vertebral column and sacrum), the sphenoid and ethmoid belong to the prechordal territories. The simiiforms are the only mammals where embryonic kinetics breaks the alignment by a flexure sitting at the chordal-prechordal limit because of increasing tensions acting during neurulation. The degree of verticality of both facial and axial skeletons (i.e. the position of the cerebellar fossa) of the two temporo-mandibular joints and the mandibular dental arch depend on these late embryonic kinetics. The future occlusion between the maxillar and the mandibular dental arches requires coherent dynamics between the three sphenoidal synchondroses. Materials and Methods: These correlations were analyzed by using a metric methodology applied to x-rays or CT scan images of extant and fossil skulls. Results and conclusions: This approach presents major interests for the study of occluso-postural balances in fossil hominids as well as for the analysis of the evolutionary mode, tempo and phylogenetic association, in particular when dealing with the emergence of the contemporary occlusion at about 7,000 years BP. A better knowledge of this transition can be useful to understand the increasing ageneses and occluso-postural dysharmonies in modern populations.

Key words: occlusion, posture, biodynamics, ontogeny, hominids, phylogeny, evolution.