Loss of molar occlusion and mandibular morphology in adults in an ancient human population consuming a coarse diet.

The purpose of the study is to investigate the link between number of molar teeth retained in occlusion and mandibular morphology in adults in an ancient, high dental wear human population. The study material comprises skeletons from Mediaeval Wharram Percy, England (N = 50 female, 69 male adults). It was hypothesized that adults retaining fewer occluding molars would show reduction in mandibular dimensions, particularly in the ascending ramus and gonial regions where the main muscles of mastication have their insertions. Molar occlusal status is assessed using the concept of functional units. Mandibular morphology is assessed using a suite of ten linear measurements plus the mandibular angle. Results show no evidence for any association between number of molars retained in occlusion and mandibular angle. There was an association between mandibular size and number of molars retained in occlusion, with smaller mandibular dimensions in those retaining fewer occluding molars. Some measurements were affected more than others so that there was also some shape alteration. Alteration of mandibular dimensions was more clearly demonstrable in females than in males. Only in females could significant reduction in the ascending ramus and gonial regions be demonstrated. Reasons for the apparent difference in response to loss of molar occlusion between male and female mandibles are unclear, but sex differences in bony metabolism mediated by hormonal factors may be implicated. Results suggest that care should be exercised when including mandibles from individuals showing loss of molar occlusion in morphological studies.

Mays SA 《-》

Resorption of mandibular alveolar bone following loss of molar teeth and its relationship to age at death in a human skeletal population.

Estimating adult age at death in skeletal remains is problematic, particularly in older adults. Molar wear is arguably the most reliable ageing technique for palaeopopulations, but many older adult skeletons have lost their molar teeth ante mortem, precluding its application. Resorption of the alveolar process occurs following tooth loss, and this appears to continue for a prolonged period. The current work investigates the relationship of this process to individual age in a nineteenth century AD European archaeological skeletal series of known age at death (N = 92 individuals), and discusses its potential as an age indicator. Mandibular corpus height was measured at the different molar positions. In females, reduction of corpus height with age was found at molar positions showing ante mortem loss. In both sexes, a relationship was found between age and a simple composite measure of corpus height in the molar region in those showing ante mortem loss of one or more mandibular molars. The correlation was stronger in females (r = -0.74) than in males (r = -0.49), appeared approximately linear, and continued into the ninth decade, the oldest age group in the study material. The results suggest that investigation of height of the posterior part of the mandibular corpus as a skeletal age indicator for individuals that have lost one or more molar teeth is merited in other palaeopopulations.

Mays S 《-》

Mandibular morphology in two archaeological human skeletal samples from northwest Europe with different masticatory regimes.

Mandibular morphology, assessed osteometrically, is studied in two historic human skeletal series (N = 64 individuals) from northwest Europe, one from Zwolle, the Netherlands (19th century CE), the other from Wharram Percy, England (10th-19th century). Both groups show greater dental wear than modern Western populations, but the rate of wear is greater at Wharram Percy than at Zwolle, suggesting a more vigorous masticatory regime. The aim is to evaluate any differences in mandibular morphology between the two groups that might relate to the inferred difference in biomechanical loading upon the chewing apparatus consequent upon the different physical properties of the diets consumed. Results indicate that the mandibles from Zwolle are generally smaller than those from Wharram Percy, especially in the gonial and ramus region and in the height of the post-canine corpus. These differences are consistent with those predicted on biomechanical grounds. That clear differences were observed in two samples whose masticatory regimes were distinct but not very different is an indication of the sensitivity of mandibular morphology to biomechanical input, and supports its value for investigating differences in physical properties of diets in palaeopopulations.

Mays S 《-》

Mandibular molar root morphology in Neanderthals and Late Pleistocene and recent Homo sapiens.

Neanderthals have a distinctive suite of dental features, including large anterior crown and root dimensions and molars with enlarged pulp cavities. Yet, there is little known about variation in molar root morphology in Neanderthals and other recent and fossil members of Homo. Here, we provide the first comprehensive metric analysis of permanent mandibular molar root morphology in Middle and Late Pleistocene Homo neanderthalensis, and Late Pleistocene (Aterian) and recent Homo sapiens. We specifically address the question of whether root form can be used to distinguish between these groups and assess whether any variation in root form can be related to differences in tooth function. We apply a microtomographic imaging approach to visualise and quantify the external and internal dental morphologies of both isolated molars and molars embedded in the mandible (n=127). Univariate and multivariate analyses reveal both similarities (root length and pulp volume) and differences (occurrence of pyramidal roots and dental tissue volume proportion) in molar root morphology among penecontemporaneous Neanderthals and Aterian H. sapiens. In contrast, the molars of recent H. sapiens are markedly smaller than both Pleistocene H. sapiens and Neanderthals, but share with the former the dentine volume reduction and a smaller root-to-crown volume compared with Neanderthals. Furthermore, we found the first molar to have the largest average root surface area in recent H. sapiens and Neanderthals, although in the latter the difference between M(1) and M(2) is small. In contrast, Aterian H. sapiens root surface areas peak at M(2). Since root surface area is linked to masticatory function, this suggests a distinct occlusal loading regime in Neanderthals compared with both recent and Pleistocene H. sapiens.

Kupczik K ，Hublin JJ 《-》

Changes in mandibular dimensions during the mediaeval to post-mediaeval transition in London: a possible response to decreased masticatory load.

Biomechanical forces, such as those produced during mastication, are considered a primary agent in stimulating craniofacial growth and development. There appears to be a strong connection between the strength of the masticatory muscles and the dimensions of the craniofacial complex, with changes in biomechanical force and muscular strength influencing and altering the underlying bony tissues. This is markedly apparent in the mandible and it is possible to infer that changes to mandibular form are due in part to dietary changes. This study aims to investigate this idea by using an archaeological sample from a period that experienced important dietary changes as a result of the Industrial Revolution. 279 skeletons from the mediaeval and post-mediaeval periods in London were selected for analysis, and a detailed metric examination of each mandible was carried out. Males and females were analysed separately and statistically significant reductions were observed in nearly all post-mediaeval measurements. This effect was most pronounced in the areas of the mandible associated with masticatory muscles attachment, including the gonial angle, ramus height and width, bi-gonial breadth and bi-condylar breadth. These recorded changes in mandibular morphology of mediaeval and post-mediaeval Londoners are most likely the result of a shift in diet (and associated decrease in masticatory function) observed in the period surrounding the Industrial Revolution.

Rando C ，Hillson S ，Antoine D 《-》