Kupczik, Kornelius Florian; (2004) Tooth root morphology in primates and carnivores. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

There are comparatively few studies of mammalian tooth root morphology. This thesis sets out to investigate tooth root morphology in a range of catarrhine primates and carnivores (Carnivora, Pinnipedia and Dasyuromorphia). The primary hypothesis tested in this thesis is that different dietary adaptations are reflected in root morphology and size - and in particular root surface area. Computed tomography scans were taken of the jaws and full adult dentitions of two Papio anubis, four Pan troglodytes, two Gorilla gorilla, two Pongo pygmaeus and two Homo sapiens as well as of 157 loose extracted human teeth. In addition, jaws and dentitions (one each) of Canis familiaris, Panthera pardus, Crocuta crocuta, Ursus americanus and Ailuropoda melanoleuca as well as of Phoca vitulina and Thylacinus cynocephalus were CT-scanned. Three-dimensional imaging software was then used to visualise the teeth in situ in order to describe root morphology and to take linear, angular, planimetric and volumetric measurements of both roots and crowns. The results show that differences in tooth root size (surface area, volume, length, bifurcation height, crown base area and spread of roots) in both primates and carnivores are strongly related to both differential tooth use and material properties of foods. Teeth which have to sustain large occlusal forces exhibit particularly large root surface areas and volumes. However, root number is not necessarily related to an increase in root surface area or an increase of the crown base. Root surface area and volume, at least in humans, do not show a strong relationship with crown size. The observed pattern, or gradient, of root surface area along the tooth row is likely to limit on masticatory muscle activity. Great apes, humans, and some carnivores are characterised by a mesio-distal reduction in root surface area as part of a complex mechanism to prevent the TMJ from being subjected to tensile forces. However, in those carnivores where the mesio-distal gradient of root surface area continues to increase, a well developed TMJ is required to resist these high tensile forces. Tooth root morphology has wider implications for the study of diets and the masticatory apparatus of extant and extinct mammalian species. This thesis concludes that root size is not only related to masticatory function but is constrained by jaw dimensions, dental development and tooth eruption.

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