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Session Schedule & Abstracts
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|Thursday 30th June, 2016|
|Moderator(s): O. Panagiotopoulou & J. Iriarte-Diaz|
MFS1-1 9:30 am Not all bones are created equal: Intrinsic and extrinsic influences on phenotypic expression in the developing skull. Ravosa MJ*, University of Notre Dame; Weiss-Bilka HE, University of Notre Dame; Franks EM, University of Notre Dame; Scott JE, Southern Illinois University; McAbee KR, University of Notre Dame; Brill JA, University of Notre Dame; Pax KC, University of Notre Dame; Pasquinelly AC, University of Notre Dame; Mazur MM, University of Notre Dame; Scollan JP, University of Notre Dame; Eastman MM, University of Notre Dame Matthew.J.Ravosa.email@example.com |
Abstract: In vivo and ex vivo analyses facilitate a unique knowledge of how anatomical structures and their cellular constituents respond to external stimuli, information critical for understanding connective-tissue mechanobiology and phenotypic evolution. In mammals, diet-related variation in loading patterns induces a cascade of changes at the gross, tissue, cellular, protein and genetic levels, with such tissue modeling and remodeling maintaining the integrity of craniomandibular structures. Investigating these phenomena using a novel rabbit model of long-term dietary plasticity, we document the presence of considerable intracranial variation in reaction norms within and between masticatory and non-masticatory elements. In addition, we show that early onset and duration of a loading stimulus associated with a feeding behavior can result in levels of intraspecific variation that mirror morphological differences between sister taxa with disparate diets. Lastly, the rabbit longitudinal data are integrated with evidence about the intrinsic proliferative activity and load-induced responses of osteoblasts from the calvaria, basicranium and mandible in neonate mice. In highlighting the potential cellular bases of relative growth in the skull, our research suggests that cranial osteoblasts are not a homogeneous group of cells, but rather exhibit distinct behaviors depending on their anatomical location and embryological origin. Such findings are important for highlighting why bone should not be viewed as similar across skeletal regions with respect to its intrinsic growth potential or osteogenic responses to external stimuli, an assumption inherent to most comparative and experimental studies. Funding: NSF (BCS-1029149/1214767), Indiana CTSI (NIH TL1TR001107 to A. Shekhar), Wenner-Gren Foundation, and Leakey Foundation.
MFS1-2 10:00 am Tooth wear, textures, and feeding biomechanics . Schulz-Kornas E*, Max Planck Weizmann Center for Integrative Archaeology and Anthropology firstname.lastname@example.org |
Abstract: Most mammals use differentiated cheek teeth for chewing, to divide food into small pieces. The occlusal surface and the occlusal gap are the spatial requirements of any tooth function. The dental tissues enamel, dentin and cementum built an antagonistic grinding system with the tooth tissues. Nevertheless the multi-body dynamics of the processes of wear are still not well understood. Therefore the review presented here aims to pinpoint these developments compiling an overview of the main controversies in the field of tooth wear analyses in vertebrate morphology. Main developments from the early days of traceology till recent discoveries analyzing surface textures are discussed. Wear traces on teeth have been described extensively and a guideline to the quantitative approaches that have been developed during the last fifteen years is given. The tribological concept understanding tooth surfaces as antagonists of a tribosystem is introduced and illustrated with data from controlled feeding experiments. Furthermore it is shown how surface textures can be related not only to dietary composition but additionally to chewing direction and feeding biomechanics. Some concluding remarks are given reminding to technical pit falls and presenting open questions for future research directions.
MFS1-3 10:30 am Performance and integration in mammalian dentitions: from blade sharpness and dental complexity to the inhibitory cascade. Evans A.R.*, Monash University email@example.com |
Abstract: Teeth play a very important role in the mammalian feeding system, enabling effective breakdown of a variety of foods and helping to fuel the high metabolic rates of mammals. We can examine teeth as tools for the breakdown of food. Efficient mastication requires three important elements: 1) effective tool shape, 2) appropriate number of tools on the tooth, and 3) precise alignment of tool components. Fundamental tool types include blades, cusps and basins. Within each of these types, the shape of particular surfaces affects how much force or energy is taken by the tool to divide food. Here I report on experiments using idealised 3D printed tools to examine the specific effect of parameters such as blade sharpness, rake angle and approach angle on fracturing both simulant and real foods. The greater the number of tools on a tooth or toothrow, the more opportunity there is for food fracture during an occlusal stroke, but the less space between tools. The number of tools on a tooth can be estimated by the Orientation Patch Count (OPC) metric of dental complexity. Disparity in mammal diets is reflected in differences in their dental complexity, such that carnivores have simpler teeth than herbivores. While this information is useful for estimating diets of extinct species, it also gives clues to the limits on tooth function in mammals. For tools such as blades to work effectively, upper and lower teeth must precisely align during the occlusal stroke, but it is unknown how this alignment is established during development and evolution. Earlier work has shown that mammal teeth develop and evolve according to a pattern known as the inhibitory cascade. It is likely that the inhibitory cascade is instrumental in ensuring precise alignment of occluding teeth, and was a key characteristic enabling the evolution of mastication in mammals. As an example, we show that hominin dental evolution was tightly constrained by the inhibitory cascade.
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