Doctoral Dissertation Improvement: 3-D Modeling of in vivo Bite Force Production and Efficiency in Recent Humans as a Baseline for Evolutionary Change in Homo

在美国国家科学基金会的支持下，该项目将详细分析在世人类面部形态和咬合力之间的关系，为未来尼安德特人面部形态的研究奠定基础。面部骨骼的形状受到多种因素的影响，包括遗传因素和环境因素。影响面部骨骼的最重要的环境因素之一是咀嚼力（如咬合力）的产生。虽然咀嚼生物力学在面部发育中的重要性在进化和临床环境中都得到了认可，但这些变量之间关系的确切性质仍然知之甚少。了解这种关系对于尼安德特人的面部非常重要，因为高强度咬合力的产生和消散已被用作解释尼安德特人面部解剖结构进化发展的工作模型，这与现代人的面部形态有很大不同。对尼安德特人咬合力的产生进行适当的评估是不可能的，因为咬合力的产生是骨骼和肌肉组织相互作用的结果，而后者并没有保存在化石中。因此，先前对尼安德特人咀嚼能力的分析仅限于数学模型，其准确性尚未得到很好的确立。考虑到这些限制，研究人员必须转向一个活体模型，它不仅能提供骨骼和软组织数据，还能提供实际的咬合力测量。这个项目的目标是双重的。首先，研究人员将检查活人样本中咬合力产生和面部形态之间的关系，以确定面部骨骼的大小和形状是否与实际咬合力测量相关。这将通过爱荷华大学人类学系与爱荷华大学医院和诊所的耳鼻喉科和放射科的共同努力来完成。将对招募的受试者进行咬合力测量，并与从受试者的CT扫描中获得的骨骼和肌肉数据进行比较。其次，该项目的数据将用于验证定制的计算机程序，该程序仅基于骨骼变量对咬合力产生进行数学建模。通过使用受试者CT扫描的骨骼数据，研究人员将对他们的咬合力产生数学估计，并将这些结果与实际值进行比较。经过验证后，该程序将作为未来研究的宝贵工具，准确估计尼安德特人的咬合力产生。面部解剖学和咬合力的人类学和临床研究在历史上是相互独立的。这是不幸的，因为这两个领域都有独特的视角，可以相互补充。因此，这项研究的更广泛的影响是，它将结合这两个操作上不同的研究领域。这样，在进化框架中提出的问题可以帮助完善和改进临床颅面治疗，而在研究活人中获得的临床知识可以丰富我们化石人类祖先颅面生物学的解释和重建。

With National Science Foundation support, this project will provide a detailed analysis of the relationship between facial form and bite force production in living humans to establish a baseline for future studies of Neandertal facial form. The form of the facial skeleton is influenced by a variety of factors, both genetic and environmental. One of the most important environmental factors affecting the facial skeleton is the production of masticatory forces (e.g., bite force). While the importance of masticatory biomechanics in facial development is recognized in both evolutionary and clinical contexts, the exact nature of the relationship between these variables is still poorly understood. Understanding this relationship is important with respect to the Neandertal face as the production and dissipation of high magnitude bite forces has been used as a working model to explain the evolutionary development of Neandertal facial anatomy which differs substantially from the facial form of living people. A proper assessment of Neandertal bite force production has not been possible since bite force production results from an interaction of both skeletal and muscle tissue, and the latter is not preserved in fossils. Therefore, previous analyses of Neandertal masticatory performance have been restricted solely to mathematical modeling, the accuracy of which is has not been well established. Given these limitations, researchers must turn to a living model that provides not only bone and soft tissue data but also actual bite force measurements.The objectives of this project are twofold. First, the investigators will examine the relationship between bite force production and facial morphology in a living human sample to determine if the size and shape of the facial skeleton correlate with actual bite force measurements. This will be accomplished through a joint effort of the Department of Anthropology at The University of Iowa along with the Departments of Otolaryngology and Radiology at The University of Iowa's Hospitals and Clinics. Bite force measures will be taken from recruited subjects and compared to skeletal and muscle data taken from CT scans of the subjects. Second, the data from this project will be used to validate a custom written computer program that mathematically models bite force production based solely on skeletal variables. By using skeletal data from the subjects' CT scans, the investigators will produce mathematical estimates of their bite force production and compare these results to actual values. When validated, this program will then serve as an invaluable tool for future studies that will accurately estimate Neandertal bite force production. Anthropological and clinical studies of facial anatomy and bite force have historically operated independently of one another. This is unfortunate given that both fields have unique perspectives that complement one another. Thus the broader impacts of this study are that it will marry these two operationally distinct research areas. In this way, questions posed in an evolutionary framework can help refine and improve clinical craniofacial treatment, while the clinical knowledge gained in studying living humans can enrich the interpretation and reconstruction of the craniofacial biology of our fossil human ancestors.