下颌牙槽嵴条件对全口义齿人工牙排列的影响及预测研究

As the aging society approaches, the number of edentulous patients is increasing. The occlusal support function of majority of elders from 65 to 74 years old in China become weaken or even lost. The edentulous become a common oral disease of the aged, which means that the increase in demand for complete denture. To date, many researchers have reported arrangement methods for artificial teeth. However, there are many unclear points concerning the effect of these arrangement methods on denture mobility. Some studies have shown that the arrangement of artificial teeth in the neutral zone is conducive to the stability of the denture in the pronunciation and swallowing function, but alveolar ridge resorption degree effects the artificial teeth arrangement position that tend to the buccal side of alveolar ridge crest. At the same time, the research suggests that the alveolar ridge condition is an important influence factor in mechanical behavior of complete denture. Preliminary tests have shown that the effect of alveolar cross-section shape on curve characteristics in loading-displacement curve of denture base and loading- peak stress curve of mucous membrane is remarkable. For understanding the mechanism of action, the experimental mechanics research will be based on the preliminary tests. The displacement of denture is analysed by 3D laser scanning image overlay method. The measurement analysis of alveolar cross-section shape at different regions is obtained with three-dimensional reconstruction of CT scan images. The relationship between the thickness and elasticity of the denture supporting tissue can be examined separately with an ultrasonic thickness gauge and a tactile sensor, but separate measurements were difficult to apply clinically, so that the alveolar mucosa viscoelastic is measured with oral mucosa viscoelastic measurement system that is a simultaneous measuring system of load and thickness.The influence of mandibular alveolar ridge conditions on reasonable degree of buccal position of artificial teeth arrangement in complete denture with different mucosal conditions is investigated and forecasted by two methods of experimental mechanics and numerical calculation, and the results will be validated with denture stability measurement system composed of personal computer and web camera and pressure sensor. In order to explore the method to predict the buccal position of teeth arrangement by analyzing alveolar conditions, and provide the experimental data for depth study of customized artificial teeth arrangement method in complete denture.

研究认为全口义齿人工牙排列在中性区有利于义齿在发音和吞咽功能时的稳定性，但牙槽嵴吸收程度影响人工牙排列位置，而且都偏牙槽嵴顶颊侧。同时，研究提示牙槽嵴条件是影响全口义齿力学行为的重要因素之一。前期研究显示加载部位下不同牙槽嵴断面形态对应的加载位置-义齿位移及黏膜应力峰值曲线不同，使义齿位移和黏膜压应力峰值突然增大的颊侧加载位置也不同。本项目拟在此研究的基础上进行实验力学研究。采用三维激光扫描图像叠加法分析义齿位移，运用CT扫描三维重建图像测量分析不同区域牙槽嵴断面形态，使用口腔黏膜粘弹性测量系统分析牙槽黏膜的粘弹性，通过实验力学和数值计算两种方法研究不同黏膜条件下牙槽嵴断面形态对全口义齿人工牙颊向排列合理度的影响，并采用口内义齿稳定性测量系统对结果进行验证，旨在理解其作用机制，以期探寻通过牙槽嵴条件预测人工牙颊向排列合理度的方法，为今后深入研究全口义齿个性化人工牙排列法提供实验依据。

全口义齿人工牙排列位置和角度影响义齿的稳定性。以往研究认为全口义齿人工牙排列在中性区有利于口腔发音和吞咽功能时的义齿稳定性，但按此方法排列的人工牙多位于牙槽嵴顶偏颊侧，而经典的全口义齿排牙方法认为人工牙排在牙槽嵴顶上义齿更稳定。另一方面，以往研究提示牙槽嵴条件是影响全口义齿力学行为的重要因素之一。因此，依据个体差异较大的患者牙槽嵴条件确定人工牙排列的最佳位置和角度，从而提高全口义齿在口腔功能状态时（咀嚼，发音和吞咽）的稳定性就显得十分重要，也是建立个性化排牙方法所必须解决的问题，但至今未见有关依据患者牙槽嵴条件建立全口义齿人工牙排列预测模型的研究报导。. 本研究的主要内容是通过对下颌无牙颌牙槽嵴黏膜厚度及形态的测量，建立参数化三维模型，采用三维有限元方法计算和分析下颌无牙颌牙槽嵴形态条件对义齿稳定性的影响，进而通过统计分析影响义齿稳定性的主要牙槽嵴形态因素，建立可根据一定部位的牙槽嵴形态数据预测全口义齿人工牙最佳排列位置和角度的方法。.目前取得的重要结果有：① 测量了下颌无牙颌牙槽嵴义齿承托区黏膜厚度及其分布，显示下颌牙槽嵴厚度分布不均匀，黏膜平均厚度在牙槽嵴顶约为2.3mm，在唇颊侧及前牙区舌侧约为1.8mm，在后牙区舌侧约为1.4mm；② 探讨了下颌牙槽嵴高度，丰满度及下颌弓高度等因素对义齿稳定性的影响，结果显示牙槽嵴前牙区和前磨牙区高度，以及下颌弓高度的大小与义齿稳定性呈正相关。当加载位于牙槽嵴顶偏颊侧1.5mm以内时，相同高度的牙槽嵴丰满度对义齿稳定性影响较小；③ 建立了具有可重复性较高的下颌无牙颌牙槽嵴牙位划分的方法，形成了通过下颌弓高宽比为校对参数的各牙位划分角度方程；④ 建立了更接近实际情况的下颌无牙颌牙槽嵴，黏膜及义齿的参数化三维模型；⑤ 讨论了根据特定部位牙槽嵴形态数据预测义齿咬合面加载位置及方向的方法，建立了相应的预测模型，为个性化全口义齿修复及全口义齿的CAD-CAM提供了实验依据，具有重要的科学价值和临床意义。