下颌全口义齿牙合托咬合面不同加载点对牙合托位移的影响

目的：分析下颌全口义齿胎托后牙区咬合面不同加载点及不同牙槽嵴丰满度对胎托位移的影响，初步探讨人工后牙偏颊侧位置排列的适合范围。方法：利用激光三维扫描仪取得下颌无牙颌标准模型牙槽嵴表面形态数据，通过计算机辅助工程（CAE）软件形成下颌全口义齿殆托，以及标准牙槽嵴（S）、丰满牙槽嵴（U）和刃状牙槽嵴（V）等3种断面形态的牙槽嵴黏膜三维有限元模型。在胎托模型咬合面左侧第一前磨牙区（P），第一磨牙区（M1）和第二磨牙区（M2）分别设定始于牙槽嵴顶（PT，M1T和M2T）并向颊侧排列的加载点（PBl-9，M181-9，M281-9，同部位各加载点间距为0．5mm），共计30个加载点，垂直加载9．8N的力，利用三维有限元分析各条件下骀托的最大综合位移。结果：随着单侧加载点由牙槽嵴顶部向颊侧移动，各牙槽嵴条件下胎托的位移都呈现出增加的趋势，但增加的幅度因牙位而不同；在P加载时的胎托位移增幅较M1和M2的大；在M1和M2加载时，加载点在牙槽嵴顶至颊侧1．5mm范围内，各牙槽嵴条件下骀托位移的增幅都较小且相近，超出此范围，胎托位移增幅显著加大。结论：不同牙位偏牙槽嵴顶颊侧加载对全口义齿胎托位移影响的程度不同。在各牙槽嵴丰满度条件下，前磨牙区人工牙偏颊侧排列较磨牙区更易破坏义齿稳定性，而在磨牙区偏颊侧1．5mm范围内排列人工牙则对义齿稳定性影响较小。

Influence of different loading points at occlusal surface on displacement of bite plate in mandibular complete denture

Objective： To analyze the influence of different loading points at occlusal surface of posterior-tooth area and different residual alveolar ridges on displacement of bite plate, and investigate the suitable range ofbuccal arrangement for posterior artificial teeth in mandibular complete denture. Methods： Three-dimensional laser scanner was used to obtain the standard model of mandibular edentulous alveolar morphologic data. Computer-aided engineering （CAE） software was used to form dimensional finite element model of the mandibular denture and three models of mucosa morphology of different alveolar sections： standard alveolar ridge （S）; busty alveolar ridge （U）; blade-like alveolar ridge （V）. Alveolar crest of the left first premolar region （P）, left first molars （Ml） and left second molars （M2） were set as load points, then the points begins with the alveolar crest （PT, M1T and M2T） to the buccal and equally arranged load points （PB1-9, M1B1-9, M2B1-9, the same spacing between each loading points is 0.5mm）. There were a total of 38 load points. The vertical load force was 9.8N. Three-dimensional finite element was used to analyze the conditions of the maximum displacement of the denture.Results： With unilateral loading moved from alveolar crest toward buccal edge, the bite plate displacements showed a rising trend and the tendency of displacement was different at different loading positions. When loading on P area, the displace- ment of bite plate was bigger than loading on the MI and M2 position. When the loading was on M1 and M2 and the load points ranged from crest to buccal 1.5ram, approximately similar bite plate displacement of model U, model S and model V was observed and bite plate displacements were very small. Beyond this range, bite plate displacement was big. Conclusion： Different buccal loading points at occlusal surface of posterior-tooth area had different influence on the stability of bite plate in mandibular complete denture. At different alveolar ridges, premolar artificial teeth＇ s buccal arrangements may deteriorate the denture stability obviously. However buccally arranged artificial molar within 1.5mm buccal range from the crest has few influence to denture stability.