从生物力学角度探讨牙列完整和牙列缺损时的应力变化

The biomechanical research on the different stress distributions between complete and defective dentition

目的:从生物力学角度对牙间的邻面接触关系的生理作用进行观察,探讨在咀嚼受力时牙冠组织的应力分布状况。方法:选用1具成人头颅颌骨标本,牙列完整,覆牙合、覆盖正常,咬合关系良好,牙之间接触关系紧密。标本经处理后,在每颗牙的牙冠区贴1mm×1mm箔式电阻应变片。在上下牙列正中咬合状态时垂直加载,加载力为20kg。用YJD-17型电阻应变仪,测量牙冠组织的应力值(GPa)。实验分为3组,即完整牙列组,第一磨牙缺失组,下颌右侧第一磨牙、侧切牙、中切牙缺失组。结果:完整牙列时测得应力值分别为:第二磨牙3.4641,第二前磨牙0.5132,尖牙1.0264,其余均为0。第一磨牙缺失时所测得应力值分别为:第二磨牙5.003,第二前磨牙1.4113,其余牙位与完整牙所测得数据相似。第一磨牙、侧切牙、中切牙缺失的牙列缺损时应力值分别为:第二磨牙5.2603,第二前磨牙1.6679,尖牙3.2075,第一前磨牙0。结论:完整牙列受力时,牙合力通过牙之间的接触区传递分散,牙冠的应力值很小。牙列缺损缺牙区邻近牙组织应力值明显增加。

PURPOSE:To evaluate the stress distribution of crowns under mastication from the biomechanical respect, and observe the physical effects on different teeth through the interproximal contacts.METHODS:A healthy adult skull with both maxilla and mandible was selected , which had normal overbite and overjet, standard occlusal relationship, and tightly contacting with interproximal teeth. After preparation, a 1mm×1mm strain foil was bonded on every crown. In centric occlusion, 20 kg vertical load was applied on it. The stress value of crown(GPa) was detected by the YJD-17strain gauge . There were three groups: group 1 with complete dentition, group 2 with the first molar missing, and group 3 with missing of right mandibular first molar, lateral incisor and central incisor. RESULTS:The stress value in complete dentition was 3.4641 in second molar, 0.5132 in second premolar, 1.0264 in canine, and 0 in others. In group 2, the stress value was 5.003 in second molar, 1.4113 in second premolar, the values of other teeth equal to that of group1. In group 3, the stress value was 5.2603 in second molar,1.6679 in second premolar,3.2075 in canine,0 in first premolar, respectively.CONCLUSION: In complete dentition, the occlusal strength is distributed through the contact area between interproximal teeth, therefore, the stress value of crown is low. However, in the area near the defective dentition, it will be obviously high.