Effect of occlusion on mechanical stress of the TMJ

为了确定由于后牙缺失导致的咬合变化是否会导致牙齿和颞下颌关节的功能过载，这与牙周病和颞下颌关节疾病有关，我们研究了缩短牙弓对咬合和关节负荷的影响。实验记录了5名有齿被试在对称SDAs的口腔内矫治器上最大咬合时的咬合力和咀嚼肌肌电图。从记录的肌电图中估计的肌肉力被输入到计算咬合力和关节载荷的有限元颚模型中。计算和实测的咬合力比较，保证了节点载荷具有代表性。缺磨牙合时，各牙的咬合力增加，而关节负荷减少。每根表面积的咬合力在最后牙上总是最大的，并且这些值是最恒定的。研究结果没有提供证据表明SDA会导致关节和牙齿超载

To determine whether the changes of occlusion due to the loss of the posterior teeth cause functional overloading of the teeth and the temporomandibular joints, which has been implicated in periodontal diseases and temporomandibular disorders, we investigated the influences of SDA (shortened dental arch) on occlusal and joint loads. Bite forces and masticatory muscles' electromyograms were recorded in five dentate subjects who clenched maximally on intra-oral appliances creating symmetrical SDAs experimentally. Muscular forces estimated from the recorded electromyograms were fed into a finite element jaw model calculating bite forces and joint loads. Comparison between the measured and the calculated bite forces assured that the joint loads were representative. The bite force on each tooth increased with missing molar occlusions while joint loads decreased. The bite force per root surface area was always greatest on the most posterior tooth, and these values were most constant. The findings provide no evidence suggesting that SDA causes overloading of the joints and the teeth