Effect of occlusion on mechanical stress of the TMJ

为了确定由于后牙缺失引起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紊乱病有关，我们研究了SDA（缩短的牙弓）对咬合和关节负荷的影响。本研究记录了五名受试者在口内矫治器上最大限度地握紧时的咬合力和咀嚼肌肌电，并进行了对称性SDAs实验。从记录的肌电图估计的肌肉力量被送入有限元颌骨模型计算咬合力和关节负荷。测量的咬合力和计算的咬合力之间的比较确保了关节载荷具有代表性。每颗牙齿上的咬合力随着磨牙咬合缺失而增加，而关节负荷则减少。每根表面积的咬合力总是最大的最后牙，这些值是最恒定的。研究结果没有提供任何证据表明SDA会导致关节和牙齿过载

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