Functional Analysis of the Temporal Muscle during Open-Close Movement Using an Autonomous Jaw-Movement Simulator

为了明确下颌运动的控制机制，我们开发了一种自主下颌运动模拟器JSN/ I D，该模拟器采用电缆-肌腱直流伺服执行器，模拟咬肌、颞肌、翼侧肌和二腹肌。利用咬合力、齿面接触、拉索张力和拉索长度等数据，采用阻抗控制机制对执行器进行自适应控制。为了在模拟器上实现更逼真的开合运动，我们引入了一个控制假设，即在闭合过程中，下颌水平位置是由颞肌后部和翼状外侧肌肉的拮抗活动决定的。这一假设通过后颞肌致动器的阻抗控制和翼状外侧肌的拮抗张力控制得以实现。执行器以以下方式激活，以免与颌骨的解剖学和生理学知识相矛盾。更多的促动器仅仅在咬的时候被激活，以施加咬合力。在阻抗控制下的前颞肌执行器单独负责确定闭合时下颌骨的垂直位置，并在咬合时支持咬肌执行器。打开时，联合激活二腹肌和外侧翼状骨致动器使下颌骨下降。由于在相应的肌肉中缺乏肌肉主轴，两个致动器都在张力控制下驱动。在静止状态下，所有的执行器都像实际的肌肉一样作为一个弱弹性体发挥作用。实验结果表明，上述控制方案可以在模拟器上产生可重复的逼真的开合运动，而较少激活后颞肌α -gammalinkage的参考实验显示出运动不稳定，特别是在关闭阶段。所有这些都表明，通过控制颞后肌的位置和拮抗翼状外侧肌的张力控制，可以在闭合时稳定下颌骨。这种控制方案的一个替代方案是使用两个肌肉的过度共同激活，使下颌头的位置不那么柔顺。然而，这是难以接受的，因为在闭合时，两块肌肉都没有观察到如此强烈的活动。对所提出的控制方案进行生理验证是一项应在后续研究中处理的任务。少

In order to clarify the control mechanism of jaw movements, we developed an autonomousjaw-movement simulator, JSN/ I D, which incorporates cable-tendon DC-servo actuators, simulating the masseter, temporalis, lateral pterygoid and digastric muscles. The actuators were controlled adaptively under an impedance-control mechanism, utilizing data of bite-force, tooth contact, cable-tension and cable-length. In order to achieve more life-like open-close movement on the simulator, we introduced a control hypothesis that during closing, the horizontal mandibular position is determined by antagonistic activities of the posterior portion of the temporalis muscles and the lateral pterygoid muscles.This hypothesis was materialized by an impedance control of the posterior temporalis actuators and an antagonizing tension-control of the lateral pterygoid muscles. The actuators were activated in the following manner, so as not to contradict anatomical and physiological knowledge of the jaws. The masse … More ter actuators were activated merely during biting, in order to exert bite force. The anterior temporalis actuators under an impedance control were solely responsible to determine the vertical position of the mandible during closing, and supported the masseter actuator during biting. During opening, the digastric and lateral pterygoid actuators were co-activated to descend the mandible. Both actuators were driven under a tension control, due to the lack of the muscle spindles in corresponding muscles. At rest, all the actuators functioned as a weak elastic body like actual muscles.Experimental results demonstrated that the afore-mentioned control scheme can produce a reproducible life-like open-close movement on the simulator, while referential experiments with less activation of the alpha-gammalinkage of the posterior temporalis control showed the kinetic instability, particularly in the closing phase. All these suggest a possibility of stabilizing the mandible during closing through the position control of the posterior temporalis muscles and antagonizing tension-control of the lateral pterygoid muscles. A single alternative to this control scheme is to employ an excessive co-activation of the two muscles to make the position of the mandibular head less compliant. This is hardly acceptable, however, because no such strong activities are observed in both muscles during closing.Physiological certification of the proposed control scheme is a task that should be dealt with in a subsequent study. Less