The mechanism for regulating the isometric contraction of masseter muscles is involved in determining the vertical dimension of occlusion.
The mechanism for regulating the isometric contraction of masseter muscles is involved in determining the vertical dimension of occlusion.
复制标题
调节咬肌等长收缩的机制涉及确定咬合的垂直尺寸。
DOI：
10.1152/jn.00301.2022
复制
发表时间：
2023
影响因子：
2.5
通讯作者：
Kang Y.
中科院分区：
文献类型：
--
作者：
Tanaka Y;Sato H;Toyoda H;Saito M;Maeda Y;Kang Y.
我们以前证明，准确调节的等长收缩（IC）的下颌闭合肌肉，以抵消斜坡负荷施加到下巴在下颌打开的方向是通过校准之间的两种感觉所产生的肌梭（MS）和牙周机械感受器（PMR）。然而，目前还不清楚这种校准机制是否能在任何钳口位置准确工作，即，任何咬合垂直尺寸（VDO）。在本研究中，我们探讨了改变VDO对IC的咬肌在完全有牙和无牙科目。在高于原始VDO（O-VDO）的VDO下，咬肌肌电活动的均方根（RMS）随着负荷的增加而急剧增加，导致过度抵消。随着VDO的增加，负荷-RMS关系的回归系数显著增加，这表明随着VDO的增加，高估变得更加明显。同样，在无牙受试者中，在比O-VDO更高的VDO下，RMS的陡峭增加出现在对相同斜坡负载的响应延迟中，而即使在较低的VDO下也令人惊讶地看到类似的陡峭增加。因此，无牙颌受试者表现出延迟的斜坡负荷高估，可能是由于更少和缓慢敏感的粘膜机械感受器（MMR）在牙槽嵴相比，PMR。两者合计，准确校准之间的两种感觉所产生的MS和PMR/MMR的，可以只在O-VDO，这表明O-VDO是最好的校准点进行准确的IC。新&值得注意的是，自1934年以来，在无牙个体的咬合垂直尺寸（VDO）已被解剖学上确定主要是通过参考休息颌骨位置。然而，这种静态方法并不总是准确的。考虑到紧咬/咀嚼的动态性质，期望动态地确定VDO。我们证明，VDO可以准确地确定通过测量咬肌肌电在自愿的等长收缩的下颌闭合肌肉施加对斜坡负荷在下颌开放的方向。
We previously demonstrated that accurate regulation of isometric contraction (IC) of jaw-closing muscles to counteract the ramp load applied to the jaw in the jaw-opening direction is achieved through the calibration between the two sensations arising from muscle spindles (MSs) and periodontal mechanoreceptors (PMRs). However, it remains unclear whether this calibration mechanism accurately works at any jaw positions, i.e., any vertical dimensions of occlusion (VDO). In the present study, we examined the effects of altering VDO on the IC of the masseter muscles in complete dentulous and edentulous subjects. At a VDO higher than the original VDO (O-VDO), the root mean square (RMS) of masseter EMG activity increased more steeply with a load increase, resulting in an over-counteraction. The regression coefficient of the load-RMS relationship significantly increased as the VDO was increased, suggesting that the overestimation became more pronounced with the VDO increases. Consistently also in the edentulous subjects, at a higher VDO than the O-VDO, a steeper increase in the RMS emerged with a delay in response to the same ramp load whereas a similar steeper increase was seen surprisingly even at a lower VDO. Thus, the edentulous subjects displayed a delayed overestimation of the ramp load presumably due to less and slowly sensitive mucous membrane mechanoreceptor (MMR) in alveolar ridge compared with the PMR. Taken together, the accurate calibration between the two sensations arising from MSs and PMRs/MMRs can be done only at the O-VDO, suggesting that the O-VDO is the best calibration point for performing accurate IC.NEW & NOTEWORTHYSince 1934, the vertical dimension of occlusion (VDO) in edentulous individuals has been anatomically determined mostly by referring to the resting jaw position. However, such a static method is not always accurate. Considering the dynamic nature of clenching/mastication, it is desirable to determine VDO dynamically. We demonstrate that VDO can be accurately determined by measuring masseter EMG during the voluntary isometric contraction of jaw-closing muscles exerted against the ramp load in the jaw-opening direction.