The difference pattern of regulation by muscle spindles during the various cortically-induced rhythmic movements

已有经验表明，在精神压力下，骨骼肌张力增加，并可不知不觉地引起咬合或磨牙等副功能，这表明口腔颌面系统与精神状况之间存在密切关系。因此，在这项研究中，我们调查了心理应激对口腔颌面系统的影响以及咬合夹板的影响。健康的成年志愿者参与了这项研究。一项为期2小时的字母识别任务被用作压力源。记录患者的颞肌、咬肌、食指掌侧和额部出汗率、食指掌侧皮肤血流量、咬肌局部肌肉氧合情况。心率频谱分析评价自主神经功能。采用两种不同硬度的咬合夹板，在心理作业过程中，咬肌和颞肌的综合肌电活动、组织血氧饱和度(StO2)和交感神经活动的标志LO/Hi比值较心理作业前增加。至少在30到60分钟后，这些增加在统计学上显著；之后没有发现显著变化。皮肤综合血流量和汗液排出无明显变化。与硬夹板相比，软夹板的综合肌电活动和LO/Hi值增加，而硬夹板的增加不明显。这些结果表明，咬合夹板的硬度可以影响应激条件下咀嚼肌活动和自主神经系统活动。

It has been known empirically that under mental stress, skeletal muscle tone is increased and parafunction such as clenching or teeth grinding can be caused unconsciously, which suggests that a close relationship exists between the stomatognathic system and the mental condition. In this study, therefore, we investigated what the effect of mental stress on the stomatognathic system is and what the effect of occlusal splints is.Healthy adult volunteers participated in this study. A letter identification task over a 2-hour period was employed as a stressor. Electromyographic records were taken from the temporal and masseteric muscles, sweat rates from the palmar surface of index finger and from forehead, skin blood flow from the palmar surface of index finger, local muscle oxygenation from the masseter muscle. Assessment of autonomic function was made by heart rate spectral analysis. Two occlusal splints of different hardness were employed.During the mental task, the integrated EMG activity of masseteric and temporal muscles, tissue hemoglobin O_2 saturation (StO_2), and the Lo/Hi ratio (a marker of sympathetic activity) increased as compared before the mental task. These increases were statistically significant after at least 30 to 60 minutes ; afterwards no notable changes were found. The integrated skin blood flow and sweat expulsion did not change significantly. The integrated temporal EMG activity and Lo/Hi ratio increased with the soft splint, but did not with the hard splint. These results indicate that the hardness of an occlusal splint can affect the masticatory muscle activity and autonomic nervous system activity under stressful conditions.