The influence of clenching on head posture and body equilibrium

本研究的目的是阐明咬牙、头部姿势和身体平衡之间的关系。结果表明，与静止的下颌位置相比，在VMC条件下，颈部向前弯曲。在单侧咬合支撑条件下，颈部向咬合支撑侧侧弯。无论是闭眼状态还是睁眼状态，闭口肌和胸锁乳突肌的不对称指数均呈正相关(r=0.78，p&lt；0.05)。胸锁乳突肌的不对称指数与侧弯角度呈正相关(r=0.43，p&lt；0.05)。结果表明，咬合与头部姿势有密切关系，在10%、50%和100%的VMC和Rp的动态事件中，头部和身体之间存在协同运动，而冲击负荷干扰了身体平衡。从头部运动角度分析，RP组的最大侧弯和旋转角度明显大于10%、50%和100%VMC组(p&lt；0.05)。从头部运动和身体摆动的分析来看，RP组的总轨迹长度显著大于10%、50%和100%VMC组(p&lt；0.05)。从肌电活动分析，随着咬合力的增加，胸锁乳突肌活动的测量值有统计学意义的增加(p&lt；0.05)。从这些结果推测，牙齿咬合抑制了动态项目中头部的运动和身体的摆动。这一推测得到了前人研究的支持，即胸锁乳突肌的活动与闭口肌的活动是同步的。结论：口颌功能和身体平衡是相互依存的关系。

The purpose of this study was to elucidate the relationship among teeth clenching, head posture and body equilibrium.Results were as follows,In comparison to the rest mandibular position, neck was flexed anteriorly in the VMC condition. In the condition of unilateral occlusal support, neck was bent laterally to the occlusal support side. Positive correlation was found between the asymmetry index of the jaw closing muscles and the sternocleidomastoid muscle under both the eyes-closed condition (r=0.57, p<0.05) and the eyes-opened condition (r=0.78, p<0.05). Positive correlation was found between the asymmetry index of the sternocleidomastoid muscle and the angle of the lateral bending (r=0.43, p<0.05). From these results, it was suggested that there is a close relationship between occlusion and head posture.Against the impact load disturbing the body balance, cooperative movement between the head and body was observed during the dynamic event in 10%, 50%, and 100%VMC and RP. From the analysis of head movement, the maximum angle of lateral bending and rotation in RP was statistically greater than those in 10%, 50% and 100%VMC (p<0.05). From the analysis of head movement and body sway, total locus length in RP was statistically greater than those in 10%, 50% and 100%VMC (p<0.05). From the analysis of EMG activity, as the clenching force increased, the measurement of sternocleidomastoid muscle activity statistically increased (p<0.05). It is speculated from these results that the teeth clenching suppresses the head movement and body sway during the dynamic event. This speculation is supported by previous studies that activities of sternocleidomastoid muscles are synchronized to activities of jaw closing muscles during VMC.It is concluded that stomatognathic function and body equilibrium have an interdependent relationship.