单侧下颌第一磨牙缺失对咀嚼肌肌电的影响

Influence of unilateral mandibular first molar loss on the activities of masticatory muscles

目的探讨长期单侧下颌第一磨牙缺失患者在下颌功能运动中双侧颞肌前束(TA)和咬肌(MM)的肌电活动特征。方法选择单侧下颌第一磨牙缺失1年或以上并未行修复治疗者18例作为实验组,关系正常者18例作为对照组,应用BioEMGⅢ肌电仪记录下颌姿势位(MPP)、牙尖交错位(ICP)最大紧咬状态及咀嚼运动中双侧TA和MM的肌电活动值,并进行统计分析。结果实验组缺失侧在MPP时TA和MM的肌电平均值明显高于对照组,缺失侧大于非缺失侧(P<0.05);ICP最大紧咬状态下和咀嚼运动中实验组TA和MM的肌电平均值小于对照组,咀嚼运动中的差异有统计学意义(P<0.05);MPP和ICP最大紧咬状态下实验组TA和MM的不对称指数差异有统计学意义(P<0.05)。结论长期单侧下颌第一磨牙缺失对咀嚼肌电活动及其对称性均有影响,对缺失侧和咀嚼运动状态下的影响更加显著,并可能成为咀嚼系统功能紊乱的诱发原因之一。

Objective To investigate the electromyographic changes in the of patients with long-term unilateral mandibular first molar loss. Methods anterior temporal and masseter muscles Eighteen patients with one-year or more than one-year loss of unilateral mandibular first molar were selected as experimental group, and eighteen volunteers from similar places, had similar dietary habits in the same age and gender with normal occlusion were recruited as control group. Surface electromyography was used for the evaluation of the electrical activities of bilateral anterior temporal and masseter muscles in mandibular postural position （MPP） , maximal clenching in intercuspal position （ICP） and masticating situations. The data were analyzed using SPSS 17.0 software package to compare the differ- ences among groups. Results The average electrical activities of anterior temporal and masseter muscles in MPP of experimental group were significantly higher than the contral group, and the missing side was higher than the non-missing side （P 〈 0. 05 ）. The average electrical activities of anterior temporal and masseter muscles in maximal clenching and masticating were significantly lower than the control group, especially in the masticating situation （P 〈 0. 05 ）. The asymmetry index of anterior temporal muscles and masseter muscles in MPP and maximal clenching were significantly different （P 〈 O. 05）. Conclusion Long-term loss of unilateral mandibular first molar can affect the electrical activities of the anterior temporal muscles and masseter muscles in the experimental group, especially for the missing side and in the masticating situation. These results also suggest that it might be one of the potential factors on mastication system disorders.