中文摘要：

目的探讨应用咬肌活动不对称指数（asymmetry index of masseter muscles，ASMM）早期诊断偏侧咀嚼不良习惯。方法用肌电图仪分别记录双侧咀嚼组（30人）和偏侧咀嚼组（52人）分别在下颌姿势位（mandibular postural position，MPP）、牙尖交错位（intercuspal position，ICP）的最大紧咬运动和咀嚼运动时的咬肌肌电图，计算ASMM，进行统计学分析。结果①偏侧咀嚼组在MPP、ICP最大紧咬运动和咀嚼运动中ASMM显著高于双侧咀嚼组（P〈0．01）。②双侧咀嚼组不同性别间MPP、ICP最大紧咬运动和咀嚼运动中ASMM差异无统计学意义。③双侧咀嚼组ASMM的95％百分位数参考值：在MPP为5．66％、ICP最大紧咬运动中为10．65％和咀嚼运动中为12．73％。结论偏侧咀嚼者在MPP、ICP最大紧咬运动和咀嚼运动中的咬肌活动明显存在不对称。ASMM可用于检测偏侧咀嚼。

英文摘要：

Objective To provide evidence for diagnosis of unilateral mastication in the early stage by means of the surface electromyography （sEMG） of masseter muscle （MM）. Methods 30 subjects with bilateral chewing and 52 subjects with unilateral chewing were measured by means of sEMG. The subjects were instructed to stay at mandibular postural position （MPP） and to make maximum clenching at intercuspal position （ICP） and chewing. The sEMG of left and right masseter muscles were separately recorded. Asymmetry index of masseter muscles （ASMM） was calculated and compared. Results ①ASMM at MPP,during maximum clenching and chewing in unilateral chewing group were significantly higher than those in bilateral chewing group （P 〈 0.01 ）. ②There was no statistical difference in ASMM at MPP,during maximum clenching and chewing between the males and the females among bilateral chewing subjects. ③In bilateral chewing group, the 95th percentile of ASMM at MPP, during maximum clenching and chewing were 5.66% , 10.65% and 12.73% ,respectively. Conclusions At MPP,during maximum clenching and chewing,the bilateral symmetry of masseter muscles in unilateral chewing people was obviously less than in bilateral chewing people.