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目的计算嚼肌在牙尖交错位(ICP)紧咬时表面肌电的最大Lyapunov指数,引入一个新的量化指标,分析咀嚼系统肌电信号的混沌特征。方法于2009年5—7月在中山大学医学院在校学生中选取20名口颌系统基本正常的个体,其中男、女各10名。在ICP位紧咬时采集其左、右嚼肌的表面肌电,利用小数据量法计算嚼肌肌电信号的最大Lyapunov指数,并进行统计学分析。结果男性个体左、右两侧嚼肌最大Lyapunov指数分别为17.882±1.7498和18.244±1.3028,女性为14.839±1.8198和14.866±1.3947。对数据进行两因素析因设计的方差分析,性别差异具有统计学意义,女性的最大Lyapunov指数小于男性(F=41.158,P<0.001);左、右侧部位差异无统计学意义(F=0.151,P=0.700)。结论嚼肌在ICP位紧咬时表面肌电具有混沌特征,适合用非线性动力学方法进行分析。
Objective To calculate the maximal Lyapunov exponent of myoelectrical surface when the chewing muscle is bitten by the cusp position (ICP), and introduce a new quantitative index to analyze the chaotic characteristics of the myoelectric signal of the chewing system. Methods From May to July 2009, 20 students with normal oral machinery were selected among the students in Zhongshan University School of Medicine, including 10 males and 10 females. The surface EMGs of the left and right chewing muscles were collected during bit-bite at ICP and the maximum Lyapunov exponent of chewing muscle EMGs was calculated by the small data volume method and statistically analyzed. Results The maximum Lyapunov exponent of the masticatory muscles in the left and right sides of males were 17.882 ± 1.7498 and 18.244 ± 1.3028 respectively, while those in females were 14.839 ± 1.8198 and 14.866 ± 1.3947. The analysis of variance of two factors factorial design was statistically significant. The maximum Lyapunov exponent of females was smaller than that of males (F = 41.158, P <0.001). There was no significant difference between the left and right sides (F = 0.151 , P = 0.700). Conclusions The myoelectricity of the chewing muscles has chaotic characteristics when the bit is bitten at the ICP and is suitable for analysis by nonlinear dynamics method.