Agrawal K R, Lucas P W, Bruce I C, Prinz J F
Department of Anatomy, University of Hong Kong, SAR, PR China.
J Dent Res. 1998 Nov;77(11):1931-8. doi: 10.1177/00220345980770111101.
The rate of breakdown of food in mastication depends on the ratio of two mechanical properties of the food--the toughness and modulus of elasticity (Agrawal et al., 1997)--a result which can be predicted by an analysis of the energetics of fracture. The work input to produce food fragmentation is provided by the masticatory muscles, the activity levels of which depend on sensory feedback from the mouth. Here, we test the hypothesis that the activity of a representative of this musculature is modulated by the above combination of food properties. The surface electrical activity (EMG) of the anterior temporalis muscles of ten human subjects was recorded while subjects chewed standardized volumes of 15 food types. The integrated EMG in these muscles was highly significantly related to the square root of the ratio of the above two food properties. Significant correlations were found between this food property index and integrated EMG, both when data for all chews and all subjects were lumped together (r = -0.86; p < 0.0001) and when correlation coefficients between the index and EMG were plotted for each chew made by each subject. Except for two subjects in the first chew, these coefficients reached and maintained highly significant levels throughout the masticatory sequence. Thus, a clear relationship between the electrical activity of a jaw-closing muscle and the mechanical properties of food has been found for the first time.
食物咀嚼过程中的分解速率取决于食物的两种机械特性的比值——韧性和弹性模量（阿格拉瓦尔等人，1997年）——这一结果可以通过对断裂能量学的分析来预测。产生食物破碎所需的功由咀嚼肌提供，咀嚼肌的活动水平取决于来自口腔的感觉反馈。在此，我们检验这样一个假设：这种肌肉组织的一个代表的活动受上述食物特性组合的调节。在10名人类受试者咀嚼15种标准化体积的食物时，记录了他们颞肌前部的表面电活动（肌电图）。这些肌肉中的肌电图积分与上述两种食物特性比值的平方根高度显著相关。当将所有咀嚼和所有受试者的数据汇总在一起时（r = -0.86；p < 0.0001），以及当绘制每个受试者每次咀嚼时该食物特性指数与肌电图之间的相关系数时，在该食物特性指数与肌电图积分之间均发现了显著相关性。除了第一次咀嚼时有两名受试者外，这些系数在整个咀嚼过程中都达到并保持了高度显著水平。因此，首次发现了下颌闭合肌的电活动与食物机械特性之间的明确关系。
