ASSOCIATION OF EMG ACTIVITY OF THE LIPS WITH MASTICATORY MUSCLE IN INDIVIDUALS WITH MALOCCLUSION

在嘴唇正常的受试者中，咀嚼食物时嘴唇轻微闭合。然而，在一些唇部功能不全的患者中，唇部在咀嚼功能时并不总是闭合的。闭着嘴唇咀嚼是一种不自觉的行为，无论是在不称职的嘴唇还是称职的嘴唇上。相比之下，对于嘴唇不健全的人来说，闭着嘴唇咀嚼并不是一种自然的行为。本研究的目的是探讨下唇活动与咀嚼肌的关系。结果(1)咬肌主动收缩期和非主动（强直）收缩期咀嚼时下唇肌电活动波幅均明显高于正常唇组。(2)强直性咬肌活动与唇接触时肌电活动的持续时间较强抿组短。我们的研究结果表明，封唇失败可能是由于面部形态的不协调，这种失败也影响了咀嚼功能。

In subjects with competent lips, the lips are lightly closed during chewing food. However, in some patients with incompetent lips, the lips are not always closed during masticatory function. Chewing with the lips closed is an involuntary act in both subjects with incompetent lips and competent lips. In contrast, chewing with the lip closed is not a natural act in subjects with incompetent lips. The purpose of this study was to investigate the relationship between activities of lower lip and masticatory muscles.Results(1)The amplitudes of EMG activity of lower lip during chewing with lip in contact and apart during masseter active and non-active (tonic) contraction phases were significantly higher in the incompetent lip group than in competent lip group.(2)The duration of EMG activity during tonic masseter activity with lip contact was shorter in incompetent lip group than in competent lip group.Our results suggested that failure of lip sealing is probably due to facial morphological disharmony and that such failure also affects the masticatory function.