Tomiyama Nozomi, Ichida Toshimichi, Yamaguchi Kazunori
Department of Orthodontics, Kyushu Dental College, Kitakyusyu, Fukuoka, Japan.
Angle Orthod. 2004 Feb;74(1):31-6. doi: 10.1043/0003-3219(2004)074<0031:EAOLLM>2.0.CO;2.
Masticatory muscle activity is coordinated with perioral muscle during chewing. Subjects with competent lips usually chew with the lips in light contact, whereas subjects with incompetent lips possibly have dysfunctional chewing. In this study, the electromyographic (EMG) activities of the lower lip and masseter muscles were recorded when chewing with the lips in contact and apart. At first, 37 subjects were divided into an incompetent lip group and competent lip group on the basis of EMG activity of the lower lip muscle at rest. The durations of the masseter nonactive phase and total phase when chewing with lips in contact were shorter in the incompetent lip group than in the competent lip group. In the incompetent lip group, when chewing with the lips apart, the EMG activity of lower lip in the masseter nonactive phase was significantly (P < .05) higher than in the competent lip group, but there was no difference in the EMG activity in the masseter active phase between two groups. Our results suggest that subjects with incompetent lips have difficulty chewing while their lips are relaxed. We conclude that the inability of sealing the lips and lip dysfunction could possibly affect masticatory function.
咀嚼过程中，咀嚼肌活动与口周肌肉相互协调。唇部功能正常的受试者在咀嚼时，嘴唇通常处于轻微接触状态，而唇部功能不全的受试者可能存在咀嚼功能障碍。在本研究中，记录了嘴唇接触和分开时咀嚼过程中下唇和咬肌的肌电图（EMG）活动。首先，根据静息时下唇肌肉的肌电图活动，将37名受试者分为唇部功能不全组和唇部功能正常组。唇部功能不全组在嘴唇接触时咀嚼时咬肌无活动期和总时长均短于唇部功能正常组。在唇部功能不全组中，嘴唇分开咀嚼时，咬肌无活动期下唇的肌电图活动显著高于唇部功能正常组（P < 0.05），但两组在咬肌活动期的肌电图活动无差异。我们的结果表明，唇部功能不全的受试者在嘴唇放松时咀嚼困难。我们得出结论，无法闭合嘴唇和唇部功能障碍可能会影响咀嚼功能。
