Michelotti A, Farella M, Vollaro S, Martina R
Department of Orthodontics, University of Naples Federico II, Italy.
J Prosthet Dent. 1997 Jul;78(1):48-53. doi: 10.1016/s0022-3913(97)70087-8.
The determination of a correct vertical dimension of occlusion is a critical procedure in clinical dentistry.
The objectives of this study were to analyze the relation between mandibular rest position and electrical activity of masticatory muscles and to compare clinical and electromyographic rest position in subjects with different vertical facial morphologic features.
Clinical rest position and electromyographic rest position were investigated in 40 subjects. Electromyographic rest position ranged from 0.4 to 12.7 mm (average 7.7 +/- 2.7 mm). Clinical rest position ranged from 0.1 to 4.4 mm (average 1.4 +/- 1.1 mm). The average difference between electromyographic rest position and clinical rest position was 6.3 +/- 2.5 mm (range 0.3 to 10.3 mm). Sixteen subjects were selected according to the Frankfort mandibular plane angle and separated in two groups having a mandibular plane angle > or = 28 degrees.
Rest position was significantly greater (p < 0.05) in the low-angle group (2 +/- 1.3 mm) than in the high angle group (0.8 +/- 0.8 mm). Electromyographic rest position did not differ between subjects with different facial morphologic features (8.1 +/- 1.7 mm low-angle group; 7.6 +/- 4.1 mm high angle group). By varying the vertical dimension millimeter by millimeter, masseter and anterior temporal electromyographic activity demonstrated a considerable decrease over an interocclusal distance of 3 to 4 mm. Further mandibular opening up to 18 mm corresponded to small changes in postural activity.
This study suggests that a jaw posture with a few millimeters of interocclusal distance involves a great reduction of masticatory muscle activity.
确定正确的咬合垂直距离是临床牙科中的关键步骤。
本研究的目的是分析下颌休息位与咀嚼肌电活动之间的关系，并比较具有不同垂直面部形态特征的受试者的临床休息位和肌电图休息位。
对40名受试者的临床休息位和肌电图休息位进行了研究。肌电图休息位范围为0.4至12.7毫米（平均7.7±2.7毫米）。临床休息位范围为0.1至4.4毫米（平均1.4±1.1毫米）。肌电图休息位与临床休息位之间的平均差异为6.3±2.5毫米（范围0.3至10.3毫米）。根据法兰克福下颌平面角选择16名受试者，并将其分为两组，下颌平面角≥28度。
低角组（2±1.3毫米）的休息位明显大于（p<0.05）高角组（0.8±0.8毫米）。不同面部形态特征的受试者之间的肌电图休息位没有差异（低角组8.1±1.7毫米；高角组7.6±4.1毫米）。通过逐毫米改变垂直距离，咬肌和颞前肌的肌电图活动在3至4毫米的咬合间隙内显示出显著下降。下颌进一步张开至18毫米对应姿势活动的微小变化。
本研究表明，咬合间隙为几毫米的颌骨姿势会使咀嚼肌活动大幅降低。
