Byrd K E
Department of Basic Sciences, University of Southern California School of Dentistry, Los Angeles 90089-0641.
J Dent Res. 1988 Oct;67(10):1284-8. doi: 10.1177/00220345880670100801.
Frontal plane mandibular movements and the associated superficial masseter EMG signals of six 39-day-old rats were simultaneously recorded and digitized at a rate of 1 kHz by the optoelectronic method in order to investigate the loci and attributes of masseteric silent periods during mastication of hard (pellets) and soft (slurry) food items. The marked silent periods, defined as cessations of EMG activity during the slow-close (SC) phase of single chewing cycles, were analyzed for their (1) onset and offset durations relative to physiological centric occlusion (PCO), (2) frontal vertical (FV) and frontal horizontal (FH) loci relative to PCO, and (3) FV and FH velocities and accelerations of masticatory mandibular movements in relation to PCO. The start (SSP) and end (ESP) of silent period loci relative to PCO moved superiorly as sequences of pellet mastication progressed. All silent period attributes during slurry consumption were significantly different (p less than or equal to 0.01) from pellet attributes: Slurry SSP and ESP loci were closer to PCO than were pellet loci; durations of silent period loci during pellet mastication were more variable than were slurry durations. FV distance and velocity values for pellets were greater than with pellets. Although FV velocities during both pellet and slurry mastication decreased at ESP relative to SSP values, their FH velocities at ESP actually increased relative to SSP velocities. Loci attributes of EMG silent periods appeared largely dependent on the consistency of the food item being masticated.
为了研究在咀嚼硬食物（颗粒）和软食物（糊状物）时咬肌静息期的位置和特征，采用光电方法同时记录了6只39日龄大鼠的额平面下颌运动以及相关的咬肌表面肌电图信号，并以1 kHz的速率进行数字化处理。对单个咀嚼周期的慢闭（SC）阶段肌电图活动停止所定义的明显静息期进行了分析，包括其（1）相对于生理正中咬合（PCO）的起始和结束持续时间，（2）相对于PCO的额垂直（FV）和额水平（FH）位置，以及（3）相对于PCO的咀嚼下颌运动的FV和FH速度及加速度。随着颗粒咀嚼序列的进行，相对于PCO的静息期位置的起始（SSP）和结束（ESP）向上移动。在食用糊状物期间，所有静息期特征与颗粒特征均有显著差异（p≤0.01）：糊状物的SSP和ESP位置比颗粒位置更接近PCO；颗粒咀嚼时静息期位置的持续时间比糊状物的持续时间更具变异性。颗粒的FV距离和速度值大于糊状物的。尽管在颗粒和糊状物咀嚼过程中，相对于SSP值，FV速度在ESP时均降低，但其FH速度在ESP时相对于SSP速度实际上增加了。肌电图静息期的位置特征似乎很大程度上取决于所咀嚼食物的稠度。
