Immediate effects of temporary bite-raising with light-cured orthodontic band cement on the electromyographic response of masticatory muscles

Abstract Objective: To assess the immediate effects of temporary bite-raising using light-cured orthodontic band cement on the superficial masseter and anterior temporalis electromyography (EMG) activity in healthy adults. Materials and Methods: Surface EMG signals were recorded bilaterally from the superficial masseter and anterior temporalis muscles of 30 volunteers with a normal occlusion, before and after having temporary bite-raising. The bite-raising was done by adding light-cured orthodontic band cement (3x5x2 mm WxLxH) on the lingual cusps of both upper first molars. The measurements were recorded (i) at rest, (ii) while clenching in centric occluding position and (iii) while chewing on an artificial test food. The EMG activity at rest and during clenching, the maximum voltage, and the duration of the identified EMG signal burst while chewing the artificial test food before and after temporary bite-raising were statistically compared using the paired t-test or the Wilcoxon signed-rank test based on the normality of the variables. The significance level was set at 5%. Results: After temporary bite-raising, we found no significant change in integral EMG activity at rest position for the superficial masseter (mean difference (MD)=7.5 μVs) and for the anterior temporalis muscle (MD=36.8 μVs); however, the integral EMG activity during clenching was significantly reduced for the superficial masseter (MD=201.2 μVs) and for the anterior temporalis muscle (MD=151.8 μVs). During mastication, the maximum voltage of the identified burst was significantly reduced on the preferred chewing side of the superficial masseter and anterior temporalis muscles (MD=127.9 and 47.7 μV, respectively), while no significant change was found for the duration of the identified burst (MD=-34.1 and 3.4 ms, respectively) after temporary bite-raising. Conclusion: The results point to an altered neuromuscular behavior during clenching and chewing immediately after temporary bite-raising with light-cured orthodontic band cement. This information is relevant for orthodontists to inform their patients what will happen to their masticatory muscle activity when this bite-raising method is used.摘要 目的：评估采用光固化正畸带环粘固剂（light-cured orthodontic band cement）进行暂时性抬颌，对健康成年人浅层咬肌与颞前肌肌电图（electromyography, EMG）活动的即时影响。 材料与方法：招募30名咬合正常的志愿者，在暂时性抬颌操作前后，双侧采集其浅层咬肌与颞前肌的表面肌电信号。抬颌操作方式为：在双侧上颌第一磨牙的舌侧牙尖粘贴尺寸为3×5×2 mm（宽×长×高）的光固化正畸带环粘固剂。分别在三种状态下记录测量数据：(i)静息状态；(ii)正中咬合位紧咬时；(iii)咀嚼人工试验食物时。根据变量的正态性分布，采用配对t检验或Wilcoxon符号秩检验，对暂时性抬颌前后的下述指标进行统计学比较：静息与紧咬状态下的肌电活动、最大电压，以及咀嚼人工试验食物时识别到的肌电信号爆发持续时长。显著性水平设定为5%。 结果：暂时性抬颌后，浅层咬肌（平均差值(MD)=7.5 μVs）与颞前肌（MD=36.8 μVs）在静息状态下的积分肌电活动无显著变化；但紧咬时的积分肌电活动在浅层咬肌（MD=201.2 μVs）与颞前肌（MD=151.8 μVs）中均显著降低。咀嚼过程中，受试者优势咀嚼侧的浅层咬肌与颞前肌的信号爆发最大电压显著降低（分别为MD=127.9 μV和47.7 μV），而信号爆发持续时长无显著变化（分别为MD=-34.1 ms和3.4 ms）。 结论：研究结果显示，采用光固化正畸带环粘固剂完成暂时性抬颌后，紧咬与咀嚼状态下的神经肌肉行为即刻出现改变。该研究结果可为正畸医师向患者告知该抬颌方法应用时咀嚼肌活动的变化提供参考。