Department of Morphology, Piracicaba Dental School, University of Campinas, Av Limeira 901, Piracicaba, SP, Brazil.
Arch Oral Biol. 2013 Sep;58(9):1100-8. doi: 10.1016/j.archoralbio.2013.04.006. Epub 2013 May 16.
The aim of this study was to evaluate the maximal bite force (MBF), electromyographic (EMG) activity and thickness of the masseter, anterior part of the temporalis and sternocleidomastoid (SCM) muscles in a group of young adults with and without temporomandibular disorders (TMDs).
Nineteen individuals comprised the TMD group (6 males/13 females, aged 25.4±3.8 years), classified based on the Research Diagnostic Criteria for TMD (RDC/TMD), and 19 comprised the control group (6 males/13 females, aged 24.1±3.6 years). The MBF was determined with a transducer placed between the dental arches at the first molars level (N). The muscles were evaluated bilaterally at rest and during maximal voluntary clenching (MVC) by assessing EMG activity and performing ultrasonography (USG). The mean values of these measures for both sides of the mouth were used. The normality of the distributions was assessed by the Shapiro-Wilks test. Variables between groups and genders were compared using two-way factorial ANOVA test and correlated using the Spearman coefficient (α=0.05). Unpaired t test was used to compare variables between TMD subgroups. Logistic regression analysis was used to identify the variables associated with the presence of TMD.
MBF, EMG and USG data were similar among clinical groups and among TMD subgroups. The thickness of masseter and SCM muscles in the relaxed and clenching states were significantly higher in males than females. On the other hand, the EMG of the temporalis muscle in the rest state was significantly higher in females than males. Additionally, the MBF was positively correlated with the USG characteristics of masseter and SCM muscles, as well as with the EMG activity of masseter and temporalis muscles in the TMD group. In this group, there was also a positive correlation between the thickness of the masseter muscle and its activity. On the other hand, the thickness of the SCM muscle was negatively correlated with its activity. A lower MBF was independently associated with the presence of TMD.
Subjects with TMD exhibited similar values of MBF, thickness and electrical activity of masticatory and cervical muscles when compared with controls; positive correlations observed between these variables may suggest a muscular alteration in TMD patients and a co-activation of masticatory and cervical muscles during mandibular movement. This fact may also be confirmed by the negative association between bite forces and presence of TMD.
本研究旨在评估一组患有和不患有颞下颌关节紊乱（TMD）的年轻成年人的最大咬合力（MBF）、肌电图（EMG）活动以及咀嚼肌（咬肌、颞肌前区）和胸锁乳突肌（SCM）的厚度。
19 名个体组成 TMD 组（6 名男性/13 名女性，年龄 25.4±3.8 岁），根据研究诊断标准（RDC/TMD）进行分类，19 名个体组成对照组（6 名男性/13 名女性，年龄 24.1±3.6 岁）。MBF 通过放置在第一磨牙水平的牙弓之间的换能器（N）来确定。在休息和最大自主紧咬（MVC）期间，通过评估 EMG 活动和进行超声检查（USG）来评估双侧肌肉。使用口腔两侧的这些测量值的平均值。使用 Shapiro-Wilk 检验评估分布的正态性。使用双因素方差分析检验组间和性别间的变量差异，并使用 Spearman 系数进行相关性分析（α=0.05）。使用未配对 t 检验比较 TMD 亚组之间的变量。使用逻辑回归分析识别与 TMD 相关的变量。
MBF、EMG 和 USG 数据在临床组和 TMD 亚组之间相似。在放松和紧咬状态下，男性的咬肌和 SCM 肌肉厚度均显著高于女性。另一方面，在休息状态下，女性的颞肌 EMG 显著高于男性。此外，在 TMD 组中，MBF 与咬肌和 SCM 肌肉的 USG 特征以及咬肌和颞肌的 EMG 活动呈正相关。在该组中，咬肌厚度与其活动之间也存在正相关。另一方面，SCM 肌肉的厚度与其活动呈负相关。较低的 MBF 与 TMD 的存在独立相关。
与对照组相比，患有 TMD 的受试者的 MBF、咀嚼肌和颈部肌肉的厚度和电活动值相似；这些变量之间的正相关可能表明 TMD 患者的肌肉发生了改变，并且在下颌运动期间咀嚼肌和颈部肌肉会协同激活。MBF 与 TMD 的存在呈负相关，这一事实也证实了这一点。
