Discipline of Orthodontics, Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
University of Zurich, Zurich, Switzerland.
J Oral Rehabil. 2021 Sep;48(9):979-988. doi: 10.1111/joor.13219. Epub 2021 Jul 12.
Little is known about wake-time masseter activity of patients with masticatory muscle pain in real-life settings.
The aims of this study were (1) to assess wake-time masseter activity of women with masticatory muscle pain (MMP) and compare it with that of pain-free women; and (2) to investigate the association between objectively measured masseter contractions and self-reported oral behaviours.
Adult women (N = 27) diagnosed with MMP were age-matched with pain-free women (N = 26). The electromyographic (EMG) activity of the masseter muscle when awake was recorded unilaterally for two consecutive days. The number of contraction episodes and relative contraction time (%) were calculated using cut-off thresholds of 3%, 5% and 10% of maximum voluntary contraction (MVC). Self-reported daytime oral activity was assessed using the Oral Behaviours Checklist (OBC, items 3-21). Data were analysed using univariate tests and mixed-model analyses.
The number of contraction episodes was similar between groups for all detection thresholds, but the relative contraction time at the lower detection thresholds (i.e. 3% MVC and 5% MVC) was significantly longer (1.5-fold) in the MMP than in the pain-free group. The OBC scores were significantly higher in the women with MMP than in controls, but no positive association could be found between EMG variables and OBC scores.
Women with MMP engage in low-level masseter muscle contractions, which last longer than those of pain-free controls. There was no relationship between self-reported oral behaviours and masseter activity when awake. These findings support the notion that prolonged low-level clenching when awake may play a role in the pathophysiology of MMP.
在现实环境中，对于咀嚼肌疼痛患者清醒时的咬肌活动知之甚少。
本研究旨在：（1）评估患有咀嚼肌疼痛（MMP）的女性在清醒时的咬肌活动，并与无痛女性进行比较；（2）探讨客观测量的咬肌收缩与自我报告的口腔行为之间的关系。
将患有 MMP 的成年女性（N=27）与无痛女性（N=26）进行年龄匹配。连续两天记录单侧咬肌在清醒时的肌电图（EMG）活动。使用最大自主收缩（MVC）的 3%、5%和 10%的截断阈值计算收缩发作次数和相对收缩时间（%）。使用口腔行为检查表（OBC，项目 3-21）评估白天的自我报告口腔活动。使用单变量检验和混合模型分析进行数据分析。
对于所有检测阈值，两组的收缩发作次数相似，但在 MMP 组中，较低检测阈值（即 3%MVC 和 5%MVC）的相对收缩时间显著更长（1.5 倍）。MMP 组的 OBC 评分明显高于对照组，但 EMG 变量与 OBC 评分之间没有发现正相关关系。
患有 MMP 的女性会进行低水平的咬肌收缩，持续时间长于无痛对照组。自我报告的口腔行为与清醒时的咬肌活动之间没有关系。这些发现支持这样一种观点，即清醒时长时间的低水平紧咬牙可能在 MMP 的病理生理学中起作用。
