J Oral Facial Pain Headache. 2019 Winter;33(1):14–24. doi: 10.11607/ofph.2011. Epub 2018 Aug 20.
To investigate whether static jaw clenching can activate endogenous pain modulation and to compare the magnitude between healthy individuals and patients with temporomandibular disorder (TMD) myalgia.
Thirty-three healthy volunteers (17 women and 16 men) and 20 women with TMD myalgia participated. Exercise-induced hypoalgesia (EIH) was examined by recording pressure pain thresholds (PPTs) in the masseter (MA) and brachioradialis (BR) muscles during tooth clenching until exhaustion. Pain and fatigue were assessed before and after clenching, and pain amplification was examined by applying a painful mechanical pressure at the MA for 2 minutes while assessing pain every 30 seconds. Analyses of data included repeated measures analysis of variance.
In the contracting MA, PPTs increased over time in all three groups (P < .001), while PPTs in the relaxed BR increased only in the men (P = .045). Pain intensity and fatigue in the MA increased after contraction in all groups (P < .003) and was higher in the women with TMD than in the healthy women (P < .001). Only the women with TMD showed pain amplification (P < .001).
Tooth clenching until exhaustion could activate EIH locally; ie, the magnitude of EIH in the MA was similar in women with TMD myalgia and pain-free women, indicating no deficient EIH in women with TMD. However, only women with TMD showed pain amplification during application of continuous painful pressure.
研究静息性下颌紧咬是否能激活内源性疼痛调制，并比较健康个体与颞下颌关节紊乱病（TMD）肌痛患者之间的差异。
共纳入 33 名健康志愿者（17 名女性，16 名男性）和 20 名 TMD 肌痛女性患者。通过记录咬肌（MA）和肱桡肌（BR）在牙齿紧咬至力竭过程中的压力疼痛阈值（PPT）来评估运动诱发性镇痛（EIH）。紧咬前后评估疼痛和疲劳程度，并用机械压痛仪在 MA 上持续施压 2 分钟，每 30 秒评估 1 次疼痛，以检测疼痛放大效应。数据分析采用重复测量方差分析。
在收缩的 MA 中，所有 3 组的 PPT 均随时间增加（P <.001），而放松的 BR 中的 PPT 仅在男性中增加（P =.045）。所有组的 MA 疼痛强度和疲劳在收缩后均增加（P <.003），TMD 女性的疼痛强度和疲劳程度均高于健康女性（P <.001）。仅 TMD 女性出现疼痛放大（P <.001）。
力竭性牙齿紧咬可局部激活 EIH；即，TMD 肌痛女性与无痛女性的 MA 中 EIH 幅度相似，表明 TMD 女性的 EIH 无缺陷。然而，只有 TMD 女性在持续施加压痛时出现疼痛放大。
