Fatigue of temporomandibular joint (TMJ) tissues reflects the effects of magnitude (energy density; ED) and frequency of loading (jaw muscle duty factor; DF). This observational study measured these variables and tested for differences in mechanobehavior scores (MBS = ED2 × DF) and component variables in subjects with and without TMJ disc displacement (±D). In accordance with Institutional Review Board and STROBE guidelines, written informed consent was obtained, and examination and imaging protocols identified eligible adult subjects. Specifically, magnetic resonance imaging was used to assign subjects’ TMJs to ±D groups. Subjects were trained to record in-field jaw muscle activities, from which DFs (percentage of recording time) were determined. EDs (mJ/mm3) were estimated using modeled TMJ loads and in vivo dynamic stereometry. Multivariate analysis of variance, post hoc independent t tests, and K-means cluster analysis identified significant group differences ( P < 0.05). Of 242 individuals screened, 65 females (TMJs: 78 +D, 52 −D) and 53 males (TMJs: 39 +D, 67 −D) participated. Subjects produced 312 daytime and 319 nighttime recordings of average duration 6.0 ± 0.2 h and 7.6 ± 0.1 h, respectively, and 219 (114 right, 105 left) intact dynamic stereometry recordings. Average EDs were 2-fold and significantly larger in +D than −D TMJs ( P < 0.0001). DFs were on average 3-fold larger during the daytime versus nighttime for both masseter and temporalis muscles and 1.8- and 3.0-fold larger for the masseter versus temporalis muscle during the daytime and nighttime, respectively. Daytime masseter MBSs for +D TMJs in females were the largest overall at 621 ± 212 (mJ/mm3)2% and 2- to 43-fold larger versus −D TMJs in both sexes during daytime and nighttime. Cluster analysis ( P < 0.0001) identified groups 2 and 3, which comprised 87% +D TMJs and had average MBSs 21-fold larger than group 1. The results show MBS as a potential biomarker to predict homeostasis versus progression or reversal of degenerative TMJ structural changes.

中文翻译：

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力学和行为相关的颞下颌关节差异


颞下颌关节 （TMJ） 组织的疲劳反映了量级（能量密度;ED） 和负荷频率（下颌肌肉占空比;DF） 的 S S这项观察性研究测量了这些变量，并测试了有和没有 TMJ 椎间盘移位 （±D） 的受试者机械行为评分 （MBS = ED2 × DF） 和成分变量的差异。根据机构审查委员会和 STROBE 指南，获得了书面知情同意书，并确定了符合条件的成年受试者。具体来说，磁共振成像用于将受试者的 TMJ 分配到 ±D 组。受试者接受训练以记录场内下颌肌肉活动，从中确定 DF （记录时间的百分比）。使用建模的 TMJ 负载和体内动态立体测量法估计 EDs （mJ/mm3）。多因素方差分析、事后独立 t 检验和 K-means 聚类分析确定了显著的组间差异 （ P < 0.05）。在筛选的 242 名个体中，65 名女性 （TMJ： 78 +D， 52 −D） 和 53 名男性 （TMJ： 39 +D， 67 −D） 参与。受试者制作了 312 份日间和 319 份夜间记录，平均持续时间分别为 6.0 ± 0.2 小时和 7.6 ± 0.1 小时，以及 219 份（114 份右，105 份左）完整的动态立体测量记录。平均 ED 是 -D TMJ 的 2 倍，并且 +D 中显著大于 −D TMJ （ P < 0.0001）。咬肌和颞肌的 DFs 在白天与夜间相比平均大 3 倍，咬肌与颞肌在白天和夜间的 DFs 分别大 1.8 倍和 3.0 倍。女性 +D TMJ 的白天咬肌 MBS 总体最大，为 621 ± 212 （mJ/mm3）2%，白天和夜间两性与 -D TMJ 相比大 2 至 43 倍。 聚类分析 （P < 0.0001） 确定了第 2 组和第 3 组，占 87% +D TMJ，平均 MBS 比第 1 组大 21 倍。结果表明，MBS 是一种潜在的生物标志物，可以预测稳态与退行性 TMJ 结构变化的进展或逆转。