Kawakami Shigehisa, Kumazaki Yohei, Manda Yosuke, Oki Kazuhiro, Minagi Shogo
Department of Occlusal and Oral Functional Rehabilitation, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
PLoS One. 2014 Jul 10;9(7):e101882. doi: 10.1371/journal.pone.0101882. eCollection 2014.
The role of parafunctional masticatory muscle activity in tooth loss has not been fully clarified. This study aimed to reveal the characteristic activity of masseter muscles in bite collapse patients while awake and asleep.
Six progressive bite collapse patients (PBC group), six age- and gender-matched control subjects (MC group), and six young control subjects (YC group) were enrolled. Electromyograms (EMG) of the masseter muscles were continuously recorded with an ambulatory EMG recorder while patients were awake and asleep. Diurnal and nocturnal parafunctional EMG activity was classified as phasic, tonic, or mixed using an EMG threshold of 20% maximal voluntary clenching.
Highly extended diurnal phasic activity was observed only in the PBC group. The three groups had significantly different mean diurnal phasic episodes per hour, with 13.29±7.18 per hour in the PBC group, 0.95±0.97 per hour in the MC group, and 0.87±0.98 per hour in the YC group (p<0.01). ROC curve analysis suggested that the number of diurnal phasic episodes might be used to predict bite collapsing tooth loss.
Extensive bite loss might be related to diurnal masticatory muscle parafunction but not to parafunction during sleep.
Although mandibular parafunction has been implicated in stomatognathic system breakdown, a causal relationship has not been established because scientific modalities to evaluate parafunctional activity have been lacking.
This study used a newly developed EMG recording system that evaluates masseter muscle activity throughout the day. Our results challenge the stereotypical idea of nocturnal bruxism as a strong destructive force. We found that diurnal phasic masticatory muscle activity was most characteristic in patients with progressive bite collapse.
The incidence of diurnal phasic contractions could be used for the prognostic evaluation of stomatognathic system stability.
咀嚼肌异常功能活动在牙齿缺失中的作用尚未完全阐明。本研究旨在揭示咬殆丧失患者在清醒和睡眠状态下咬肌的特征性活动。
纳入6例进行性咬殆丧失患者（PBC组）、6例年龄和性别匹配的对照受试者（MC组）以及6例年轻对照受试者（YC组）。使用动态肌电图记录仪在患者清醒和睡眠时连续记录咬肌的肌电图（EMG）。根据最大自主紧咬时20%的肌电图阈值，将日间和夜间咀嚼肌异常功能肌电图活动分为相位性、紧张性或混合性。
仅在PBC组观察到高度延长的日间相位性活动。三组每小时的平均日间相位性发作次数有显著差异，PBC组为每小时13.29±7.18次，MC组为每小时0.95±0.97次，YC组为每小时0.87±0.98次（p<0.01）。ROC曲线分析表明，日间相位性发作次数可用于预测咬殆丧失性牙齿缺失。
广泛的咬殆丧失可能与日间咀嚼肌异常功能有关，而与睡眠期间的异常功能无关。
尽管下颌异常功能被认为与口颌系统功能紊乱有关，但由于缺乏评估异常功能活动的科学方法，尚未建立因果关系。
本研究使用了一种新开发的肌电图记录系统，该系统可全天评估咬肌活动。我们的结果挑战了夜磨牙作为强大破坏力的刻板观念。我们发现，进行性咬殆丧失患者的日间相位性咀嚼肌活动最为特征性。
日间相位性收缩的发生率可用于口颌系统稳定性的预后评估。
