Validity of clinical diagnostic criteria for sleep bruxism by comparison with a reference standard using masseteric electromyogram obtained with an ultraminiature electromyographic device.

Evaluation of sleep bruxism (SB) in clinical practice is currently conducted based on clinical findings, i.e., clinical diagnostic criteria consisting of medical interview, findings of tooth wear, and symptoms of temporomandibular joint (TMJ) and muscles. However, there are many unclear points about validity of the criteria. In this study, validity tests were conducted to clarify the accuracy of the clinical diagnostic criteria for SB by comparison with a reference standard using a single-channel masseteric electromyogram (EMG) obtained with ultraminiature electromyographic devices. The subjects included 30 'probable' bruxers (P-bruxers) who were clinically diagnosed as having SB and 30 non-bruxers. EMG was recorded during sleep under unrestrained and accustomed condition at each subject's home using ultraminiature cordless EMG devices. Bursts with amplitudes of more than 5%, 10%, 20% of the maximum voluntary contraction (MVC) value (EMG-burst-5%, EMG-burst-10%, and EMG-burst-20%) and episodes of sleep bruxism (EMG-episode) were selected for analyses. In all conditions for burst selection, the P-bruxer group showed a significantly larger number of bursts and episodes than those in the non-bruxer group. Accuracy of the clinical diagnosis criteria was 66.7% with the reference standard using EMG-burst-5%/h and 58.3% with that using EMG-episodes/h. By applying single-channel EMG as the reference standard, we were able to conduct validity tests of clinical diagnostic criteria with a larger sample. It was clarified that the level of accuracy of clinical diagnostic criteria for SB were not high despite using the combination of an interview and clinical findings.