Background Electromyography (EMG) biofeedback (BF) training is potentially an effective cognitive‐behavioural approach to regulate bruxism. Objective This study examined sleep bruxism regulation by daytime clenching control using a single‐channel auditory EMG BF device. Methods Seventeen male subjects (mean age, 24.4 ± 3.1 years; mean ± SD) with self‐reported awake/sleep bruxism were recruited and divided into a BF (n = 10) and a control (CO) group (n = 7). All subjects underwent four EMG recording sessions during both daytime and sleep over 3 weeks. During the daytime, in week 2, the BF group received feedback alert signals when excessive EMG activity with certain burst duration was detected while the subjects performed regular daily activities. The CO group underwent EMG recording sessions without receiving any alerts of parafunctional activity. The number of phasic burst events during sleep was compared between the BF and CO groups. Results While the number of phasic EMG events was not significantly different between the BF and CO groups at baseline, significantly smaller phasic events were observed in the BF compared to the CO group at the follow‐up session (week 3) (P = .006, Tukey's HSD). Since daytime BF training is aimed at raising awareness of awake bruxism, it does not interrupt the sleep sequence or involve associated side effects. Conclusion The present results suggest that EMG BF targeting for tonic EMG events during the daytime can be an effective method to regulate phasic EMG events during sleep.

This study aimed to evaluate the effects of the tooth portion evaluated and the colors of the abutment tooth and resin luting agent on the final color of monolithic zirconia crowns. Methods: Monolithic zirconia crowns were fabricated for left maxillary central incisors using two shades (A2 and A3) of highly translucent monolithic zirconia disks. A model of the abutment tooth was fabricated using resin core materials (white: W; dentin: D). The color of the crowns was measured with try-in pastes (clear: C; brown: B) as a resin-luting agent substitute. The measurement was performed after placing the crown on the model with the attached abutment tooth with try-in paste. The color of three labial portions (cervical, body, and incisal) was evaluated using a dental spectrophotometer. The color difference (ΔE) between the CIELab values of the zirconia disks and the final measurement of zirconia crowns was calculated. Results: The ΔE between the crown of the A2 shade and the zirconia disk of the A2 shade had the highest ΔE value in the body portion with W-B (ΔE=3.92). Similarly, the A3 shade had the highest ΔE value in the cervical portion, with W-B (ΔE=4.27). The results of three-way ANOVA showed that the ΔE values were influenced by the tooth portion evaluated and the color of the abutment tooth. Conclusions: The final color of the monolithic zirconia crowns was significantly influenced by the tooth portion evaluated and the color of the abutment tooth.

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Bruxism is a repetitive masticatory muscle activity characterized by the clenching or grinding of teeth and/or bracing or thrusting of the mandible. Bruxism can occur in any individual and is considered a risk factor for the sleep-related disorder [1]. However, bruxing can cause various harmful outcomes, such as temporomandibular disorders, tooth attrition, cracks, fractures, prosthesis destruction, and the progression of periodontal disease [2][3][4][5][6]. Bruxism can be classified as awake bruxism (AB) or sleeping bruxism (SB). Assessment methods have been continuously considered for each type [1]. However, a consensus has not been reached on many aspects of AB, such as the test method, assessment criteria for test results, diagnosis, and assessment of therapeutic effects. Based on these perspectives, it is important to discuss bruxing habits in a clinical setting for dental treatment. To date, the assessment of bruxism has been predominantly based on self-reports, has been reported [7][8][9][10][11][12][13]. However, the diagnostic accuracy of self-reported bruxism is generally low and appropriate scientific information and reliability are lacking. In addition, clinical findings, such as tooth attrition, may not be sufficiently strong to prove an active bruxer because it may be a residual effect of previous tooth grinding. For SB diagnostic criteria, a cutoff value recorded with polysomnography (PSG) has been recommended [14]. However, recording a PSG using audio-video equipment during the day in a natural environment to assess AB is unrealistic. A single-channel electromyography (EMG) recording device provides parafunctional muscle activity. However, EMG signals, together with bruxism behavior, may also comprise other functional activities such as eating, speaking, or laughter [15]. Recently, the use of ecological momentary assessment (EMA) has been reported as a strategy to solve these problems [16][17][18][19]. The EMA can confirm the relevance of phenomenon assessment because it records and assesses a particular behavior at that moment in daily life [20]. To date, AB has been independently analyzed using EMA or EMG. Therefore, the present study was undertaken to propose a validated cutoff value to diagnose AB based on the simultaneous recording of EMA and EMG. Materials and Methods Study participantsThe study participants were recruited from among outpa-J Prosthodont Res. 2023; **(**):