Does Sleep Bruxism Relate to TMJ Click Incidence in Adolescence?

Objectives: This study aimed to estimate the fluctuation of temporomandibular joint (TMJ) click in an adolescent population and evaluated the effect of sleep bruxism (SB) frequency on the incidence of TMJ click. Methods: Students of a high school in Okayama, Japan were epidemiologically surveyed twice at the first and third grades with 2-year interval. These two surveys consisted of TMJ click examination performed by pre-calibrated examiners and SB assessment by using an EMG-based SB detection device (BiteStrip®, S.L.P., Israel). Of which 127 subjects (male/female: 49/78) who participated in the first survey, 76 subjects (male/female: 29/47) joined the second. Among them, the subjects without click at the first survey (68 subjects) were divided into 2 groups according to their TMJ click fluctuation patterns, e.g., click-free group and click-appear group. The subjects were also classified into severe and non-severe SB groups at the first survey with three cut-offs (scores 1, 2, 3). The Relative Risk (RR) and the confidence interval (CI) were calculated to verify the effect of SB severity on the incidence of TMJ click by chi square tests. Results: Severe SB showed 2.18 (score 3; CI: 0.57-8.30, p=0.27), 1.83 (score 2; CI: 0.59-5.71, p=0.31) and 1.27 (score 1; CI: 0.36-4.48, p=1.00) times higher risk inducing TMJ click than non-severe SB. Although RR was increased according to the SB severity, the effect was not reached significance. Conclusion: Even with the weak tendency observed between the SB severity and RR levels for SB, SB severity had non-significant effect on TMJ click incidence during the two years in this age subjects (16~18 years old). This study protocol was approved by Ethical Committee for Human Research in Okayama University (#69, #173).