Journal of dental research
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The clinical validity of diagnostic criteria for sleep orofacial motor activity--more specifically, bruxism--has never been tested. Polysomnographic recordings from 18 bruxers and 18 asymptomatic subjects, selected according to American Sleep Disorders Association criteria, were analyzed (1) to discriminate sleep bruxism from other orofacial motor activities and (2) to calculate sensitivity, specificity, and predictive values of research criteria. Clinical observations and reports revealed that all 18 bruxers reported frequent tooth-grinding during sleep. ⋯ Based on the present findings, the following polysomnographic diagnostic cut-off criteria are suggested: (1) more than 4 bruxism episodes per hour, (2) more than 6 bruxism bursts per episode and/or 25 bruxism bursts per hour of sleep, and (3) at least 2 episodes with grinding sounds. When the polysomnographic bruxism-related variables were combined under logistic regression, the clinical diagnosis was correctly predicted in 81.3% of the controls and 83.3% of the bruxers. The validity of these clinical research criteria needs now to be challenged in a larger population, over time, and in subjects presenting various levels of severity of sleep bruxism.
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The purpose of this study was to assess the prevalence and pattern of self-reported TMD jaw pain in a randomized stratified sample from the general population living in the Province of Québec, Canada. Through a telephone survey, standardized questions were asked to 897 French-speaking respondents, aged 18 years old and over, regarding frequency, severity, daily pattern of jaw pain, presence of difficulty in opening, joint clicking, and sleeping problems. All prevalence estimates were adjusted to the sociodemographic distribution of the non-institutionalized population. ⋯ Approximately one in four subjects with frequent episodes of jaw pain also reported frequent joint clicking or difficulty in opening, and a strong association (Gamma coefficient > 0.6) was found among all three TMD symptoms. Our data suggest that the prevalence of clinically significant TMD-related jaw pain (frequent jaw pain of moderate to severe intensity) is approximately 5% in the general population of the Province of Québec. In the nine months preceding the survey, about 2% of the total population sought treatment for a TMD symptom.
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Human individuals were hypothesized to use the same pattern of jaw muscle activity to produce the same bite force. To test this hypothesis, we used a 2-mm-thick force transducer to monitor the magnitude and direction of a bite force between a single pair of occluding first molars. Five subjects performed standardized bite force tasks. ⋯ In contrast, when the magnitude of bite force was the same but the directions were different, the ratio was not constant. We conclude that the direction of a bite force, not its magnitude, determines the pattern of activity of jaw-closing muscles. The shared patterns of muscle activation may be the result of a subconscious optimization of jaw muscle forces to improve efficiency.