SummaryIn 2013, consensus was obtained on a definition of bruxism as repetitive masticatory muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible and specified as either sleep bruxism or awake bruxism. In addition, a grading system was proposed to determine the likelihood that a certain assessment of bruxism actually yields a valid outcome. This study discusses the need for an updated consensus and has the following aims: (i) to further clarify the 2013 definition and to develop separate definitions for sleep and awake bruxism; (ii) to determine whether bruxism is a disorder rather than a behaviour that can be a risk factor for certain clinical conditions; (iii) to re-examine the 2013 grading system; and (iv) to develop a research agenda. It was concluded that: (i) sleep and awake bruxism are masticatory muscle activities that occur during sleep (characterised as rhythmic or non-rhythmic) and wakefulness (characterised by repetitive or sustained tooth contact and/or by bracing or thrusting of the mandible), respectively; (ii) in otherwise healthy individuals, bruxism should not be considered as a disorder, but rather as a behaviour that can be a risk (and/or protective) factor for certain clinical consequences; (iii) both non-instrumental approaches (notably self-report) and instrumental approaches (notably electromyography) can be employed to assess bruxism; and (iv) standard cut-off points for establishing the presence or absence of bruxism should not be used in otherwise healthy individuals; rather, bruxism­related masticatory muscle activities should be assessed in the behaviour’s continuum.

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The association of sleep bruxism and painful TMD greatly increased the risk for episodic migraine, episodic tension-type headache, and especially for chronic migraine.

To examine possible associations between self-reported bruxism, stress, desirability of control, dental anxiety and gagging. Five questionnaires were distributed among a general adult population (402 respondents): the Perceived Stress Scale (PSS), Desirability of Control Scale (DC), Dental Anxiety Scale (DAS), Gagging Assessment Scale (GAS), and Bruxism Assessment Questionnaire. A high positive correlation between DAS and GAS (R = 0·604, P < 0·001) was found. PSS was negatively correlated with DC (R = -0·292, P < 0·001), and was positively correlated with GAS (R = 0·217, P < 0·001) and DAS (R = 0·214, P < 0·001). Respondents who reported bruxing while awake or asleep showed higher levels of GAS, DAS and PSS than those who did not. There were no differences between the bruxers and the non-bruxers (sleep and aware) with regard to the DC scores. The best predictors of awake bruxism were sleep bruxism (OR = 4·98, CI 95% 2·54-9·74) and GAS (OR = 1·10, CI 95% 1·04-1·17). The best predictors of sleep bruxism were awake bruxism (OR = 5·0, CI 95% 2·56-9·78) and GAS (OR = 1·19; CI 95% 1·11-1·27). Self-reported sleep bruxism significantly increases the odds for awake bruxism and vice versa. Tendency for gagging during dental care slightly increases the odds of both types of self-reported bruxism, but desirability of control is not associated with these phenomena.

The aim of the present investigation was to perform a systematic review of the literature dealing with the issue of sleep bruxism prevalence in children at the general population level. Quality assessment of the reviewed papers was performed to identify flaws in the external and internal validity. Cut-off criteria for an acceptable external validity were established to select studies for the discussion of prevalence data. A total of 22 publications were included in the review, most of which had methodological problems limiting their external validity. Prevalence data extraction was performed only on eight papers that were consistent as for the sampling strategy and showed only minor external validity problems, but they had some common internal validity flaws related with the definition of sleep bruxism measures. All the selected papers based sleep bruxism diagnosis on proxy reports by the parents, and no epidemiological data were available from studies adopting other diagnostic strategies (e.g. polysomnography or electromyography). The reported prevalence was highly variable between the studies (3·5-40·6%), with a commonly described decrease with age and no gender differences. A very high variability in sleep bruxism prevalence in children was found, due to the different age groups under investigation and the different frequencies of self-reported sleep bruxism. This prevented from supporting any reliable estimates of the prevalence of sleep bruxism in children.