Relationship Between Cigarette Smoking and Awake Bruxism: Does Smoking Increase the Frequency of Masticatory Muscle Activities?

Background: Despite the aetiology of awake bruxism (AB) being prevalently linked to psychological factors, several studies suggested that the use of certain substances, such as tobacco smoking, can contribute to the increase in masticatory muscle activities (MMA) during wakefulness. Objective: The aim of this study is to assess whether there is a correlation between the frequency of awake bruxism behaviours and smoking habits. Methods: Participants were recruited, without gender or ethnic restriction, at the University of Siena, Siena, Italy, by advertising. Participants completed a questionnaire containing the four-item patient health questionnaire for anxiety and depression (PHQ-4) and some items from the Global Adult Tobacco Smoking (GATS) questionnaire. Moreover, they performed one week of awake bruxism behaviours monitoring via the ecological momentary assessment (EMA). Results: A total of 100 participants (university employees, dentists, undergraduate and post-graduate students) were included in the study (34 males and 66 females, mean age 24.5 years). Of them, 39% were smokers and 61% were non-smokers. The multiple variable linear regression analysis results showed a statistically significant correlation between the frequency of awake bruxism behaviours and the PHQ-4 scores. Specifically, for every 1% increase in PHQ-4 score, the mean frequency of the AB behaviours increases 5-fold. Awake bruxism behaviours did not show any statistically significant correlation with the number of smoked cigarettes (p > 0.05). Mandible bracing significantly correlated with the number of years of smoking (B = 1.58, p = 0.002). Conclusions: According to the present study's findings, the frequency of awake bruxism behaviours correlated with symptoms of anxiety and depression but not with smoking status.