No Dose-Response Association Between Self-Reported Bruxism and Pain-Related Temporomandibular Disorders: A Retrospective Study

Aims: To investigate whether a dose-response relationship exists between the intensity of pain-related temporomandibular disorders (TMDs) and the amount of self-reported bruxism activities in a group of TMD pain patients. Methods: A total of 768 patients referred to a specialized clinic for complaints of orofacial pain and dysfunction were initially enrolled in the study. Of these patients, 293 who were diagnosed with at least one type of pain-related TMD according to the Diagnostic Criteria for Temporomandibular Disorders were selected. The questionnaire-based reports of TMD pain intensity, as assessed by an 11-point numeric rating scale (NRS), were subsequently compared to the reports of sleep bruxism (single question; 5-point Likert scale) and awake bruxism (mean score of six questions; 5-point Likert scale). Spearman correlations were used to assess associations, and possible confounding effects of depression, somatic symptoms, and anxiety were taken into account. Results: Spearman correlation tests provided no significant correlation between the amount of self-reported sleep bruxism and TMD pain intensity. On the other hand, the amount of awake bruxism was positively correlated with the intensity of TMD pain; however, the latter correlation was lost when the model was controlled for the effects of depression. Conclusion: The assumption that there is a dose-response gradient association between bruxism and TMD pain, reflected in more bruxism leading to more overloading and thus to more pain, could not be justified. Parole chiave: bruxism, confounding, dose-response relationship, pain-related temporomandibular disorders, psychological factors