Objective: The Research Diagnostic Criteria (RDC) for TMD recommend the collection of clinically important patient characteristics, such as self-reported oral parafunctions. With newly developed 12-item questionnaires, not only the frequency of different types of parafunctions in (groups of) TMD patients was examined, but it was also studied how often patients think that the parafunctions they engage in are a load for their jaws. Methods: Two cohorts of consecutive TMD patients completed a specific questionnaire for either the frequency or the loading aspects of their parafunctions. Using a 5-point scale (0 = never - 4 = always), the first (‘frequency') cohort (n = 226; 88.5% women; mean age = 38.5 yrs) scored the frequency of twelve different parafunctions; the second (‘loading') cohort (n = 303; 83.8% women; mean age = 37.2 yrs) scored the frequency of parafunctions that, according to the patients' perception, actually loaded their jaws. Results: To facilitate further analyses, first a principal component analysis was used to create groups of parafunctions. Three factors were thus extracted, viz., a ‘bruxism scale' (daytime en sleep-related grinding and clenching), a ‘soft tissue scale' (e.g., playing or pushing with the tongue), and a ‘bite scale' (e.g., nail biting). A Kruskal-Wallis procedure showed that none of the scales differed significantly between groups of TMD patients who were classified according to their graded chronic pain score. Even though the three scales did not differ between men and women in the frequency cohort, higher scale scores were present in women than in men in the loading cohort (Levene's tests; 0.001 < p < 0.01). Conclusion: Independent of the graded chronic pain scores, oral parafunctions were equally reported by female and male TMD patients, but female patients judged their parafunctions to be more of a load for their jaws than did male patients.

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