Scientific methodology in temporomandibular disorders. Part I: Epidemiology

Epidemiological methodology is examined relative to the following: a) use of proper controls; b) the large magnitude of variation in published epidemiological studies on occurrence of temporomandibular disorders (TMD); c) its suitability for the study of TMD as stress disorders; d) the fact that TMD are a group of diseases each with different etiologies and symptomologies (epidemiological studies directed at the whole group may be misleading and inappropriate); and e) subjectivity of the criteria used in epidemiologic studies of TMD. This article involves the logic of the methodology and does not deal with statistical analysis.