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Background: The aim of this thesis was to delve deeper into the different aspects of temporomandibular disorders (TMD) as a public health problem among adults. The studies evaluated signs and symptoms indicative of TMD in terms of prevalence, associated factors, treatment need estimate, possible factors underpinning treatment need owing to TMD, as well as possible influences of pain conditions on TMD symptoms and diagnosis in adult populations.

Study populations and Methods: The thesis is comprised of five papers. The first four papers (I-IV) included individuals 35, 50, 65 and, 75 years old living in Västerbotten County, Sweden. The study sample was stratified based on the area of residence – coast (mainly urban area) and inland (mainly rural area). Scrutiny constituted a questionnaire and a clinical examination. Of 1200 individuals contacted (300 in each age group), 987 (82%) returned a filled-out questionnaire and 779 (65%) participated in the clinical examination. Distribution of signs and symptoms indicative of TMD in the different age groups, associations between different factors and TMD signs, symptoms and treatment need owing to TMD, as well as association between different patterns of pain to palpation and pain in the jaw-face-head region were analyzed. Paper V assessed the association between widespread pain and TMD pain in 300 individuals of which 110 diagnosed as TMD pain according to DC/TMD (arthralgia, myalgia and myofascial pain with referral). Logistic regression analysis was applied in the papers II-V and the results were presented as odds ratios (OR) with 95% confidence interval (95% CI).

Results: The prevalence of symptoms indicative of TMD and frequent headaches was high in the adult population. The age and gender patterns were, for the most part, similar for the frequent symptoms in terms of prevalence. In general, lower prevalence of frequent headaches and symptoms indicative of TMD were observed among the elderly compared to the younger age groups. Clinical signs indicative of TMD were more commonly registered among women. In the analysis of putative factors related to presence of signs and symptoms, self- perceived impaired general health status was the most consistent finding in the different age groups. The estimated treatment need owing to TMD was 15% for the total sample. The presence of TMD signs, symptoms, smoking, living on the coast, and being a woman emerged as important factors in the clinical decision- making process of treatment need due to TMD. A significant dose-response like pattern was observed between frequent pain in the jaw-face-head region and the patterns of pain elicited to palpation. Individuals with widespread pain compared to those without widespread pain significantly more often had a TMD diagnosis of myofascial pain with referral and myalgia according to the DC/TMD.

Conclusions: The age and gender differences on signs and symptoms indicative of TMD among adults are likely related to factors included in the biopsychosocial model. The associations between comorbidities and TMD may influence demand for treatment among the affected. Thus, TMD treatment should be included in the medical health care payment systems. A significant proportion of the adult population has a need of treatment related to TMD. Generalized hyperalgesia and widespread pain conditions are related to pain in the jaw-face-head region and should be acknowledged in clinical evaluations, diagnostic decisions, treatment planning as well as in research settings.