During the last few decades, and especially during the 1990s, an increase in musculoskeletal pain conditions and stress-related ill-health has been observed in Sweden. At the same time, an improvement in the oral health of the population has been noted. The overall aim of this thesis was to acquire knowledge relating to possible time trends for the presence of temporomandibular disorders (TMD) in the population. A further objective was to study factors that possibly influence the presence of these disorders and the outcome of their treatment.

Studies I–III are based on a series of repeated cross-sectional population-based investigations. Three independent samples of 130 individuals in the age groups of 3, 5, 10, 15, 20, 30, 40, 50, 60 and 70 years were randomly selected from the inhabitants of the city of Jonkoping, Sweden in 1983, 1993 and 2003. The total participation rate was 21%, 22% and 29% respectively. The participants were examined using a questionnaire, interview and a clinical examination of the stomatognathic system regarding the presence of symptoms and signs indicative of TMD. Study IV is a retrospective survey of a clinical sample of patients referred to and treated at the Department of Stomatognathic Physiology, The Institute for Postgraduate Dental Education, Jonkoping, in 1995–2002. The overall frequencies of symptoms and the rates for some clinical signs and consequently of an estimated treatment need in adults increased during the study period. In 2003, the prevalence of frequent headache in 20-year-olds, mainly females, had markedly increased. The reports of bruxism among adults increased from 1983 to 2003. Awareness of bruxism and self-perceived health impairment were associated with TMD symptoms and signs. A favourable treatment outcome was observed for the majority of patients with common TMD sub-diagnoses and no strong predictors of treatment outcome were found.

In conclusion, the results suggest some time trends towards an increased prevalence in the overall symptoms and some signs indicative of TMD in the Swedish adult population during the time period 1983–2003. A profound understanding of the social determinants of health is recommended when planning public health resources.