Studies on artificial interferences in subjects with no temporomandibular (TMD) history have shown adaptation to the interference within a fairly short period of time. The role of occlusal factors in the etiology of TMD has therefore been questioned. The results might have been different, however, if subjects with a prior TMD history had been included in the study groups. To test this assumption in a randomized double-blind clinical set-up, we included healthy women without (n = 26) as well as with (n = 21) an earlier TMD history. Both groups were randomly divided into true and placebo interference groups. Artificial interferences were introduced in the true interference groups and simulated in the placebo groups. The subjects were followed for 2 weeks, after which the interferences were removed. The subjects without a TMD history showed fairly good adaptation to the interferences, but the subjects with a TMD history and true interferences showed a significant increase in clinical signs compared to the other groups. We suggest that the etiological role of occlusal interferences in TMD may not have been correctly addressed in previous studies with artificial interferences and allow no conclusions as regards TMD etiology.

In a previous double-blind randomized controlled study, subjects with a history of temporomandibular disorder (TMD) reacted to artificial interference with more signs of TMD than did subjects with no TMD history. In the present study, we analysed the subjective reactions of these individuals on several symptom scales. Every day during the 2-week follow-up period, the subjects rated the intensity of their symptoms on 9 VAS scales (occlusal discomfort, chewing difficulties, tender teeth, fatigue in the jaws, headache, facial pain, opening difficulty, bruxism, ear symptoms). Subjects with a history of TMD and true interferences reported stronger symptoms than subjects with no TMD history and placebo interferences. The most prominent symptoms were occlusal discomfort and chewing difficulties. The difference in outcome between the groups with and without a TMD history suggests that there are individual differences in vulnerability to occlusal interferences. It is likely that the etiological role of occlusal interferences in TMD has not been correctly addressed in previous studies on artificial interferences.

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The aim was to investigate the association between temporomandibular disorders (TMD) and overall muscle tenderness, depressive symptoms, sleep difficulties, headache frequency and related symptoms in children with primary headache in comparison with controls. Based on an unselected population sample of 1135 Finnish schoolchildren classified according to the type of headache at age 12, altogether 297 children aged 13-14 from different headache groups and healthy controls were randomly selected for an interview and clinical examinations. Children with migraine had more TMD signs than children with nonmigrainous headaches or healthy controls. High TMD total scores were associated with palpation tenderness in other parts of the body and with frequent headache attacks. We conclude that children with overall headache, migraine in particular, and high total TMD scores showed an increased overall tenderness to muscle palpation and multiply manifested hypersensitivity pain.

Psychological factors appeared significant for the symptom responses to artificial interferences, and they seem to play a different role in responses in subjects with an earlier TMD history compared to those without.