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Baseline (BL) data on signs and symptoms characteristic of temporomandibular disorders (TMDs) were analysed in 67 young non-patients participating as controls in a clinical trial. Data on the incidence of demand for treatment of TMD were collected during the 4-year follow-up period, and, by means of a mailed questionnaire, during an additional 2 years. The variables analysed included palpation and auscultation of the joints, palpation of the muscles of mastication, experience of joint sounds, of pain on jaw movements, of ear symptoms, awareness of a clenching habit, and frequency of headache. A present-absent dichotomy was applied throughout. Palpation tenderness of masticatory muscles was significantly (P=0.02) more often present at BL in those who subsequently requested treatment than in those who did not. The same was true of the combination of palpatory tenderness and clenching habit (P=0.007), whereas the clenching habit alone failed to show a significant difference (P=0.06). However, the predictive values remained too low to be clinically useful, with a possible exception of the negative predictive value of muscle tenderness. The findings indicate that the variables conventionally used to describe the functional status of the masticatory system are at best of modest value in the estimation of individual risk of TMD in healthy young subjects.

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The aim of the present study was to evaluate two different methods for the assessment of the positional stability of occlusion. The time taken from first contact on closure to full intercuspation was measured by the T-scan(R), and the length of the slide between centric relation (CR) and maximum intercuspation was clinically assessed in a sample of healthy adolescents and young adults undergoing a clinical trial which involved repeated occlusal adjustment. The T-scan(R) readings and the clinical assessments of the centric slide were obtained at baseline and at the third and fourth annual examination. There was an overall, but statistically not significant, decline in the contact time. The length of the centric slide did decrease significantly. However, there was no systematic correlation between the two variables. They appear to describe different qualities of occlusion, and their validity as a measure of 'goodness' of occlusion remains an unanswered question.

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The hypothesis that the response to conventional physical therapy of patients suffering from chronic cervicobrachial pain and/or headache can be improved by adjusting dental occlusion, was tested. Forty patients seeking treatment were interviewed and examined prior to treatment, and 6 weeks, 12 months and 60 months after treatment. All patients underwent routine physical therapies. They were pairwise matched for age, gender and type of dental occlusion, and randomly allocated to a true occlusal adjustment group or to a mock adjustment group. The patients and the examiners were unaware of the type of dental treatment given. The outcome variables included subjective pain and discomfort, cervical spine mobility and pain on movement, and comparison of relative EMG activities. The short-term response to therapy was good in both groups. In the long-term, however, the response was significantly better in the patients who had undergone occlusal adjustment than in the mock-adjusted controls.

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STATEMENT OF PROBLEM: Contrary to clinical opinion, the structural risk from dental occlusion in temporomandibular disorders has been questioned or considered to be insignificant in clinical practice. PURPOSE: This study tested the effect of elimination of occlusal interference through occlusal adjustment, on the incidence of temporomandibular disorders. MATERIAL AND METHODS: In a controlled clinical trial of 146 healthy children and adolescents, half of the subjects underwent occlusal adjustment aimed at elimination of the presumed structural risk, and the other half underwent mock adjustment. Adjustments were repeated every 6 months over a period of 4 years. The outcome variable was the incidence of temporomandibular disorders, operatively defined as request for treatment of symptoms characteristic of the disorders with presence of clinical signs demonstrated in the muscles of mastication and/or jaw joint. RESULTS: The cumulative incidence rate was 9/67 in the mock adjustment group and 1/60 in the real adjustment group, for a relative risk of 8.06. The difference between groups was statistically significant (p = 0.019). CONCLUSIONS: Elimination of the presumed structural risk from the dental occlusion appeared to significantly reduce the incidence of temporomandibular disorders in a select group of young subjects.

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The use of occlusal adjustment as a treatment for temporomandibular disorders has been questioned because of lack of evidence that occlusal factors play an etiologic role; lack of evidence that this irreversible treatment modality has sufficient efficacy, when reversible modalities are available; the self-limiting character of the disorders; and the possibility of adverse effects. However, controlled clinical trials have yielded results that are difficult to explain unless occlusal factors have a causal role in temporomandibular disorders. Controlled clinical trials also suggest an effect for occlusal adjustment on chronic headaches and on chronic neck and shoulder pain in comparison with conventional treatments. Moreover, no adverse effects of properly conducted occlusal adjustments have been reported. In view of the possibility that occlusal factors have a causal role in temporomandibular disorders, research efforts on the role of occlusion should be intensified, and teaching should be revised accordingly.

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The usage of odds ratios for estimating the significance of occlusion is based on the assumption that the aetiological factors are additive and interchangeable in several different composite causes. If the factor studied is a necessary causal factor, odds ratios cannot be used in risk estimation. The present study analysed odds ratios in a sample of children half of whom had undergone an annual prophylactic elimination of occlusal interferences. The sample consisted of 178 children followed up for 5 years from the baseline age of 5 or 10. The distribution of interferences was computed for children with tenderness of the masticatory muscles ('cases'), and for children without ('controls'). Although the increase in the number of children free from interferences was not remarkable, the overall result was statistically significant (P < 0.01). None of the children free from interferences showed muscular tenderness at any of the annual examinations. Therefore, odds ratios could not be calculated in our study sample. It is concluded that estimation by means of odds ratios of the significance of occlusal factors in CMD may be misleading.

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The rejection of the old hypothesis concerning the role of occlusal factors in craniomandibular disorders has been suggested because of the lack of evidence supporting the hypothesis. However, it would be more helpful to seek tests that clearly show that the hypothesis is wrong. Most of the studies used to favor rejection of this hypothesis have incorporated designs precluding any causal conclusions on the role of occlusal factors. Time and resources have been wasted in repeated efforts to obtain what is only associative proof; studies designed to address the causal question are few. There are, as yet, no results clearly warranting the rejection of the hypothesis that occlusal factors are part of a causal complex of craniomandibular disorders.

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The association between clinical signs of craniomandibular disorders (CMD) and occlusal interferences was studied longitudinally in two cohorts of children, 5 and 10 years of age at baseline, representing the nonpatient population. They were followed up for 5 years. The range of active participants was 96 to 106 in the younger group, and 64 to 74 in the older group. The subjects were seen annually for registration of signs of CMD and for the presence of interferences, and for a real or placebo occlusal adjustment. The double-blind study design was applied. Baseline data showed no association between the variables studied; parts of data from second and third examinations disclosed significant associations; and fourth, fifth and sixth examinations disclosed a consistent pattern of significant associations.

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The prevalence and distribution of signs and symptoms of craniomandibular disorders (CMD) were studied in a random sample of 100 adult Tanzanians. The associations between subjective and objective findings were analysed. Signs and symptoms of CMD were assessed by interview and clinical examination. Twenty-six per cent of subjects reported at least one symptom, and in 40% at least one clinical sign was present. No significant differences were observed between the sexes. Tenderness of the lateral pterygoid area and crepitation of the temporomandibular joint increased significantly with age. Several significant associations between subjective and objective findings were observed. The distribution of the signs and symptoms of CMD in Tanzanians was not dissimilar to that observed in the developed countries. The prevalence was not high by comparison, but sufficient to lend credence to the general view that CMD is a universal problem.

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It has been suggested that the high prevalence of clinical signs and subjective symptoms of craniomandibular disorders (CMD) reported in many epidemiological studies mainly lie within the range of normal variation and do not indicate of a real health problem. However, other studies have shown an association between CMD and other disorders such as headache and neck pain. There also appears to be a marked association between sick leave and CMD. Successful occlusal treatment of CMD alleviates or eliminates signs and symptoms not associated with the primary diagnosis of CMD. The argument that CMD do not represent a real health problem is therefore unfounded.

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Occlusal interferences and signs of craniomandibular disorder (CMD) were studied longitudinally in 167 Finnish adolescents at the ages of 12 and 15 years in order to evaluate their importance for orthodontic diagnosis. Of the adolescents sampled 16.8 per cent had received orthodontic treatment. The results showed that occlusal interferences and signs of CMD are quite common. Of the 12-year-olds 25.7 per cent and 30.5 per cent of the 15-year-olds showed palpatory tenderness of the muscles of mastication. Clicking sounds were recorded for 6 per cent of the 15-year-olds. Opening capacity increased with age. Only tow of the adolescents at the age of 12 and none at the age of 15 fulfilled the criteria of functionally optimal occlusion. The number of occlusal interferences increased between 12 and 15 years of age. Both occlusal interferences and clinical signs of CMD were inconsistent in nature. Mediotrusion contracts and protrusion interferences were found to be the most stable occlusal interferences at adolescence. As to pain on mouth opening, the symptom group at the age of 15 consisted of entirely new individuals. No single sign or CMD symptom, nor combination of them, was consistent enough for inclusion in orthodontic screening indices. However, even though the symptomatology changed, only a few of those considered to be symptomatic at the age of 12 were asymptomatic at the age of 15. In accordance with the present state of knowledge, it would thus seem appropriate to add a general statement about the presence or absence of CMD signs and/or symptoms to orthodontic screening indices.(ABSTRACT TRUNCATED AT 250 WORDS)

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A follow-up study was performed on 12 subjects with unilateral and five subjects with bilateral reciprocal clicking and symptoms of craniomandibular disorders. After treatment for, on average, three months with a repositioning appliance, followed by occlusal adjustment, patients were examined every six months initially and, after the first two years, once a year. During the follow-up period, occlusal stability was maintained by readjustment and use of full occlusal splints at night, when needed. After four years there was a 57% success rate with regard to treated joints. After six years, the success rate had decreased to 41%. However, even the eight unsuccessful cases, with persistent clicking and adjusted occlusion, managed well with regard to other clinical findings and subjective symptoms. It is concluded that repositioning splint therapy followed by occlusal adjustment seems appropriate for elimination of subjective symptoms and clinical signs even though repositioning may subsequently fail. Results seem to remain relatively unchanged for several years but some decline in the success rate may occur with time.

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Epidemiologic studies on TMJ dysfunction etiology often suffer from methodological shortcomings. The problems may partially arise from the fact that the study subject cannot be separated from the "real world" for analyses in the same sense as in classical experimental research. A thorough discussion on the scientific principles in TMJ research is suggested.

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Subjective symptoms of craniomandibular disorder (CMD) were studied longitudinally in 167 children at the ages of 12 and 15 in order to investigate their importance for orthodontic diagnosis. The results showed that symptoms are quite common in adolescents (64-67 per cent). However, most of the adolescents experienced their symptoms only occasionally. Frequent occurrence of various, single symptoms of CMD varied from 0 to 7.2 per cent. Recurrent headache was reported by 24 per cent of the adolescents at the age of 12, and by 22 per cent of them at the age of 15. The number of reported symptoms did not increase between the ages of 12 and 15 years, which is in agreement with other studies. The symptoms of CMD did not appear to be consistent. Locking of the joint was found to be the most stable symptom. About 50 per cent of those reporting TMJ-clicking, unexplainable ear symptoms or bruxism at the age of 12, had lost this symptom by the age of 15. For pain on mouth-opening, the symptom group at the age of 15 consisted of entirely new individuals. Because of their inconsistent nature during the final stages of occlusal development, too much attention should not be paid to single occurrences of CMD symptoms. In individual cases, however, important information for diagnosis and treatment planning can be obtained. Symptoms of craniomandibular disorder, recurrent headache, and oral parafunctions should be elicited and recorded at annual dental check-ups of children and adolescents.

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No theoretical model explaining craniomandibular disorders has been generally accepted, despite the large number of studies on its etiology. This article suggests that one reason for the lack of a well-structured causal explanation could be associated with the study design most often used: cross-sectional studies of samples representative of a base population. Variation in the number of interferences was increased among the subjects by eliminating occlusal interferences annually in the treatment group (n = 53). The control group (n = 46) underwent placebo treatment. A double-blind design was used throughout the 3-year study. A cross-sectional analysis in the third year disclosed a significant association between the number of interferences and the signs of craniomandibular disorders. The results suggest that the absence of interference-free subjects in nonselected samples can be one explanation for the lack of association reported in most studies.

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According to several studies on human populations, the mandible deviates on opening significantly more often to the left than to the right. An association between the asymmetry of opening and handedness has been suggested. The present study of 143 left-handed Finnish conscripts showed no significant difference from the asymmetry reported for populations unselected for handedness. It was concluded that the opening asymmetry and handedness are not associated. The asymmetry proved also to be unassociated with the side of first unilateral tooth contact on guided hinge closure, with the side of palpatory tenderness of the muscles of mastication, and with the side of temporomandibular joint sounds.

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Sixty-two dental students judged not to be in need of treatment for craniomandibular disorder (CMD) were randomly divided into two groups, one receiving occlusal adjustment and the other mock adjustment. A double-blind study design was applied. After 2 years of education in dentistry, including courses in stomatognathic physiology, the increase in the subjective symptoms of CMD was significantly greater in the placebo control group than in the treatment group. The difference between the groups in the increase of sites tender to palpation was less clear, showing only a trend. However, the increase was statistically significant within the placebo group but not within the treatment group. Prophylactic occlusal adjustment thus appears to be effective in reducing the occurrence of symptoms of CMD, and possibly also the occurrence of clinical signs.

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Clinical signs of craniomandibular disorder, the mobility of the cervical spine, and neck-shoulder muscle tenderness were assessed or measured in a nonpatient sample of 57 and a patient sample of 76 subjects. Examinations performed after a 1-year interval showed that the frequency of signs of craniomandibular disorder had remained virtually unchanged. The functional state of the stomatognathic system was significantly associated with both mobility of the cervical spine and neck-shoulder muscle tenderness.

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