Static and dynamic occlusal characteristics in different diagnoses of TMD

Aims: To study the occlusal characteristics of subjects with temporomandibular disorders (TMD) according to Axis I of the Research Diagnostic Criteria for TMD (RDC/TMD). Methods: One hundred and seventeen dentate adults participated in this cross-sectional population-based study. All subjects were examined and answered a questionnaire about RDC/TMD. Overjet, overbite, Angle's classification and crossbite were established for each subject. Occlusal contact area and number of teeth in contact were determined at maximal intercuspal position (ICP) and at right and left lateral excursions of 1.5 mm by scanning interocclusal records and analyzing them using image software. The type of dynamic occlusion was determined for both the working and the non-working side in any lateral position. Differences between TMD and non TMD subjects, and also between subjects with different TMD diagnoses, were assessed by variance analysis or the Mann-Whitney U-test. Results: Fifty-six subjects were diagnosed with TMD. Fourteen presented myofascial pain, 44 disc displacement with reduction, and 7 arthralgia (hence, eight of them had a multiple diagnosis). Subjects diagnosed with arthralgia had a significantly lower overjet than controls. The number of posterior teeth in crossbite in subjects with disc displacement was significantly higher than the corresponding number in controls. Furthermore, there was a significant relationship between the presence of posterior crossbite on the right side and disc displacement in the left TMJ and vice versa. Subjects without TMD had a significantly larger occlusal contact area at ICP than subjects with TMD, with the disc displacement group presenting the lowest values. The type of dynamic occlusion was not associated with TMD on either the working or the non-working side. Conclusion: Despite the limitations of the study, a higher number of posterior teeth in crossbite and a lower occlusal contact area at ICP were correlated with diagnoses of TMJ disc displacement.