This study focuses on the association between psychological factors and TMJ sounds, and the most suitable research design to establish this relation. A traditional research design is simulated to demonstrate how self-report may bias findings. A refined design is presented to obtain unbiased estimates of the role of psychological variables. In the 'naïve' design the importance of psychological variables was overestimated and the role of physiological variables was underestimated. It was concluded that future studies in the aetiology of TMJ clicking should abandon the use of self-report as a proxy for objective findings. With the refined design it was found that psychological factors play only a minor role in the prevalence of TMJ sounds. Findings do not support speculation about mechanisms that relate psychological factors to the presence of TMJ sounds.
Measurement errors in recording temporomandibular joint sounds may originate from variation between observers and from variation in the phenomenon. Laboratory settings enable various procedures to be used to minimize both sources of variation. These procedures yield some excellent intra- and inter-examiner reliabilities, but this does not imply that dentists in a clinical setting are likely to evaluate temporomandibular joint sounds in a comparable way. This study was designed to evaluate clinical joint sound assessment methods (palpation and stethoscopy) without using special precautions to minimize variance. An attempt was made to quantify the signal variance. Within- and between-examiners agreement is estimated for both methods in a sample of 44 non-patients. The results show that two clinically experienced craniomandibular disorders specialists were able to reach fair to good agreement on the identification of (the number of) temporomandibular joint sounds. There was some disagreement with respect to the number of reciprocal clicks. Compared with the palpation technique, stethoscopy is more sensitive, especially with regard to crepitation. Based on the electronically recorded sounds, both examiners appeared to be overconsistent. It is concluded that the use of both palpation and stethoscopy in clinical settings can be justified but that both methods have limitations. When, in a given clinical setting, these limitations are acceptable, there appears to be no need for extra-sensitive but expensive electronic recording devices.
Various spatial and morphological aspects of the temporomandibular joint may be involved in the development of TMJ sounds. The present study examines their contribution to the prediction of sounds. A non-patient sample was studied using sensitive sound measurement and panoramic radiography. It was found that temporomandibular joint sounds are common in asymptomatic subjects showing substantial variation in several spatial and morphological parameters. An autonomous contribution of spatial relationships, asymmetries or morphology of bony structures to the prediction of joint sounds could not be detected. When unilateral sounds were present, they were more likely to be found on the side with the less steep condylar movement path. Joint imaging is not indicated in the detection of relationships between bony structures and their eventual asymmetries and joint sounds.
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