Journal of Craniomandibular Function, 02/2012

The opinion that occlusal factors do not have a significant role in the etiology of temporomandibular disorders (TMD) is common among researchers. However, most epidemiological and experimental studies drawing conclusions on the causal role of occlusion in TMD suffer from methodological problems. The comparisons have not been informative because the compared groups have not differed sufficiently with regard to suspected occlusal risk factors. In particular, subjects unexposed to the risk factors are underrepresented or missing altogether. Studies applying design and methods recommended by experts of epidemiology have been unable to exclude occlusal factors from the etiology of TMD. The currently dominating opinion does not appear to be based on evidence. Keywords: etiological epidemiology, evidence-based dentistry, inclusion criteria, occlusion, representation

Objective: A key factor for successful prosthetic rehabilitation is the reconstruction and/or stabilization of a physiological jaw relation. The bite registration technique of choice should here exhibit a high degree of reproducibility. The objective of this study was to determine how precisely the initially recorded jaw relation can be transferred to a prosthetic reconstruction, and how these two positions influence the bilateral activity of the masticatory muscles. Materials and methods: In 41 healthy subjects, 41 examiners incorporated simulated prosthetic restorations (SPRs) that were fabricated according to the procedures commonly used during prosthetic reconstructions. With the aid of the Zebris (WinJaw, Zebris Medical, Isny, Germany) jaw measurement analysis (JMA) system, the positions of the mandible were compared in intercuspation, with an incorporated centric bite record and an incorporated SPR at designated measuring locations of both condyles, the first molars on each side and at the incisal point. At the same time, the electromyographical activities of the masseter muscles and anterior temporal muscles were examined bilaterally under controlled isometric conditions. Results: The positions of the mandible with the centric bite record and the SPR differed significantly (P 0.05). A difference of approximately 0.3 mm in the absolute shift of the spatial position was determined at all five measuring points between both positions; this essentially corresponded to a caudal shift of the mandible. The electromyographical (EMG) activities in these positions showed significant differences (P 0.05) for the temporal muscles. Conclusions: In summary, the findings reveal that a centric jaw relation recorded using this technique can be transferred to a prosthetic reconstruction with the differences described in this article. Keywords: accuracy of the recording of the centric jaw relation, centric bite record, centric jaw relation, electromyography, prosthetic reconstruction

The following article describes the interdisciplinary collaboration of a dentist with a sleep medicine specialist, by presenting the case of a patient with orofacial pain and sleep disorders. Patients with myofacial pain of the masticatory musculature or arthralgia are particularly prone to suffering from insomnia or from another form of sleep disorder, such as sleep bruxism or sleep-related respiratory disturbances. The identification and reduction of these perpetuating risk factors can be beneficial, with regard to the treatment of painful craniomandibular dysfunctions in the dental practice. Keywords: arthralgia, insomnia, orofacial pain, sleep bruxism, sleep-related breathing disorders, snoring, sleep medicine, temporomandibular disorders