The quest to link bruxism and TMD pain: Tilting at windmills?

Temporomandibular disorder (TMD) pain is the most prevalent non-dental pain condition in the orofacial area. TMD pain most often originates from the masticatory muscles and aggravates during function. Over the years, several etiological models were proposed to explain the pathophysiology of myogenous TMD pain. In the everyday dental practice, myogenous TMD pain is often suggested to be the consequence of muscle overload (e.g., due to oral behaviors like sleep bruxism), sometimes in combination with psychological dysfunctions (e.g., psychological stress). These beliefs are mainly based on cross-sectional studies which used self-report to establish the diagnosis of TMD pain and oral behaviours like sleep bruxism.
The central theme of this thesis is the relation between SB and myogenous TMD pain. In several chapters, the complex interaction between SB and TMD pain is investigated using different diagnostic approaches, including polysomnographic sleep registration (PSG), which is the current “gold standard” diagnostic approach for SB. Since both SB and TMD pain can be modulated by the presence of psychological distress, psychological factors are also taken into consideration.
The findings from this thesis suggest that myogenous TMD pain is too complex to be explained by simple linear models that solely rely on SB and/or psychological distress as etiological factors. Other factors, such as genetics, general health, and demographic elements, quite possibly contribute to the presence of chronic jaw-muscle pain and should be incorporated in prediction models to better understand the association between TMD pain and SB.