How to label bruxism that is a sign of a disorder? That's the question! Response to letter by Meira e Cruz & Ettlin (2018)

Dear Editor, First of all, we would like to thank Dr. Meira e Cruz and Dr. Ettlin for their Letter to the Editor of the Journal of Oral Rehabilitation,1 in which they advocate a more comprehensive classification system that includes not only primary bruxism but also secondary bruxism. Their proposal is a reaction on the recent international consensus paper by Lobbezoo et al,2 in which separate definitions for sleep and awake bruxism are described, along with an update of the grading system that Lobbezoo et al3 proposed in 2013 to determine the likelihood that a certain assessment of bruxism actually yields a valid outcome. Further, Lobbezoo et al2 proposed a classification for bruxism based on its possible clinical consequences (viz., harmless behaviour, risk factor or protective factor). Clearly, Meira e Cruz & Ettlin appreciated this classification, because they label its underlying principle (i.e, that bruxism is no longer considered as a disorder or disease) as “most important(ly).” So far, everyone is aligned nicely. However, we do not understand the paragraphs that follow in Meira e Cruz’ & Ettlin’s Letter.1 Contrary to what Meira e Cruz & Ettlin imply, we are very much aware of the fact that bruxism can also be attributable to identifiable aetiologies, as evidenced by many of our own review articles and research papers.4-11 Specifically for that reason, both newly proposed definitions for sleep and awake bruxism end with the phrase “in otherwise healthy individuals,”2 indicating that bruxism can indeed be a sign of a disorder in some individuals. This phrase refers to the term “secondary bruxism” that is advocated by Meira e Cruz & Ettlin. Lobbezoo et al2 state that “from a nosological point of view, the adoption of different names for bruxism being or not being a sign of a disorder may be considered.” As per Meira e Cruz’ & Ettlin’s suggestion, labelling bruxism as primary or secondary could be one of the options. However, it should be pointed out that in the near future, knowledge on the physiopathology of both sleep bruxism and awake bruxism is expected to increase, thereby yielding a reduction of bruxism activity of unknown aetiology and thus rendering the debate on primary bruxism vs secondary bruxism increasingly sterile. Nevertheless, we are open for other suggestions, both for alternative names and for alternative classifications. As the title of the 2018 international consensus paper clearly states: the work is still under construction!