The bruxism construct: From cut-off points to a continuum spectrum

This commentary discusses the need to move on from the adoption of cut-off points for the definition of the presence/absence of bruxism and justifies the need to embrace an evaluation based on the continuum of jaw motor behaviours. Currently, the number of events per hour, as identified by polysomnography (PSG), is used to define the presence of sleep bruxism (SB). Whilst PSG still remains the indispensable equipment to study the neurophysiological correlates of SB, the scoring criteria based on a cut-off point are of questionable clinical usefulness for the study of oral health outcomes. For awake bruxism (AB), criteria for a definite diagnosis have never been proposed. Some goal-oriented strategies are proposed to identify bruxism behaviours that increase the risk of negative oral health outcomes (eg, tooth wear, muscle and/or temporomandibular joint [TMJ] pain, restorative complications). One possible strategy would embrace an improved knowledge on the epidemiology and natural variability of bruxism, even including study of the amount of PSG/SB and electromyography masticatory muscle activity (EMG/MMA) during sleep and the frequency/prevalence of bruxism behaviours during wakefulness that are needed to represent a risk factor for clinical consequences, if any. There should not be any preclusion about the diagnostic strategies to pursue that goal, and a combination of instrumental and non-instrumental approaches may even emerge as the best available option. Once data are available, large-scale, non-selected population samples representing the entire continuum of EMG/MMA activities are also needed, in the attempt to estimate untreated health risks in the population.