Current concepts on bruxism (part 1)

- Understanding bruxism…which is not just grinding the teeth
- Comprehending the assessment strategies
- Changing old paradigms focused on dental occlusion - neither bruxism nor Temporomandibular disorders must be treated by occlusal corrections
- Evaluating the clinical impact of different bruxism activities, from tooth wear to Temporomandibular Disorders
- Managing bruxism, bearing in mind that bruxism is a masticatory muscles activity that is a sign of some underlying conditions

In 2013, consensus was obtained on a definition of bruxism as repetitive masticatory muscle activity characterized by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible, and specified as either sleep bruxism or awake bruxism. In addition, a grading system was proposed to determine the likelihood that a certain assessment of bruxism actually yields a valid outcome. Recently, a need for an update and upgrade of such consensus emerged, with specific focus on the following aims: 1. to further clarify the 2013 definition and to develop separate definitions for sleep and awake bruxism; 2. to determine whether bruxism is a disorder rather than a behavior that can be a risk factor for certain clinical conditions; 3. to reexamine the 2013 grading system; and 4. to develop a research agenda. 

Based on that, a panel of experts prepared a new consensus document, specifying that: 1. sleep and awake bruxism are masticatory muscle activities that occur during sleep (characterized as rhythmic or non-rhythmic) and wakefulness (characterized by repetitive or sustained tooth contact and/or by bracing or thrusting of the mandible), respectively; 2. in otherwise healthy individuals, bruxism should not be considered as a disorder, but rather as a behavior that can be a risk (and/or protective) factor for certain clinical consequences; 3. both non-instrumental approaches (notably self-report) and instrumental approaches (notably electromyography) can be employed to assess bruxism; and 4. standard cut-off points for establishing the presence or absence of bruxism should not be used in otherwise healthy individuals; rather, bruxism-related masticatory muscle activities should be assessed in the behavior’s continuum. 

Approaches for assessing bruxism can be distinguished as non-instrumental or instrumental. Noninstrumental approaches for assessing bruxism include self-report (questionnaires, oral history) and clinical inspection, both for sleep and awake bruxism. Instrumental approaches for assessment are currently available for both forms of bruxism. Measurement of jaw muscle activity via polysomnography (PSG) or electromyography (EMG) is the standard of reference for sleep bruxism. Ecological momentary assessment (experience sampling methodology [EMA/ESM]) app-based assessments for real time subjective information about masticatory muscle activities at certain time points during the awake phase can also provide evidence of awake bruxism. 

For various reasons, it must be remarked that using standard cut-off points for everyone for the ‘gold-standard’ assessment of sleep bruxism or non-sleep bruxism should not be considered optimal for clinical use in otherwise healthy individuals. This issue is best exemplified by the still inconclusive literature on the polysomnographic assessment of sleep bruxism and its clinical consequences. Indeed, bruxism has always been considered a detrimental factor for the stomatognathic structures. This lecture will provide a brief overview on its role as a risk factor for the following clinical consequences: 1. Tooth wear; 2. Biological (i.e., implant failure, implant mobility, and marginal bone loss) or mechanical (i.e., complications or failures of either prefabricated components or laboratory-fabricated suprastructures) complications on dental implant-supported rehabilitations; 3. Temporomandibular disorders (TMD). In particular, the proposed mechanism for the bruxism-TMD relationship within a biopsychosocial framework at the individual level is that stress sensitivity and anxious personality traits may be responsible for those bruxism activities that may lead to TMD pain, which, in turn, is modulated by psychosocial factors (e.g., depression, anxiety, treatment-seeking behavior). 

As for bruxism management, based on available knowledge drawn from a recent systematic literature review by Manfredini and colleagues (J Oral Rehabil 2015), it can be suggested that: 1. almost every type of oral appliance (OA) (seven papers) is somehow effective to reduce SB activity, with a potentially higher decrease for devices providing large extent of mandibular advancement; 2. all tested pharmacological approaches (i.e., botulinum toxin [two papers], clonazepam [one paper], and clonidine [one paper]) may reduce SB with respect to placebo; 3. the potential benefit of biofeedback (BF) and cognitive behavioral (CB) approaches to SB management is not fully supported (two papers); and 4. the only investigation providing an electrical stimulus to the masseter muscle supports its effectiveness to reduce SB. It can be concluded that there is not enough evidence to define a standard of reference approach for SB treatment, except for the use of OA. Future studies on the indications for SB treatment are recommended. Until that, a so-called “Multiple-P” approach including Pep Talk (i.e., counseling), Plates (i.e., oral appliances), Psychology, Physiotherapy, and Pharmacology, is the best available, good-sense, option to manage bruxism and its consequences in the clinical setting.