International consensus on the assessment of bruxism (2018): sleep and awake bruxism defined apart, graded possible, probable or definite, and called a behavior rather than a disorder

What it says#

In 2013 a written consensus among an international group of bruxism experts, published as a three-page article in the Journal of Oral Rehabilitation, defined bruxism as a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible, gave it two distinct circadian manifestations, sleep bruxism and awake bruxism, and proposed a diagnostic grading system of possible, probable and definite. The definition was adopted quickly. The 2018 report notes it was cited at almost 40 times a year and taken into the third edition of the International Classification of Sleep Disorders and the American Academy of Orofacial Pain's guidelines. The grading system was not adopted quietly: it set off an exchange in the same journal about whether bruxism is a disorder, a behavior or a risk factor, and about whether a behavior can be graded diagnostically at all.

In March 2017 a full-day meeting called Assessment of Bruxism Status was held in San Francisco before the 95th General Session of the International Association for Dental Research, organized on behalf of the RDC/TMD Consortium Network, since renamed the International Network for Orofacial Pain and Related Disorders Methodology. Its four aims were to clarify the 2013 definition and write separate definitions for the two phenotypes, to settle whether bruxism is a disorder or a behavior, to re-examine the grading system, and to set a research agenda. The resulting paper is titled, deliberately, Report of a work in progress.

The single definition was retired in favor of two. Sleep bruxism is defined as a masticatory muscle activity during sleep that is characterised as rhythmic (phasic) or non-rhythmic (tonic) and is not a movement disorder or a sleep disorder in otherwise healthy individuals. Awake bruxism is defined as a masticatory muscle activity during wakefulness that is characterised by repetitive or sustained tooth contact and/or by bracing or thrusting of the mandible and is not a movement disorder in otherwise healthy individuals. Both begin with masticatory muscle activity, which the panel says is meant to put the muscles, not the teeth, at the center of the definition. Bracing and thrusting, the two terms clinicians had questioned, are explained from Dorland's: bracing as forcefully maintaining a certain mandibular position, thrusting as forcefully moving the mandible forward or laterally, both without the necessary presence of tooth contact.

On status, the panel sided with the argument that a behavior is not a diagnosis. A disorder, it says, is a condition that is a harmful dysfunction in itself; a risk factor is an attribute that raises the probability of a disorder without guaranteeing it. Bruxism, in an otherwise healthy person, falls in the second group or in neither, and the paper lists three possibilities in terms of clinical consequences: not a risk or protective factor, meaning a harmless behavior; a risk factor, associated with one or more negative health outcomes; or a protective factor, associated with one or more positive ones. The protective possibility is raised carefully, with the note that supporting evidence is still inconclusive: sleep bruxism has been proposed as the ending episode of respiratory arousals that restores upper airway patency, and as a way of increasing salivation in gastro-esophageal reflux. The two are not mutually exclusive, and the paper gives the example of a sleep apnea patient with severe tooth wear from protective sleep bruxism.

The grading system was rebuilt around one criticism: the 2013 ladder was stackable, so definite required self-report and clinical inspection and an instrumental measure together, which assumed the first two were fully sensitive. They are not. Bruxism can be found instrumentally while self-report and clinical inspection are both negative. The proposal is therefore that possible sleep or awake bruxism rests on a positive self-report only, probable on a positive clinical inspection with or without a positive self-report, and definite on a positive instrumental assessment with or without either of the others. The panel stresses that this is only a proposal and that its reliability, validity and responsiveness to change still need study.

Two practical points close the paper. Standard cut-off points for calling bruxism present or absent should not be used in otherwise healthy individuals; the panel wants the muscle activity assessed along its continuum, noting evidence that it is the general level of electromyographic activity, higher in temporomandibular disorder cases than in controls, rather than the raw count of bruxism events, that carries the risk. And any future assessment method is asked to meet what the panel calls the A4 principle: accurate, applicable, affordable and accessible.

Who it applies to#

Every patient a general dentist suspects of grinding or clenching, at any age, and both phenotypes. The consensus is a definition and assessment framework offered for clinical and research use across dental and medical fields, not a rule with a jurisdiction. What it reaches in a private practice is the language in the chart, the questions on the health history, and the confidence a clinician is entitled to claim.

It does not reach patients who are not otherwise healthy, and the panel put that phrase in both definitions on purpose. In some people bruxism is a sign of a disorder rather than a behavior, and the examples given are REM behaviour disorder, obstructive sleep apnoea and epilepsy, where the paper says the condition requires full attention by the responsible clinician. This directory's entry on the ADA policy on sleep-related breathing disorders and the entry on the AASM and AADSM oral appliance therapy guideline cover the sleep apnea side of that referral.

It also does not reach treatment. Nothing in the consensus says what to do about a positive finding, and nothing in it endorses or discourages an appliance. A clinician who tells a patient that a night guard treats a disorder is going past what this document supports.

What changed#

Against 2013, four things. One definition became two, and each one names the muscle activity rather than the tooth contact. The word disorder came out for otherwise healthy people and behavior went in, which also removed the justification for the word diagnostic in front of grading. The ladder stopped stacking, so a single positive source now sets the grade. And cut-off points, the numbers that let a sleep laboratory call a night positive or negative, were set aside for clinical use in healthy people in favor of assessing the activity in its continuum.

Against common practice in a general office, the harder change is the third one. Worn teeth, a linea alba, scalloped tongue borders and hypertrophic masseters are clinical inspection findings, so they support probable bruxism, not definite. The paper is explicit that muscle hypertrophy, tongue or lip indentations and linea alba can also follow ordinary oromotor activity such as swallowing, and that attrition, while it may indicate sleep bruxism in particular, does not rule out past bruxism with no current activity. Definite requires a measurement.

What has happened since is the Standardised Tool for the Assessment of Bruxism, published in the January 2024 issue of the same journal with its road map. The STAB is a two-axis instrument, 14 domains and 66 items, covering self-reported, clinically observed and instrumentally measured bruxism status and consequences on Axis A and risk, etiological and comorbid factors on Axis B. Its authors describe it as ready for on-field testing and further refinement, which is to say the work in progress is still in progress.

Where the source is#

The document under the title is the 2018 report itself, free in full text in PubMed Central as PMC6287494 under a Creative Commons Attribution NonCommercial NoDerivs license; the journal version is J Oral Rehabil 2018;45(11):837-844, behind Wiley's paywall at the publisher. The 2013 consensus that it updates is a short article in J Oral Rehabil 2013;40(1):2-4, and only its abstract is free on PubMed. The 2016 commentary by Raphael, Santiago and Lobbezoo that opened the disorder question is free in PubMed Central as PMC5538376. The Standardised Tool for the Assessment of Bruxism and its road map are in the January 2024 issue of the same journal; the STAB itself was published open access and can be reached through the Europe PMC record linked above.