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  • Updated 04.14.2024
  • Released 07.20.1994
  • Expires For CME 04.14.2027

Sleep-related bruxism



Bruxism is classically defined as an oral-jaw-muscle activity that can occur during wakefulness or sleep, and both forms may occur in the same individual. Bruxism tends to be variable in occurrence and magnitude over time. It is characterized during wakefulness by jaw clenching or bracing, with and without tooth contact, respectively. Bracing is an oral behavior that may or may not be included in the definition of bruxism in the literature. During sleep, it is characterized by tooth grinding, with or without sound, and jaw clenching. Bruxism is not a disorder for most individuals. For diagnosis coding purposes, the International Classification of Sleep Disorders included it in the section of sleep-related movement disorder as sleep-related bruxism. A 2018 dental sleep medicine consensus further defined it as an oral behavior. In an update, a re-emphasis was made that in the presence of other conditions or disorders, sleep-related bruxism is a “co-occurrence” instead of a comorbidity. Sleep-related bruxism is most likely an additional physiological activity that may be associated with, or may be a sign of, an underlying condition or disorder. There is no evidence that sleep-related bruxism is associated with a risk of mortality. Indeed, in most individuals, the most obvious consequences are tooth wear, grinding sounds, restoration damage, temporomandibular disorders, headaches, and orofacial pain.

It is clear in the era of personalized medicine that sleep-related bruxism is not caused by only one risk factor and cannot be explained by a single mechanism. The role of anxiety and stress are debated and may be dominant as a trigger in certain individuals. The use of antidepressive medication can be an additive risk factor. A series of physiological studies support a dominant role of sleep arousal in autonomic cardiorespiratory and brain sequences as a brief and transient facilitatory window to explain the onset of oral activity. Some evidence suggests serotonin, dopamine, or myosin as gene candidates.

The diagnosis of “possible” sleep-related bruxism is first based on reports of frequent tooth grinding by the patient and sleep partner or by the patient’s awareness of jaw clenching during sleep. A clinical examination helps to assess the level of dental damage and pain, supporting the concept of a “probable” condition. Sleep laboratory or home polysomnography can be indicated if the following co-occurring disorders are suspected: obstructive sleep apnea, comorbid obstructive sleep apnea and insomnia, or movement disorder (periodic limb movement during sleep, REM-sleep behavior disorder, or sleep-related epilepsy). Commercially portable devices can also help with diagnosis and monitoring. Devices collecting single EMG or tooth-contact data are clinically available tools. Treatment is protective, palliative, and multidisciplinary based, including oral appliances, biofeedback, behavioral therapies, and medications. The level of evidence is modest, and selection must be tailored based on consequences, health risk, and patient preference.

Key points

• Sleep-related bruxism is an oral behavior most likely centrally regulated and frequently associated with sleep arousal.

• The diagnosis is clinical, based on tooth-grinding reports, tooth wear or damage, pain, and grinding noise reported by bed partners.

• One of the biological markers of jaw muscle activity related to sleep-related bruxism is the rhythmic masticatory muscle activity (RMMA). It is collected by surface activity of masseter or temporalis muscles via EMG.

• Clinically, polysomnography with masseter or temporalis EMG (frequency and duration of RMMA) is not needed for most cases except when co-occurring sleep disorders are suspected (eg, obstructive sleep apnea, periodic leg movements, REM-sleep behavior disorder, or sleep-related epilepsy). It may also be done to assess the efficacy of treatment.

• Treatment involves oral appliances, biofeedback, behavioral therapies, and medications. No definitive cure is expected, and multidisciplinary approaches are recommended.

Historical note and terminology

The first mention of teeth grinding occurs in the Bible, where the term “gnashing of teeth” is an expression of suffering (Luke 13:28, Matthew 13:41-2, Matthew 8:12, Matthew 13:50, Matthew 22:13, and Matthew 24:51). One of the first-recorded notations of this phenomenon was from Black, who commented that teeth abrasion tends to remove the cusps quite rapidly (16). French neurologist pioneers Marie and Pietkiewicz introduced the word bruxomania in 1907 (98). In 1938, Miller re-introduced the term bruxism for bruxomania or repetitive teeth grinding in a seminal book (104). In 1941, Bodecker described a patient whose bruxism had destroyed the clinical crowns of all the lower anterior teeth (17). In the 1940s to mid-1960s, many clinicians proposed a link between bruxism (either the wake or asleep form) and periodontal disease, headaches, and occlusion (132).

In 2013 and 2018, a group of international experts compiled a work-in-progress consensus to better define bruxism (82; 83). It was proposed that bruxism is a behavior in otherwise healthy individuals characterized by the presence of repetitive jaw muscle activities, such as clenching or grinding of the teeth or bracing or thrusting of the mandible. Bracing means forcefully maintaining a mandibular position, whereas thrusting means moving the jaw forward or laterally. These two last activities were considered oral behaviors and do not necessarily require tooth contact. Note that including these last two oral behaviors in sleep-related bruxism is not universally accepted; indeed, it is debated if the term bruxism should be limited to an oral activity limited to tooth contact.

Bruxism can occur during sleep (sleep-related bruxism) or during wakefulness (awake bruxism). Moreover, a clinically empirical diagnostic system suggested grading bruxism as “possible,” “probable,” or “definite.” Possible sleep or awake bruxism is based on a positive self-report. Probable sleep or awake bruxism is based on a positive clinical inspection, with or without a positive self-report. Definite is for sleep or awake bruxism based on a positive instrumental assessment, with or without a positive self-report or a positive clinical inspection (83). The last is more confirmatory than definitive and is challenged by the fact that sleep and wake bruxism do not occur regularly; indeed, its occurrence and magnitude can vary from night to night (77; 117; 118). The validity of any instrumental toll, questionnaire or examination system, or device used for diagnostic or treatment follow-up must consider such variability. Sleep and awake bruxism appear to be distinct behaviors with different underlying causes and require different management approaches (82; 83). Both consensuses remain “work-in-progress.” In November 2023, the same group published an update in the form of an editorial to more precisely define some key elements in the definition of bruxism. The main highlight is the “co-occurrence” of sleep-related bruxism with other conditions rather than labeling it as a comorbidity.

Table 1. Sleep-Related Bruxism Current Concepts

Jaw-muscle activities:

• With tooth contact: tooth clenching, tooth grinding (high evidence)

• With no teeth contact: bracing or thrusting of the mandible (both more present for awake bruxism) (low evidence)

Sleep-related bruxism can be:

• Physiological

• A sign of an associated or co-occurring underlying condition or disorder (eg, anxiety, stress, medication use, obstructive sleep apnea, gastroesophageal reflux disease, anxiety)

• May be protective when associated with sleep-related breathing condition or disturbance

• May have negative clinical consequences (eg, tooth damage, grinding sounds, pain)

Adapted from (92)

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