Bruxism is excessive teeth grinding or jaw clenching.
It is an oral parafunctional activity;There are two main types of bruxism: one occurs during sleep (nocturnal bruxism) and one during wakefulness (awake bruxism). Dental damage may be similar in both types, but the symptoms of sleep bruxism tend to be worse on waking and improve during the course of the day, and the symptoms of awake bruxism may not be present at all on waking, and then worsen over the day.
The causes of bruxism are not completely understood, but probably involve multiple factors. Awake bruxism is more common in women, whereas men and women are affected in equal proportions by sleep bruxism. Awake bruxism is thought to have different causes from sleep bruxism. Several treatments are in use, although there is little evidence of robust efficacy for any particular treatment.
The ICSD-R states that 85–90% of the general population grind their teeth to a degree at some point during their life, although only 5% will develop a clinical condition. Some studies have reported that awake bruxism affects females more commonly than males, while in sleep bruxism, males and females are affected equally.
Children are reported to brux as commonly as adults. It is possible for sleep bruxism to occur as early as the first year of life, after the first teeth (deciduous incisors) erupt into the mouth, and the overall prevalence in children is about 14–20%. The ICSD-R states that sleep bruxism may occur in over 50% of normal infants. Often sleep bruxism develops during adolescence, and the prevalence in 18- to 29-year-olds is about 13%. The overall prevalence in adults is reported to be 8%, and people over the age of 60 are less likely to be affected, with the prevalence dropping to about 3% in this group.
According to a meta-analysis conducted in 2024, the global prevalence of bruxism (both sleep and awake) is 22.22%. The global prevalence of sleep bruxism is 21%, while the prevalence of awake bruxism is 23%. The occurrence of sleep bruxism, based on polysomnography, was estimated at 43%. The highest prevalence of sleep bruxism was observed in North America at 31%, followed by South America at 23%, Europe at 21%, and Asia at 19%. The prevalence of awake bruxism was highest in South America at 30%, followed by Asia at 25% and Europe at 18%. The review also concluded that overall, bruxism affects males and females equally, and affects elderly people less commonly.
The relationship of bruxism with temporomandibular joint dysfunction (TMD, or temporomandibular pain dysfunction syndrome) is debated. Many suggest that sleep bruxism can be a causative or contributory factor to pain symptoms in TMD.
Indeed, the symptoms of TMD overlap with those of bruxism. Others suggest that there is no strong association between TMD and bruxism. A systematic review investigating the possible relationship concluded that when self-reported bruxism is used to diagnose bruxism, there is a positive association with TMD pain, and when stricter diagnostic criteria for bruxism are used, the association with TMD symptoms is much lower. In severe, chronic cases, bruxism can lead to myofascial pain and arthritis of the temporomandibular joints.
Abfraction is another type of tooth wear that is postulated to occur with bruxism, although some still argue whether this type of tooth wear is a reality. Abfraction cavities are said to occur usually on the facial aspect of teeth, in the cervical region as V-shaped defects caused by flexing of the tooth under occlusal forces. It is argued that similar lesions can be caused by long-term forceful toothbrushing. However, the fact that the cavities are V-shaped does not suggest that the damage is caused by toothbrush abrasion, and that some abfraction cavities occur below the level of the gumline, i.e., in an area shielded from toothbrush abrasion, supports the validity of this mechanism of tooth wear. In addition to attrition, Acid erosion is said to synergistically contribute to tooth wear in some bruxists, according to some sources.
Ankyloglossia is suspected as a cause of bruxism.
Some bruxism activity is rhythmic with bite force pulses of tenths of a second (like chewing), and some have longer bite force pulses of 1 to 30 seconds (clenching). Some individuals clench without significant lateral movements. Bruxism can also be regarded as a disorder of repetitive, unconscious contraction of muscles. This typically involves the masseter muscle and the anterior portion of the temporalis (the large outer muscles that clench), and the lateral pterygoids, relatively small bilateral muscles that act together to perform sideways grinding.
Awake bruxism is thought to be usually semivoluntary, and often associated with stress caused by family responsibilities or work pressures. Some suggest that in children, bruxism may occasionally represent a response to earache or teething. Awake bruxism usually involves clenching (sometimes the term "awake clenching" is used instead of awake bruxism), but also possibly grinding, and is often associated with other semivoluntary oral habits such as cheek biting, nail biting, chewing on a pen or pencil absent mindedly, or tongue thrusting (where the tongue is pushed against the front teeth forcefully).
There is evidence that sleep bruxism is caused by mechanisms related to the central nervous system, involving Parasomnia and neurotransmitter abnormalities. Underlying these factors may be psychosocial factors including daytime stress which is disrupting peaceful sleep. Sleep bruxism is mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a frequency of about once per second, and also with occasional tooth grinding. It has been shown that the majority (86%) of sleep bruxism episodes occur during periods of sleep arousal. One study reported that sleep arousals which were experimentally induced with sensory stimulation in sleeping bruxists triggered episodes of sleep bruxism. Sleep arousals are a sudden change in the depth of the sleep stage, and may also be accompanied by increased heart rate, respiratory changes and muscular activity, such as leg movements. Initial reports have suggested that episodes of sleep bruxism may be accompanied by gastroesophageal reflux, decreased esophageal pH (acidity), swallowing, and decreased salivary flow. Another report suggested a link between episodes of sleep bruxism and a supine position (lying face up).
Disturbance of the dopaminergic system in the central nervous system has also been suggested to be involved in the etiology of bruxism. Evidence for this comes from observations of the modifying effect of medications which alter dopamine release on bruxing activity, such as levodopa, amphetamines or nicotine. Nicotine stimulates release of dopamine, which is postulated to explain why bruxism is twice as common in smokers compared to non-smokers.
Specific examples include levodopa (when used in the long term, as in Parkinson's disease), fluoxetine, metoclopramide, lithium, cocaine, venlafaxine, citalopram, fluvoxamine, methylenedioxyamphetamine (MDA), methylphenidate (used in attention deficit hyperactive disorder), and gamma-hydroxybutyric acid (GHB) and similar gamma-aminobutyric acid-inducing analogues such as phenibut. Bruxism can also be exacerbated by excessive consumption of caffeine, as in coffee, tea or chocolate. Bruxism has also been reported to occur commonly comorbid with drug addiction. Methylenedioxymethamphetamine (MDMA, ecstasy) has been reported to be associated with bruxism, which occurs immediately after taking the drug and for several days afterwards. Tooth wear in people who take ecstasy is also frequently much more severe than in people with bruxism not associated with ecstasy.
For tooth grinders who live in a household with other people, diagnosis of grinding is straightforward: Housemates or family members would advise a bruxer of recurrent grinding. Grinders who live alone can likewise resort to a sound-activated tape recorder. To confirm the condition of clenching, on the other hand, bruxers may rely on such devices as the Bruxchecker, Bruxcore, or a beeswax-bearing biteplate.
The Individual (personal) Tooth-Wear Index was developed to objectively quantify the degree of tooth wear in an individual, without being affected by the number of missing teeth. Bruxism is not the only cause of tooth wear. Another possible cause of tooth wear is acid erosion, which may occur in people who drink a lot of acidic liquids such as concentrated fruit juice, or in people who frequently vomit or regurgitate stomach acid, which itself can occur for various reasons. People also demonstrate a normal level of tooth wear, associated with normal function. The presence of tooth wear only indicates that it had occurred at some point in the past, and does not necessarily indicate that the loss of tooth substance is ongoing. People who clench and perform minimal grinding will also not show much tooth wear. Occlusal splints are usually employed as a treatment for bruxism, but they can also be of diagnostic use, e.g. to observe the presence or absence of wear on the splint after a certain period of wearing it at night.
The most usual trigger in sleep bruxism that leads a person to seek medical or dental advice is being informed by a sleeping partner of unpleasant grinding noises during sleep. The diagnosis of sleep bruxism is usually straightforward, and involves the exclusion of dental diseases, temporomandibular disorders, and the rhythmic jaw movements that occur with seizure disorders (e.g. epilepsy). This usually involves a dental examination, and possibly electroencephalography if a seizure disorder is suspected. Polysomnography shows increased masseter and temporalis muscular activity during sleep. Polysomnography may involve electroencephalography, electromyography, electrocardiography, air flow monitoring and audio–video recording. It may be useful to help exclude other sleep disorders; however, due to the expense of the use of a sleep lab, polysomnography is mostly of relevance to research rather than routine clinical diagnosis of bruxism.
Tooth wear may be brought to the person's attention during routine dental examination. With awake bruxism, most people will often initially deny clenching and grinding because they are unaware of the habit. Often, the person may re-attend soon after the first visit and report that they have now become aware of such a habit.
Several devices have been developed that aim to objectively measure bruxism activity, either in terms of muscular activity or bite forces. They have been criticized for introducing a possible change in the bruxing habit, whether increasing or decreasing it, and are therefore poorly representative to the native bruxing activity. These are mostly of relevance to research, and are rarely used in the routine clinical diagnosis of bruxism. Examples include the "Bruxcore Bruxism-Monitoring Device" (BBMD, "Bruxcore Plate"), the "intra-splint force detector" (ISFD), and electromyography devices to measure masseter or temporalis muscle activity (e.g. the "BiteStrip", and the "Grindcare").
With the following criteria supporting the diagnosis:
Sleep hygiene education should be provided by the clinician, as well as a clear and short explanation of bruxism (definition, causes and treatment options). Relaxation and tension-reduction have not been found to reduce bruxism symptoms, but have given patients a sense of well-being. One study has reported less grinding and reduction of EMG activity after hypnotherapy.
Other interventions include relaxation techniques, stress management, behavioural modification, habit reversal and hypnosis (self hypnosis or with a hypnotherapist). Cognitive behavioral therapy has been recommended by some for treatment of bruxism. In many cases awake bruxism can be reduced by using reminder techniques. Combined with a protocol sheet this can also help to evaluate in which situations bruxism is most prevalent.
Specific drugs that have been studied in sleep bruxism are clonazepam, levodopa, amitriptyline, bromocriptine, pergolide, clonidine, propranolol, and l-tryptophan, with some showing no effect and others appear to have promising initial results; however, it has been suggested that further safety testing is required before any evidence-based clinical recommendations can be made. When bruxism is related to the use of selective serotonin reuptake inhibitors in depression, adding buspirone has been reported to resolve the side effect. Tricyclic antidepressants have also been suggested to be preferable to selective serotonin reuptake inhibitors in people with bruxism, and may help with the pain.
Occlusal splints (also termed dental guards) are commonly prescribed, mainly by dentists and dental specialists, as a treatment for bruxism. Proponents of their use claim many benefits, however when the evidence is critically examined in systematic reviews of the topic, it is reported that there is insufficient evidence to show that occlusal splints are effective for sleep bruxism as well as bruxism overall. Furthermore, occlusal splints are probably ineffective for awake bruxism, since they tend to be worn only during sleep. However, occlusal splints may be of some benefit in reducing the tooth wear that may accompany bruxism, but by mechanically protecting the teeth rather than reducing the bruxing activity itself. In a minority of cases, sleep bruxism may be made worse by an occlusal splint. Some patients will periodically return with splints with holes worn through them, either because the bruxism is aggravated, or unaffected by the presence of the splint. When tooth-to-tooth contact is possible through the holes in a splint, it is offering no protection against tooth wear and needs to be replaced.
Occlusal splints are divided into partial or full-coverage splints according to whether they fit over some or all of the teeth. They are typically made of plastic (e.g. acrylate polymer) and can be hard or soft. A lower appliance can be worn alone, or in combination with an upper appliance. Usually lower splints are better tolerated in people with a sensitive gag reflex. Another problem with wearing a splint can be stimulation of salivary flow, and for this reason some advise to start wearing the splint about 30 minutes before going to bed so this does not lead to difficulty falling asleep. As an added measure for hypersensitive teeth in bruxism, desensitizing toothpastes (e.g. containing strontium chloride) can be applied initially inside the splint so the material is in contact with the teeth all night. This can be continued until there is only a normal level of sensitivity from the teeth, although it should be remembered that sensitivity to thermal stimuli is also a symptom of pulpitis, and may indicate the presence of tooth decay rather than merely hypersensitive teeth.
Splints may also reduce muscle strain by allowing the upper and lower jaw to move easily with respect to each other. Treatment goals include: constraining the bruxing pattern to avoid damage to the temporomandibular joints; stabilizing the occlusion by minimizing gradual changes to the positions of the teeth, preventing tooth damage and revealing the extent and patterns of bruxism through examination of the markings on the splint's surface. A dental guard is typically worn during every night's sleep on a long-term basis. However, a meta-analysis of occlusal splints (dental guards) used for this purpose concluded "There is not enough evidence to state that the occlusal splint is effective for treating sleep bruxism."
A repositioning splint is designed to change the patient's occlusion, or bite. The efficacy of such devices is debated. Some writers propose that irreversible complications can result from the long-term use of mouthguards and repositioning splints. Random controlled trials with these type devices generally show no benefit over other therapies.
A mandibular advancement device (normally used for treatment of obstructive sleep apnea) may reduce sleep bruxism, although its use may be associated with discomfort.
Botulinum toxin causes muscle paralysis/atrophy by inhibition of acetylcholine release at neuromuscular junctions.
"La bruxomanie" (a French term, translates to bruxomania) was suggested by Marie Pietkiewics in 1907. In 1931, Frohman first coined the term bruxism. Occasionally recent medical publications will use the word bruxomania with bruxism, to denote specifically bruxism that occurs while awake; however, this term can be considered historical and the modern equivalent would be awake bruxism or diurnal bruxism. It has been shown that the type of research into bruxism has changed over time. Overall between 1966 and 2007, most of the research published was focused on occlusal adjustments and oral splints. Behavioral approaches in research declined from over 60% of publications in the period 1966–86 to about 10% in the period 1997–2007. In the 1960s, a periodontist named Sigurd Peder Ramfjord championed the theory that occlusal factors were responsible for bruxism. Generations of dentists were educated by this ideology in the prominent textbook on occlusion of the time, however therapy centered around removal of occlusal interference remained unsatisfactory. The belief among dentists that occlusion and bruxism are strongly related is still widespread, however the majority of researchers now disfavor malocclusion as the main etiologic factor in favor of a more multifactorial, biopsychosocial model of bruxism.
In the Bible there are several references to "gnashing of teeth" in both the Old Testament, and the New Testament, where the phrase "weeping and gnashing of teeth" appears no less than 7 times in Matthew alone.
A Chinese proverb has linked bruxism with psychosocial factors. "If a boy clenches, he hates his family for not being prosperous; if a girl clenches, she hates her mother for not being dead."(男孩咬牙,恨家不起;女孩咬牙,恨妈不死。)
In David Lynch's 1977 film Eraserhead, Henry Spencer's partner ("Mary X") is shown tossing and turning in her sleep, and snapping her jaws together violently and noisily, depicting sleep bruxism. In Stephen King's 1988 novel The Tommyknockers, the sister of central character Bobbi Anderson also had bruxism. In the 2000 film Requiem for a Dream, the character of Sara Goldfarb (Ellen Burstyn) begins taking an amphetamine-based diet pill and develops bruxism. In the 2005 film Beowulf & Grendel, a modern reworking of the Anglo-Saxon poem Beowulf, Selma the witch tells Beowulf that the troll's name Grendel means "grinder of teeth", stating that "he has bad dreams", a possible allusion to Grendel traumatically witnessing the death of his father as a child, at the hands of King Hrothgar. The Geats (the warriors who hunt the troll) alternatively translate the name as "grinder of men's bones" to demonize their prey. In George R. R. Martin's A Song of Ice and Fire series, King Stannis Baratheon grinds his teeth regularly, so loudly it can be heard "half a castle away".
In rave culture, recreational use of ecstasy is often reported to cause bruxism. Among people who have taken ecstasy, while dancing it is common to use pacifiers, lollipops or chewing gum in an attempt to reduce the damage to the teeth and to prevent jaw pain. Bruxism is thought to be one of the contributing factors in "meth mouth", a condition potentially associated with long term methamphetamine use.
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