bruxism bruxism bruxism is excessive teeth grinding or jaw clenching. it is an oral parafunctional activity; i.e., it is unrelated to normal function such as eating or talking. bruxism is a common behavior; reports of prevalence range from 8% to 31% in the general population. several symptoms are commonly associated with bruxism, including aching jaw muscles, headaches, hypersensitive teeth, tooth wear, and damage to dental restorations (e.g. crowns and fillings). symptoms may be minimal, without patient awareness of the condition. if nothing is done, after a while many teeth start wearing down until the whole tooth is gone. bruxismattrition (tooth wear caused by tooth-to-tooth contact) can be a manifestation of bruxism.specialtydentistry 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. epidemiology there is a wide variation in reported epidemiologic data for bruxism, and this is largely due to differences in the definition, diagnosis and research methodologies of these studies. e.g. several studies use self-reported bruxism as a measure of bruxism, and since many people with bruxism are not aware of their habit, self-reported tooth grinding and clenching habits may be a poor measure of the true prevalence. 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. a 2013 systematic review of the epidemiologic reports of bruxism concluded a prevalence of about 22.1–31% for awake bruxism, 9.7–15.9% for sleep bruxism, and an overall prevalence of about 8–31.4% of bruxism generally. the review also concluded that overall, bruxism affects males and females equally, and affects elderly people less commonly. signs and symptoms most people who brux are unaware of the problem, either because there are no symptoms, or because the symptoms are not understood to be associated with a clenching and grinding problem. the symptoms of sleep bruxism are usually most intense immediately after waking, and then slowly abate, and the symptoms of a grinding habit which occurs mainly while awake tend to worsen through the day, and may not be present on waking. bruxism may cause a variety of signs and symptoms, including: view from above of an anterior (front) tooth showing severe tooth wear which has exposed the dentin layer (normally covered by enamel). the pulp chamber is visible through the overlying dentin. tertiary dentin will have been laid down by the pulp in response to the loss of tooth substance. multiple fracture lines are also visible. a grinding or tapping noise during sleep, sometimes detected by a partner or a parent. this noise can be surprisingly loud and unpleasant, and can wake a sleeping partner. noises are rarely associated with awake bruxism. other parafunctional activity which may occur together with bruxism: cheek biting (which may manifest as morsicatio buccarum and/or linea alba), and/or lip biting. a burning sensation on the tongue (see: glossodynia), possibly related to a coexistent "tongue thrusting" parafunctional activity. indentations of the teeth in the tongue ("crenated tongue" or "scalloped tongue"). hypertrophy of the muscles of mastication (increase in the size of the muscles that move the jaw), particularly the masseter muscle. tenderness, pain or fatigue of the muscles of mastication, which may get worse during chewing or other jaw movement. trismus (restricted mouth opening). pain or tenderness of the temporomandibular joints, which may manifest as preauricular pain (in front of the ear), or pain referred to the ear (otalgia). clicking of the temporomandibular joints. headaches, particularly pain in the temples, caused by muscle pain associated with the temporalis muscle. excessive tooth wear, particularly attrition, which flattens the occlusal (biting) surface, but also possibly other types of tooth wear such as abfraction, where notches form around the neck of the teeth at the gumline. tooth fractures, and repeated failure of dental restorations (fillings, crowns, etc.). hypersensitive teeth, (e.g. dental pain when drinking a cold liquid) caused by wearing away of the thickness of insulating layers of dentin and enamel around the dental pulp. inflammation of the periodontal ligament of teeth, which may make them sore to bite on, and possibly also a degree of loosening of the teeth. bruxism is usually detected because of the effects of the process (most commonly tooth wear and pain), rather than the process itself. the large forces that can be generated during bruxism can have detrimental effects on the components of masticatory system, namely the teeth, the periodontium and the articulation of the mandible with the skull (the temporomandibular joints). the muscles of mastication that act to move the jaw can also be affected since they are being utilized over and above of normal function. pain most people with bruxism will experience no pain. the presence or degree of pain does not necessarily correlate with the severity of grinding or clenching. the pain in the muscles of mastication caused by bruxism can be likened to muscle pain after exercise. the pain may be felt over the angle of the jaw (masseter) or in the temple (temporalis), and may be described as a headache or an aching jaw. most (but not all) bruxism includes clenching force provided by masseter and temporalis muscle groups; but some bruxers clench and grind front teeth only, which involves minimal action of the masseter and temporalis muscles. the temporomandibular joints themselves may also become painful, which is usually felt just in front of the ear, or inside the ear itself. clicking of the jaw joint may also develop. the forces exerted on the teeth are more than the periodontal ligament is biologically designed to handle, and so inflammation may result. a tooth may become sore to bite on, and further, tooth wear may reduce the insulating width of enamel and dentin that protects the pulp of the tooth and result in hypersensitivity, e.g. to cold stimuli. 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. tooth wear many publications list tooth wear as a consequence of bruxism, but some report a lack of a positive relationship between tooth wear and bruxism. tooth wear caused by tooth-to-tooth contact is termed attrition. this is the most usual type of tooth wear that occurs in bruxism, and affects the occlusal surface (the biting surface) of the teeth. the exact location and pattern of attrition depends on how the bruxism occurs, e.g., when the canines and incisors of the opposing arches are moved against each other laterally, by the action of the medial pterygoid muscles, this can lead to the wearing down of the incisal edges of the teeth. to grind the front teeth, most people need to posture their mandible forwards, unless there is an existing edge to edge, class iii incisal relationship. people with bruxism may also grind their posterior teeth (back teeth), which wears down the cusps of the occlusal surface. once tooth wear progresses through the enamel layer, the exposed dentin layer is softer and more vulnerable to wear and tooth decay. if enough of the tooth is worn away or decayed, the tooth will effectively be weakened, and may fracture under the increased forces that occur in bruxism. 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, erosion is said to synergistically contribute to tooth wear in some bruxists, according to some sources. tooth mobility the view that occlusal trauma (as may occur during bruxism) is a causative factor in gingivitis and periodontitis is not widely accepted. it is thought that the periodontal ligament may respond to increased occlusal (biting) forces by resorbing some of the bone of the alveolar crest, which may result in increased tooth mobility, however these changes are reversible if the occlusal force is reduced. tooth movement that occurs during occlusal loading is sometimes termed fremitus. it is generally accepted that increased occlusal forces are able to increase the rate of progression of pre-existing periodontal disease (gum disease), however the main stay treatment is plaque control rather than elaborate occlusal adjustments. it is also generally accepted that periodontal disease is a far more common cause of tooth mobility and pathological tooth migration than any influence of bruxism, although bruxism may much less commonly be involved in both. causes the left temporalis muscle the left medial pterygoid muscle, and the left lateral pterygoid muscle above it, shown on the medial surface of the mandbilar ramus, which has been partially removed along with a section of the zygomatic arch the left masseter muscle (red highlight), shown partially covered by superficial muscles the muscles of mastication (the temporalis, masseter, medial and lateral pterygoid muscles) are paired on either side and work together to move the mandible, which hinges and slides around its dual articulation with the skull at the temporomandibular joints. some of the muscles work to elevate the mandible (close the mouth), and others also are involved in lateral (side to side), protrusive or retractive movements. mastication (chewing) is a complex neuromuscular activity that can be controlled either by subconscious processes or by conscious processes. in individuals without bruxism or other parafunctional activities, during wakefulness the jaw is generally at rest and the teeth are not in contact, except while speaking, swallowing or chewing. it is estimated that the teeth are in contact for less than 20 minutes per day, mostly during chewing and swallowing. normally during sleep, the voluntary muscles are inactive due to physiologic motor paralysis, and the jaw is usually open. 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