Bruxism and Temporomandibular Disorders
Bruxism and Temporomandibular Disorders
Bruxism is an abnormal clenching or grinding of the teeth, either while awake or during sleep. Bruxism may play a role in temporomandibular disorders (TMD), although the exact link is unclear. A number of studies have shown a strong relationship between bruxism and TMD. Manfredini looked at 212 patients with a diagnosis of TMD and found bruxism in 87.5% of patients with myofascial pain with disc displacement and in 68.9% of patients with mysofascial pain without disc displacement. A literature review of 46 papers did not, however, show a causal link between the two. The relationship is complex and it may be that bruxism leads to symptoms of TMD or that the two co-exist.
What causes bruxism?
Bruxism can occur during sleep and when awake. Awake bruxism is thought to be related to psychosocial factors such as stress, anxiety, and depression. Habits such as nail biting, pencil chewing, jaw bracing and tongue or cheek biting are also considered to be forms of awake bruxism.
Sleep bruxism was once thought to be related to these same psychosocial factors, however, current research does not support this. It is now thought that central factors are the most likely cause of sleep bruxism. Sleep bruxism, also known as parafunction or parasomnia, is thought to be related to micro-arousals during the sleep cycle. During our normal sleep cycle we have reactivations of our brain that allow us to become more aware of our surroundings without us actually waking. These reactivations are known as micro-arousals and allow our body to readjust temperature, heart rate and breathing rate and to wake us up if any threat is perceived. These arousals usually occur once or twice a minute and last only a few seconds. One study using EEG found that sleep bruxers had a significantly higher number of sleep arousals than non bruxers. These extra arousals were more common during non-REM sleep and most episodes of bruxism also occurred during non-REM sleep. The study also found that heart rate increased during a bruxism episode. It is thought that the increase in heart rate caused by an excessive number of micro-arousals causes increased neural activity, which in turn stimulates the motor neurons resulting in rhythmic contraction of the muscles of mastication and bruxism. Interestingly, it has been found that about 60% of non-bruxers also have rhythmic contraction of the muscles of mastication but without tooth contact. It is estimated that up to 20% of the population bruxes and of those up to 20% have symptoms of TMD. Most episodes of bruxism occur in supine and are more common in those with sleep apnea, sleep disorders and in sleep walkers. Bruxism becomes less common with age.
Symptoms of Bruxism
• Sleep partner’s complaint of tooth grinding.
• Waking with teeth clenched.
• Waking with tenderness and restriction in the muscles of mastication.
• Waking with tooth or gum sensitivity.
• Indentations in the inside of the cheeks or the edges of the tongue.
• Hypertrophy of the masseter muscles.
• Excessive dental wear, including loosening or fracturing of the teeth.
• TMJ clicking or locking, TMJ pain, headache.
• Snoring can be an indicator of sleep bruxism.
Management of Bruxism
Managing bruxism that is related to symptoms of TMD usually requires a multi-factorial approach.
Physiotherapy - The patient’s temporomandibular region, cervical spine and posture should be accurately assessed. (For more information see Temporomandibular disorders.) Patients will not always offer information about bruxism, so it is important to specifically question the patient about clenching or grinding. One study looked at two groups of patients with TMD. One group of 163 patients, was specifically asked about bruxism. The other group of 200 patients, was not specifically asked about bruxism (self-reporting). Only 20.5% of the self-reporting group reported bruxism, while 65% of the other group reported bruxism when specifically asked. “It is critical to ask specifically about bruxism. Patients are more likely to report bruxism when asked specifically about it. It is important to incorporate this as part of a TMD evaluation.”
Patient Education - If the patient’s bruxism is occurring during the day then education and advice is needed to help change habits such as nail biting, pencil chewing and jaw clenching. Helping patients to identify and address stressors in their daily life can be helpful. In some cases patients may benefit from relaxation therapy, breathing training and exercises. Referral to a psychologist may help some patients.
Sleep Hygiene - Education about good sleep hygiene can also be helpful. Patients should be advised to avoid large meals, alcohol and caffeine within three hours of bedtime and to improve their sleep environment by ensuring low or no light, minimal noise, no pets or children in the bedroom when sleeping and to try to go to bed and get up at the same time each day.Sleep Studies - If a sleep disorder such as sleep apnea or other sleep disorders are suspected, the patient may benefit from a referral to a sleep clinic for studies.
Breathing Difficulties - If the patient is suffering any respiratory disorders, including allergies they need to see their doctor for investigation and management.
Occlusal Splints - There is evidence to support the use of occlusal splints at night for patients with sleep bruxism. The aim of these splints is to hold the teeth slightly apart even when a patient clenches or grinds. This reduces the compression of the temporomandibular joint (TMJ) and may also reduce long-term damage to the teeth. Research has also shown a reduction in masseter and temporalis activity levels and pain after using an occlusal splint at night.
Recent Related Research (from Pubmed)
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- Manfredini D; Cantini E; Romagnoli M; Bosco M; Prevalence of bruxism in patients with different research diagnostic criteria for temporomandibular disorders (RMC/TMD) Cranio, Vol. 21, No. 4, pg. 279-285, 2003.
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