| Bruxism | |
|---|---|
| Classification and external resources | |
A profile of a smile, exhibiting significant wear, especially on the maxillary incisors. Even though the teeth are in an edge-to-edge position, the teeth are in maximum intercuspation; this patient has a Class III malocclusion. |
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| ICD-10 | F45.8 |
| ICD-9 | 306.8 |
| DiseasesDB | 29661 |
| MedlinePlus | 001413 |
| MeSH | D002012 |
Bruxism (from the Greek βρυγμός (brygmós), "gnashing of teeth") is characterized by the grinding of the teeth and typically includes the clenching of the jaw. It is an oral parafunctional activity that occurs in most humans at some time in their lives. In most people, bruxism is mild enough not to be a health problem.[1] While bruxism may be a diurnal or nocturnal activity,[2] it is bruxism during sleep that causes the majority of health issues; it can even occur during short naps. Bruxism is one of the most common sleep disorders.[3]
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Bruxism is a habit rather than a reflex chewing activity. Reflex activities happen reliably in response to a stimulus, without involvement of subconscious brain activity. Chewing and clenching are complex neuromuscular activities that can be controlled either by subconscious processes or by conscious processes within the brain. During sleep, (and for some during waking hours while conscious attention is distracted) subconscious processes can run unchecked, allowing bruxism to occur.
Some bruxism activity is rhythmic with bite force pulses of tenths of a second (like chewing), and some has a longer bite force pulses of 1 to 30 seconds (clenching). Researchers classify bruxism as "a habitual behavior, and a sleep disorder."[4]
The etiology of problematic bruxism can be quite varied, from allergic reactions or medical ailments, to trauma (such as a car crash) to a period of unusual stress, but once bruxism becomes a habit, the original stimulus can be removed without ending the habit. Certain medical conditions can trigger bruxism, including digestive ailments, anxiety, and hypermyotonia due to consumption of amphetamine and related stimulants.[5]
Most people are not aware of their bruxism. Only an estimated 5% go on to develop symptoms, such as jaw pain and headaches, which prompt treatment.[6] A sleeping partner or parent may notice the behavior first, although sufferers may notice pain symptoms without understanding the cause.
Bruxism can result in occlusal trauma, the abnormal wear patterns of the occlusal surface, abfractions and fractures in the teeth. Over time, dental damage increases. Bruxism is the leading cause of occlusal trauma and a significant cause of tooth loss and gum recession. Bruxism can be loud enough to wake a sleeping partner. Some individuals clench without significant lateral movements.
In a typical case involving lateral motion, the canines and incisors of the opposing arches are moved against each other laterally, i.e., with a side-to-side action, by the medial pterygoid muscles that lie medial to the temporomandibular joints bilaterally. This movement abrades tooth structure and can lead to the wearing down of the incisal edges of the teeth. People with bruxism may also grind their posterior teeth, which will wear down the cusps of the occlusal surface. 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 neither masseter nor temporalis muscle groups. Teeth hollowed by previous decay (caries), or dental drilling, may collapse from bruxism's cyclic pressures.
Patients may present with a variety of symptoms, including:[7]
Eventually, bruxism with lateral movements shortens and blunts the teeth being ground and may lead to myofascial muscle pain, temporomandibular joint dysfunction and headaches. If enough enamel has been abraded, the softer dentin will be exposed, and abrasion will accelerate. This opens the possibility of dental decay and tooth fracture, and in some people, gum recession. Early intervention by a dentist is advisable. In severe, chronic cases, bruxism can lead to arthritis of the temporomandibular joints. The jaw clenching that is often part of bruxism can be an unconscious neuromuscular daytime activity, which should be treated as well, usually through physical therapy (recognition and stress response reduction).
Bruxism is not the only cause of tooth wear, making it difficult to diagnose by visual evidence alone. Abraded teeth are usually brought to the patient's attention during a routine dental examination.
The most reliable diagnostic technique is measuring EMG (electromyography). These measurements pick up electrical signals from the chewing muscles (masseter and temporalis). This method is commonly used in sleep labs. Three forms of EMG measurement are available outside of sleep labs.
"Bedside" EMG units are similar to those used by sleep labs. These units pick up their signals from facial muscles through wires connecting the bedside unit to electrodes that are adhesively attached to the user's face. TENS electrodes or ECG electrodes may be used.
A biofeedback headband may be used in silent mode to record the total number of clenching incidents and the total clenching time each night. These two numbers easily distinguish clenching from rhythmic grinding and allow dentists to quantify severity levels. Biofeedback headbands do not require adhesive electrodes or wires attached to the face. They do not record the exact time, duration, and strength of each clenching incident as bedside EMG monitors do.
Bedside EMG units and biofeedback headbands can both be used either as a diagnosis measurement or in biofeedback mode as a treatment to help patients break their bruxism habit.
"Disposable" EMG monitors adhesively mount to the side of the face over the masseter muscle. They monitor one night and provide a single-digit measure of bruxism severity.
The following factors may be associated with bruxism (whether by cause or effect):
If diagnosed early, finding and eliminating the original cause(s) may cure bruxism. Later on, habitual bruxism can be treated by habit-modification.[16] Treating associated factors can reduce or eliminate the behavior in cases where bruxism has not become habitual.[10]
A dental guard or splint can reduce tooth abrasion. Dental guards are typically made of plastic and fit over some or all of upper and/or lower teeth. The guard protects the teeth from abrasion and can 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. Dental guards do not cure the condition.
A repositioning splint is designed to change the patient's occlusion, or bite.
Another option is an NTI-tss (nociceptive trigeminal inhibitor) dental guard. Nociceptor nerves sense and respond to pressure. The trigeminal nerve supplies the face and mouth. The NTI appliance snaps onto the front teeth. Normally when the mouth is closed, the upper and lower front teeth overlap: The NTI prevents this overlap and translates the bite force from attempts to close the jaw normally into a forward twisting of the lower front teeth. The intent is for the brain to interpret the nerve sensations as undesirable, automatically and subconsciously reducing clenching force. Unfortunately, for patients who do not subconsciously clench less using an NTI devce, the NTI can lead to more severe damage from clenching. The NTI device must be fitted by a dentist.[17]
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. Randomly controlled trials with these type devices generally show no benefit over other therapies.[18][19][20] Clenching hard while wearing an NTI device may cause worse damage, because the NTI changes the forces on the teeth and the tempormandibular joint. NTI patients require ongoing monitoring by a dentist.
While there is some debate on this approach, the use of mouthguards can protect the skull from ongoing deterioration and damage. Some studies have found inter sutural bleeding occurs while grinding at night. The mouthguard may not entirely prevent the clenching or grinding motion but it can lessen the impact the TMJ impact has on the rest of the skull. Craniosacral therapy is said to both alleviate these inter sutural imbalances as well as alleviate the internal stress which is at the source of the grinding.
A device monitors the electromyographic (EMG) activity of the temporalis muscle. When the muscle contracts, the device records the muscle activity and sends out a contingent electrical stimulation (CES) to receptors in the skin. The contingent electrical stimulation is designed to trigger an inhibitory reflex in the brain stem that relaxes the jaw-muscles and inhibits the bruxing event without waking up the user. The function of the device is therefore different from other devices in the market, which wake up the user acoustically to stop the grinding. The device has an electrode with three metal contact pads to record the muscle activity and send out the CES. The electrode is attached to the skin with a disposable gel-pad.[21]
The level of stimulation is set by the user at the same time as the calibration, that must be done by the user in order for the bruxing events to be detected correctly. The stimulation intensity is clearly perceived by the user -but not painful. All user interaction with the device is done via a menu on the display of the device. The device is intended for use during sleep – although it may also be used while the user is awake. The device reportedly reduces grinding, usually without interfering with sleep.[22]
Various biofeedback devices are currently available, and effectiveness varies significantly depending on whether the biofeedback is used only during waking hours, or during sleep as well. Many authorities remain unconvinced of the efficacy of daytime-only biofeedback.[23] The efficacy of nighttime biofeedback can depend strongly on daytime training, which is used to establish a Pavlovian response to the biofeedback signal that persists during sleep.
The first wearable nighttime bruxism biofeedback device (a biofeedback headband) was introduced in 2001. A biofeedback headband is a battery-powered device that sounds a tone when it senses EMG muscle activity in the temporalis muscles. The tone starts off at a low volume and gets louder until the clenching incident stops, or until a maximum volume level is reached. The intent is to allow people to stop clenching without awakening. The biofeedback headband also tallies nightly data on the number of events that last for at least two seconds and the total accumulated duration of those events. A "fast-response" headband catches events that last for as little as 0.2 seconds. The volume of the biofeedback tone and the bite force required to trigger the device are adjustable. Clinical trials have shown that after three brief sessions of Pavlovian response conditioning and subsequent use of a biofeedback headband during sleep, more than 75% of bruxism sufferers experience more than a 60% reduction in nighttime clenching from the first day of biofeedback onward, and more than 50% of bruxism sufferers experience more than an 80% reduction in bruxism within the first month.[24]
Another therapy relies on stimulating the taste buds.[25] The therapy involves suspending sealed packets containing a harmless but bad-tasting substance (e.g. hot sauce, vinegar, denatonium benzoate, etc.) between the rear molars using an orthodontic-style appliance. Attempts to bring the teeth together ruptures the packets, alerting the user. The Taste-Based Approach claims to suffer less from desensitization over time than sound-based biofeedback approaches, but may interrupt sleep more.
Another device (patented in 2005) forces the patient to switch from breathing through the nose to breathing through the mouth.The device responds to muscle activity by signaling a mechanical actuator that slowly reduces airflow (without closing them) to the nostrils to force breathing to occur through the mouth. Once the patient stops clenching, the flaps open.[26]
Botulinum toxin (Botox) can lessen bruxism's effects. An extremely dilute form of Botox is injected to weaken (partially paralyze) muscles and has been used extensively in cosmetic procedures to 'relax' the muscles of the face.
Botox was originally developed for use in treating strabismus (misalignment of eyes), during trials of which its effects on wrinkles in the eye area were discovered. It was, and continues to be, used to treat diseases of muscle spasticity such as strabismus, blepharospasm (eyelid spasm), and torticollis (wry neck). Bruxism can also be regarded as a disorder of repetitive, unconscious contraction of the masseter muscle (the large muscle that moves the jaw). In the treatment of bruxism, Botox weakens the muscle enough to reduce the effects of grinding and clenching, but not so much as to prevent proper use of the muscle. Botox treatment typically involves five or six injections into the masseter muscles. It takes a few minutes per side, and the patient starts feeling the effects the next day. Occasionally, bruising can occur, but this is quite rare. Injections must be repeated more than once per year.
The optimal dose of Botox must be determined for each person as some people have stronger muscles that need more Botox. This is done over a few touch-up visits with the physician. The effects last for about three months. The muscles do atrophy, however, so after a few rounds of treatment, it is usually possible either to decrease the dose or increase the interval between treatments.[27][28][29]
There is anecdotal evidence that suggests taking certain combinations of dietary supplements may alleviate bruxism; pantothenic acid, magnesium,[30] and calcium are mentioned on dietary supplement websites. Calcium is known to be a treatment for gastric problems, and gastric problems such as acid reflux are known to increase bruxism..
Damaged teeth can be repaired by replacing the worn natural crown of the tooth with prosthetic crowns. Materials used to make crowns vary; some are less prone to breaking than others and can last longer. Porcelain fused to metal crowns may be used in the anterior (front) of the mouth; in the posterior, full gold crowns are preferred. All-porcelain crowns are now becoming more and more common and work well for both anterior and posterior restorations. To protect the new crowns and dental implants, an occlusal guard should be fabricated to wear during sleep.
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