Bruxism

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.

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

Introduction

Bruxism is excessive teeth grinding or jaw clenching, an oral parafunctional activity that is unrelated to normal functions such as eating or talking Bruxism is a common behavior, with prevalence rates ranging from 8% to 31% in the general population It can lead to several symptoms, including hypersensitive teeth, aching jaw muscles, headaches, tooth wear, and damage to dental restorations (e.g., crowns and fillings) In some cases, symptoms may be minimal, and patients may not be aware of their condition.

Bruxism can be categorized into two main types: nocturnal bruxism, which occurs during sleep, and awake bruxism, which occurs during wakefulness Dental damage may be similar for both types; however, sleep bruxism symptoms are often worse upon waking and improve throughout the day, while awake bruxism symptoms may not be present upon waking and worsen as the day progresses The causes of bruxism are not completely understood and likely involve multiple factors. Awake bruxism is more common in females, while sleep bruxism affects males and females in equal proportions. Although several treatments are in use, there is limited evidence for the robust efficacy of any particular treatment

Signs and symptoms

Most people who experience bruxism are unaware of the problem, either because there are no symptoms or because the symptoms are not understood to be associated with clenching and grinding Sleep bruxism symptoms are usually most intense immediately after waking and slowly abate, while awake bruxism symptoms may not be present upon waking and worsen throughout the day. Bruxism may cause a variety of signs and symptoms, including:

Excessive tooth wear, particularly attrition, which flattens the occlusal (biting) surface, and 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 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 cause a degree of loosening. A grinding or tapping noise during sleep, sometimes detected by a partner or parent. This noise can be surprisingly loud and unpleasant, and can wake a sleeping partner. Noises are rarely associated with awake bruxism. Other parafunctional activities that may occur together with bruxism, such as cheek biting (which may manifest as morsicatio buccarum and/or linea alba).

A burning sensation on the tongue (glossodynia). 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. Trismus (restricted mouth opening). Pain or tenderness of the temporomandibular joints Clicking of the temporomandibular joints. Headaches, particularly pain in the temples. The muscles of mastication that move the jaw can also be affected, as they are utilized over and above their normal function.

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 common type of tooth wear in bruxism and affects the occlusal surface (the biting surface) of the teeth. The exact location and pattern of attrition depend 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 forward, 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.

Other effects

In addition to tooth wear, bruxism can lead to other dental issues, such as tooth mobility and damage to dental restorations. 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.

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 mainstay 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.

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 the 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 between bruxism and 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

Treatment

Several treatments are in use for bruxism, although there is little evidence of robust efficacy for any particular treatment. The main goal of treatment is to manage symptoms, reduce damage to teeth and dental restorations, and improve sleep quality. Treatment options include:

Dental treatments

Occlusal splints: These are custom-made, removable devices that fit over the teeth and help protect them from damage caused by grinding or clenching. They may also help reduce muscle strain and temporomandibular joint pain. The splints can be made from hard or soft materials and are generally worn at night.

Occlusal adjustment: In some cases, selective reshaping of the biting surfaces of the teeth (also known as occlusal equilibration) may be necessary to achieve a more harmonious bite. However, this treatment is considered controversial and should be used cautiously, as the benefits are not well-established.

Behavior modification

Stress management: Since stress and anxiety can contribute to bruxism, various stress-reduction techniques may help alleviate the condition. These can include relaxation techniques, meditation, or counseling.

Sleep hygiene: Improving sleep habits, such as maintaining a consistent sleep schedule, creating a comfortable and quiet sleep environment, and avoiding stimulating activities before bedtime, may help reduce bruxism.

Habit awareness: Becoming more aware of the habit and using strategies to break it, such as placing a reminder on the bathroom mirror or setting an alarm on a smartphone, can help reduce daytime clenching and grinding.

Medications

Although there is no specific medication for bruxism, certain medications may help manage symptoms or address underlying causes.

Botulinum toxin: Injections of botulinum toxin (Botox) into the masseter and temporalis muscles have been used to reduce muscle activity and alleviate bruxism symptoms in some cases. However, more research is needed to determine the safety and efficacy of this treatment.

Conclusion

Bruxism is a common condition that can cause tooth wear, pain, and sleep disturbances. Although the exact causes of bruxism are not fully understood, it is thought to involve a combination of genetic, psychological, and environmental factors. Treatment options include dental interventions, behavior modification, and medications, but there is no one-size-fits-all solution. It is important for individuals who suspect they have bruxism to consult with a dental professional to discuss their symptoms and develop a personalized treatment plan to manage the condition effectively.

See also

• Dentistry
• Temporomandibular joint dysfunction
• Sleep hygiene

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