A para-functional habit or parafunctional habit is the habitual exercise of a body part in a way that is other than the most common use of that body part. The term is most commonly used by dentists, orthodontists, or maxillofacial specialists to refer to parafunctional uses of the mouth, tongue and jaw.

Oral para-functional habits may include

• Bruxism (tooth-clenching or grinding),
• Tongue Thrusting,
• Mouth Breathing,
• Thumb sucking and
• any other habitual use of the mouth unrelated to eating, drinking or speaking.

Contrary to common belief, functional habits such as chewing are not the main cause of the wearing of teeth. Parafunctional habits are the most destructive forces for several reasons. Whereas teeth rarely come into contact during normal chewing, grinding of teeth may occur 1 - 4 hours in a 24 hour period, most often during sleep.

Bruxism (from the Greek word (brugmós), gnashing of teeth) is grinding of the teeth, typically accompanied by clenching of the jaw. It is an oral parafunctional activity that occurs to some extent in most humans. Bruxism is caused by the activation of reflex chewing activity; it is not a learned habit.

Chewing is a complex neuromuscular activity that is controlled by reflex nerve pathways, with higher control by the brain. During sleep, the reflex part is active while the higher control is inactive, resulting in bruxism. In most people, bruxism is mild enough not to be a health problem; however, some people suffer from significant bruxism that can become symptomatic.

Bruxism often occurs during sleep and can even occur during short naps. Bruxism is one of the most common sleep disorders. 30 to 40 million Americans grind their teeth during sleep.

Associated factors

The etiology of bruxism is unknown; the following factors may be associated with the condition.

• Disturbed sleep pattern/other sleep disorders (obstructive sleep apnea, snoring, moderate daytime sleepiness)
• Malocclusion, in which the upper and lower teeth fit together in a dysfunctional way
• Relatively high levels of consumption of caffeinated drinks and foods, such as coffee, colas, and chocolate
• High levels of alcohol consumption
• >Smoking
• High levels of anxiety and/or stress
• Digestive problems

Signs, symptoms and sequelae of bruxism

Bruxism can result in abnormal wear patterns of the occlusal surface, abfractions and fractures in the teeth. This type of damage is categorised as a sign of occlusal trauma.

Over time, dental damage will usually occur. Bruxism is the leading cause of occlusal trauma and a significant cause of tooth loss and gum recession.

Eventually, bruxing shortens and blunts the teeth (Attrition) being ground, and may lead to myofacial muscle pain and headaches. In severe, chronic cases, it can lead to arthritis of the temporomandibular joints.

Most bruxers are not aware of their bruxism and only 5-10% go on to develop symptoms such as jaw pain and headache. Teeth hollowed by previous decay (caries), or dental drilling, may collapse, as the cyclic pressure exerted by bruxism is extremely taxing on the tooth structure.

Diagnoses of bruxism

Bruxism is not the only cause of Tooth Wear.

• Attrided teeth are usually brought to the patient's attention during a routine dental examination.
• If enough enamel has been attrited, the softer dentine will be exposed and attrition will accelerate. This opens the possibility of Tooth Decay and tooth fracture, and in some people, gum recession.
• Many a time due to the exposure of the underlying dentine the patient may complain of severe Sensitivity of teeth to hot and cold.
• In severe bruxers there is fracture of dental restorations (fillings).
• Nocturnal (Night time) Bruxers complain of pain in the jaws on awakening. Early intervention by a dentist is advisable.

Treatment of bruxism

There is no accepted cure for bruxism.

Mouthguards and repositioning splints

Ongoing management of bruxism is based on minimizing the attrition of tooth surfaces by the wearing of an acrylic dental guard or splint, designed to the shape of an individual's upper or lower teeth from a bite mould. Mouthguards are obtained through visits to a dentist for measuring, fitting, and ongoing supervision. There are four possible goals of this treatment:

• constraint of the bruxing pattern such that serious damage to the TMJ joints is prevented,
• stabilization of the occlusion by minimizing the gradual changes to the positions of the teeth that typically occur with bruxism,
• prevention of tooth damage, and
• the enabling of a bruxism practitioner to judge — in broad terms — the extent and patterns of bruxism, through examination of the physical indentations on the surface of the splint.

A dental guard is typically worn on a long-term basis during every night's sleep.