Bruxism

Definition

Bruxism, commonly known as tooth grinding, is a repetitive activity of the masticatory muscles. Per the international consensus of Lobbezoo et al., 2018, this activity has two main forms: clenching, meaning pressing the teeth together without movement, and grinding, meaning rubbing the teeth against each other; it sometimes also appears as bracing or thrusting of the jaw. Bracing means holding the jaw rigidly in a fixed position through isometric contraction of the masticatory muscles — the jaw is "locked" in a defined position without the teeth necessarily pressing together or moving. Thrusting means repetitive pushing or advancing of the mandible (a protrusive movement), which can likewise occur without tooth contact.

An important point is that, by this definition, clenching is also classified as part of bruxism, not a separate phenomenon — unlike the everyday term "tooth grinding," which refers only to the grinding sound. Bruxism is divided into two types: sleep bruxism, which occurs at night and has a central neurological origin, and awake bruxism, which occurs during the day and is more often associated with stress.

Concept Boundary & Misconceptions

The most common mistake is to see a bruxing patient and treat the activity itself as a disease to be definitively "cured." The current consensus does not classify this behavior as a disorder in a healthy individual; it is regarded more as a risk factor that, depending on severity, may or may not produce consequences.

A second misconception lies at the level of diagnosis. Seeing several wear facets on the teeth is not enough to conclude with certainty that a patient is a bruxer, since those facets may be old or may have a different origin. A precise diagnosis requires polysomnography combined with EMG of the jaw muscles; anything short of that is, at best, "possible bruxism," not a definitive diagnosis. And contrary to what was taught for years, a poor occlusion or premature contacts are not the primary cause of sleep bruxism; its origin is predominantly central and neurophysiological.

Role in Clinical Decision-Making

Since the behavior itself cannot be eliminated, treatment focuses on protecting the structures this force damages. This is the logic behind night-guard design, behind choosing a thicker, more resistant material for crowns in a bruxing patient, behind greater caution in implant prognosis, and in some cases, behind botulinum toxin injection to reduce muscular activity. A dentist who ignores this and designs a restoration as if for a non-bruxing patient should expect early failure.