In sleep bruxism especially, there is no evidence that removal of occlusal interferences has any impact on the condition. People with no teeth at all who wear dentures can still have bruxism, although dentures also often change the original bite. Most modern sources state that there is no relationship, or at most a minimal relationship, between bruxism and occlusal factors. The findings of one study, which used self-reported tooth grinding rather than clinical examination to detect bruxism, suggested that there may be more of a relationship between occlusal factors and bruxism in children. However, the role of occlusal factors in bruxism cannot be completely discounted due to insufficient evidence and problems with the design of studies. A minority of researchers continue to claim that various adjustments to the mechanics of the bite are capable of curing bruxism (see Occlusal adjustment/reorganization). Psychosocial factors
Many studies have reported significant psychosocial risk factors for bruxism, particularly a stressful lifestyle, and this evidence is growing, but still not conclusive. Some consider emotional stress and anxiety to be the main triggering factors. It has been reported that persons with bruxism respond differently to depression, hostility and stress compared to people without bruxism. Stress has a stronger relationship to awake bruxism, but the role of stress in sleep bruxism is less clear, with some stating that there is no evidence for a relationship with sleep bruxism. However, children with sleep bruxism have been shown to have greater levels of anxiety than other children.
This typically involves the masseter muscle and the anterior portion of the temporalis (the large outer muscles that clench), and the lateral pterygoids, relatively small bilateral muscles that act together to perform sideways grinding. Multiple causes
The cause of bruxism is largely unknown, but it is generally accepted to have multiple possible causes. Bruxism is a parafunctional activity, but it is debated whether this represents a subconscious habit or is entirely involuntary. The relative importance of the various identified possible causative factors is also debated. Awake bruxism is thought to be usually semivoluntary, and often associated with stress caused by family responsibilities or work pressures. Some suggest that in children, bruxism may occasionally represent a response to earache or teething. Awake bruxism usually involves clenching (sometimes the term "awake clenching" is used instead of awake bruxism), but also possibly grinding, and is often associated with other semivoluntary oral habits such as cheek biting, nail biting, chewing on a pen or pencil absent mindedly, or tongue thrusting (where the tongue is pushed against the front teeth forcefully).There is evidence that sleep bruxism is caused by mechanisms related to the central nervous system, involving sleep arousal and neurotransmitter abnormalities. Underlying these factors may be psychosocial factors including daytime stress which is disrupting peaceful sleep. Sleep bruxism is mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a frequency of about once per second, and also with occasional tooth grinding. It has been shown that the majority (86%) of sleep bruxism episodes occur during periods of sleep arousal.