Editing Bruxism (section)

===Multiple causes===
The cause of bruxism is largely unknown, but it is generally accepted to have multiple possible causes.<ref name="Cawson 2002">{{cite book |vauthors=Cawson RA, Odell EW, Porter S |title = Cawsonś essentials of oral pathology and oral medicine. |year = 2002 |publisher = Churchill Livingstone |location = Edinburgh |isbn = 978-0443071065 |pages = {{formatnum:6566364 }},366|edition=7th}}</ref><ref name="Shetty 2010" /><ref name="Lobbezoo 2001">{{cite journal |vauthors=Lobbezoo F, Naeije M |s2cid=16681579 |title=Bruxism is mainly regulated centrally, not peripherally |journal=Journal of Oral Rehabilitation |volume=28 |issue=12 |pages=1085–91 |date=December 2001  |pmid=11874505 |doi=10.1046/j.1365-2842.2001.00839.x}}</ref> Bruxism is a parafunctional activity, but it is debated whether this represents a subconscious [[habit (psychology)|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.<ref name="Shetty 2010" /> Some suggest that in children, bruxism may occasionally represent a response to earache or teething.<ref name="mayo clinic website" /> Awake bruxism usually involves clenching<ref name="Shetty 2010" /> (sometimes the term "awake clenching" is used instead of awake bruxism),<ref name="Manfredini 2009">{{cite journal |vauthors=Manfredini D, Lobbezoo F |title=Role of psychosocial factors in the etiology of bruxism |journal=Journal of Orofacial Pain |volume=23 |issue=2 |pages=153–66 |year=2009 |pmid=19492540}}</ref> but also possibly grinding,<ref name="Cawson 2002" /> 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).<ref name="Cawson 2002" />

There is evidence that sleep bruxism is caused by mechanisms related to the [[central nervous system]], involving [[Parasomnia|sleep arousal]] and [[neurotransmitter]] abnormalities.<ref name="Wassell 2008" /> Underlying these factors may be psychosocial factors including daytime [[stress (psychology)|stress]] which is disrupting peaceful sleep.<ref name="Wassell 2008" /> 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.<ref name="Lavigne 2007">{{cite journal |vauthors=Lavigne GJ, Huynh N, Kato T |title=Genesis of sleep bruxism: motor and autonomic-cardiac interactions |journal=Archives of Oral Biology |volume=52 |issue=4 |pages=381–4 |date=April 2007  |pmid=17313939 |doi=10.1016/j.archoralbio.2006.11.017|display-authors=etal}}</ref> It has been shown that the majority (86%) of sleep bruxism episodes occur during periods of sleep arousal.<ref name="Lavigne 2007" /> One study reported that sleep arousals which were experimentally induced with sensory stimulation in sleeping bruxists triggered episodes of sleep bruxism.<ref name="LOBBEZOO 2006" /> Sleep arousals are a sudden change in the depth of the sleep stage, and may also be accompanied by increased heart rate, respiratory changes and muscular activity, such as leg movements.<ref name="Shetty 2010" /> Initial reports have suggested that episodes of sleep bruxism may be accompanied by gastroesophageal reflux, decreased esophageal [[pH]] (acidity), swallowing,<ref name="LOBBEZOO 2006" /> and decreased salivary flow.<ref name="Macedo 2009" /> Another report suggested a link between episodes of sleep bruxism and a [[supine position|supine sleeping position]] (lying face up).<ref name="LOBBEZOO 2006" />

Disturbance of the dopaminergic system in the central nervous system has also been suggested to be involved in the etiology of bruxism.<ref name="Macedo 2009" /> Evidence for this comes from observations of the modifying effect of medications which alter dopamine release on bruxing activity, such as levodopa, amphetamines or nicotine. [[Nicotine]] stimulates release of dopamine, which is postulated to explain why bruxism is twice as common in smokers compared to non-smokers.<ref name="Shetty 2010" />