|Classification and external resources|
|ICD-10||K13.1 (ILDS K13.110)|
Morsicatio buccarum (also termed chronic cheek biting and chronic cheek chewing) is a condition characterized by chronic irritation or injury to the buccal mucosa (the lining of the inside of the cheek within the mouth), caused by repetitive chewing, biting or nibbling.
Since the lesion occurs on the buccal mucosa in the mouth, the ICD-10 classifies morsicatio buccarum under "diseases of oral cavity, salivary glands and jaws" and then under "other diseases of lip and oral mucosa". It could be considered a cutaneous condition, and really is a type of frictional keratosis. The term is derived from the Latin words, morusus meaning "bite" and bucca meaning "cheek". This term has been described as "a classic example of medical terminology gone astray".
Signs and symptoms 
The lesions are located on the mucosa, usually bilaterally in the central part of the anterior buccal mucosa and along the level of the occlusal plane (the level at which the upper and lower teeth meet). Sometimes the tongue or the labial mucosa (the inside lining of the lips) is affected by a similarly produced lesion, termed morsicatio linguarum and morsicatio labiorum respectively. There may be a coexistant linea alba which corresponds to the occlusal plane. The lesions are white with thickening and shredding of mucosa commonly combined with intervening zones of erythema (redness) or ulceration. The surface is irregular, and people may occasionally have lose sections of mucosa that comes away.
The cause is chronic parafunctional activity of the masticatory system, which produces frictional, crushing and incisive damage to the mucosal surface and over time the characteristic lesions develop. Most people are aware of a cheek chewing habit, although it may be performed subconsciously. Sometimes poorly constructed prosthetic teeth may be the cause if the original bite is altered. Usually the teeth are placed too far facially (i.e. buccally and/or labially), outside "the neutral zone", which is the term for the area where the dental arch is usually situated, where lateral forces between the tongue and cheek musculature are in balance. Glassblowing involves chronic suction and may produce similar irritation of the buccal mucosa. Identical, or more severe damage may be caused by self mutilation in people with psychiatric disorders, learning disabilities or rare syndromes (e.g. Lesch-Nyhan syndrome and familial dysautonomia).
The diagnosis is usually made on the clinical appearance alone, and biopsy is not usually indicated. The histologic appearance is one of marked hyperparakeratosis producing a ragged surface with many projections of keratin. Typically there is superficial colonization by bacteria. There may be vacuolated cells in the upper portion of the prickle cell layer. There is a similarity between this appearance and that of hairy leukoplakia, linea alba and leukoedema. In people with human immunodeficiency virus, who are at higher risk of oral hairy leukoplakia, a tissue biopsy may be required to differentiate between this and frictional keratosis from cheek and tongue chewing.
Treatment and prognosis 
The lesions are harmless, and no treatment is indicated beyond reassurance, unless the person requests it. The most common and simple treatment is construction of a specially made acrylic prosthesis that covers the biting surfaces of the teeth and protects the cheek, tongue and labial mucosa (an occlusal splint). This is either employed in the short term as a habit breaking intention, or more permanently (e.g. wearing the prosthesis each night during sleep). Psychological intervention is also reported, but does not appear to be beneficial.
This phenomenon is fairly common, with one in every 800 adults showing evidence of active lesions at any one time. It is more common in people who are experiencing stress or psychologic conditions. The prevalence in females is double the prevalence in males, and it is two or three times more prevalent in people over the age of thirty-five.
- Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0.[page needed]
- Scully, Crispian (2008). Oral and maxillofacial medicine : the basis of diagnosis and treatment (2nd ed. ed.). Edinburgh: Churchill Livingstone. pp. 223, 349. ISBN 9780443068188.
- "Online Etymology Dictionary". Retrieved 4 February 2013.
- Bouquot, Brad W. Neville , Douglas D. Damm, Carl M. Allen, Jerry E. (2002). Oral & maxillofacial pathology (2. ed. ed.). Philadelphia: W.B. Saunders. pp. 253–254. ISBN 0721690033.