title: Association between posterior crossbite, masticatory muscle pain, and disc displacement: a systematic review.
abstract: BACKGROUND
  Among different malocclusions, posterior crossbite is thought to have a strong impact on the correct functioning of the masticatory system.
  
  
  OBJECTIVE
  To assess, by systematically reviewing the literature, the association between posterior crossbite and different temporomandibular disorder (TMD) diagnosis: disc displacement and masticatory muscle pain.
  
  
  METHODS
  A literature survey covering the period from January 1965 to April 2012 was performed. Two reviewers extracted the data independently and assessed the quality of the studies.
  
  
  RESULTS
  The search strategy resulted in 2919 citations, of which 43 met the inclusion criteria. The scientific and methodological quality of these studies was found to be medium-low, independently by association reported. In several studies, posterior crossbite is reported to be associated to the development of disc displacement, muscular pain, and tenderness, possibly linked to a skeletal and muscular adaptation of the stomatognathic system. However, the lack of consistency of the results reported deeply reduces the external validity of the studies, with a consequent impossibility to draw definite conclusions.
  
  
  CONCLUSIONS
  It is not possible to establish an association between posterior crossbite, muscle pain, and disc displacement because the distribution of the studies supporting or not supporting the association is similar. The consequences of posterior crossbite on the development of TMDs deserve further investigations, with high sample size, well-defined diagnostic criteria, and rigorous scientific methodologies. Finally, long-term controlled studies are needed to identify posterior crossbite as a possible risk factor for TMDs.
authors.affiliation: Department of Dental and Maxillo-Facial Sciences, Section of Orthodontics and Gnathology, University of Naples 'Federico II' and.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Iodice
authors.forename: Gianluca
authors.initials: G
authors.lastname: Danzi
authors.forename: Roberta
authors.initials: R
authors.lastname: Cimino
authors.forename: Sergio
authors.initials: S
authors.lastname: Paduano
authors.forename: Ambra
authors.initials: A
authors.lastname: Michelotti
mesh_terms: D006801:Humans; D007405:Intervertebral Disc Displacement / Q000175:diagnosis / Q000453:epidemiology*; D008310:Malocclusion / Q000175:diagnosis / Q000453:epidemiology*; D008410:Masticatory Muscles / Q000503:physiopathology*; D063806:Myalgia / Q000175:diagnosis / Q000453:epidemiology*; D018401:Sample Size; D013705:Temporomandibular Joint Disorders / Q000175:diagnosis / Q000453:epidemiology*