Residents' Journal Review Articles Selected and Reviewed By: Senior Orthodontic Residents, Arizona School of Dentistry and Oral Health

Temporomandibular disorder (TMD) is a generic term for several clinical signs and symptoms involving the masticatory muscles, the temporomandibular joints, and the associated head and neck structures. Clinical signs include clicking, disc displacement and tenderness on palpation of the masticatory muscles, and patient complaints of headaches. The authors noted that there is controversy on whether posterior crossbites are associated with TMD. Posterior crossbites can be classified into skeletal, dentoalveolar, and those associated with forced guidance of the mandible (functional types). The authors investigated whether certain signs or symptoms of TMD are associated with the types of posterior crossbite mentioned above. Comprehensive MEDLINE electronic database and hand searches from 1970 to 2009 were done, including only randomized controlled trials, retrospective studies with controlled groups, controlled clinical trials, and prospective studies. The searches yielded 14 articles, of which 8 reported an association with TMD (total n5 6675) and 6 reported no association (total n 5 6298). Many articles did not mention the type of posterior crossbite, although 3 reported the functional type and found it to be significantly associated with TMD signs and symptoms (n 5 5226). Forced guidance of the mandible could result in asymmetric activity of the masticatory muscles, thus modifying growth and development. When themandible is displaced into an intercuspal position, the condyle on the crossbite side would be forced upward and laterally against the glenoid fossa, resulting in a changed condylar position that could produce temporomandibular joint pain and clicking. These authors suggested a need to distinguish between the different types of crossbite in future studies and a need to intervene early when there is a functional crossbite. Reviewed by Leo Toureno