The relationship between posterior crossbites and temporomandibular disorders
Thilander B, Bjerklin K. Posterior crossbite and temporomandibular disorders (TMDs): need for orthodontic treatment? Eur J Orthod 2011 Sep 6 [Epub ahead of print]
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 n = 6675) and 6 reported no association (total n = 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 = 5226). Forced guidance of the mandible could result in asymmetric activity of the masticatory muscles, thus modifying growth and development. When the mandible 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
Transversal maxillary dentoaveolar changes with self-ligating brackets
Cattaneo P, Treccani M, Carlsson K, Thorgeirsson T. Transversal maxillary dento-alveolar changes in patients treated with active and passive self-ligating brackets: a randomized clinical trial using CBCT-scans and digital models. Orthod Craniofac Res 2011;14:222-33
The aim of this randomized clinical trial was to compare the outcome of treatments with active or passive self-ligating brackets. Pretreatment and posttreatment cone-beam computed tomography scans and digital models were used to assess transversal tooth movement and buccal bone modeling of the maxillary lateral segments. Forty-one patients from the orthodontic department at Aarhus University in Denmark were randomly selected and assigned to either a passive self-ligating group (Damon 3 MX) or an active self-ligating group (In-Ovation R). Measurements before and after treatment were made on cone-beam computed tomography scans and digital models by a blinded observer. T tests were used to statistically analyze the differences between transversal expansion, buccolingual inclination, and bone area modeling. The results showed that transversal expansion was achieved by buccal tipping in all but 1 patient in each group. There were no noted differences in the buccolingual inclination of the maxillary posterior teeth between the 2 groups. The bone areas buccal to the second premolars decreased by an average of 20% in the passive self-ligating group and by 14% in the active self-ligating group. This study showed that, despite dental expansion, hardly any buccal bone augmentation could be seen. Despite limitations in the measurement of alveolar bone changes on the cone-beam computed tomography images, the authors reported that the expected expansion by translation and buccal bone modeling using active or passive self-ligating brackets could not be confirmed. Individual factors such as initial tooth inclination and occlusion influenced the treatment outcomes; therefore, the authors recommended performing future, patient-specific analyses.
Reviewed by Jamie Haas
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