Orthognathic treatment and temporomandibular disorders - part 1.

DATA SOURCES: MEDLINE, bibliographies, and reference lists of identified publications and reviews, were utilised, along with personal communications with experts and specialists. STUDY SELECTION: Randomised controlled trials (RCT), cohort studies and case-control studies were included if participants (of age 14 years or over) received orthognathic treatment. Studies were excluded if participants had either craniofacial syndromes or cleft lip or palate; a history of facial fractures from trauma; were undergoing orthognathic surgery purely to correct TMD; or orthognathic treatment and concomitant joint disc surgery; or, finally, if they were animal studies. DATA EXTRACTION AND SYNTHESIS: Data extraction was conducted independently by two reviewers, and any discrepancies discussed until agreement was reached. A quality-assessment scale was constructed specifically for this study with sections for selection, performance, measurement and outcome, and attrition. A narrative synthesis is presented as meta-analysis was not either feasible or appropriate.
RESULTS: A total of 53 articles (41 cohorts, 8 case-control and 3 RCT) were analysed for the review. Almost half (20) did not explicitly state whether the study was retrospective or prospective, it could be determined for the majority with 21 being retrospective, 28 prospective and, in the case, four articles not being sufficiently clear. There was great variability between studies in their assessment of any association between TMD and orthognathic treatment. This variability included how TMD was classified, the signs and symptoms recorded, and the time intervals reported. Perhaps most important was the great variation in the malocclusions in the studies. Although some studies included participants with a specific skeletal discrepancy, others included various skeletal deformities, so that comparisons were not always possible and, when carried out, could be a source of heterogeneity. Most studies that did report a reduction in TMD signs and symptoms after orthognathic treatment reported this association in skeletal Class II patients. A decrease was reported in some studies in the prevalence of signs and symptoms of more than 50% of people postsurgery, compared with the presurgery state, whereas fewer subjects with skeletal Class III or a high mandibular plane angle seemed to benefit from surgery. Thus, the participants' skeletal deformity could have had a direct impact on TMD, especially after surgery.
CONCLUSIONS: The diversity of diagnostic criteria and classification methods used in the included studies makes interstudy comparisons difficult. Well-designed studies are needed that have standardised diagnostic criteria and classification methods for TMD.