Orthodontics and temporomandibular disorder: a meta-analysis.

As the importance of evidence-based health care has grown, meta-analysis has become more widely used in the medical and dental fields. In this meta-analysis, the relationship between traditional orthodontic treatment, including the specific type of appliance used and whether extractions were performed, and the prevalence of temporomandibular disorders (TMD) was investigated. After an exhaustive literature search of 960 articles, we found 31 that met the inclusion criteria (18 cross-sectional studies or surveys and 13 longitudinal studies). We divided and extracted data from the 31 articles according to study designs, symptoms, signs, or indexes. Due to severe heterogeneity, the results were summarized without further statistical analysis. The heterogeneous result might originate from lack of a universal diagnostic system and the variability of TMD. Because of heterogeneity, a definitive conclusion cannot be drawn. The data included in this comprehensive meta-analysis do not indicate that traditional orthodontic treatment increased the prevalence of TMD. It is apparent that a reliable and valid diagnostic classification system for TMD is needed for future research.