Systematic Review The effectiveness of non-surgical maxillary expansion: a meta-analysis

To evaluate and compare the effectiveness of rapid maxillary expansion (RME) and slow maxillary expansion (SME). Materials and methods: PubMed, Embase, Web of Science, CENTRAL, ProQuest Dissertations & Theses, ClinicalTrial.gov, and SIGLE were searched from January 1980 to October 2012 for randomized or nonrandomized controlled trials. The processes of study search, selection, and quality assessment were conducted independently and in duplicate. Original outcome data underwent statistical pooling through Review Manager 5. Results : Fourteen eligible studies were finally included and two interventions ( RME and SME) studied. Four outcomes ( maxillary intermolar width, maxillary intercanine width, maxillary interpremolar width, and mandibular intermolar width) during three time periods ( expansion, retention, and net change) were statistically pooled. The sensitivity analysis revealed that the results from the meta-analysis were generally robust. Egger's test and Begg's test detected no publication bias except for maxillary intercanine width in expansion period for SME versus control. Conclusions: SME is effective in expanding maxillary arch, while we cannot determine its effectiveness in mandibular arch expansion. RME is effective in expanding both maxillary and mandibular arches. Furthermore, SME is superior to RME in expanding molar region of maxillary arch, while similar with RME in mandibular arch expansion. However, we cannot compare their effectiveness in maxillary anterior region.