Rapid palatal expansion (RPE): Meta-analysis of long-term effects

Rapid palatal expansion (RPE) is a widespread orthopaedic procedure used in several clinical situations. The aim of the study was to provide a systematic review and meta-analysis of transverse intercanine and intermolar width changes after RPE and long-term effects. SETTING AND SAMPLE POPULATION: A systematic literature search was conducted until January 2018 on original studies with RPE treatment. MATERIAL AND METHODS: Intercanine and intermolar distance were measured at the start of RPE (T1, median age 9.2 years) and at the end of treatment (T2). The long-term evaluation was conducted on a subset of articles with 5-year follow-up (T3). RESULTS: Eighteen studies T1-T2 and 5 studies T3 were selected. Regarding the intercanine distance, the RPE resulted in a gain of space T1-T2 of 3.73 mm with a significant heterogeneity (P < 0.0001; I2 = 94.21%) and a relapse T2-T3 of -0.81 mm with a significant heterogeneity (P < 0.0001; I2 = 95.8%); the overall gain of space was 2.91 mm. Regarding the intermolar distance, the RPE resulted in a gain of space T1-T2 of 4.85 mm with a significant heterogeneity (P < 0.0001; I2 = 92.41%) and a relapse T2-T3 of -0.47 mm with a significant heterogeneity (P < 0.0001; I2 = 87.5%); the overall gain of space was 4.38 mm. Meta-regression analysis showed that at younger age, the amount of anterior expansion is similar to posterior. With increasing age, the anterior opening diminishes significantly more than the posterior, being half of the posterior at 15 years. CONCLUSION: Because long-term results were obtained with simultaneously fixed appliances and long upper retention, RPE should be carefully considered before using.