Bingshuang Zou

Introduction: Maxillary expansion is common in orthodontic practice and there are many different expansion protocols, including Alternating Rapid Maxillary Expansion and Constriction (Alt-RMEC). Objectives: to analyze the dentoalveolar, skeletal and circummaxillary sutural changes, using retrospective Cone Beam Computed Tomography (CBCT) records, to compare 2 different maxillary expansion protocols: conventional Rapid Maxillary Expansion (RME) and Alt-RMEC. Methods: Data was collected from 34 growing Class III (maxillary deficient) patients, aged between 7.2 – 12.5 years old, who were randomly 1:1 allocated to either treatment group. Pre-treatment (T0) and post-treatment (T1) CBCT records were used to measure dentoalveolar, skeletal and circummaxillary sutural variables. Cervical Vertebral Maturation Stage (CVMS) and Mid-Palatal Suture Density (MPSD) ratio were measured using pre-treatment CBCTs. Differences between the two protocols were analyzed using students’ t-tests and linear regression models. Results: both expansion protocols produced pyramidal expansion patterns, both anterior-posteriorly and inferior-superiorly, except at the anterior nasal level where Alt-RMEC resulted in parallel expansion. Alt-RMEC produced statistically and clinically significantly less amount of maxillary 1st molar tipping (P
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