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UBC Theses and Dissertations

Comparison of transverse dentoalveolar and circummaxillary sutural changes in different maxillary expansion protocols : a retrospective study Thong, Emily Katherine Weng-Yun


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 < 0.05) and resulted in increased nasal aperture widening (P < 0.05) as a result of distraction of multiple midline craniofacial sutures. Males had larger amounts of posterior and middle palatal basal width expansion than females, with sex accounting for 20.0% and 20.5% of treatment change variation. Increasing CVMS and females produced larger amounts of right nasomaxillary suture opening, with both explanatory variables accounting for 34.0% of the variation in treatment change. Age and MPSD ratio were not correlated with any dentoalveolar, skeletal or sutural treatment change. Conclusions: our study found that RME and Alt-RMEC resulted in similar transverse dentoalveolar and skeletal measurements in addition to circummaxillary sutural changes. Aside from Alt-RMEC causing less maxillary 1st molar tipping and increased widening of the nasal aperture, the complexities of the protocol may not justify its use over conventional maxillary expansion in terms of maxillary expansion only. One should continue to consider factors such as age and skeletal maturity, as assessed by CVMS, when considering maxillary expansion in an orthodontic patient.

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