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3D mandibular positioning after rapid maxillary expansion in Class II malocclusion
Carolina Baratieri1, Matheus Alves, Eduardo Franzotti Sant'anna
1Department of Orthodontics, Dental School, University of Rio de Janeiro, RJ, Brazil.
Brazilian Dental Journal
|October 21, 2011
Summary
Rapid maxillary expansion (RME) in children with Class II Division 1 malocclusion caused temporary downward and backward mandibular positioning. A 6-month retention period resulted in significant forward mandibular shift, improving the initial position.
Area of Science:
- Orthodontics
- Craniofacial Imaging
- Pediatric Dentistry
Background:
- Class II Division 1 malocclusion often involves maxillary constriction.
- Rapid maxillary expansion (RME) is a common treatment for this condition.
- Understanding mandibular response to RME is crucial for treatment planning.
Purpose of the Study:
- To investigate the three-dimensional spatial positioning of the mandible following RME in Class II Division 1 malocclusion.
- To evaluate immediate and long-term mandibular changes after RME and retention.
Main Methods:
- Prospective study of 17 children (mean age 10.36 years) with Class II Division 1 malocclusion undergoing RME (Haas' protocol).
- Cone beam computed tomography (CBCT) scans taken before treatment (T1), immediately after expansion (T2), and after 6 months retention (T3).
- Mandibular landmarks analyzed using Dolphin Imaging software for transverse, anteroposterior, and vertical displacements; statistical analysis using paired Student's t-test (p<0.05).
Main Results:
- Immediately post-RME, the mandible showed significant downward displacement of gonion and menton, with backward displacement of menton.
- During the 6-month retention, significant forward displacement of gonion and menton was observed.
- No significant transverse (lateral) mandibular displacement was detected throughout the study.
Conclusions:
- RME in Class II Division 1 malocclusion induces a transient backward and downward mandibular repositioning.
- The retention phase facilitates a significant forward shift of the mandible, resulting in a more anterior position compared to baseline.
- CBCT assessment reveals dynamic mandibular changes following RME, highlighting the importance of the retention period.
