Bone-borne surgically assisted rapid maxillary expansion: A retrospective three-dimensional evaluation of the asymmetry in expansion

Abstract Purpose Asymmetrical expansion occurs in patients treated with Surgically Assisted Rapid Maxillary Expansion (SARME). In the clinical setting, this asymmetrical expansion is seen in multiple directions. However, the frequency, actual directions and amount of asymmetry are unclear. Hence, the aim of this study was to analyze the directions and amount of asymmetrical lateral expansion in non-syndromic patients with transversal maxillary hypoplasia on employing bone-borne transpalatal distraction by means of SARME. Treatment involved corticotomies of all four bony supports, including pterygomaxillary disjunction. Materials and methods A retrospective case series was formed from patients treated with SARME. Pre- and postdistraction Cone Beam Computed Tomography scans were superimposed. A reference frame was created to analyze lateral expansion asymmetries in five directions. Results Clinical relevant asymmetries (>3.0 mm) in at least one of the investigated directions occurred in 55% of the patients. Lateral expansion asymmetries occurred mostly in the inferior-anterior part between the left and right segment and asymmetry in total expansion was noted between the anterior and posterior part of the maxilla. Conclusion This study confirms the clinical suspicion that using SARME with a bone-borne distractor and pterygomaxillary disjunction to treat non-syndromic patients with transversal maxillary hypoplasia, results in regular asymmetrical lateral expansion.