Three-dimensional insights into miniscrew-assisted rapid palatal expansion asymmetry: A novel cone-beam computed tomography-based analysis

Abstract

Introduction: Miniscrew-assisted rapid palatal expansion (MARPE) is a predictable option for nongrowing patients with maxillary transverse deficiency manifesting as posterior crossbite. However, recent evidence suggests a high frequency of asymmetrical expansion as a complication of MARPE. Methods: Retrospective analysis of 9 patients (mean age: 21.7 years; 65% female; average Yonsei Transverse Index: -4.6 mm) included superimposition of pre (T1) and posttreatment (T2) cone-beam computed tomographies using a voxel-based technique on the anterior cranial base. T1 and T2 cone-beam computed tomographies were digitized in a common Cartesian plane, enabling linear and angular measurements using T1 landmarks as the reference to compare T2 landmarks. Geometric analyses included linear Euclidean left vs right and transverse distances, 3-dimensional (3D) angulation, and 3D matrix rotations to quantify asymmetry. Asymmetry thresholds were set at 2 mm or 2 degrees. Stepwise regression was used to determine the association between potential explanatory variables and asymmetry. Results: There was no statistically or clinically significant asymmetry of the ANS-PNS vector. Linear, angular, or zygomaticomaxillary roll of jugale, keyridge, or zygomaticofrontal suture around the ANS-PNS vector was found (P >0.05). Statistically but not clinically significant linear asymmetry of keyridge (0.9 +/- 0.9 mm; P = 0.02) and first molar furcation (0.7 +/- 0.8 mm; P = 0.02) was found. Stepwise regression did not find any potential explanatory variables explaining the keyridge and the first molar furcation linear asymmetry. Conclusions: Under the conditions of this study and 3D analyses, MARPE resulted in statistically significant linear asymmetry of the keyridge and the first molar furcation. Statistical significance does not equate clinical significance or relevance.