Comparison of soft and hard tissue changes between symmetric and asymmetric extraction patterns in patients undergoing orthodontic extractions

Abstract

Background. Orthodontic treatment modalities and biomechanics are important factors influencing soft and hard tissues. Objectives. The aim of this study was to compare soft and hard tissue changes after implementing asymmetric and symmetric extraction patterns. Material and methods. A retrospective cross-sectional study was conducted using the orthodontic files of 62 patients from the dental clinics of a tertiary care hospital. Patients were divided into 2 groups, each of 31 patients. Group 1 referred to the symmetric extraction patterns (SEP), whereas group 2 regarded the asymmetric extraction patterns (AEP). The Wilcoxon signed-rank test was used to determine differences between the initial and final cephalometric parameters. The Mann–Whitney U-test was used to compare the treatment changes between SEP and AEP. The SEP and AEP groups were divided into subgroups for further analyses. The Kruskal–Wallis test was used to determine significant differences in the cephalometric changes among the different subgroups. In order to further establish inter-group differences, a pairwise comparison between the subgroups was made using the Mann–Whitney U-test. Results. In the symmetric group, the pre-and post-treatment values for all soft tissue variables, upper incisor-sella-nasion plane angle (UI-SN), lower incisor mandibular plane angle (L-IMPA), and Frankfurt-mandibular plane angle (FMA) showed significant differences (p ≤ 0.05). In the asymmetric group, none of the soft tissue parameters showed any significant difference in the pre-and post-treatment values; however, FMA and L-IMPA differed significantly (p ≤ 0.05). The parameters UI-SN and FMA as well as all soft tissue variables except Z-angle (Z), were significantly different between the SEP and AEP groups. The medians and interquartile ranges (IQRs) of the cephalometric changes among the subgroups were compared using the Kruskal–Wallis test. All soft tissues parameters except Z showed significant differences. Conclusions. The symmetric extraction patterns leads to a greater change in the patient’s profile, whereas asymmetric extractions can be carried out to remedy occlusal discrepancies without the risk of profile flattening. While employing premolar extractions aiming to reduce the facial height, due consideration with respect to biomechanics must be given.