Irfan Sarah, Fida Mubassar
Section of Dentistry, Department of Surgery, Aga Khan University Hospital, Karachi, Pakistan.
Dent Med Probl. 2019 Jul-Sep;56(3):257-263. doi: 10.17219/dmp/109568.
Orthodontic treatment modalities and biomechanics are important factors influencing soft and hard tissues.
The aim of this study was to compare soft and hard tissue changes after implementing asymmetric and symmetric extraction patterns.
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.
In the symmetric group, the preand post-treatment values for all soft tissue variables, upper incisor-sella-nasion plane angle (UI-SN), lower incisor mandibular plane angle (L-IMPA), and Frankfurtmandibular 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 preand 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.
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.
正畸治疗方式和生物力学是影响软硬组织的重要因素。
本研究旨在比较采用不对称和对称拔牙模式后软硬组织的变化。
采用一家三级医院牙科诊所62例患者的正畸档案进行回顾性横断面研究。患者分为2组，每组31例。第1组为对称拔牙模式（SEP），第2组为不对称拔牙模式（AEP）。采用Wilcoxon符号秩检验确定初始和最终头影测量参数之间的差异。采用Mann-Whitney U检验比较SEP和AEP之间的治疗变化。将SEP和AEP组进一步分为亚组进行分析。采用Kruskal-Wallis检验确定不同亚组之间头影测量变化的显著差异。为了进一步确定组间差异，使用Mann-Whitney U检验对亚组进行两两比较。
在对称组中，所有软组织变量、上切牙-蝶鞍-鼻根平面角（UI-SN）、下切牙-下颌平面角（L-IMPA）和法兰克福-下颌平面角（FMA）的治疗前后值均有显著差异（p≤0.05）。在不对称组中，软组织参数的治疗前后值均无显著差异；然而，FMA和L-IMPA有显著差异（p≤0.05）。SEP和AEP组之间的UI-SN和FMA参数以及除Z角（Z）外的所有软组织变量均有显著差异。采用Kruskal-Wallis检验比较亚组之间头影测量变化的中位数和四分位数间距（IQR）。除Z角外的所有软组织参数均有显著差异。
对称拔牙模式会使患者侧貌发生更大变化，而不对称拔牙可用于纠正咬合差异，而无侧貌变平的风险。在采用拔除前磨牙以降低面部高度时，必须充分考虑生物力学因素。
