Stabilität kieferorthopädischer Behandlungsergebnisse im unteren Zahnbogen nach Nonextraktionstherapie im Vergleich zu Extraktionstherapie der ersten Prämolaren unter Verwendung von passiven selbstligierenden Brackets

Abstract

Purpose This study aimed to evaluate the effects of lower premolar extraction on posttreatment stability one year following fixed orthodontic treatment with passive self-ligating brackets (Damon system, Ormco, Orange, CA, USA). Methods All patients were treated with fixed orthodontic appliances using passive self-ligating brackets (Damon). For retention, removable Hawley retainers were used. Two groups of patients were included in the study. Each group consisted of 23 patients: group Ex consisted of 10 male and 13 female patients (13.4 ± 1.6 years old) with extraction of lower first premolars and group NonEx consisted of 11 male and 12 female patients (13.4 ± 3.9 years old) without dental extractions. The patients’ dental models and photographs were assessed at T0 (pretreatment), T1 (the end of active orthodontic treatment: 3.3 ± 1.0 years in the Ex and 2.3 ± 0.8 years in the NonEx group) and at T2 (1 year posttreatment). All lower casts were scanned and the following dental parameters were recorded and compared between the two groups: intercanine width (ICW), anterior arch width (AAW), intermolar width (IMW), Little’s irregularity index (LII) and gingival recessions. Results An increase in ICW (group Ex: 1.20 ± 2.51 mm and group NonEx: 0.84 ± 1.48 mm) by the end of active treatment (T1; P < 0.05), as well as a relapse regarding the ICW (group Ex: −0.1 ± 0.47 mm and group NonEx: −67% ± 0.38 mm) one year post-treatment (T2) were recorded in the samples. Relapse in the non-extraction group was statistically and clinically significant, whereas ICW values remained relatively stable in the extraction group during the posttreatment period (T1–T2). The irregularity index decreased during treatment (group Ex: −8.79 ± 6.36 mm and group NonEx: −5.24 ± 2.99 mm) and relapsed in both groups (group Ex: 0.57 ± 90 mm and group NonEx: 0.27 ± 0.53). The rate of relapse in LII was correlated to the relapse rate of ICW. A reduction of IMW was recorded in the Ex group (−1.89 ± 1.82 mm) during active treatment (P < 0.05), which remained stable 1 year posttreatment. AAW increased in both groups (group Ex: 2.77 ± 1.77 mm and group NonEx: 1.77 ± 2.04 mm) throughout active treatment and remained stable at T2. Conclusion Intergroup comparison revealed that ICW remained stable 1 year posttreatment in the Ex group, whereas high relapse of ICW was recorded in the NonEx group. Furthermore, risk of a relapse of LII appears to be higher in cases with a relapse of the ICW.