The influence of orthodontic extraction treatment on dental structures: A two-factor evaluation

Abstract

The purpose of this investigation was to evaluate the effects of different growth patterns and treatment types on dentoalveolar structures in patients treated with fixed Edgewise mechanics and the extraction of four first premolars. A total of 41 patients with a mean chronological age of 14 years 7 months and skeletal age of 14 years 6 months were included in the study. The type of growth pattern was assessed as mesio- or hyper-divergent, and the treatment type as the use or non-use of headgear. The results were analysed by two-way analysis of variance (ANOVA). The decrease in overbite in the mesiodivergent group was statistically significant when compared with the increase in the hyperdivergent group (P < 0.01). Extrusion of the lower molar was observed in all groups, and a statistically significant difference was found between the mesio- and hyperdivergent groups (P < 0.05). Interaction between growth pattern and treatment type was not found to be significant for any variable. It can be concluded that premolar extractions and the use of headgear with fixed appliances does not significantly change the overjet, occlusal plane angle, upper and lower anterior dentoalveolar heights, upper posterior dentoalveolar height, or the inclination of the upper and lower incisors. The only significant changes were observed in overbite as a result of treatment mechanics and in lower posterior dentoalveolar height due to the growth pattern.