Does extraction patterns influence craniofacial vertical dimension in orthodontic treatment

Objectives: It's believed that extraction of posterior teeth is favorable for the subjects with excessive vertical dimension than anterior teeth in orthodontics while the rationale for it is still uncertain. So this paper was designed to investigate whether different extraction patterns may exert different effects on craniofacial vertical dimension in orthodontic treatment. Methods: 43 subjects were divided into two groups. Group A included 26 patients aged from 14.1 to 19.6, for whom extraction of four first premolars was the first step of orthodontic plan. While group B consisted of 17 subjects aged from 15.2 to 17.8, whom had their four fifth premolars extracted for orthodontic treatment. No anchorage reinforcement was introduced. Treatment procedure followed MBT technique principles strictly. Cephalograms were taken on each subject before and after orthodontic treatment respectively. Cephalometrics was performed to evaluate the vertical dimension regarding to the skeletal and the dental. Independent-samples t test was used to evaluate vertical dimension between group A and B before treatment. One-sample t test was employed to compare the measurements before and after orthodontic treatment within either group A or B. Results: Initially, there is no significant difference between group A and B (P>0.05) in vertical plane of space. After orthodontic treatment, no significant skeleton difference was found in each group by comparing items before and after (P>0.05). As to dental position, little difference emerged and did not get to the significant level (P>0.05). Conclusions: During orthodontic treatment, different extraction patterns had no effect on craniofacial vertical dimension both in terms of the skeletal and the dental. So during orthodontic treatment planning, it's inappropriate to rely on posterior teeth extraction to control vertical dimension in vertical excess cases.