Vertical changes in Class I malocclusion between 2 different extraction patterns

Objectives: To compare vertical changes occurring in Class I patients after orthodontic treatment with different extraction patterns in a retrospective study. Methods: Records of 47 patients with extraction of maxillary first premolars and mandibular second premolars (4/5, Group A) and 46 patients with extraction of fourth first premolars (4/4, Group B) were obtained in the Orthodontic Department, West China Hospital of Stomatology, Chengdu, Sichuan, China from April 2008 to July 2012. Pretreatment and posttreatment cephalograms were digitized, 8 skeletal and 10 dental cephalometric measurements were selected to evaluate vertical changes. Changes of measurements resulting from orthodontic treatment in each group were compared by paired t-test; changes between 2 groups were compared by Independent t-test. Results: Before treatment, subjects in Group A showed larger angle formed by the intersection of NA and NB lines, overjet, and overbite than those in Group B. After treatment, both groups showed significant vertical changes after orthodontic treatment without remarkable differences between groups. Conclusion: No differences of vertical change were found between the 2 extraction patterns. The hypothesized wedge effects due to mesial movement of posterior teeth might be balanced by the extrusion of posterior teeth as well as the residual growth potentials.