Which one closes extraction spaces faster: En masse retraction or two-step retraction? A randomized prospective clinical trial

Objectives: To compare the time to close extraction spaces between en masse (ER) and two-step retraction (TSR). Materials and Methods: Forty-eight patients with bimaxillary protrusion underwent treatment with extraction of four first premolars. All patients were randomly allocated to one of two groups: ER (n ¼ 24) or TSR (n ¼ 24). The main outcome was the time required to close spaces between ER and TSR; the closing time of spaces between females and males was a secondary outcome. The size of premolars was measured on the models and data were collected on clinical records at the following times: retraction start date (T1) and space closure completion date (T2). The total time to close the extraction spaces was calculated for each extracted premolar (T1 to T2). The Kaplan Meier method and the Log-Rank test were used to compare the groups. Results: The time to close extraction spaces showed significant differences between the ER and TSR groups. While ER took between 12.1 and 13.8 months, TSR took between 24.7 and 26.8 months. The TSR group showed a significant difference between sexes; male patients took 5.5 months longer than female patients for the extraction spaces to close. Conclusions: TSR takes between 1.8 and 2.2 times longer than ER to close the extraction spaces and it took longer in males than females.