Treatment effects of mini-implants for en-masse retraction of anterior teeth in bialveolar dental protrusion patients: a randomized controlled trial.

INTRODUCTION: The purpose of this randomized controlled trial was to quantify the treatment effects of en-masse retraction of anterior teeth with mini-implants as anchor units in bialveolar dental protrusion patients undergoing extraction of all 4 first premolars.

METHODS: A total of 40 patients (mean age, 17.5 years; SD, 3.2 years) were randomly assigned either to group 1 (G1), anterior space closure with mini-implants as anchor units, or group 2 (G2), anterior space closure with conventional methods of anchorage (without mini-implants). Skeletal, dental, and soft-tissue changes were analyzed in both groups on lateral cephalograms taken before retraction and after space closure.

RESULTS: Student paired and unpaired t tests were used to analyze the treatment changes in the 2 groups. For the skeletal parameters, a statistically significant decrease in the facial vertical dimensions was seen in G1, but the variables in G2 showed no significant differences (P >0.05). Anchorage loss, in both the horizontal and vertical directions, was noted in G2, whereas G1 showed distalization (anchorage gain) and intrusion of molars. Although the soft-tissue response was variable, facial convexity angle, nasolabial angle, and lower lip protrusion had greater changes in G1. No differences were found in the amount of upper lip retraction between the groups (P >0.05).

CONCLUSIONS: Mini-implants provided absolute anchorage to allow greater skeletal, dental, and esthetic changes in patients requiring maximum anterior retraction, when compared with other conventional methods of space closure. The treatment changes were favorable. However, no differences in the mean retraction time were noted between the 2 groups.