ORIGINAL ARTICLE Treatment effects of mini-implants for en-masse retraction of anterior teeth in bialveolar dental protrusion patients: A randomized controlled trial Madhur Upadhyay, a Sumit Yadav, b K Nagaraj, c and Sameer Patil d Farmington, Conn, Indianapolis, Ind, and Belgaum, India 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 cephalo- grams 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. (Am J Orthod Dentofacial Orthop 2008;134:18-29) B ialveolar dental protrusion is common in many ethnic groups around the world. 1-3 It is charac- terized by dentoalveolar flaring of both the maxillary and mandibular anterior teeth with resultant protrusion of the lips and convexity of the face. Dentists often refer to this condition as just “bimaxil- lary protrusion,” a simpler term but a misnomer, since it is not the jaws but the teeth that protrude. 4 The present trend to treat bialveolar protrusion is extraction of the 4 first premolars, followed by anterior tooth retraction to obtain the desired dental and soft-tissue profile changes. Several authors have reported definite correlations between incisor movements and changes in the overly- ing soft-tissue profile. Drobocky and Smith 5 showed that 95% of the patients with 4 premolars extracted had decreased lip protrusion relative to the E-line, with averages of 3.4 mm for the upper lip and 3.6 mm for the lower lip. In another study, it was shown that a 1-mm mandibular incisor tip retraction produced 0.4 mm of retraction of the most anterior point on the upper lip and 0.6 mm of retraction of the lower lip. 6 Furthermore, it was reported that maxillary incisor retraction causes upper lip retraction, increases lower lip length, and increases the nasolabial angle, 7 whereas mandibular incisor position determines lower lip position and shape. 8 Although much research regarding soft-tissue re- sponse to anterior tooth retraction has been performed, a Fellow, Division of Orthodontics, Department of Craniofacial Sciences, School of Dental Medicine, University of Connecticut, Farmington, CT; Assistant professor and researcher, Department of Orthodontics, KLES’ Acad- emy of Higher Education and Research, Belgaum, India. b PhD student, Dental Sciences, Mineralized Tissue Histology and Research Laboratory, Section of Orthodontics, Indiana School of Dentistry, Indiana University-Purdue University, Indianapolis, Ind. c Assistant professor, Department of Orthodontics, KLES’ Institute of Dental Sciences, Belgaum, India. d Professor, Department of Orthodontics, KLES’ Academy of Higher Education and Research; consultant orthodontist, Cleft & Craniofacial Unit, KLES Hospital & Medical Research Center, Belgaum, India; The Smile Train Project, New York, NY. Reprint requests to: Madhur Upadhyay, Division of Orthodontics, Department of Craniofacial Sciences, School of Dental Medicine, University of Connecti- cut, Farmington, CT 06030; e-mail, madhurup@yahoo.com. Submitted, December 2006; revised and accepted, March 2007. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.03.025 18