ORIGINAL ARTICLE Evaluation of orthodontic mini-implant anchorage in premolar extraction therapy in adolescents Judah S. Garfinkle, a Larry L. Cunningham, Jr, b Cynthia S. Beeman, c G. Thomas Kluemper, d E. Preston Hicks, e and Mi-Ok Kim f Portland, Ore, Lexington, Ky, and Cincinnati, Ohio Introduction: The purpose of this study was to determine the success rate, positional stability, and patient evaluation of orthodontic mini-implants (OMIs). Methods: Thirteen patients (8 girls, 5 boys; average age, 14 years 10 months) were treated with 82 OMIs measuring 1.6 mm in diameter and 6 mm in length placed in the buccal alveoli (1 unloaded OMI and 1 loaded OMI per quadrant). The right or left side of each arch was randomly selected for immediate loading with up to 250 g of direct force; the contralateral side was loaded 3 to 5 weeks later. Serial impressions, clinical observations, and orthodontic maintenance were performed until adequate space closure was achieved. Results: The overall OMI success rate was 70.73%. As calculated with a mixed-model analysis, there was no statistically significant difference between the success rates of immediately loaded OMIs (80.0%) and delayed loaded OMIs (80.95%). The combined success rate for loaded OMIs (80.49%) was significantly higher than that of unloaded OMIs (60.98%). Patients’ motivation for OMI treatment was primarily the desire to avoid headgear. Using a 100-mm visual analog scale, the patients indicated average scores of 54.77 for the amount of pain during OMI placement and 27.10 for the amount of pain during OMI removal. Conclusions: OMIs are a predictable, effective, and well-tolerated anchorage source for adolescents. Neither the timing of force application nor the force itself precipitated failure of the OMIs. Orthodontic forces can be applied immediately to OMIs. Various anatomic and behavioral conditions unique to adolescents and a clinical learning curve can affect the success rate of OMIs. (Am J Orthod Dentofacial Orthop 2008;133:642-53) D uring orthodontic treatment, achieving maxi- mum or absolute anchorage with traditional approaches can be a biomechanical challenge. Attempts at overcoming this challenge have led to extensive investments of both clinical and academic resources. The search for an ideal anchorage unit has resulted in bone-borne, or skeletal, anchorage devices that do not rely on patient compliance, soft tissues, or the dentition. Over the last 60 years, skeletal anchorage devices have used various materials, designs, and placement locations. 1 Although most of these devices have quickly fallen into and out of favor, some have proved to be effective in providing maximum or abso- lute orthodontic anchorage. In 1997, Kanomi 2 published a case report on the use of mini-implants for orthodontic anchorage. These de- vices held promise as a low-cost anchorage technique that would be well tolerated by patients, would be clinically and anatomically flexible, and could be loaded immedi- ately. That report started intense clinical interest in and experimentation with orthodontic mini-implants (OMIs), a term that concisely communicates the function (ortho- dontic), the size (mini: diameter 2 mm), and the shape of the device implant. From the growing body of case reports 2-27 and clinical animal 28-31 and human studies 32-39 with OMIs, it is possible to draw some conclusions and identify some aspects that require further clarification. OMIs can offer great anatomic and biomechanical flexibility in providing anchorage for the effective movement of teeth. The risks to soft tissue, bone, teeth, and other a Director of craniofacial orthodontics and assistant professor, Department of Plastic Surgery and Orthodontics, Oregon Health and Science University; private practice, Portland, Ore. b Associate professor and residency director, Oral and Maxillofacial Surgery, College of Dentistry, University of Kentucky, Lexington. c Associate professor, Department of Orthodontics, College of Dentistry, University of Kentucky, Lexington. d Division chief and associate professor, Department of Orthodontics, College of Dentistry, University of Kentucky, Lexington. e Program director and associate professor, Department of Orthodontics, Col- lege of Dentistry, University of Kentucky, Lexington. f Assistant professor, Center for Epidemiology and Biostatistics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio. This study was awarded the 2006 AAO Harry Sicher First Research Essay Award. Reprint requests to: Judah S. Garfinkle, 1616 SW Sunset Blvd. Su. G, Portland, OR 97239; e-mail, judah@garfinkleortho.com. Submitted, February 2006; revised and accepted, April 2006. 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2006.04.053 642