ONLINE ONLY Noncompliance maxillary molar distalization with the First Class Appliance: A randomized controlled trial Moschos A. Papadopoulos, a Aristides B. Melkos, b and Athanasios E. Athanasiou c Thessaloniki and Evosmos, Greece Introduction: The aim of this study was to evaluate the treatment effects of the First Class Appliance (FCA) (Leone, Firenze, Italy) used for the distalization of maxillary first molars in patients with Class II malocclusion and mixed dentition. Methods: According to the results of the power analysis for sample size calculation, 32 consecutive patients with bilateral Class II molar relationships were initially included in the study. After appli- cation of the inclusion and exclusion criteria, 26 patients remained for the final evaluation. They were random- ized into 2 groups: treatment group (n 5 15) and untreated control group (n 5 11). Lateral cephalograms and dental casts were obtained before and immediately after distalization for the treatment group, and initially and approximately 22 weeks later for the control group. Statistical evaluation of the variables included the mixed 2-way analysis of variance at P \0.05. The method error was also estimated. Results: The mean treatment period to achieve a full Class I molar relationship was 17.2 weeks. Analysis of the data showed significant distalization of the maxillary first molars produced by the FCA (mean: 4.00 mm) when compared with the untreated group (mean: 0.95 mm). The rate of molar movement was 1.00 mm per month, which, however, was associated with distal tipping of the first molars (8.56  ) and anchorage loss of the anterior dental unit in terms of overjet increase (0.68 mm), and mesial movement (1.86 mm) and inclination (1.85  ) of the first premolars or first deciduous molars. The maxillary first molars also moved buccally (1.37 mm), but no significant distal rotation occurred. Conclusions: The FCA is an efficient noncompliance appliance to distalize molars in the mixed dentition without distal rotations. However, these movements are associated with distal molar tipping and anchorage loss of the anterior teeth. (Am J Orthod Dentofacial Orthop 2010;137:586.e1-586.e13) A common strategy to treat Class II malocclu- sions by a nonextraction protocol is to initially distalize the maxillary molars to create a Class I relationship. Various concepts, biomechanics, and ap- pliances have been routinely used, including extraoral traction, removable appliances with springs, and Class II intermaxillary elastics. 1-6 Since the patients’ compliance is a presupposition for the effectiveness of these modalities, the development and use of techniques and appliances that minimize the need for patient cooperation provides a reliable and more predictable treatment alternative. 7 The category of non- compliance mechanics includes a variety of intramaxil- lary appliances such as Jones jig, distal jet, pendulum appliance, Keles slider, repelling magnets, compressed coil springs, molar distalizing bows, and orthodontic implants or miniscrew implants. 7-21 Noncompliance distalization methods, however, are not problem free. They have some undesirable side ef- fects that diminish their clinical effectiveness, including anchorage loss (posterior: distal molar crown tipping or distal rotation of molar crowns; anterior: mesial move- ment and proclination of the maxillary anterior teeth). These side effects can vary among the different tech- niques and appliances, but they are always associated with maxillary molar distalization. 11 Open-coil springs combined with various noncom- pliance appliances have been used for a long time to distalize maxillary molars. 13,17,22-24 The First Class Appliance (FCA) (Leone, Firenze, Italy) was recently introduced for unilateral or bilateral noncompliance distalization of the maxillary molars. 25-27 Until now, a Associate professor and program coordinator, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece. b Private practice limited to orthodontics, Evosmos, Greece. c Professor and head, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece. The authors report no commercial, proprietary, or financial interest in the products or companies described in this article. Reprint requests to: Moschos A. Papadopoulos, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, GR-54124 Thessalo- niki, Greece; e-mail, mikepap@dent.auth.gr. Submitted, July 2009; revised and accepted, October 2009. 0889-5406/$36.00 Copyright Ó 2010 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2009.10.033 586.e1