Comparison of treatments with the Forsus fatigue resistant device in relation to skeletal maturity: A cephalometric and magnetic resonance imaging study Aynur Aras, a Emel Ada, b Hatice Saraco glu, c Naciye S. Gezer, d and Isil Aras e Izmir and Canakkale, Turkey Introduction: The aim of this study was to compare the dentoskeletal changes and alterations of mandibular condyle-disc-fossa relationships in subjects at the peak and the end of the pubertal growth period treated with the Forsus fatigue resistant device (3M Unitek, Monrovia, Calif). Methods: The sample consisted of 29 subjects with Class II Division 1 malocclusions who were classified according to their hand-wrist radiographs. Fifteen patients were at or just before the peak phase of pubertal growth (peak pubertal group). Fourteen patients were near the end of the pubertal growth period (late pubertal group). The study was conducted by using lateral cephalometric radiographs and magnetic resonance images obtained at the beginning and at the end of the application of the Forsus fatigue resistant device. The treatment period was 9 months. Results: The Wilcoxon signed rank test was used to evaluate differences within groups. The changes observed in both groups were com- pared by using the Mann-Whitney U test. There were statistically significant group differences in mandibular length and ramus length, with significant increases of these parameters in the peak pubertal group (P \0.05). No significant differences were observed between the groups concerning dental parameters (P .0.05), with the exception of mandibular molar vertical movements, which were significantly greater in the peak pubertal group (P \0.05). Analysis of the magnetic resonance images showed no positional changes of the mandibular condyle in relation to the glenoid fossa in either group (P .0.05). Although the articular disc was positioned more anteriorly in the peak pubertal group compared with its pretreatment position (P \0.05), the position of the disc was still within the physiologic range. No significant intergroup difference was observed for disc-condyle relationship (P .0.05). Conclusions: The Forsus fatigue resistant device did not appear to cause significant in- creases in mandibular dimensions in subjects in late puberty. According to the magnetic resonance image findings, Forsus treatment is not a risk factor for the development of temporomandibular dysfunction in subjects with no signs and clinical symptoms of dysfunction. (Am J Orthod Dentofacial Orthop 2011;140:616-25) C lass II malocclusions are a major part of ortho- dontic irregularities. The research suggests that mandibular retrognathia is the underlying cause, rather than maxillary prognathism. 1 In these patients, to stimulate mandibular growth by forward positioning of the mandible, removable or fixed functional orthope- dic appliances are used. 2-4 It has been reported that the effectiveness of func- tional therapy depends on both the treatment timing (skeletal maturity at the start of functional therapy) and the type of functional appliance. 5-7 According to several studies, mandibular growth can extend beyond puberty, and minimal residual growth can only be stimulated with fixed functional appliances. 8-12 Ruf and Pancherz, 9,10 Konik et al, 11 and Kinzinger and Diedrich 12 stated that the treatment of late adoles- cents and young adults with rigid fixed functional appli- ances such as the Herbst or functional mandibular advancer resulted in correction of the Class II malocclu- sion with the skeletal and dental changes. However, the a Professor, Department of Orthodontics, Faculty of Dentistry, Ege University, Izmir, Turkey. b Professor, Department of Radiodiagnostics, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey. c Private practice, Canakkale, Turkey. d Resident, Department of Radiodiagnostics, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey. e Postgraduate student, Department of Orthodontics, Faculty of Dentistry, Ege University, Izmir, Turkey. The authors report no commercial, proprietary, or financial interest in the prod- ucts or companies described in this article. Reprint requests to: Aynur Aras, Ege University, Faculty of Dentistry, Department of Orthodontics, Bornova, 35100-Izmir, Turkey; e-mail, aynuraras@yahoo.com. Submitted, February 2010; revised and accepted, December 2010. 0889-5406/$36.00 Copyright Ó 2011 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2010.12.018 616 ORIGINAL ARTICLE