ORIGINAL ARTICLE Effects of mandibular symphyseal distraction osteogenesis on mandibular structures Sıddık Malkoç, a Haluk I ˙ s¸ eri, b Ali I ˙ hya Karaman, c Necip Mutlu, d and Hasan Küçükkolbas¸ı e Konya and Ankara, Turkey Introduction: The purpose of this study was to evaluate the effects of mandibular symphyseal distraction osteogenesis on dental and mandibular skeletal structures with a tooth- and bone– borne distraction device. Methods: The sample comprised 20 patients, ranging in age from 15.8 to 23.3 years (mean, 20.1  2.3 years) at the start of treatment. The distraction device was activated 1 mm per day. The device was usually maintained in position about 90 days after surgery. Records were obtained at the start of treatment, at the end of distraction (11.4  2.2 days after surgery), and at follow-up periods (24.1  4.2 months after surgery). The records included posteroanterior cephalograms and study casts. The data were analyzed statistically by using the repeated measure analysis of variance and paired t test. Results: Posteroanterior cephalometric analysis demonstrated no significant changes in bigonial widths and ramal angles at the end of distraction period. On the other hand, bimolar widths were significantly increased, whereas bicondylar widths were markedly decreased. The dental cast analysis indicated that the maximum amount of increase was found between the mandibular canines, and the widening effect gradually decreased from the mandibular canines to the second molars. The follow-up data confirmed that the treatment results were stable. Conclusions: The long-term findings indicate that mandibular symphyseal distraction osteogenesis is an efficient nonextraction treatment alternative for mandibular dental crowding to increase mandibular skeletal and dental arch widths. (Am J Orthod Dentofacial Orthop 2006;130:603-11) T ransverse skeletal deficiencies are common clinical problems usually associated with nar- row basal bone and dentoalveolar structures, and dental crowding, but have received little attention compared with maxillary deficiencies. 1-3 Transverse mandibular deficiencies are commonly managed by orthodontic mechanics that might include extraction, dental compensation, arch expansion, and stripping of the teeth. 4-8 With traditional orthodontic treatment, extractions are usually unavoidable in pa- tients with severe crowding. Excessive overjet, an unattractive convex profile, a deep curve of Spee, or a combination of these also contributes to the extraction decision. However, extraction treatment can have com- plications, including changes in the facial profile, lack of improvement of dark buccal corridors, tendency of extraction spaces to reopen, and sometimes objections to extraction by patients and their parents. 9 Stripping is not suitable in all patients, and it depends on the thickness of interproximal enamel. 4 Orthodontic dental compensation (protrusion of the mandibular anterior teeth) might be unstable because of tipping of the teeth and bending of the alveolar bone, 10,11 and this approach can lead to periodontal complications and also loss of alveolar bone. 6 Dental expansion in adults or expansion in the mandibular anterior area tend to relapse toward the original dimensions and with a compromised peri- odontium created by moving teeth out of their support- ing alveolar bones. 11-17 Little et al 16 evaluated changes in mandibular align- ment from 10 to 20 years postretention and demon- strated contributing decreases in mandibular arch lengths and also relapses in orthodontically corrected arches after active growth. They even suggested that most premolar extraction cases were unacceptable and recommended lifetime retention. As a rule of thumb in orthodontics, the mandibular arch should be neither expanded nor changed in arch form. 11-18 An interesting dilemma also exists between the choice of long-term stability and esthetics. Attention to transverse deficiency is vital in planning treatment for patients who require increases in the lateral dimensions a Assistant professor, Department of Orthodontics, School of Dentistry, Uni- versity of Selçuk, Konya, Turkey. b Professor and chairman, Department of Orthodontics, School of Dentistry, University of Ankara, Ankara, Turkey. c Professor, Department of Orthodontics, School of Dentistry, University of Selçuk, Konya, Turkey. d Associate professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Selçuk, Konya, Turkey. e Assistant professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Selçuk, Konya, Turkey. Reprint requests to: Sıddık Malkoç, Selçuk Üniversitesi, Dis¸ Hekimlig˘i Fakültesi, Ortodonti Anabilim Dalı, Kampüs, Konya, Turkey; e-mail, siddikmalkoc@yahoo.com. Submitted, October 2004; revised and accepted, February 2005. 0889-5406/$32.00 Copyright © 2006 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.02.024 603