Long-term skeletal effects of mandibular symphyseal distraction osteogenesis. An implant study.

The purpose of this study was to investigate the long-term skeletal effects of mandibular symphyseal distraction osteogenesis (MSDO) with a tooth- and bone-borne distraction device, analysed using the metallic implant method. The study sample comprised 20 patients between 15.8 and 25 years of age, with a mean age of 20.01 +/- 2.25 years at the start of treatment. In 12 subjects, titanium implants were inserted in the mandible to analyse mandibular skeletal changes in the short and long term. A custom-made intraoral, tooth- and bone-borne distractor was designed and used. After a latency period of 7 days, the distractor was activated twice daily, by a total amount of 1 mm. Postero-anterior (PA) cephalograms were obtained at the start of distraction and at the end of consolidation (94.95 +/- 5.79 days after surgery) and follow-up periods (21.5 +/- 4.6 months after consolidation). The data were analysed statistically using paired t-tests. The mean amount of screw activation was 8.10 +/- 1.68 mm. The inter-symphyseal and inter-molar implant distances and the bimolar width significantly increased during the consolidation period (P < 0.001) and were maintained at the end of the follow-up. On the other hand, the bicondylar width was markedly decreased (P < 0.05), while no significant skeletal changes were observed in bigonion and biantigonion widths, inter-ramal implant distance, or inter-ramal and implant angles at the end of the consolidation period. The long-term findings of this study indicate that MSDO provides an efficient and stable non-extraction treatment alternative, mainly by increasing the anterior mandibular skeletal and dental arches.