Long-term skeletal and dental effects of mandibular symphyseal distractionosteogenesis

The purpose of this study was to evaluate the effects of mandibular symphys eal distraction osteogenesis using a tooth-borne expansion device. The samp le included 20 Hispanic nonsyndromic patients (11 males and 9 females) betw een 13.5 years and 37.3 years of age. Predistraction (1.5 months before sur gery), postdistraction (1 month after surgery), and long-term follow-up (1. 3 year after surgery) records included posteroanterior, lateral, and panora mic radiographs and models. Postdistraction radiographic evaluation showed that symphyseal distraction osteogenesis produced insignificant increases i n the bicondylar, bigonion, and biantegonion widths; intermolar and, especi ally, intercanine widths increased significantly and a distraction gap was observed in the symphyseal region. Follow-up model analysis showed the larg est width increases between the first molars and second premolars and the s mallest width increases between canines and first premolars. The difference between the postdistraction and long-term follow-up width changes was expl ained by the postdistraction orthodontic effect, which modified the shape o f the dental arch. A disproportionate pattern of distraction, characterized by significantly greater dental than skeletal widening, was observed in th e second molar and antegonion region. Distraction osteogenesis without pres urgical orthodontic treatment produced significant proclination of the mand ibular incisors; no proclination was observed in cases with predistraction orthodontic treatment, Dental crowding was resolved by the movement of teet h into the distraction regenerate and concomitant orthodontic treatment. Fo llow-up radiographs showed transverse skeletal stability of the distraction procedure. We conclude that mandibular symphyseal distraction osteogenesis increased mandibular arch width and partially corrected dental crowding, w ith a potential for disproportionate distraction patterns and proclination of the mandibular incisors.