Objectives: The aim of this study was to evaluate tooth movement following mandibularsymphyseal distraction osteogenesis together with the assessment of the effects of distraction on mandibular skeletal structures using three dimensional radiography and finite element analysis.Materials and methods: Six female subjects with an age range of 15-21 years old with severe lower arch crowding with and without scissorbite for whom extraction or expansion might have produced detrimental occlusal relationship and soft tissue outcomes have underwent mandibular symphyseal distraction osteogenesis using a bone-borne distractor device. A latency period of 7 days and a consolidation period of 6 weeks were followed. Distraction was performed at a rate and rhythm of 1mm/day for 2 weeks. CBCT was performed for each subject during the latency period and at the end of consolidation period. A finite element analysis was performed to compare the results with actual clinical outcomes on subjects.Results: At the end of the treatment period, all cases showed increases in the mandibular interdental spaces as well as transverse symphyseal bony widening without any periodontal ortemporomandibular joint derangements. Crowding was solved by movement of teeth into the bone regenerate which proceeded at a rate of 0.5 mm/week. Significant changes took place at the condylar region which mainly involved posteromedial rotation, but it was not associated with any TMD signs or symptoms. No crestal bone loss or periodontal problems were manifested. No root resorption of the anterior teeth moved into the disraction gap was evident. It was revealed that anterior transverse expansion was greater than posterior expansion. Moreover there was more expansion at the basal bone than the alveolar bone.The finite element method allowed the analysis of the amount of stress falling on the skeletal mandibular structures and it confirmed the clinical findings whereby displacement was found to be highest in the anterior region and decreased gradually posteriorly.Conclusion: Mandibular symphyseal distraction osteogenesis is an efficient nonextraction treatment alternative for mandibular dental crowding to increase mandibular skeletal and dental arch widths by gradual osteodistraction. Potentially, symphyseal distraction provides the esthetic advantages associated with typical orthodontic expansion procedures but without the same risk of relapse.