Purpose: This raport presents the results of distraction osteogenesis using extraoral device among 32 patients with different grades of vertical mandibular ramus hypoplasia and analises the stability of ramus elongation. Material and Methods: A total of 32 patients at the age 2-15 years displaing hypoplastic mandibles were treated with unilateral or bilateral lengthening of the ascending ramus using uni and bilateral extraoral devices (Molina distractor). 5 patients suffered from bilateral hypoplasia and further 27 patients suffered from unUateral hypoplasia. In order to select the appropriate placement of the distractor device,as well as to determinate the placement of the mandibular osteotomy, 3D-CT and cephalometrric radiographs were analised. After 5-day latency period, distraction was commenced in compliance with the standard protocol, until the desired length of distraction was achieved. 3 months after the distraction, the device was removed which allowed the bone and the tissue to stabilise. The evaluation took account of 3D-CT, lateral and P.A. cephalograms, panoramic radiographs, dental models as well as facial photographs before 3, 6 and 12 months after the distraction osteogenesis. Results: Total distraction distances amounted to 5-37 mm with a mean lengthening distance equalling 16,5 mm. With the use of clinical results and radiografic data it became clearly evident that mandibular distraction occurred among all the patients. Lateral, P.A. cephalometric as well as panoramic radiographs displayed progressive ossification of distraction regenerate. No relapses were oberved. rlanned over correction of dental occlusion was achieved to overcome deficient mandibular growth. A coordinated growth between maxillary and mandibular arches witgh stable occlusion are being observed among our patients. Conclusion: Mandibular distraction osteogenesis has proved to offer new Derspectives as far as treatment of mandibular deficiency is concerned. Careful and intact planning of treatment coupled with control of distraction vector can bring about predictable results with minimal morbidities. Nevertheless, it is our conclusion that good and effective orthodontics within the period of consolidation is the key to achive satisfactory stability results.

National Research Institute for Mother and Child Centre for Craniofacial Disorders Warsaw PL