The Experimental Research Of Alveolar Ridge Augmentation By Distraction Osteogenesis

Distraction Osteogenesis(DO) become popular in maxillofacial surgery in resent years. There are many reports on alveolar ridge augmentation by DO. In majority of these studies, dogs.as the main animal models,were extracted their mandible teeth and then three or six months later, DO began. There have no reports about vertical tooth distraction.Our research tried to develop a new experimental model by using no-tooth area and the first premolar area of sheep and to study the feasibility and availability of this model in part I, and compared the effects of three methods in alveolar ridge augmentation with this model in part II. The purpose of our research is to create a simple and convenient animal model for alveolar ridge augmentation by DO and give help to clinic.Part 1: This part developed a new experimental model by using no-tooth area and the first premolar area of sheep mandible and discussed the character of DO bone formation and the function of bone sialoprotein (BSP) in DO.Methods: One side of 6 Shanxi native sheep' mandibular alveolar ridge was chosen randomly as experimental side.A box-shaped osteotomy of the experimental side of the no-tooth area and the first premolar area was carried out and vertical distraction apparatus was placed. After a latent period of 7 days, the alveolar ridge was augmented vertically by distraction for 8 days, the distraction rate was 1.0mm per day and the distraction frequency was once per day. The animals were sacrificed at 4 or 8 weeks after completion of distraction. The effect was observed by X-ray, clinic, histology and immunohistochemistry.Results: During the distraction period the bone transporter together with the first premolar was lifted gradually. The alveolar ridge was vertically augmented 7.5mm in 4 weeks and the interspace of the distraction site was disappeared. In 8 weeks the new bone was the same as the original alveolar ridge and the alveolarridge was vertically augmented 7.0mm. All the distraction teeth were stable and no colour changed.X-ray image showed that after the equipment of the distractor, there was a little space between bone transporter and base bone and the first mandibular premolar was in the bone transporter.Immediately after the distraction there was no bone formation in the interspace of the distraction site while 2 weeks later new bone began to generate.4 weeks later the area was replaced by the low density bone and there was no difference between new bone and original bone in 8 weeks.Histologically, after 4 weeks' consolidation there was short and netlike new bone formation with a number of osteoblasts around. The new bone trabecula was oriented to the distraction direction. Two distraction teeth were morphological normal while another one had root resorption.The well bone formation were observed in 8 weeks after diatraction.The new bone trabecula was oriented to the distraction direction and the distraction teeth were morphological normal without root resorption. BSP immunohistochemistry stain showed that osteoblasts and some of the new osteocytes were brown stained after 4 weeks' consolidation and in 8 weeks after distraction bone matrix and osteocytes were weak positive.The results shows that it is feasible and available to use no-tooth area and the first premolar area of sheep mandible as an animal model for DO. It is pssible to distract tooth vertically. BSP is an important role in the bone formation of DO.Part Eh This part compared the effects of three methods, which are DO, autogenous bone graft and the latter with biological absorbable membrane.in alveolar ridge augmentation by using sheep mandibular no-tooth area model.Methods: Two sides of all the 6 Shanxi native sheep' mandible no-tooth area alveolar ridge was chosen. A box-shaped osteotomy was carried out in this area. In group A(DO) a vertical distraction apparatus was placed. After a latent period of 7 days, the alveolar ridge was augmented vertically by distraction for 8 days, the distraction rate was 1.0mm per day and the distraction frequency...