| Objective: The purpose of this study is to establish a periosteal distraction model on rabbit mandiblar ramus, to observe the formation of newly formed bone and its structure in each phase after distraction of periostea, to observe the changes of periostea after being secondary to distraction forces, to investigate the possibility of osteogenesis by periosteal distraction in oral and maxillofacial region, and to study the possibility of a new restoration method of clincal alveolar and other bony defect.Material and methods:The experiment included two sections:1. The establishment of model of osteogenesis by periosteal distraction and the research of formation of newly formed bone 1.1 A self-made titanium periosteal distraction device and titanium mesh were surgically implanted onto the lateral aspect of the mandibular ramus and fixed through titanium pins in 20 adult New Zealand rabbits. The periosteal distraction was begun 7 days after the placement of the distraction device. The titanium mesh placed under the periosteum was distracted 2mm from the surface of the mandible for the first time. During the following 15 days, the mesh was further distracted 1 mm every 3 days. Finally the periosteum was distracted 7mm from the surface of mandibular ramus 22 days after the operation.1.2 Every 5 animals were killed postoperatively at days 28,35,42 and 56 respectively. All the specimens were subjected to X-ray andhistomorphometric examination. The 3 of each 5 specimens were subjected to hematoxylin-eosin stain (HE stain) examination, and 2 were subjected to picricacid-fuchsin stain examination. 2, Histological changes of periostea on the mandibular ramus after the periosteal distraction:2.1 20 adult New Zealand rabbits were operated and distracted with the same methods mentioned above.2.2 Every 5 animals were killed postoperatively at days 28,35,42 and 56 respectively. The periostea of both experimental and control side of the mandibular ramus were taken and prepared, 2 of each 5 rabbits in a group were prepared for HE stain detection and 3 for proliferating cell nuclear antigen (PCNA) immunohistochemical detection.Results:1, The newly formed bone was detected on the lateral aspect of mandibular ramus after periosteal distraction. The bone was shaped like a hill. It looked very low and was full of holes at postoperative day 28. With the time of consolidation period lengthened, the newly formed bone matured gradually. X-ray examination showed the new bone shaped like a hill. The average values of new bone height at postoperative days 28,35,42 and 56 were 1.86 + 0.15mm, 2.29 + 0.29mm,3.19 + 0.13mm and 4.70 + 0.45mm. Histological examination of both HE stain and picricacid-fuchsin stain showed the increase in the number of osteoblasts and the change in the orientation of collagen fibers and bone trabecula. There were no significant differences between newly formed bone and original bone on the lateral aspect of mandibular ramus at postoperative day 56 histologically.2 Compared with the control side, the distracted periostea proliferated obviously under the microscope, and the number of periostealcells increased with satiation of cellular nuclear per unit area. The images of PCNA immunohistochemical stain of periosteum showed that the experimental periosteum proliferated obviously after distraction compared with the control side. The PCNA positive cells were densely, and the number of PCNA positive cells was more than that of the control side per unit area. Positive cells in periosteum adjacent to the surface of bone were much more in number and much denser in density. With the time of consolidation period lengthened, the number of positive cells gradually decreased.Conclusions:The results of this study that newly formed bone was detected on the lateral aspect of mandibular ramus at skeletally matured rabbits after gradual and regular distraction of periosteum indicate that osteogenesis by periosteal distraction is feasible in the oral and maxillofacial region. Periosteum proliferated obviousl...
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