EVALUATION OF DISTRACTION OSTEOGENESIS BY SCANNING ELECTRON-MICROSCOPY

A model of bifocal distraction osteogenesis in the canine model was us ed to assess and quantitate the mineral content of the newly forming b one within the canine mandible. A 2-cm defect was created in the body of the mandible, and after a posterior osteotomy, the transport disk w as advanced at 0.25 mm per 8 hours for 21 days and then held in rigid fixation for an additional week. As a control for this study, three ad ditional dogs underwent the same procedure with the exception that the transport disk was not advanced. Electron dispersive spectroscopy ana lysis was performed on the newly formed regenerate bone and compared w ith areas of existing cortical bone of both the transport disk and the mandible. In the control model, special note was made of the pericort ical callus at the osteotomy site as well as of the regenerative bone that filled the 2-cm defect in the body of the mandible. Calcium/phosp horous ratios were used to assess the composition of the mineralized r egions of the mandible. The regenerate bone that filled the defect and the mineralized callus surrounding the site of osteoclasis in the con trol mandible were significantly different in composition when compare d with the regenerate bone that formed during distraction osteogenesis . This suggests that distraction osteogenesis may effect an initial ma trix production that is more similar in composition to the mature cort ical bone from which it was derived than does periosteal regeneration and filling of an osseous defect.