TEMPORAL DYNAMICS OF HEALING IN RABBIT CRANIAL DEFECTS USING GUIDED BONE REGENERATION

Purpose: The objective of this study was to histologically evaluate th e early stages of bone regeneration using rabbit calvaria defects in c onjunction with guided tissue regeneration. Materials: A semilunar cut aneous-periosteal flap was raised on the forehead of four rabbits expo sing the top of the skull. A standardized transosseous skull defect (g reater-than-or-equal-to 15 mm in diameter) was made in the area of the right parietal bone with a rotating round bur. Care was taken not to damage the underlying dura. A flat expanded polytetrafluoroethylene (e PTFE) membrane was placed to cover the defect. The membrane was tightl y adapted, extending at least 4 mm onto intact bone, and the flap was sutured. One, 2, 3, and 5 weeks later, the specimens were removed and processed using standard, undecalcified, hard-tissue histologic techni ques. Contact radiographs were also taken. Results: Bone growth increa sed with time, starting at the borders of the defect. At 1 week, trabe culae of woven bone grew into the highly vascularized loose connective tissue occupying the defect. Two weeks postsurgery, isolated islands of new bone were detected in this connective tissue. Subsequently, nei ghboring small islands merged to form large islands. in later stages, the primary trabeculae of woven bone were reinforced by layers of regu larly deposited lamellar bone. Conclusion: Rabbit calvaria defects tre ated by guided tissue regeneration heal by ingrowth of woven bone from the defect margins and by formation of bony islands within the defect area. Bone healing showed the histophysiological characteristics of i ntramembranous bone.