Effects of various implant materials on regeneration of calvarial defects in rats

The purpose of the present study was to determine the best implant material , the best conditions to substitute absorbable membrane for non-absorbable membrane, and the factors influencing guided regeneration of critical size defects using experimental rats. An 8-mm circular transosseous calvarial bo ny defect was made and implant materials, such as demineralized freeze-drie d bone (DFDB), absorbable membrane (BioMesh; Samyang Co., Seoul Korea), non -absorbable membrane (Millipore filter; Micro Filtration System, MA, USA) o r a combination of these materials, was placed on the defect. As for the re sults of sequential time-based guided bone regeneration, histological, hist ochemical, immunohistochemical and histomorphometric aspects were observed, and a statistical comparative analysis was performed, with control group o f a soft tissue flap. Bone formation was significantly enhanced when DFDB w as retained within the defect with a protective absorbable membrane. Infram embranous DFDB-filling was required to prevent membrane collapse and to pre serve spaces for bone regeneration. The absorbable membrane which was recom mended to overcome the disadvantages of the non-absorbable membrane should remain intact for more than 5 weeks in order for it to be effective. The ma crophages recruited by grafts were involved partly in decreasing bone regen eration via the sequential events of releasing fibronectin, and in chemotac tic effect of the fibronectin to fibroblasts and collagen lay-down. Thus, t he activity of new bone formation was dependent upon the physical barrier e ffect of the membrane, such as the preserving ability to secure spaces and the suppression ability of early infiltration of collagen and epithelium, i nducible ability of inflammation by the implant material, and potential in guiding bone regeneration of the grafts.