EFFICACY OF BONE MORPHOGENETIC PROTEIN (BMP) WITH OSTEOPROMOTIVE MEMBRANES - AN EXPERIMENTAL-STUDY IN RAT MANDIBULAR DEFECTS

The effect of bone morphogenetic protein (BMP) on healing of standardi zed bone defects was studied with and without the placement of osteopr omotive membranes. Two different bovine BMP (bBMP) preparations were t ested. These contained primarily collagen as a carrier. Standardized t ransosseous bone defects, 5 mm in diameter, were created in mandibles of rats. If left untreated, such ''critical size defects'' never heal during the lifetime of the animal, whereas covering with an osteopromo tive membrane is known to cause complete healing of the defects in 6 w eeks. The bBMP was implanted in defects and were either covered with a n expanded polytetrafluoroethylene (e-PTFE) membrane (GORE-TEX(R)) or were left uncovered. Control defects did not receive any bBMP and were either covered with membrane or were left uncovered. Histological eva luation was made after 12 d and 24 d of healing, respectively Implanta tion of bBMP alone was associated with formation of voluminous amounts of new bone, resulting in essentially complete defect healing at 24 d . However, the combination of membrane and bBMP was clearly less effec tive in stimulating bone healing, being only about as efficient as whe n using membranes alone. It was concluded that whereas both bBMP prepa rations were strongly osteoinductive, no further improvement of bone h ealing was seen when the membrane technique was supplemented with bBMP , compared to membrane alone. An explanation may be that the presence of an e-PTFE membrane prevents the degradation of the carrier material in the preparations, thus strongly reducing the availability of bBMP.