Bone regeneration by a combination of osteopromotive membranes with different BMP preparations: a review

The aim of these studies was to see if a combination of osteopromotive membranes of expanded polytetrafluoroethylene (e-PTFE; GORE-TEX) and BMP, known to separately promote bone healing, would be stimulatory if combined. Bilateral transosseous 'critical size' defects at the mandibular angles in adult male rats were treated with either (i) various BMP preparations only; ii) lateral and medial coverage with e-PTFE membranes only; iii) a combination of various BMPs and membranes; or iv) left untreated. Two semi-purified bovine BMPs (bBMP), comprising collagen as carrier material, and recombinant human (rh) BMP-2 (1, 2 or 8 micrograms), delivered in either biodegradable beads of polylactide/polyglycolide acid (PLA/PGA) or purified collagen, were tested. After 12 or 24 days, block biopsies were taken for histological analysis. The different materials were well tolerated by the hosts and elicited large amounts of newly formed bone widely spread in the surrounding soft tissue. The combinations of bBMP and membranes did not improve the rate of bone healing compared to membranes only. In contrast, the combination of rhBMP-2 in PLA/PGA with membranes was more efficacious than membrane placement only and resulted in bone bridging at 24 days, with a bone contour resembling the original anatomy. The combination of membrane placement with rhBMP-2 may be of value in the clinic for bone regenerative purposes. The results are also of general importance for choosing carrier materials for delivery of other growth-stimulatory substances in combination with membranes.