Ectopic bone induction in porous apatite-wollastonite-containing glass ceramic combined with bone morphogenetic protein.

To accelerate the integration of ceramic implants with the surrounding bone and to search for a suitable carrier for bone morphogenetic protein (BMP), we studied ectopic bone induction in porous apatite-wollastonite-containing glass ceramic (A-W GC) combined with partially purified bovine BMP (bBMP) and recombinant Xenopus BMP-4/7 (rxBMP-4/7). Porous A-W GC rods [4 mm in diameter, 5 mm in height, 70% porosity, 200 microns mean pore size, 17.54 +/- 3.82 MPa (mean +/- SD) compressive strength] were used. An apatite coating formed on the surface of porous A-W GC that had been immersed in simulated body fluid at 36.5 degrees C for 7 days. In experiment 1, porous A-W GC rods were combined with either bBMP, collagen, or with both bBMP and collagen. The rods were implanted into subcutaneous pouches in rats and were harvested 4 weeks after implantation. Low-energy radiographic, scanning electron microscopic (SEM), and histological examinations showed ectopic bone formation and within the rods only in the porous A-W GC combined with the bBMP and collagen group. Quantitative analysis also revealed that this group alone showed a significant increase in bone formation. In experiment 2, porous A-W GC rods were combined with rxBMP and collagen, implanted into rats, and harvested as described above. SEM and histological examination showed ectopic bone formation around and within the rods. Because of its relatively high mechanical strength, ease of handling, and good osteoinductivity, porous A-W GC combined with BMP and collagen may be clinically useful in patients with large cancellous bone defects or craniomaxillofacial lesions.