[Bone inductive activity of beta-tricalcium phosphate-bone morphogenetic protein complex].

For the development of new implantable biomaterials as bone substitutes in the treatment of jaw bone defects, bone morphogenetic protein (BMP) bound to porous beta-tricalcium phosphate (beta-TCP) was investigated in the present experimental study in mice. The BMP was extracted from bovine cortical bone while the beta-TCP was synthesized by a mechanochemical method. The affinity of BMP to beta-TCP was examined by means of beta-TCP column chromatography. The porous beta-TCP combined with the BMP by dialysis was implanted in the muscle pouches of mice. The beta-TCP or BMP alone was also implanted in the same places in the controls. Three weeks after the implantation a new bone formation was observed in the exterior surface of the beta-TCP/BMP complex, but not in that of the beta-TCP control. The quantity of bone induced by the beta-TCP/BMP complex was determined on the X-ray film by a computer supported image analysis system. The osteoinductive activity of the complex was higher than that of the BMP alone. The histological relationship between the beta-TCP/BMP complex and the original tissues was excellent. The result of the present study may indicate that the beta-TCP/BMP complex can be used as an osteogenetic biomaterial for the treatment of bone tissue defects.

[Bone inductive activity of bone morphogenetic protein combined to beta-tricalcium phosphate].

For the development of a new delivery system for bone morphogenetic protein (BMP), BMP was bound to beta-tricalcium phosphate (beta-TCP). Powder beta-TCP was synthesized from calcium hydrogenphosphate and calcium carbonate by the dry process method to make the best use of the advantages of the BMP, which show good bone inductive activity on the surface and enhancement of new tissue by reducing the area that the implant material occupies. The beta-TCP + BMP complex and beta-TCP for the controls only were implanted in the muscle pouches of mice. Three weeks later new bone formation was observed on the exterior surface of beta-TCP + BMP complex but not of beta-TCP controls. The bone inductive activity of the beta-TCP + BMP complex is better than the BMP alone. The histological relation between the original tissue and the newly induced bone formation was normal and that of new bone and beta-TCP was also good. Consequently, the beta-TCP + BMP complex has good histocompatibility when implanted.

[Color and discoloration of dental alloys with low noble metal content].

Diffused reflectance of dental casting alloys with low noble metal content by the spectrophotometer with an integrating sphere was used to determine the color of the alloy and the tarnish in 0.1% Na2S solution, to study whether or not the tarnish can be affected by the nobility and the microstructure of the alloy. The alloys which had a high atomic ratio of Au + Pt + Pd + In + Zn to Ag had higher tarnish resistance. However the alloys which had high content of In showed two phases, but these alloys had high tarnish resistance. This suggests that alloys which have only a small difference of nobility between the compound and the matrix, and in which the low tarnish resistance area is small, may have a high tarnish resistance.

Osteoinductive activity of composites of bone morphogenetic protein and pure titanium.

Titanium sponges were infused with bone morphogenetic protein (BMP-Ti), and the osteoinductivity of the resultant composite was measured. New bone formation occurred three weeks after implantation and was identified by soft x-ray analysis. Quantitative analysis showed no significant difference between BMP-Ti composites and control samples (BMP only). Consequently, pure titanium neither inhibited nor promoted BMP activity. Chondrocytes and new bone formation occurred in direct contact with the surfaces of the titanium. X-ray microanalysis demonstrated new bone formation inside the pores of the titanium sponges. The BMP-Ti composite has interesting properties as an osteoinductive implant and has potential practical clinical applications.

[Bone inductive activity of hydroxyapatite-bone morphogenetic protein complex].

Bone morphogenetic protein (BMP) is known to be a protein which induces new bone at heterotopic sites. Purification of BMP has not been perfected, and obtaining large amounts of BMP is very difficult, so it seems better to use some carrier or frame material for BMP to work effectively. Various kinds of hydroxyapatite (HAP) have been used to repair periodontal osseous defects, but they do not have osteogenetic or osteoinductive properties. If osteoinductive proteins such as BMP could retain their biologic properties after being implanted into living tissue with HAP, it would be an advantage in repairing periodontal osseous defects. In this experiment, we prepared BMP-HAP complex and investigated its osteoinductive activity. BMP was extracted from bovine cortical bones in accordance with the Urist's procedure. The ability of this BMP to stimulate new bone growth was ensured by implantation in the muscle pouch of mice. HAP was synthesized by the wet method. The BMP-HAP complex was implanted in the muscle pouch of mice, and osteoinduction was examined 3, 7, 14, and 21 days after implantation to assess its osteo-inductive ability. New bone formation was studied by roentgenographic and histologic observation. In the BMP-HAP group, new bone formation was seen on the roentgenograms and new cartilage and bone were observed histologically in the tissue surrounding the apatite. In the HAP group, no new cartilage or bone formation was noted.