Apatite-collagen complex as a possible bone substitute

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A new apatite-collagen complex was prepared in calcium beta-glycerophosphate solutions at pH 8.50. In one preparation, reconstituted type I collagen was cross-linked with phosvitin in the presence of alkaline phosphatase by the use of cross-linking agent of dimethyl subrimidate. After two weeks of immersion in daily-renewed solution of calcium beta-glycerophosphate, apatite deposited on the collagen fibrils. The apatitte-collagen complex thus prepared contained apatite approximately two times the modified collagen in weight. When viewed under a scanning electron microscope, needle-like crystals precipitated densely on the collagen fibrils. In some portion of the complex, however, dotlike precipitate was observed as well. X-ray diffraction and IR analyses of the complex suggested that apatite precipitated on the collagen fibrils was very similar to bone mineral in two aspects, crystallinity and carbonate content. When implanted for one month as a bone substitute in dog jaw after teeth w … More ere extracted, the complex was found resorbed without no substantial foreign body response. The site where the complex was implanted was filled with newly formed bone. This finding may suggest that the apatite-collagen, -complex prepared here is biodegrable and osteogeneiic as well.In the second preparation, atelocollagen sheets (MEIPAK) with apatite deposited on were laminated in apatite cement consisting of an equisolar mixture of Te-CP and DCPD under isostatic pressure of 600 MPa, which was later immersed in distilled water at 37ﾟC for 7 days to completely transform the sement portion into apatite. The sheet-collagen laminated apatite blocks thus obtained were subjected to four points bending test with a loading direction perpendicular to the sheets inside the block. The load was plotted as a function of longitudinal displacement of the block specimen. Comparison of data obtained from the block specimens with and without the collagen sheets showed that presence of the collagen sheet failed to increase the bending strength but increased the work done on the specimen. Non-treated collagen sheet was also tried to laminate in apatite. However, it was practically impossible to prepare compacted blocks. This finding suggests that predeposition of apatite crystals on collagen sheet is a key step to successfully combine collagen and apatite, indicating that apatite deposited on collagen sheet acts as seed crystal for the sement setting process. Less