OSTEOGENESIS PROMOTED BY CALCIUM-PHOSPHATE N,N-DICARBOXYMETHYL CHITOSAN

The effects of N,N-dicarboxymethyl chitosan (DCMC) on the precipitatio n of insoluble calcium salts, namely phosphate, sulfate, oxalate, carb onate, bicarbonate and fluoride, and magnesium salts, namely phosphate and carbonate, were studied. Results indicated that the chelating abi lity of DCMC interfered effectively with the well-known physico-chemic al behaviour of magnesium and calcium salts. Dicarboxymethyl chitosan formed self-sustaining gels upon mixing with calcium acetate, as a con sequence of calcium chelation. DCMC mixed with calcium acetate and wit h disodium hydrogen phosphate in appropriate ratios (molar ratio Ca/DC MC close to 2.4) yielded a clear solution, from which, after dialysis and freeze-drying, an amorphous material was isolated containing an in organic component about one half its weight. This compound was used fo r the treatment of bone lesions in experimental surgery and in dentist ry. Bone tissue regeneration was promoted in sheep, leading to complet e healing of otherwise non-healing surgical defects. Radiographic evid ence of bone regeneration was observed in human patients undergoing ap icectomies and avulsions. The DCMC-CaP chelate favoured osteogenesis w hile promoting bone mineralization. (C) 1998 Elsevier Science Ltd. All rights reserved.