COBEM99

S2 Bioengenharia e Qualidade de Vida

Title:

INFLUENCE OF POLYMERIC ADDITIVES ON CALCIUM PHOSPHATE CEMENT

Summary :

ABSTRACT. RECENTLY, GREAT ATTENTION HAS BEEN PAID TO CALCIUM PHOSPHATE CEMENTS, BECAUSE OF THEIR ADVANTAGES COMPARED TO CONVENTIONAL CALCIUM PHOSPHATE BIOCERAMICS EMPLOYED FOR BONE REPAIRING, REGARDING "IN SITU" HANDLING AND SHAPING ABILITIES. NEVERTHELESS THE CALCIUM PHOSPHATE CEMENTS EXHIBIT RELATIVELY LOW MECHANICAL STRENGTH. THE AIM OF THIS WORK WAS THE IMPROVEMENT OF THE COMPRESSIVE STRENGTH OF A-TRICALCIUM PHOSPHATE-BASED CEMENT. THE HYDRAULIC SETTING REACTION OF THIS SYSTEM PRODUCES A CALCIUM DEFICIENT HYDROXYAPATITE PHASE SUITABLE FOR BONE REPAIRING: A- CA3(PO4)2 + H2O ® CA9(HPO4)(PO4)5OH MECHANICAL STRENGTH CAN BE IMPROVED USING TECHNOLOGICAL SOLUTIONS DEVELOPED FOR OTHER APPLICATIONS, SUCH AS PORTLAND CEMENT AND DUAL-SETTING GLASS-IONOMERS, BY USING POLYMERIC ADDITIVES. THE ADDITIVES USED IN THIS WORK WERE SODIUM ALGINATE, SODIUM POLYACRYLATE AND AN "IN SITU" POLYMERIZATION SYSTEM RESULTING IN A POLYACRYLAMIDE CROSSLINKED HYDROGEL.PARAMETERS EVALUATED WERE SETTING TIME, COMPRESSIVE STRENGTH BEFORE AND AFTER IMMERSION IN SIMULATED BODY FLUID, DENSITY, POROSITY, CRYSTALLINE PHASES AND MICROSTRUCTURE.SODIUM ALGINATE AND SODIUM POLYACRYLATE WERE DELETERIOUS TO BOTH SETTING TIME AND MECHANICAL STRENGTH.WHEN THE "IN SITU" POLYMERIZATION SYSTEM WAS ADDED TWO SETTING REACTIONS PROGRESSED IN PARALLEL: THE CONVENTIONAL HYDRAULIC REACTION AND THE COPOLYMERIZATION OF ACRYLAMIDE AND CROSSLINKING WATER-SOLUBLE MONOMERS. THE INITIAL AND FINAL SETTING TIMES OF THE "DUAL-SETTING" CEMENT WERE 9 AND 35 MIN, RESPECTIVELY AND THEY CAN BE REGULATED VARYING THE INITIATOR, CATALYST AND MONOMERS CONCENTRATIONS. THE INITIAL COMPRESSIVE STRENGTH OF THE "DUAL-SETTING" CEMENT (6,8 MPA AT 0 H, AND 15,2 MPA AT 24 H) IS HIGHER THAN THAT OF UNMODIFIED CEMENT. MAYOR CRYSTALLINE PHASE AFTER SETTING IS HYDROXYAPATITE. THE "DUAL SETTING" CEMENT SEEMS TO BE SUITABLE FOR CLINICAL APPLICATIONS IN BONE REPAIRING AND REMODELING. KEY WORDS: A-TRICALCIUM PHOSPHATE, CALCIUM PHOSPHATE CEMENT, HYDROXYAPATITE, BIOCERAMIC, BIOMATERIAL.

Author :

Carrodeguas, Raúl Garcia
Oliveira, Luci C. de
Rigo, Eliana C. S.
Santos, Luís A. dos

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