title: Influence of polymeric additives on the mechanical properties of alpha-tricalcium phosphate cement.
abstract: Recently, great attention has been paid to calcium phosphate cements, because of their advantages in comparison with 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 alpha-tricalcium phosphate-based cement. The hydraulic setting reaction of this system produces a calcium-deficient hydroxyapatite phase suitable for bone repairing: alpha-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. The major crystalline phase after setting is hydroxyapatite. The dual-setting cement seems to be suitable for clinical applications in bone repairing and remodeling.
authors.affiliation: Faculdade de Engenharia Mecânica, Universidade Estadual de Campinas, São Paulo, Brazil. arruda@dep.fem.unicamp.br
authors.forename: L A
authors.initials: LA
authors.lastname: dos Santos
authors.forename: L C
authors.initials: LC
authors.lastname: De Oliveria
authors.forename: E C
authors.initials: EC
authors.lastname: Rigo
authors.forename: R G
authors.initials: RG
authors.lastname: Carrodeguas
authors.forename: A O
authors.initials: AO
authors.lastname: Boschi
authors.forename: A C
authors.initials: AC
authors.lastname: De Arruda
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000464:Alginates / Q000737:chemistry; D001826:Body Fluids / Q000737:chemistry; D001843:Bone Cements / Q000737:chemistry*; D018786:Bone Substitutes / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D019245:Compressive Strength; D003432:Cross-Linking Reagents / Q000737:chemistry; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011108:Polymers / Q000737:chemistry; D016062:Porosity; D013499:Surface Properties; D014961:X-Ray Diffraction; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D000464:Alginates; D001843:Bone Cements; D018786:Bone Substitutes; D002130:Calcium Phosphates; D003432:Cross-Linking Reagents; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D011108:Polymers; D000099166:Polyacrylamides; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C006903:carbopol 940; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous