title: The formation of hydroxyapatite-ionomer cements at 38 degrees C.
abstract: This study describes the formation of a calcium polyacrylate-hydroxyapatite cement. Our hypothesis was that calcium phosphates would rapidly hydrolyze in the presence of polyacrylic acid (PAA) to form a cement. PAA, tetracalcium phosphate (TetCP), and dicalcium phosphate (DCP) were reacted together and formed calcium polyacrylate (CPA) and hydroxyapatite(HAp) within 10 h at 38 degrees C, resulting in hardened masses. Reaction times increased with decreasing (HApreactants)/PAA ratios. In the first of three reaction stages, the pH increased while CPA and dicalcium phosphate dihydrate (DCPD) formed. Two steady-state pH conditions occurred during the second stage as TetCP reacted with DCPD and DCP. The first steady-state pH was the result of DCPD and TetCP reacting at near-equilibrium conditions. The second steady-state pH resulted as the reaction became limited by DCP dissolution. The third, diffusionally controlled, stage occurred as DCP and previously formed HA preacted to produce calcium-deficient HAp (Ca/P = 1.5). The emphasis of this investigation was to establish the mechanistic path involved and the rate-limiting steps of the reaction.
authors.affiliation: Department of Materials Science, Penn State University, University Park 16802.
authors.forename: K S
authors.initials: KS
authors.lastname: TenHuisen
authors.forename: P W
authors.initials: PW
authors.lastname: Brown
mesh_terms: D000180:Acrylic Resins / Q000138:chemical synthesis* / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D002151:Calorimetry; D003738:Dental Cements / Q000138:chemical synthesis* / Q000737:chemistry; D004338:Drug Combinations; D017886:Durapatite / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006882:Hydroxyapatites / Q000138:chemical synthesis*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D002130:Calcium Phosphates; D003738:Dental Cements; D004338:Drug Combinations; D005899:Glass Ionomer Cements; D006882:Hydroxyapatites; C485828:alpha-tricalcium phosphate; C086855:calcium polyacrylate-hydroxyapatite cement; C485830:tetracalcium phosphate; C006903:carbopol 940; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous