title: Evaluation of a porosity measurement method for wet calcium phosphate cements.
abstract: The porosity of a calcium phosphate cement is a key parameter as it affects several important properties of the cement. However, a successful, non-destructive porosity measurement method that does not include drying has not yet been reported for calcium phosphate cements. The aim of this study was to evaluate isopropanol solvent exchange as such a method. Two different types of calcium phosphate cements were used, one basic (hydroxyapatite) and one acidic (brushite). The cements were allowed to set in an aqueous environment and then immersed in isopropanol and stored under three different conditions: at room temperature, at room temperature under vacuum (300 mbar) or at 37℃. The specimen mass was monitored regularly. Solvent exchange took much longer time to reach steady state in hydroxyapatite cements compared to brushite cements, 350 and 18 h, respectively. Furthermore, the immersion affected the quasi-static compressive strength of the hydroxyapatite cements. However, the strength and phase composition of the brushite cements were not affected by isopropanol immersion, suggesting that isopropanol solvent exchange can be used for brushite calcium phosphate cements. The main advantages with this method are that it is non-destructive, fast, easy and the porosity can be evaluated while the cements remain wet, allowing for further analysis on the same specimen.
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Ajaxon
authors.affiliation: Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgy, Technical University of Catalonia (UPC), Barcelona, Spain.
authors.forename: Yassine
authors.initials: Y
authors.lastname: Maazouz
authors.affiliation: Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgy, Technical University of Catalonia (UPC), Barcelona, Spain.
authors.forename: Maria-Pau
authors.initials: MP
authors.lastname: Ginebra
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Öhman
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden cecilia.persson@angstrom.uu.se.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Persson
mesh_terms: D001843:Bone Cements / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D019245:Compressive Strength; D006882:Hydroxyapatites / Q000737:chemistry*; D008422:Materials Testing; D016062:Porosity
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D006882:Hydroxyapatites; C475044:hydroxyapatite cement; C494366:calcium phosphate, dibasic, dihydrate
keywords: Calcium phosphate; bone cement; brushite; hydroxyapatite; porosity; solvent exchange