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Illuminating the Role of Agglomerates on Critical Physicochemical Properties of Amorphous Calcium Phosphate Composites



Justin N. O'Donnell, Joseph M. Antonucci, Drago Skrtic


Amorphous calcium phosphate (ACP) composites show promise in a number of anti-cariogenic applications. The objectives of this study are to compare the water sorption (WS), mechanical strength and ion release of polymeric composites formulated with either as-made or milled ACP after 1, 2 and 3 mo of aqueous exposure. The photo-curable resin comprised an ethoxylated bisphenol A dimethacrylate (62.8 mass %), triethylene glycol dimethacrylate (23.2 mass %), 2-hydroxyethyl methacrylate (10.4 mass %) and methacryloxyethyl phthalate (2.6 mass %). Composites were prepared with either as-made (median diameter, dm = 70.88 ?m) Zr-ACP or milled Zr-ACP (dm = 3.10 ?m) as the filler phase at 40 mass %. The unfilled resins (copolymers) and composites were evaluated for WS (gravimetrically) after water vapor exposure. Composites were immersed in saline (pH = 7.40; 23 oC) and assessed for Ca and PO4 release as well as for their biaxial flexure strength (BFS) both dry and after aqueous immersion.The mean WS (mass %) peaked at 3 mo with as-made ACP composite (2.73 0.09) > milled ACP composite (1.63 0.24) = copolymer (1.47 0.11). In both the dry state and after 1 mo immersion, the BFS (in MPa) of milled ACP composites approached the BFS of the copolymers (96 32), and was significantly higher than the BFS of as-made ACP composites. BFS of both composite types declined with water aging. However, at 3 mo the BFS of milled ACP composites still remained higher than the BFS of as-made ACP composites [(55 10) vs. (43 11)]. The maximum Ca and PO4 (in mmol/L) released from the as-made and milled ACP composites were [Ca=(0.97 0.16), PO4=(0.39 0.07)] and [Ca=(0.59 0.08), PO4=(0.22 0.03)], respectively. Despite moderately reduced ion release, milled ACP composites are superior to the as-made ACP composites due to significantly lower WS and higher BFS after prolonged aqueous exposure.
Journal of Composite Materials


amorphous calcium phosphate, biaxial flexural strength, ion release kinetics, particle size distribution, water sorption


O'Donnell, J. , Antonucci, J. and Skrtic, D. (2008), Illuminating the Role of Agglomerates on Critical Physicochemical Properties of Amorphous Calcium Phosphate Composites, Journal of Composite Materials, [online], (Accessed May 29, 2023)
Created October 30, 2008, Updated October 12, 2021