caa a22 4500 475783131 CHVBK 20180406123650.0 cr unu---uuuuu 170329e20000501xx s 000 0 eng 10.1023/A:1008961314500 doi (NATIONALLICENCE)springer-10.1023/A:1008961314500 Effect of mixing ratio and pH on the reaction between Ca4(PO4)2O and CaHPO4 [Elektronische Daten] [S. Matsuya, S. Takagi, L.C. Chow] The reaction of Ca(PO4)2O (TTCP) and CaHPO4 (DCPA) in an aqueous solution has been shown to be responsible for the hardening of a calcium phosphate cement. This reaction was investigated by monitoring pH changes and composition of solid phases. In the first set of experiments (no attempt to control pH), 2.5 g each of mixtures of TTCP/DCPA, molar ratio from 0.25 to 2, was placed in 12.5 mL of 0.15 mol/L KCl solution, at initial pH about 7, and the pH was allowed to drift for 24 h. Results show that at any time up to 24 h, the pHs were higher for slurries with higher TTCP/DCPA molar ratios. For the slurries with TTCP/DCPA molar ratio of ≥ 0.83, the 24 h pHs of the slurries were 9 to 11, whereas for those with TTCP/DCPA of ≤ 0.67, the pHs were between 5.3 and 7. The slurries with TTCP/DCPA molar ratios between 0.5 and 1 (Ca/P molar ratio=1.5 to 1.67) reacted completely within 24 h to form hydroxyapatite(OHAp), Ca5(PO4)3OH. In the second set of experiments, 2 g of an equimolar TTCP and DCPA mixture was placed in 20 mL of 0.15 mol/L KCl solution. The pH values were kept constant (6, 8 or 10) by using H3PO4 and Ca(OH)2 or HCl and KOH as titrant solutions. At pH 8, DCPA and TTCP dissolved at about the same rate, whereas at pH 10, DCPA was consumed more rapidly than TTCP. At both pHs, OHAp was the only product formed. However, at pH 6, the composition of reaction products depended on the types of the titrants used. Specifically when H3PO4 and Ca(OH)2 were used, hydrolysis of TTCP was the predominant reaction and both octacalcium phosphate and OHAp were formed. But, when HCl and KOH were used, only OHAp was formed. In this case hydrolysis of TTCP and DCPA appeared to proceed independently with TTCP hydrolysis beginning immediately and progressing slowly through 48 h while the DCPA hydrolysis began several hours after the reaction started but was completed in 24 h. ©2000 Kluwer Academic Publishers Kluwer Academic Publishers, 2000 Matsuya S. Department of Dental Materials Engineering, Faculty of Dentistry, Kyushu University, 812-8582, Fukuoka, Japan aut Takagi S. Paffenbarger Research Center, National Institute of Standards and Technology, American Dental Association Health Foundation, 20899, Gaithersburg, MD, USA aut Chow L.C. Paffenbarger Research Center, National Institute of Standards and Technology, American Dental Association Health Foundation, 20899, Gaithersburg, MD, USA aut Journal of Materials Science: Materials in Medicine Kluwer Academic Publishers 11/5(2000-05-01), 305-311 0957-4530 11:5<305 2000 11 10856 https://doi.org/10.1023/A:1008961314500 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1008961314500 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Matsuya S. Department of Dental Materials Engineering, Faculty of Dentistry, Kyushu University, 812-8582, Fukuoka, Japan aut NATIONALLICENCE 700 1- Takagi S. Paffenbarger Research Center, National Institute of Standards and Technology, American Dental Association Health Foundation, 20899, Gaithersburg, MD, USA aut NATIONALLICENCE 700 1- Chow L.C. Paffenbarger Research Center, National Institute of Standards and Technology, American Dental Association Health Foundation, 20899, Gaithersburg, MD, USA aut NATIONALLICENCE 773 0- Journal of Materials Science: Materials in Medicine Kluwer Academic Publishers 11/5(2000-05-01), 305-311 0957-4530 11:5<305 2000 11 10856 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer