Setting reaction and hardening of an apatitic calcium phosphate cement.
The combination of self-setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the setting and hardening mechanisms of a cement-type reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were alpha-tricalcium phosphate containing 17 wt% beta-tricalcium phosphate, and 2 wt% of precipitated hydroxyapatite as solid phase and an aqueous solution 2.5 wt% of disodium hydrogen phosphate as liquid phase. The transformation of the mixture was stopped at selected times by a freeze-drying techniques, so that the cement properties at various stages could be studied by means of x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Also, the compressive strength of the cement was measured as a function of time. The results showed that: (1) the cement setting was the result of the alpha-tricalcium phosphate hydrolysis, giving as a product calcium-deficient hydroxyapatite, while beta-tricalcium phosphate did not participate in the reaction; (2) the extent of conversion of alpha-TCP was nearly 80% after 24 hr; (3) both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the setting reaction proceeded were responsible for the mechanical behavior of the cement; and (4) the microstructure of the set cement consisted of clusters of big plates with radial or parallel orientations in a matrix of small plate-like crystals.
Ginebra
M P
MP
Department of Materials Science and Metallurgy, ETSEIB, Universitat Politècnica de Catalunya, Barcelona, Spain.
Fernández
E
E
De Maeyer
E A
EA
Verbeeck
R M
RM
Boltong
M G
MG
Ginebra
J
J
Driessens
F C
FC
Planell
J A
JA
D001843:Bone Cements / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D019245:Compressive Strength; D003738:Dental Cements / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry; D006244:Hardness; D006868:Hydrolysis; D007700:Kinetics; D016018:Least-Squares Analysis; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
D001843:Bone Cements; D002130:Calcium Phosphates; D003738:Dental Cements; D017886:Durapatite; D002118:Calcium