Setting Reaction and Hardening of an Apatitic Calcium Phosphate Cement

Abstract

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.

Si-TCP synthesized from "Mg-free" reagents employed as calcium phosphate cement

“…For both cements the values obtained using the Gilmore Needles 19 were higher when compared to the values reported on the literature 20,21 . Initial setting time was 15 minutes for α-TCP and 30 minutes for Si-α-TCP.…”

Novel grout material comprised of calcium phosphate compounds: In vitro evaluation of crystal precipitation and strength reinforcement

“…Consequently, CPC hardens after injection into soil and rock because of the self-setting mechanism (Ginebra et al, 1997).…”

Robocasting of biomimetic hydroxyapatite scaffolds using self-setting inks

“…The skeletal density of the reference material (a-TCP/water) was 2.84 AE 0.01 g ml À1 , consistent with a CDHA (the theoretical density of stoichiometric HA is 3.14 g ml À1 32 This is considered as an advantage of the biomimetic self-setting scaffolds, since the high SSA, together with the lower crystallinity and non-stoichiometry of the CDHA, 14 contributes to a higher reactivity, and therefore a higher resorption rate is to be expected.…”