Fabrication of carbonate apatite blocks from set gypsum based on dissolutionprecipitation reaction in phosphate-carbonate mixed solution

Abstract

Carbonate apatite (CO 3 Ap), fabricated by dissolution-precipitation reaction based on an appropriate precursor, is expected to be replaced by bone according to bone remodeling cycle. One of the precursor candidates is gypsum because it shows self-setting ability, which then enables it to be shaped and molded. The aim of this study, therefore, was to fabricate CO 3 Ap blocks from set gypsum. Set gypsum was immersed in a mixed solution of 0.4 mol/L disodium hydrogen phosphate (Na 2 HPO 4 ) and 0.4 mol/L sodium hydrogen carbonate (NaHCO 3 ) at 80-200°C for 6-48 h. Powder X-ray diffraction patterns and Fourier transform infrared spectra showed that CO 3 Ap block was fabricated by dissolution-precipitation reaction in Na 2 HPO 4 -NaHCO 3 solution using set gypsum in 48 h when the temperature was 100°C or higher. Conversion rate to CO 3 Ap increased with treatment temperature. CO 3 Ap block containing a larger amount of carbonate was obtained when treated at lower temperature.

Fabrication of Carbonate Apatite Block through a Dissolution–Precipitation Reaction Using Calcium Hydrogen Phosphate Dihydrate Block as a Precursor

“…CO 3 Ap block has been fabricated using dissolution–precipitation and precursors such as calcite [CaCO 3 ] [8,9], gypsum [CaSO 4 ·2H 2 O] [10,11], and α-tricalcium phosphate (TCP; [α-Ca 3 (PO 4 ) 2 ]) [12,13,14]. When osteoclasts were incubated on the surface of CO 3 Ap blocks, osteoclastic resorption pits similar to bone were observed [8].…”

Fabrication of bone cement that fully transforms to carbonate apatite

“…The setting reaction of apatite cements is similar to that of gypsum, in that the solubility difference between the starting material and the final product is a critical factor 25) . In a dissolution-precipitation reaction, precipitation cannot occur without prior dissolution of the starting material.…”

Carbonate Apatite Bone Replacement

“…There are many precursors for the fabrication of carbonate apatite including calcium carbonate, calcium phosphates, and phosphate compound such as zinc phosphate [12][13][14][15][16][17][18][19]. There are advantage and disadvantage based on the chemical and physical properties of the precursors.…”

“…In contrast to calcium carbonate and calcium phosphates that contain two components for the fabrication of carbonate apatite, calcium sulfate contains only one component, calcium, for the fabrication of carbonate apatite. Therefore, both phosphate and carbonate need to be supplied from the solution during the dissolutionprecipitation reaction [19]. Calcium sulfate when dissolved releases Ca 2+ and SO 4 2À into the solution as shown in Eq.…”

“…Therefore, carbonate apatite block should be fabricated based on dissolution-precipitation reaction using a suitable precursor [12][13][14][15][16][17][18][19]. The precursor should contain at least one component of the carbonate apatite since the solution needs to be supersaturated with respect to the carbonate apatite based on the dissolution of the precursor.…”