Characterization of a novel calcium phosphate/sulphate bone cement

Abstract

Apatitic cements have shown excellent biocompatibility and adequate mechanical properties but have slow resorption in the human body. To assure that new bone tissue grows into the bone defect, a certain porosity is necessary although hard to achieve in injectable cements with suitable mechanical properties. An attempt was made by mixing alpha-tricalcium phosphate (alpha-TCP), calcium sulphate hemihydrate (CSH) and an aqueous solution containing 2.5 wt% of Na(2)HPO(4). The aim was to obtain a material containing two phases: a) one apatitic phase (calcium-deficient hydroxyapatite; CDHA) and b) one resorbable phase (calcium sulphate dihydrate; CSD). alpha-TCP and CSH mixtures were produced at relative intervals of 20 wt%. The liquid-to-powder (L/P) ratio to obtain a paste was 0.32 mLg(-1). The highest compressive strength (34 MPa) was obtained for the pure alpha-TCP sample. The strength was, in a first approximation, directly correlated to the weight proportions of the powders. X-ray diffraction analysis showed that the relative intensity for CDHA increased linearly, and the one for CSD decreased exponentially, when the amount of alpha-TCP increased. Thus, CSH ceased to transform to CSD when the amount of alpha-TCP increased. Observations in environmental scanning electron microscopy confirmed the X-ray diffraction results. CSH-crystals (100 microm) were embedded in the HA-matrix permitting gradual porosity in the material when resorbed.

Effect of preparation conditions on the nanostructure of hydroxyapatite and brushite phases

“…Several researchers under different preparation conditions studied the synthesis of calcium phosphate extensively (Nilsson et al 2002;Ren et al 2012;Kundu et al 2010a). By varying temperature, pH and initial reagent concentrations, one can obtain different calcium phosphate phases (Kundu et al 2010b).…”

Calcium carbonate–calcium phosphate mixed cement compositions for bone reconstruction

“…It has been suggested that controlling the thickness of hydroxyapatite on a CaCO 3 matrix could control the rate of resorption of the implant and its replacement by newly formed bone [24]. The concept of biphasic ceramics has however sparsely been developed in view of controlling the resorption of ionic cements [25][26][27][28][29]. Calcium carbonate compounds have a higher solubility than apatite [30][31] and although some mineral cements containing calcium carbonate have already been proposed, the use of very large proportions of calcium carbonate (≥ 20% w/w in the dry powder ingredients) opens new possibilities which have not yet been explored [4,26,[32][33].…”

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“…The Si-OH functional groups on the surface of silicate material, such as silicate glasses and ceramics, have been shown to act as nucleation centres for hydroxyapatite precipitation 3,41,42 . Recent research has shown that an increase in the super saturation of Ca + is not sufficient to promote the formation of new crystals of hydroxyapatite on the material surface in the SBF environment 43,44 and the formation of this homogeneous hydroxyapatite layer is dependent on the content of silicate material 15 . This explains why OPC shows lower intensity peak of www.scienceasia.org hydroxyapatite than WPC.…”