ABSTRACT
Bone cements based on magnesium phosphates such as newberyite (N; MgHPO4.3H2O) have been shown as potential bone substitutes due to their biocompatibility, biodegradability and ability to support osteoblast differentiation and proliferation. Newberyite can hydrolyze to hydrated magnesium phosphate compounds (e.g. bobierite (Mg3(PO4)2.8H2O)) at alkaline conditions. In this study, 25 and 50 wt% of crystalline ß -wollastonite (woll; CaSiO3) was admixed to newberyite powder in order to both enhance the acid-base hydrolysis of newberyite and to produce a functional bone cement. The setting process of wollastonite/newberyite cement mixtures started with the hydrolysis of the wollastonite with further transformation of newberyite into bobierite and the formation of magnesium silicate phase. The results demonstrated that 25 wollastonite/newberyite and 50 wollastonite/newberyite cement pastes at optimal powder/liquid ratios had final setting times of â¼34 and 25 min and compressive strength values of 18 and 32 MPa after seven days setting, respectively. The tests of cytotoxicity of cement extracts on osteoblastic cells and contact cytotoxicity of the cement substrates showed different results. The osteoblasts cultured in cement extracts readily proliferated which confirmed the non-cytotoxic concentration of ions released from both cements. On the other hand, a strong cytotoxic character of 25 wollastonite/newberyite sample surface in contrary to high (â¼80%) proliferation activity of cells on the 50 wollastonite/newberyite cement substrate was observed. The differences in cell proliferation activity was attributed to different surface topographies of cement substrates, where needle-like precipitated microcrystals of magnesium phosphate phase (in 25 wollastonite/newberyite cement) prevented the adhesion and proliferation of osteoblasts contrary to the smoother surface covered by extremely fine nanoparticles in the 50 wollastonite/newberyite cement.
Subject(s)
Bone Cements/chemistry , Bone Substitutes/chemistry , Calcium Compounds/chemistry , Magnesium Compounds/chemistry , Osteoblasts/cytology , Phosphates/chemistry , Silicates/chemistry , Animals , Cell Line , Cell Proliferation , Cell Survival , Compressive Strength , Hydrogen-Ion Concentration , Hydrolysis , Materials Testing , MiceABSTRACT
Development of a new calcium phosphate cement (CPC) system as an alternative to that commonly used, basically consisting of tetracalcium phosphate and dicalcium phosphate self-setting mixtures, could be of interest in achieving special properties of the product. Powder mixtures of Ca(OH)(2) and KH(2)PO(4) were studied to assess their potential for the precipitation of apatite-like phase with the use of potassium phosphate salt solution as the cement liquid. X-ray diffraction and infrared (IR) spectroscopy studies and pH and setting time measurements were performed. The set cement was revealed to consist of a low crystalline carbonate-substituted apatite-like phase. The setting time of the cement was about 5 min. Its dissolution in distilled water led to an increase in solution pH to about 11.5, the pH slowly decreasing to 10.2 at day 10. The results showed the cement to be of an increased carbonate substitution ability compared to the tetracalcium phosphate-dicalcium phosphate anhydrous cement.
