Abstract
The addition of tricalcium silicate (C3S) to apatite cements results in an increase of bioactivity and improvement in the mechanical properties. However, adding large amounts raises the local pH at early stages, which retards the precipitation of hydroxyapatite and produces a loss of mechanical strength. The introduction of Pozzolanic materials in cement pastes could be an effective way to reduces basicity and enhance their mechanical resistance; thus, the effect of adding silica on the chemical, mechanical and biological properties of α-tricalcium phosphate/C3S cement was studied. Adding silica produces a reduction in the early pH and a decrease in setting times; nevertheless, the presence of more calcium silicate hydrate (C-S-H) delays the growth of hydroxyapatite crystals and consequently, reduces early compressive strength. The new formulations show a good bioactivity, but higher cytotoxicity than traditional cements and additions higher than 2.5% of SiO2 cause a lack of mechanical strength and an elevated degradability.
Highlights
Calcium phosphate cements (CPCs) are a clinical alternative to traditional bioceramics because they are easy to handle and shape, mold themselves well to the contours of defective surfaces, and set in situ in the bone cavity to form a solid restoration[1]
One of the most important formulations is based on α-tricalcium phosphate [α-Ca3(PO4)[2]; α-TCP], which sets in situ and forms a calcium-deficient hydroxyapatite [Ca9(HPO4)(PO4)5(OH); CDHA] when hydrated[3]
In view of the excellent bioresorbability of CDHA, researchers have focused their efforts on overcoming the mechanical weakness of calcium phosphate cements by using different fillers, fibers and reinforcing additives that lead to the formation of various multiphase composites, based on the idea that the filler in the matrix may eliminate crack propagation[7]
Summary
Calcium phosphate cements (CPCs) are a clinical alternative to traditional bioceramics because they are easy to handle and shape, mold themselves well to the contours of defective surfaces, and set in situ in the bone cavity to form a solid restoration[1]. Since their development in the mid-80’s, CPCs have attracted great interest due to their chemical similarity to the mineral phase of bone tissue and their good osteoconductivity[2]. It is difficult to increase the strength of these cements without negatively affecting other properties
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