R Shiri - Department of nanotechnology and advanced material, Materials and energy research center, karaj, Iran
S Hesaraki
E Ghasemi - Institute for color science and technology, Tehran, Iran

Injectable calcium phosphate cements (CPC) are widely used as bone substitutes in minimally invasive surgery. The rheological properties play an important role in the process of cement delivery into the bone defects. In this study the influence of Cephalexin on the rheological behavior of CPC was investigated at 25°C. Different amounts of antibiotic (0–10 wt.%) were added to CPC pastes composed of calcium hydrogen phosphate dihydrate and tetracalcium phosphate at a mass ratio of 1:1 and 3wt.% nanocrystalline hydroxyapatite (nHA) as a nucleating agent. In all exams, amount of CPC was constant, but P/L ratio increased with increasing amount of antibiotic. Rheological properties were measured with rheometer in rotation and oscillation modes. The results showed that CPC pastes containing different percentages of antibiotic at different shear ratesexhibited different rheological behaviour. Viscosityincreased as amount of antibiotic was increased. Although shear thinning is the main rheologicalbehaviour for all samples at low shear rates. But shear thickening behaviour can be seen at higher shear rates. It reveals that increasing of antibiotic concentration can change the viscosity behaviour of pastes, and it was made by interaction between particles of CPC and antibiotic.

Rheology, Calcium phosphate cement, Nano-hysroxyapatite, Antibiotic