(190b) Rapidly Setting Calcium Phosphate Cements Based on Amorphous Tricalcium Phosphate Nanoparticles

Bone repair and regeneration of defects arising from trauma, tumor or bone diseases display a complex and serious clinical problem in orthopedic surgery. Bioactive bone substitute materials, in particular resorbable calcium phosphate compounds, have gained importance due to their great biocompatibility, bioactivity and osteoconductivity. Next to a series of polymers, the use of exclusively calcium phosphate based injectable bone cements has received great attention for their possible use in minimal invasive surgery.

Naturally, an injectable, yet inorganic material must consist of an extremely fine material of suitable reactivity. Numerous two component cements on the basis of calcium and phosphate-rich components have been investigated previously. Here, we present the advantageous application of a single component, fully inorganic cement based in amorphous tricalcium phosphate nanoparticles [2,3] synthesized by flame spray synthesis. The required driving force for setting is taken from an enthalpy gain by using amorphous tricalcium phosphate nanoparticles as starting materials. Use of nanoparticles enables formation of smoothly injectable cements. The reactivity of these novel cements was investigated by isothermal calorimetry, electron microscopy, nitrogen adsorption and X-ray diffraction. Cement properties were further discussed in terms of setting time, microhardness, apparent porosities, specific surface area and possible clinical applications [4].

References: [1] R.N. Grass, W.J. Stark, Chem. Commun., 14, 1767-1769 (2005), [2] S. Loher, W.J. Stark, M. Maciejewski, A. Baiker, S.E. Pratsinis, D. Reichardt, F. Maspero, D. Günther, W.J. Stark, Chem. Mater. 17 (1), 36-42 (2005), [3] S. Loher, V. Reboul, T.J. Brunner, M. Simonet, C. Dora, P. Neuenschwander W.J. Stark, Nanotechnology, 17(8), 2054-2061 (2006) [4] T.J. Brunner, M. Bohner, C. Dora, C. Gerber, W.J. Stark, Biomaterials, in review (2006)