Mechanical and rheological improvement of a calcium phosphate cement by the addition of a polymeric drug.

A polymeric acrylic system supporting a derivative of the aminosalicylic acid was incorporated in a calcium phosphate cement, with the aim not only to achieve some pharmacological effects but to obtain an improvement of its mechanical and rheological properties. It is known that, besides the analgesic and anti-inflammatory properties, the salicylic group presents a calcium complexation ability. The inorganic phase of the cement consisted of alpha-tricalcium phosphate [alpha-Ca(3)(PO(4))(2)] and precipitated hydroxyapatite added as a seed. The liquid phase was an aqueous solution of Na(2)HPO(4). The polymeric drug increased the injectability of the cement. The hydrolysis of the alpha-tricalcium phosphate into calcium-deficient hydroxyapatite proceeded at a lower rate because of the addition of the polymeric drug. As a consequence, the cement hardening was slightly slower, although the final compressive strength was 25% higher. The bending strength increased from 5 to 9 MPa with the addition of the polymeric drug. The strengthening of the structure was related to the reduction of porosity and the lower size of the precipitated crystals, as observed by scanning electron microscopy.