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 ac id was incorporated in a calcium phosphate cement, with the aim not only to achieve some pharmacological effects but to obtain an improvement of its m echanical and rheological properties. It is known that, besides the analges ic 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(PO4)(2)] and precipitated hydroxyapatit e added as a seed. The liquid phase was an aqueous solution of Na2HPO4. The polymeric drug increased the injectability of the cement. The hydrolysis o f the alpha -tricalcium phosphate into calcium-deficient hydroxyapatite pro ceeded at a lower rate because of the addition of the polymeric drug. As a consequence, the cement hardening was slightly slower, although the final c ompressive strength was 25% higher. The bending strength increased from 5 t o 9 MPa with the addition of the polymeric drug. The strengthening of the s tructure was related to the reduction of porosity and the lower size of the precipitated crystals, as observed by scanning electron microscopy. (C) 20 01 John Wiley & Sons, Inc.