Properties of elastomeric calcium phosphate cement-chitosan composites

Objective. Self-hardening calcium phosphate cements (CPC) have been shown to be efficacious in a number of clinical applications. For some applications it is desirable to have CPC in a non-rigid resorbable elastomeric matrix. In the present study, chitosan was evaluated as the matrix for preparing CPC-chitosan composites. Methods. Cement specimens were prepared by mixing CPC powder (an equimolar mixture of tetracalcium phosphate and dicalcium phosphate anhydrous) with a chitosan solution at a powder/liquid ratio of 2-2.5. The setting time was measured by a Gilmore needle method. A standard three-point flexural test was used to fracture the specimens at a crosshead speed of 0.5 mm/min. Powder X-ray diffraction analysis was used to determine the conversion of the CPC to hydroxyapatite. Results. The CPC-chitosan composites were more stable in water than conventional CPC. They did not disintegrate even when placed in water immediately after mixing. The CPC-chitosan paste hardened within 10 min in all cases. The 1 d mean flexural modulus (GPa) for the control CPC was 5.3 (0.3) (mean (standard deviation); n = 5), and that for CPC-chitosan composites were between 2.7 (0.3) and 4.7 (0.3). The 1 d mean flexural strength (MPa) for the control was 16.6 (1.9), and that for the CPC-chitosan ranged from 4.5 (0.5) and 12.0 (1.0) (n = 5). Chitosan did not interfere the conversion of CPC components to hydroxyapatite. Significance. This study demonstrates that CPC-chitosan composites are stable in a wet environment and have acceptable mechanical strengths for clinical applications. Published by Elsevier Ltd on behalf of Academy of Dental Materials.