Effects of hydroxypropyl methylcellulose and other gelling agents on the handling properties of calcium phosphate cement.

The calcium phosphate cement (CPC) used in this study was formed by combining equimolar amounts of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). This powder, when mixed with water, sets to a hard cement in about 30 min. However, the water-based CPC paste is not highly cohesive and is vulnerable to washout until hardening occurs. The objectives of this study were to investigate the effects on handling properties, washout resistance, cement hardening behavior, and mechanical properties of adding several gelling agents to CPC paste. Aqueous solutions that contained a mass fraction of 2-4% of hydroxypropyl methylcellulose (HPMC), carboxyl methylcellulose (CMC), chitosan acetate, and chitosan lactate were used as cement liquids. Hardening time was measured by the Gilmore needle test; resistance to washout was evaluated by the disintegration of the cement specimen in water with agitation; and mechanical strength was evaluated by the measurement of diametral tensile strength and compressive strength. Handling properties were greatly improved by the addition of HPMC, CMC, chitosan acetate, and chitosan lactate. Hardening time was retarded by the additions of HPMC and CMC, and mechanical strength was weakened by the addition of either the chitosan lactate or the chitosan acetate.