Calcium Aluminum Cement - Effect of Water Reducing Agents

Calcium aluminate cements have been developed for restorative applications and have demonstrated good esthetic, working, and mechanical properties. Objectives: comparison of CAC hardness with differing water reducing agents to determine optimal mechanical properties. The hypothesis for this study is that water reducing agents will increase hardness of CAC materials. Methods: Samples were prepared using a mixture of calcium aluminates powder (70%) & colloidal silica (30%). Additions of 0.0% (control), 0.5%, 1.0%, 1.5%, and 2.0% (w/w %) of four of the following water reducing agents were utilized: sodium citrate, disodium EDTA, Castomet F10 & sodium lignosulfonate. Five microhardness (Vickers) values were then taken, statistical analysis performed and means calculated. Results: Greatest hardness (HV0.5) increase was seen with treatment of 1.5% Castomet F10, 115.1 compared to 72.6 for control and was significantly higher than both the control 0.5, 1.0, and 2.0% samples (p<0.05). 0.5% EDTA produced slightly higher hardness than the control and 1.0, 1.5, and 2.0% caused slightly lower hardness. 1.5% sodium lignosulfonate demonstrated a 30% increase in hardness over control and 0.5% and 1.0% sodium lignosulfonate produced statistically similar hardness values, 2.0% sodium lignosulfonate produced 32% lower hardness. Hardness values of all sodium citrate treatments were marginally higher, average 10 greater than control. All sodium citrate additions produced statistically significant increases in hardness than the control (p<.001), increases ranged from to 9 to 16%. Conclusion: Castomet F10, sodium lignosulfonate, and Sodium Citrate all increase the hardness of CAC formulations, while disodium EDTA decreases hardness of CAC formulations, Water reducing agents increase the hardness of CAC formulations, in some cases as much as 40%. While working time was not considered in this study, a balance between water reduction and physical properties is essential and should be focused on in future studies. Partially funded by NIDCR DE07057.