Objectives: To determine the effect of CAC additions on the hardness of glass ionomer cement.
Methods: Specimens were prepared using GC Fuji I Glass Ionomer Luting Cement (Tokyo, Japan) and Secar 71 CAC Cement (Lafarge Calcium Aluminates, Chesapeake, VA). The CAC is composed of approximately 45% CaAl2O4, 54% CaAl4O7, and 1% Ca12Al14O33. The liquid to powder ratio was kept constant; however, part of the powder was replaced by CAC to produce nine concentrations between 0 and 100% CAC. The liquid and power were mixed for 100 seconds and then placed into silicone molds and stored under 100% relative humidity until fully set. They were then removed from the molds and stored at 100% relative humidity for one week. Knoop hardness testing was done with a 100 gram load. ANOVA, Tukey, and linear regression statistical tests were done with α=0.05.
Results: The hardness decreased with increasing amounts of CAC. Statistical differences were found between the hardness means for highest and lowest amounts of CAC (p≤0.05). The highest hardnesses were found with 0% CAC, 58 KNH; and the lowest with 87.5% CAC, 33 KNH. Linear regression produced the following equation for the relationship between percent CAC and hardness: Hardness (KHN) = -0.28 (Percent CAC) + 58; r2 = 0.56
Conclusion: Addition of CAC caused reduced hardness in a glass ionomer cement.