The purpose of this study was to measure the flexural strength and hardness of four core materials in 4 different medias and to evaluate the relationship between the physical properties.

For the flexural strength, the specimens were prepared from each of the following materials: Bisfil Core, Core Max, Fuji IX GP, Miracle Mix and randomly divided into four groups and stored at 37 degree C in the following medias: distilled water for 24 hours (DW/1), distilled water for 30 days (DW/30). 2% NaF for 30 days (NF/30), 0.02N lactic acid for 30 days (LA/30). After storage, the specimens were subjected to flexural strength testing and calculated to flexural modulus.

For hardness testing, specimens were prepared from four materials and storaged in the uniform way. After storage, the specimens were subjected to Vicker's hardness testing.

1. The flexural strength of Core Max were the highest, and the flexural strength of Miracle Mix were the lowest.

2. The hardness of Bisfil Core were the highest.

3. The hardness of Core Max were the highest.

4. The hardness of Miracle Mix were the lowest.

5. 2% NaF and 0.02N lactic acid negatively affected the flexural strength and hardness of four core materials.