Effect of Water on Mechanical Properties of Core Build-up Materials

Method: Four materials were investigated: Grandio core, Core.X flow, Bright flow core, and Speedee. The flexural strength and compressive strength were determined by using uniaxial three-point bending test (25 mm x 2 mm x 2 mm) and (6 mm high x 4 mm diameter) respectively.  160 Specimens for flexural strength and compressive strength were tested (80 specimens for each test) after being incubated for 30 days (10 specimens were stored dry and 10 specimens were stored wet for each material) at 37 ºC, and at cross head speed of 0.5mm/min, using a Universal Testing Machine (Zwick/Roell Z020, Leominster,UK). The data was analysed with One-Way (ANOVA) followed by Tukey post-hoc test (P<0.05) to detect the differences (for each property) between the tested materials in the dry and wet conditions. Independent-samples T-test was used to analyse the wet and dry condition for each material (for each property) (P<0.05).

Result:   The mean flexural strength, compressive strength and standard deviation of the tested materials were calculated and summarized in Table 1. Same superscript letters indicate no statistical difference within the same column (P<0.05). While values followed by different superscript numbers show statistical difference within the same row for each property (P<0.05). 

Conclusion: Water storage significantly reduced the flexural strength of the tested materials.  The compressive strength of the tested materials was not significantly affected by water storage.