eMax CAD vs eMax Press: a fracture mechanics characterization

Materials and Methods:

For determining K_IC, (6x6x6x12) mm triangular prism test specimens (20 per group) were manufactured either by cutting and grinding eMax CAD (Ivocalr-Vivadent, Schaan, Liechtenstein) blocks or by pressing eMax Press (Ivocalr-Vivadent, Schaan, Liechtenstein) ingots into moulds obtained by the lost wax technique. The notchless triangular specimen (NTP) K_IC test was used to determine K_IC. The samples (with a small defect induced in the middle of the edge to assist with the crack initiation) were mounted in the sample holder and tested with a universal testing machine (Instron model 4301, Instron Canada, Inc) at a cross-head speed of 0.1 mm/min. The maximum load at fracture was used to calculate K_IC. The results were analysed using t-test (α=0.05). Weibull statistical analysis was used to evaluate the characteristic strength and the reliability (Weibull modulus m) of each material. Fractured surfaces were characterized using scanning electron microscopy (SEM).

Result:

Table summarizes the results. The fracture toughness of eMax Press was significantly higher than that of eMax CAD; based on the Weibull analysis, both the characteristic strength and the reliability of eMax Press were higher than that of eMax CAD.

Conclusion: The results of this study suggest that eMax Press is superior to eMax CAD.

Acknowledgement: The study was kindly sponsored by Ivoclar Vivadent.

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