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Objective: To evaluate the relationship between relative translucency and fracture toughness obtained from the chevron notched beam (CNB) method of different zirconia ceramics.
Materials and Methods: Ten specimens of two commercial zirconia ceramics were cut into tiles to investigate their relative translucency: translucency parameters (TP) and contrast ratio (CR) using a spectrophotometer. Additionally, bar specimens were prepared to determine the fracture toughness using the CNB method and a four-point flexural test. Data were analyzed using one-way ANOVA, and Tukey’s HSD test (=0.05). The CR value ranged between 0.69 to 0.74 with no significant differences among the groups except Prettau anterior (PRTA), which had significantly a lower CR value than other tested groups. For InCoris group, the TP was in the range of 12 to 13 with no significant differences between groups, whereas there was a significant difference between Prettau and PRTA. The PRTA has the highest translucency with the TP of 14.30±0.75 and the largest grain size, but the least fracture toughness.
Results: The results of the present study showed that more translucent zirconia had a lower fracture toughness compared with those of less translucent ones. Moreover, zirconia ceramics, that were purported to be translucent by the manufacturer may not precisely be more translucent than the conventional zirconia core materials.
Conclusion: It was found that more translucent zirconia seemed to have a larger grain size and a lower fracture toughness compared with more opaque zirconia.
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