The biaxial flexural strength and fatigue property of Lava™ Y-TZP dental ceramic

Objectives: The development of yttrium oxide partially stabilized zirconia (Y-TZP) has allowed the use of ceramic in load-bearing sites. The aim of this study was to evaluate and compare the biaxial flexural strength, hardness and fatigue life of colored and uncolored zirconia in the LAVA™ system. Materials and methods: Eight groups (n = 30) of standardized disc specimens (15 mm × 1.3 mm) were used to examine the biaxial flexural strength (ISO 6872 standard) using a Dartec HC10 Fatigue Tester (Zwick Ltd., UK) and Vickers hardness was also measured. The uncolored, FS4, FS7 groups were also submitted to dynamic fatigue testing to produce stress-number curves. The strength reliability was analyzed using Weibull distribution. Results: All groups had a mean biaxial flexural strength, hardness and Weibull modulus (m) of approximately 1100 MPa, 1300 HV and 9.8-12.9, respectively. One-way analysis of variance (ANOVA) showed no significant difference in biaxial flexural strength among the eight groups (p > 0.05). Two-way ANOVA showed no significant differences in hardness values among groups except FS1 and FS5 which had significantly higher hardness values than FS4 and FS7 (p < 0.001) and FS5 also had a higher hardness value than FS3 (p < 0.05). Additionally, uncolored, FS4 and FS7 survived at 5 × 10⁵ cycles at a stress level in the range of 60-65% of the mean biaxial flexural strength. Conclusion: There was no difference in flexural strength of uncolored and colored Y-TZP ceramic. The fatigue limit of uncolored, FS4 and FS7 zirconia may be defined as lying between 60 and 65% of the stress to failure.