Biaxial flexural strength of lithium-based CAD/CAM dental glass-ceramics

Abstract

Abstract: Objective: The aim of this study was to evaluate the biaxial flexural strength of four CAD/CAM dental glass-based ceramics containing lithium in the crystalline structure.

Material and methods: A universal testing machine is used to evaluate the biaxial flexural strength of four groups of ceramic materials: IPS e.max CAD, GC LiSi Block, CEREC Tessera, and unbranded. Each group contains 20 samples, for a total of 80 samples. In addition to that, the microstructure was examined using SEM. Results were analyzed using one-way ANOVA followed by the Tukey test for multiple comparisons, with statistical significance set at p < 0.05 and a 95% confidence interval. Weibull Analysis was used to assess the biaxial flexural strength and was also based on the 66% log-likelihood parameter for the different ceramics.

Result: CEREC Tessera demonstrated the highest BFS, while GC LiSi Block was the lowest. There were no statistically significant differences between IPS e.max CAD, CEREC Tessera, and unbranded (p>0.05), whereas GC LiSi Block exhibited significant differences (p<0.05). The chemical composition and microstructure of the tested samples varied significantly, including the presence of zirconium oxide (ZrO₂) in IPS e.max CAD and distinct crystal morphologies across the materials.

Conclusion: Statistically significant differences in biaxial flexural strength (BFS) were observed between GC LiSi Block and the other ceramic groups, with GC LiSi Block exhibiting the lowest flexural strength (p < 0.05). Additionally, the chemical composition and microstructure of the tested samples varied significantly. Therefore, both null hypotheses of this study were rejected. From a clinical perspective, despite these variations, all tested materials exceeded the ISO 6872:2015 threshold of 300 MPa, confirming their suitability for various restorative applications.