Effect of Aging on the Flexural Strength of Lithium Disilicate and Advanced Lithium Disilicate CAD-CAM Ceramic Materials: An in Vitro Study

Abstract

Objectives. Flexural strength is a critical property of a dental ceramic material as it indicates its ability to withstand occlusal forces without breaking or cracking. This in vitro study aimed to investigate the effect of thermomechanical fatigue loading on the flexural strength of lithium disilicate (LDS) and advanced lithium disilicate (ALDS) ceramic materials. Materials and methods. 80 specimens of LDS (IPS e.max CAD) and ALDS (CEREC Tessera) were prepared measuring 12 mm in length, 3 mm in thickness, and 4 mm in width. The specimens of each material were divided into two subgroups: one group underwent simulated aging for 1,200,000 cycles in a mastication simulator, while the other group was not subjected to aging conditions. The flexural strength was measured using a 3-point bend test on a universal testing machine. Two-way ANOVA and Independent sample t test were used to evaluate the results assuming a level of significance at p < 0.05. Results. Both material type and aging had significant effect on the flexural strength mean values (P < 0.001). Without aging, ALDS exhibited a significantly higher mean flexural strength (585.97 ± 29.09 MPa) compared to LDS glass ceramic (388.26 ± 34.33 MPa) (P < 0.001). After aging, the mean flexural strength of ALDS and LDS were 462.05 ± 14.71 MPa, and 310.14 ± 14.33 MPa respectively (P < 0.001). Conclusion. The flexural strength of advanced lithium disilicate glass ceramic was higher than lithium disilicate glass ceramic. Aging affected negatively the flexural strength of both materials.