Fatigue behaviour of fully crystallised glass-based CAD/CAM ceramics

This study aimed to investigate the fatigue behaviour of a novel fully crystallised lithium disilicate CAD/CAM ceramic in comparison to glass-based CAD/CAM materials.

The fully crystallised lithium disilicate (Initial LiSi Block; LISI), along with a fully sintered zirconia-containing lithium silicate (ZLS) (Celtra DUO; DUO) and a leucite-based glass ceramic (Empress CAD; EMP), were investigated. Flexural strength and flexural modulus (n = 15) were tested via three-point bending. After adhesively luting to dentine analogue abutments (30 % glass fibre reinforced polyamide-nylon 6,6; RPN), CAD/CAM-fabricated anatomic maxillary premolar crowns were subjected to wet cyclic step-stress loading until fracture (500 N initial load, 100 N step size, 100,000 cycles per step, 20 Hz frequency; n = 12). After testing the data normality and homogeneity of variance, statistical analysis was performed using one-way ANOVA, Kruskal-Wallis test, and median-rank Weibull analysis, with survival probability assessed by Mantel-Cox Log-Rank test (α = 0.05, 95 % CI).

Significant difference in flexural strength was detected among three glass-based ceramics (p < 0.001), while no significant difference was observed in flexural modulus (p = 0.630). No significant difference was found in the fatigue failure load (FFL) and number of cycles until failure (NCF) among groups (p = 0.106 and 0.061, respectively), except for the significantly higher NCF of LISI than EMP (p = 0.049). Despite similar survival probabilities (p = 0.165), LISI showed the highest FFL and structural reliability, and the lowest relative standard deviation (RSD).

Three chairside glass-based CAD/CAM materials presented satisfactory fatigue properties for single-unit restorations, with LISI showing higher reliability under fatigue loading.