Effect of Aging on Fracture Load and Reliability of Cemented Glass-Ceramics.

PURPOSE: Lithium disilicate (LD) and lithium silicate (LS) glass-ceramics may show a different acid etching behavior and mechanical integrity after aging. This study evaluated the influence of aging on the fracture load and reliability of glass-ceramics after different etching protocols. MATERIALS & METHODS: Specimens were fabricated and divided according to the etching time (10% hydrofluoric acid (HF) for 20s, 40s, and 60s). Etched surfaces were examined under microscopy. The ceramics were resin cemented to a dentin analog material. Samples were tested after 24 h (I) (n=20) or stored in 37°C water for 1 year (A)(n=20). A compressive load (0.1 mm/min) was applied to the samples until failure was detected by acoustic emission. The influence of aging on the fracture load (Lf) was tested by 2-way ANOVA and Tukey tests (α=0.05). The characteristic fracture load (L0) and Weibull modulus (m) values were calculated. RESULTS: LS etching for 20 s resulted in the highest immediate Lf, which was significantly decreased after aging (P≤0.05). Water-storage had no effect in this glass-ceramic Lf etched for 40 and 60s (P0.05). For LD, the etching time had no significant effect on the immediate and aged Lf (P0.05). The Lf was significantly reduced after aging (A) for LD (P≤0.05). Radial cracks were the predominant failure mode. Surface topography was more regular after lower etching times for LD, at after higher times for LS. CONCLUSIONS: After 1-year water-assisted aging, the evaluated etching times had no influence on the load-bearing capacity and structural reliability of resin-bonded glass-ceramics.