Impact of water on the fracture behavior of an advanced lithium disilicate

Objective To investigate the influence of water on the monotonic and fatigue strength of a lithium disilicate glass-ceramic. Methods Ninety bar-shaped specimens (1.0 × 1.0 × 12.0 mm) were prepared from Advanced Lithium Disilicate (CEREC Tessera; Dentsply Sirona). Half of the specimens were stored in deionized water (W) at 37 °C for 30 days, while the other specimens stayed dry (D). A three-point bending test was carried out in a dry/wet environment (subgroup d/w) to determine monotonic strength. A stepwise fatigue test was conducted for dry-stored specimens in a dry environment (Dd) and wet-stored specimens in water (Ww). Results For monotonic strength, the testing environment had a significant effect (p < 0.001), whereas the storage environment did not (p = 0.054). Testing in water generated a lower monotonic strength (Dw: 243 ± 35 MPa; Ww: 250 ± 57 MPa) than in a dry environment (Dd: 324 ± 74 MPa; Wd: 376 ± 60 MPa). Wet storage combined with testing in water exhibited similar fatigue strength (Ww: 148 ± 39 MPa) to the group without water intervention (Dd: 152 ± 36 MPa). Conclusions While storage in 37 °C water for 30 days causes ion release from lithium disilicate, it does not decrease its monotonic strength. The compressive loading in water resulted in a degradation of around 30%. The fatigue protocol in this study resulted in about 50% of the initial strength regardless of testing conditions.