Fatigue performance of adhesively cemented glass-, hybrid- and resin-ceramic materials for CAD/CAM monolithic restorations

Objective: To evaluate the fatigue failure load, number of cycles until failure, and survival probability of adhesively cemented materials with different microstructures (glass-, hybrid- and resin-ceramic) used to manufacture CAD/CAM monolithic restorations. Methods: Disc-shaped specimens (n = 15; Ø = 10 mm; thickness = 1.0 mm) were produced from CAD/CAM blocks as follows: feldspathic (FEL); leucite (LEU); lithium disilicate (LD); zirconia-reinforced lithium silicate (ZRLS); polymer-infiltrated ceramic network (PICN); and resin nanoceramic (RNC). Adhesive cementation was performed onto epoxy discs (dentin analogue- Ø = 10 mm; thickness = 2.5 mm). The cemented assemblies were subjected to fatigue testing using a step–stress approach (400 N–2200 N; step-size of 200 N; 10,000 cycles per step; 1.4 Hz). Fatigue data were analyzed using Kaplan–Meier and Mantel–Cox (log-rank) tests (p < 0.05) and Weibull statistical analysis. Fractographic analysis was also performed. Results: All RNC specimens survived the fatigue test (100% probability of survival at 2200 N; 100,000 cycles) and presented occlusal deformation in response to loading, while all other tested materials failed in distinct loading steps with radial cracks starting from the bonding surface. LD (1146.7 N; 47,333) and ZRLS (1013.3 N; 40,666) materials obtained the highest fatigue failure loads and cycles until failure, meanwhile all PICN specimens failed during the first step (0% probability of survival at 400 N; 10,000). FEL had similar Weibull modulus to LD and ZRLS and higher than LEU for both load and number of cycles outcomes. Significance: The microstructure of adhesively cemented glass-, hybrid- and resin-ceramic CAD/CAM restorative materials influence their response during fatigue testing, which aids in suggesting the best clinical indications.