Leucite-Reinforced Glass-Ceramic: Degradation of the Mechanical Properties Under Fatigue

Objectives: To investigate the mechanical behavior of a leucite-reinforced glass-ceramic subjected to a fatigue test using the boundary technique.
Methods: Fifty ceramic slices (1.5 x 8.3 x 8.4 mm) were produced by cutting CAD-CAM blocks and cemented with resin cement over dentin analogue substrate (fiber-reinforced epoxi resin). For the monotonic test (n=20), a gradual compressive load (0.5 mm/min) was applied by a spherical stainless steel piston (6-mm diameter) to the center of the specimen immersed in 37° C water, using a universal testing machine. The initial crack was detected using an acoustic device. The fatigue test was performed in a mechanical cycling machine (37° C water, 2 Hz) (n=30). Specimens were tested at two different load levels for each preset lifetime (10,000 and 100,000 cycles) following the boundary technique. Failure analysis was performed with transillumination. Monotonic fracture load data were evaluated with Weibull analysis.
Results: Characteristic fracture load of 1,037 N and Weibull modulus of 5 were obtained with the monotonic test. Fracture load values estimated for 50% and 5% probability of failure after 10,000 cycles were 83 N and 48 N, respectively. A 19% decrease in fracture load was observed when the number of cycles increased from 10,000 to 100,000 cycles. The most frequent failure mode was radial crack.
Conclusions: Fatigue proved to be an important factor for the degradation of the mechanical properties of a leucite-reinforced glass-ceramic.