How oral environment simulation affects ceramic failure behavior

Publication date: Available online 18 September 2017
Source:The Journal of Prosthetic Dentistry
Author(s): Ediléia Lodi, Kátia R. Weber, Paula Benetti, Pedro H. Corazza, Álvaro Della Bona, Márcia Borba
Statement of problemInvestigating the mechanical behavior of ceramics in a clinically simulated scenario contributes to the development of new and tougher materials, improving the clinical performance of restorations. The optimal in vitro environment for testing is unclear.PurposeThe purpose of this in vitro study was to investigate the failure behavior of a leucite-reinforced glass-ceramic under compression loading and fatigue in different simulated oral environment conditions.Material and methodsFifty-three plate-shaped ceramic specimens were produced from computer-aided design and computer-aided manufactured (CAD-CAM) blocks and adhesively cemented onto a dentin analog substrate. For the monotonic test (n=23), a gradual compressive load (0.5 mm/min) was applied to the center of the specimens, immersed in 37ºC water, using a universal testing machine. The initial crack was detected with an acoustic system. The fatigue test was performed in a mechanical cycling machine (37ºC water, 2 Hz) using the boundary technique (n=30). Two lifetimes were evaluated (1×10⁶ and 2×10⁶ cycles). Failure analysis was performed using transillumination. Weibull distribution was used to evaluate compressive load data. A cumulative damage model with an inverse power law (IPL) lifetime-stress relationship was used to fit the fatigue data.ResultsA characteristic failure load of 1615 N and a Weibull modulus of 5 were obtained with the monotonic test. The estimated probability of failure (Pf) for 1×10⁶ cycles at 100 N was 31%, at 150 N it was 55%, and at 200 N it was 75%. For 2×10⁶ cycles, the Pf increased approximately 20% in comparison with the values predicted for 1×10⁶ cycles, which was not significant. The most frequent failure mode was a radial crack from the intaglio surface. For fatigue, combined failure modes were also found (radial crack combined with cone crack or chipping).ConclusionsFatigue affects the fracture load and failure mode of leucite-reinforced glass-ceramic.



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