Static and fatigue mechanical behavior of three dental CAD/CAM ceramics

Abstract

PurposeThe aim of this study was to measure the mechanical properties and fatigue behavior of three contemporary used dental ceramics, zirconia Cercon® (ZC), lithium disilicate e.max® CAD (LD), and polymer-infiltrated ceramic Enamic® (PIC). MethodsFlexural strength of each CAD/CAM ceramic was measured by three point bending (n=15) followed by Weibull analysis. Elastic modulus was calculated from the load–displacement curve. For cyclic fatigue loading, sinusoidal loading with a frequency of 8Hz with minimum load 3N were applied to these ceramics (n=24) using three point bending from 103 to 106 cycles. Fatigue limits of these ceramics were predicted with S–N fatigue diagram. Fracture toughness and Vickers hardness of the ceramics were measured respectively by single edge V-notch beam (SEVNB) and microindentation (Hv 0.2) methods. Chemical compositions of the materials׳ surfaces were analyzed by EDS, and microstructural analysis was conducted on the fracture surfaces by SEM. One-way ANOVA was performed and the level of significance was set at 0.05 to analyze the numerical results. ResultsThe mean flexural strength of ZC, LD, and PIC was respectively 886.9, 356.7, and 135.8MPa. However, the highest Weibull modulus belonged to PIC with 19.7 and the lowest was found in LD with 7.0. The fatigue limit of maximum load for one million cycles of ZC, LD, and PIC was estimated to be 500.1, 168.4, and 73.8GPa. The mean fracture toughness of ZC, LD, and PIC was found to be respectively 6.6, 2.8, and 1.4MPam1/2, while the mean Vickers hardness was 1641.7, 676.7, and 261.7Hv. Fracture surfaces followed fatigue loading appeared to be smoother than that after monotonic loading. ConclusionsMechanical properties of ZC were substantially superior to the two other tested ceramics, but the scattering of data was the least in PIC. The fatigue limit was found to be approximately half of the mean flexural strength for all tested ceramics.