Fatigue testing of two porcelain–zirconia all-ceramic crown systems

The fracture load and failure types of veneered anterior zirconia crowns: An analysis of normal and Weibull distribution of complete and censored data

“…The fatigue of tested groups was not considered in this study. Certainly fatigue aspect is often the clinical phenomena particularly in aged restorations [26][27][28][29]. Further studies should investigate the aging of all-ceramic systems and compare the data with the findings of this study.…”

Biomechanical evaluation of internal and external hexagon platform switched implant-abutment connections: An in vitro laboratory and three-dimensional finite element analysis

“…Three specimens of each group underwent single-load-to-fracture (SLF) testing at a crosshead speed of 1 mm/min in a universal testing machine (INSTRON 5666, Canton, MA, USA) with a flat tungsten carbide indenter applying the load on the lingual side of the crown, close to the incisal edge. Based upon the mean load to failure from SLF, three step-stress accelerated life-testing profiles were determined for the remaining 18 specimens of each group which were assigned to a mild (n = 9), moderate (n = 6), and aggressive (n = 3) fatigue profiles (ratio 3:2:1, respectively) [30,33]. Mild, moderate and aggressive profiles refer to the increasingly step-wise rapidness in which a specimen is fatigued to reach a certain level of load, meaning that specimens assigned to a mild profile will be cycled longer to reach the same load of a specimen assigned to either moderate or aggressive profiles.…”

“…Thus, during SSALT each specimen was submitted to constant stress during a predetermined length of time. The stress on this specimen is thus increased step by step until failure (bending or fracture of the fixation screw and/or abutment) or survival (no failure occurred at the end of step-stress profiles, where maximum loads were up to 600 N) [30,33]. Based upon the step-stress distribution of the failures, the fatigue data were analyzed using a power law relationship for damage accumulation and the use level probability Weibull curves (probability of failure vs. cycles) at a use stress load were determined for life expectancy calculations by using the software Alta Pro 7 (Reliasoft, Tucson, AZ) [34].…”

“…The Beta (ˇ) values and associated upper and lower bounds derived from use level probability Weibull calculation (probability of failure vs. number of cycles) of 1.31 (0.75-2.28) and 1.83 (1.01-3.32) for platformswitched implants (groups SWT-EH and SWT-IH, respectively), and ˇ values of 1.55 (0.78-3.06) and 1.82 (1.02-3.25) for regular platform implants (groups REG-EH and REG-IH, respectively) indicated that fatigue was an accelerating factor for all groups. The Beta value describes failure rate changes over time (ˇ < 1: Failure rate is decreasing over time, commonly associated with "early failures" or failures that occur due to egregious flaws; ∼ 1: failure rate that does not vary over time, associated with failures of a random nature; ˇ > 1: Failure rate is increasing over time, associated with failures related to damage accumulation) [30,45,46].…”

“…Controversially, several published studies [1,12,13,15,16,19,[25][26][27] related to the mechanics of platformswitched implants have been restricted to analyzing the stress distribution on peri-implant bone and not on the overall system biomechanical behavior. To date, studies evaluating the mechanical behavior of platform-switched implants considering the stress distribution in implantabutment complex are scarce and restricted to computer simulations [14,17,28,29], which do not consider several clinical variables (influence of fatigue damage accumulation and wet environment) previously reported as important factors to reproduce clinically observed failure modes [30].…”