Fatigue is one of the most important properties to be considered in ceramic
dental implants due to cyclic mechanical stresses arising from the chewing
process. In this work, the fatigue behaviour of hydrothermally degraded
ZrO2-based ceramics stabilized with 3mol% Y2O3 (3Y-TZP) was studied in
4-point bending tests. Samples of 3Y-TZP were compacted (100MPa), sintered
at 1475 ?C for 2 h, polished and hydrothermally degraded in an autoclave as
described in the ISO-13356 standard. The samples were characterized by their
relative density, crystalline phase composition, microstructure and surface
roughness. The highly dense (>99.6%TD) sintered 3Y-TZP ceramics has only
tetragonal t-ZrO2 phase, even after hydrothermal ageing. Furthermore, the
ceramic materials presented a Vickers hardness of 12.7?0.2GPa, a fracture
toughness of 7.1?0.3MPa?m1/2 and a 4-point bending strength of 940.1?67MPa.
Based on the bending test results 5 different stress levels for the fatigue
tests were selected and conducted by cyclic 4-point bending obtaining the
S-N curve. Weibull statistics was used for the statistical analysis. The
fatigue tests indicate that the limit of fatigue resistance of this 3Y-TZP
ceramics is around 550MPa, i.e. higher than the limits established in the
ISO-13356 standard for the use of Y-TZP ceramics for the manufacture of
implants. The fatigue behaviour of the investigated 3Y-TZP ceramics was
related to the toughening mechanisms acting in Y-TZP ceramics, such as
transformation toughening related to t?m phase transformation and
microcracking.