Method: Anatomically-correct monolithic crowns of glazed translucent zirconia (inCoris TZI, Sirona), sintered via three different processes (n = 10): Super-speed sintering (SS, 1580°C – 10 min); Speed sintering (S, 1510°C – 60 min); and Long-term sintering (LT, 1510°C – 7h), were tested in a mouth-motion chewing simulator (Willytec). Steatite balls (r= 3 mm) were used as antagonist at a maximum load of 200 N, 1.6 Hz, for 1.2 million cycles, while thermal cycling between 5 – 55 °C. Fatigue damage sustained in both crown and the antagonist was analyzed using SEM. Vickers hardness and toughness, as well as microstructure and composition of the three zirconia groups and for the steatite were analyzed.
Result: Vickers hardness (HV – GPa), toughness (KIC – MPa.m1/2), and grain size (D– μm) are show in the table bellow:
Groups |
HV (GPa) |
KIC (MPa.m1/2) |
D (μm) |
LT |
13.3 (0.1)a |
3.8 (0.1)a |
0.65 |
S |
13.1 (0.2)b |
3.4 (0.1)b |
0.54 |
SS |
13.1 (0.2)b |
3.7 (0.1)a |
0.56 |
Steatite |
04.3 (0.4) |
3.7 (2.0) |
- |
Microstructural analysis of the steatite revealed three different phases with crystal in a wide range of sizes. Sliding fatigue caused substantial wear of the glaze layer, exposing the underlying zirconia. LT zirconia group showed more pits on the worn surface and less but deeper cracks on the cross section, relative to S and SS zirconia groups. The steatite indenters exhibited significant wear in the sliding contact area, and the wear characteristics were substantially similar among the groups.
Conclusion: The glazed monolithic translucent zirconia can be considered a suitable option for long-lasting esthetic restorations with improved resistance to fracture. Supported by NIH/NIDCR 2R01 DE017925.