Objective: Zirconia ceramics with higher translucency are suitable for monolithic dental restorations. Aim of this study was in vitro wear characterization after hydrothermal accelerated aging of a new zirconia.
Methods: Steatite spheres were used as antagonists (Ceramtec, Ø 6 mm). 3M ESPE Lava Plus High Translucency Zirconia (LPZ) and 3M ESPE experimental veneering material (VM) were used as initial material groups (n=4). VM samples were tested with 9 µm diamond suspension polished surface. LPZ samples were tested polished (LPZp) and with as fired surface (LPZr). Groups (n=4) of LPZp and LPZr were hydrothermally aged in a steam autoclave at 135°C, 2 bar for 5 hours and 30 hours respectively.
Spheres and samples were fixed in a longitudinal moving abrasion test device (Elcometer 1720). Spheres were slid under water across material plates at a constant load of 5 N (path length 32 mm, 37 cycles/min for 120 min).
X-ray measurements were performed by micro diffraction (diameter 200 µm) in Bragg-Brentano geometry (Bruker D8 Discover) and semi-quantitative phase analysis of monoclinic phase (M) was done by the Rietveld method (Bruker TOPAS software).
Waviness depth (Wd) after abrasion was determined by profilometry (Mahr S2) at 6 positions per sample and surface roughness was measured before (Ra0) and after abrasion (Ra1). Sphere abrasion was measured by microscopy (Zeiss SV11) and volume loss (Vl) was calculated.
Results: Mean values (standard deviation) for Vl, Wd, Ra0, Ra1 and M are summarized in following table. For Vl two sample t-tests (p<0.05) were performed between the groups.
Conclusion: The VM has shown a statistically significant higher antagonist wear compared to Lava Plus zirconia LPZp before and after aging. Hydrothermal accelerated aging induced monoclinc crystal phase at the outer sample surface of LPZ, however wear properties did not show a significant change for LPZp and LPZr.
Keywords: Aging, CAD/CAM, Ceramics, Surfaces and Wear
See more of: Dental Materials 3: Ceramic-based Materials and Cements