Title: Clinically-relevant Surface Treatments on Zirconia Phase Transformation and Lattice Deformation
Hazem Shuaeib (Presenter)
New York University
Minglei Zhao, New York University
Marina Kaizer, New York University
Yu Zhang, New York University
Objectives: Although the clinically-relevant surface treatments like grinding, polishing, and sandblasting have shown tremendous impact on the mechanical and optical properties of dental zirconia, the influence of such treatments on zirconia phase transformation remains elusive. The objective of this study is to shed light on the mechanism of phase transformation of zirconia subjected to clinically-relevant surface treatments and aging.
Methods: Lightly sintered zirconia blanks (3Y-0.25Al-TZ, Tosoh, Japan) were obtained and sectioned into plates of 15 mm (width) × 15 mm (length) × 1 mm (height). The plates were then sintered at 1350 oC for 2 h with a heating/cooling rate 8 oC/min. Five surface treatments were applied on sintered specimens: wet grinding with high-speed diamond burs, dry grinding with slow-speed adjusting burs, dry grinding followed by polishing with rubber burs, sandblasting, and simulated glaze firing at 950 oC for 1 min. Finally, the above five specimen groups together with an untreated control group were subjected to the low temperature degradation (LTD) test at 120 oC for different time intervals. The phase fraction before and after various surface treatments were comparatively studied by x-ray diffraction (XRD, PANalytical X’Pert diffractometer).
Results: Clinically-relevant surface treatments showed significant influence on the LTD of zirconia. Among these treatments, dry grinding yielded the most significant phase transformation in terms of decreasing the intensity of tetragonal phase and the formation of a shoulder on the left side of the dominant peak (101), accompanied by lattice deformation and domain switching. The results showed that simulated glaze firing can recover the tetragonal peak intensity, but the domain switching remained unchanged.
Conclusions: Each clinically-relevant surface treatment of zirconia gives a different phase transformation mode, among which simulated glaze firing and LTD have the same phase transformation mode regardless of the previous treatments.