Effects of surface treatments and low temperature degradation on zirconia phase transformations



Niyati Reddy

Reddy, Niyati1, Shauib, Hazem2, Lim, Chek Hai1, Zhang, Yu1
1University of Pennsylvania School of Dental Medicine, Department of Preventive and Restorative Sciences
2NYU College of Dentistry, Biomaterials and Biomimetics

Introduction

There has been evidence that clinically relevant surface treatments such as grinding, polishing, and sandblasting have shown marked effects on the mechanical and optical properties of dental zirconia but their effects on zirconia Low-Temperature Degradation (LTD) and phase transformation is still elusive. This study is designed to shed light on the LTD of dental zirconia based on clinically relevant surface treatments.

Methods

Zirconia blanks were obtained from Tosoh Corporation and sectioned into 72 plate-shaped specimens (ϕ14x1 mm). Specimens were divided into two main groups: glazed and non-glazed. The glazed specimens were annealed at 950°C for 1 minute using a simulated glaze firing protocol. These were further divided into six groups: glazed control, glazed sandblasting, glazed grinding, non-glazed control, non-glazed sandblasting, non-glazed grinding. All specimens were subjected to LTD testing at 120°C for different time intervals. Phase transformation was analyzed using the X-ray diffraction (XRD) technique to unravel the potential effects of these surface treatments on mechanical properties.

Results

The clinically relevant surface treatments on dental zirconia showed phase transformation in all specimens. A partial recovery of the transformed phase to tetragonal was observed, but domain switching remained unchanged after annealing the specimens using a simulated glaze firing protocol. The non-glazed surface-treated specimens have the highest monoclinic content among all LTD tested specimens compared to glazed specimens.

Conclusion

Surface treatments play a role in transforming the phase of dental zirconia, which significantly affects the following clinical glazing procedure and their subsequent effects on LTD in simulated oral environments.