Phase Transformations and Subsurface Changes in Three Dental Zirconia Grades after Sandblasting with Various Al2O3 Particle Sizes

Abstract

Although sandblasting is mainly used to improve bonding between dental zirconia and resin cement, the details on the in-depth damages are limited. The aim of this study was to evaluate phase transformations and subsurface changes after sandblasting in three different dental zirconia (3, 4, and 5 mol% yttria-stabilized zirconia; 3Y-TZP, 4Y-PSZ, and 5Y-PSZ). Zirconia specimens (14.0 × 14.0 × 1.0 mm3) were sandblasted using different alumina particle sizes (25, 50, 90, 110, and 125 µm) under 0.2 MPa for 10 s/cm2. Phase transformations and residual stresses were investigated using X-ray diffraction and the Williamson-Hall method. Subsurface damages were evaluated with cross-sections by a focused ion beam. Stress field during sandblasting was simulated by the finite element method. The subsurface changes after sandblasting were the emergence of a rhombohedral phase, micro/macro cracks, and compressive/tensile stresses depending on the interactions between blasting particles and zirconia substrates. 3Y-TZP blasted with 110-µm particles induced the deepest transformed layer with the largest compressive stress. The cracks propagated parallel to the surface with larger particles, being located up to 4.5 µm under the surface in 4Y- or 5Y-PSZ subgroups. The recommended sandblasting particles were 110 µm for 3Y-TZP and 50 µm for 4Y-PSZ or 5Y-PSZ for compressive stress-induced phase transformations without significant subsurface damages.

Effect of 9% Hydrofluoric Acid Gel Hot-Etching Surface Treatment on Shear Bond Strength of Resin Cements to Zirconia Ceramics

“…Previous studies have shown that sandblasting with aluminium oxide particles increases or decreases the strength of zirconia [ 38 , 39 ]. In addition, sandblasting can be affected by various factors, such as the injection pressure and time, particle shape, and size of the aluminium oxide particles [ 38 , 40 ]. The use of sandblasting presents a problem in terms of long-term stability due to surface phase transformation (t-m).…”

Effect of the Plasma Gas Type on the Surface Characteristics of 3Y-TZP Ceramic

“…By estimating from the slope and y-intercept of the W-H plot with Scherrer’s equation [ 36 , 37 ], strain and particle size were compared. Since the positive slope indicates the tensile strain [ 15 ], the development of a compressive strain could be estimated from the flatter slope in the N 2 /Ar group. A decrease in crystallite size, due to the lattice shrinkage and the occurrence of compressive strain in the N 2 /Ar group, could contribute to the peak broadening.…”

“…The data were collected in the 2θ range of 20–90 with a step size of 0.02 and a step time of 4 s/step. The quantitative phase analysis was obtained by Rietveld refinement implemented in the Fullprof program [ 15 ]. Especially, Williamson–Hall (W–H) analysis was used to determine the changes in the crystallite size and the lattice strain induced by the plasma treatment using the formula as given below [ 50 ]: where β is the integral breadth or the full width at half maxima, D is the crystallite size, K is a shape factor (0.9), and ɛ is the strain.…”

“…However, zirconia is characterized by a chemically inert surface with low reactivity which limits a reliable bonding with resin cement, cell adhesion, or osseointegration [ 13 , 14 ]. Although mechanical surface treatments tended to increase the bond strength of zirconia with resin cement through micromechanical retention, the induced cracks and surface damages could cause a deterioration of fracture resistance of zirconia [ 15 ]. Therefore, the plasma surface treatment has been considered as an alternative to the mechanical surface treatment aiming to raise the surface energy of materials by the generation of polar groups at the surface [ 16 ].…”

Effect of hot etching with HF on the surface topography and bond strength of zirconia

“…The reason may be that the concentration of HF selected in this experiment is higher than that of You-Jung's experiment. In previous studies, some scholars pointed out that the concentration of HF would affect the effect of hot etching on zirconia and found that with the increase of the concentration of HF, the surface roughness would increase accordingly (Kim et al, 2021). Moreover, this finding explains why the two experiments above have different results.…”