Restor Dent Endod.  2020 Feb;45(1):e6. 10.5395/rde.2020.45.e6.

Effect of hydrofluoric acid-based etchant at an elevated temperature on the bond strength and surface topography of Y-TZP ceramics

• Yu MK
• Lim MJ
• Na NR
• Lee KW

• KMID: 2470341
• DOI: http://doi.org/10.5395/rde.2020.45.e6

Abstract

OBJECTIVES
This study investigated the effects of a hydrofluoric acid (HA; solution of hydrogen fluoride [HF] in water)-based smart etching (SE) solution at an elevated temperature on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics in terms of bond strength and morphological changes.
MATERIALS AND METHODS
Eighty sintered Y-TZP specimens were prepared for shear bond strength (SBS) testing. The bonding surface of the Y-TZP specimens was treated with 37% phosphoric acid etching at 20°C-25°C, 4% HA etching at 20°C-25°C, or HA-based SE at 70°C-80°C. In all groups, zirconia primers were applied to the bonding surface of Y-TZP. For each group, 2 types of resin cement (with or without methacryloyloxydecyl dihydrogen phosphate [MDP]) were used. SBS testing was performed. Topographic changes of the etched Y-TZP surface were analyzed using scanning electron microscopy and atomic force microscopy. The results were analyzed and compared using 2-way analysis of variance.
RESULTS
Regardless of the type of resin cement, the highest bond strength was measured in the SE group, with significant differences compared to the other groups (p < 0.05). In all groups, MDP-containing resin cement yielded significantly higher bond strength values than MDP-free resin cement (p < 0.05). It was also shown that the Y-TZP surface was etched by the SE solution, causing a large change in the surface topography.
CONCLUSIONS
Bond strength significantly improved when a heated HA-based SE solution was applied to the Y-TZP surface, and the etched Y-TZP surface was more irregular and had higher surface roughness.

Keyword

Y-TZP; HA-based etchant; Temperature elevation; Bond strength

MeSH Terms

Ceramics*
Hot Temperature
Hydrofluoric Acid
Microscopy, Atomic Force
Microscopy, Electron, Scanning
Resin Cements
Hydrofluoric Acid
Resin Cements

Figure

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  Figure 1. Shear bond strength values of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in each group etched under various conditions with different resin cements. MDP, methacryloyloxydecyl dihydrogen phosphate; PA, phosphoric acid; HA, hydrofluoric acid; SE, smart etching. Identical uppercase letters indicate no statistically significant differences (p > 0.05).

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  Figure 2. Scanning electron microscopy (SEM) images at 30,000 times magnification of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) surfaces etched under different conditions. (A) Etching-free specimen (control); (B) 37% phosphoric acid (PA)-etched specimen; (C) 4% hydrofluoric acid (HA)-etched specimen; (D) HA-based smart etching (SE)-etched specimen.

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  Figure 3. Atomic force microscopy images of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) surfaces etched under different conditions. (A) Etching-free specimen (control); (B) 37% phosphoric acid (PA)-etched specimen; (C) 4% hydrofluoric acid (HA)-etched specimen; (D) HA-based smart etching (SE)-etched specimen.

Reference

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