Changes in Bond Strength and Topography for Y-TZP Etched with Hydrofluoric Acid Depending on Concentration and Temperature Conditions

• Main Authors: Hyo-Eun Kim, Myung-Jin Lim, Mi-Kyung Yu, Kwang-Won Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Medicina
• Subjects: hydrofluoric acid; hot etching; shear bond strength; surface roughness; Y-TZP
• Online Access: https://www.mdpi.com/1010-660X/56/11/568

<i>Background and objectives</i>: This study aimed to investigate the change in bond strength between resin cement and tetragonal zirconia polycrystalline stabilized with 3 to 8 mol% yttrium oxide (Y-TZP) and observe the topographical change of the Y-TZP surface when etched with hydrofluoric acid (HF) solution under different concentration and temperature conditions. <i>Materials and Methods</i>: Non-etched sintered Y-TZP specimens under two different temperature conditions (room temperature and 70–80 °C, respectively), were used as a control, while experimental groups were etched with 5%, 10%, 20%, and 40% HF solutions for 10 min. After zirconia primer and MDP-containing resin cement were applied to the Y-TZP surface, the shear bond strength (SBS) of each experimental group was measured. <i>Results</i>: Under room temperature conditions, the highest SBS value was measured in the 40% HF etching group, representing a significant deviation from the other groups (<i>p</i> < 0.05). In the 70–80 °C tests, the 40% HF etching group also had the highest SBS value, but there was no significant difference when compared to the 20% HF etching group (<i>p</i> > 0.05). From SEM and AFM observations, the HF solution increasingly dissolved the Y-TZP surface grain structure as the concentration and application temperature rose, resulting in high surface roughness and irregularities. <i>Conclusions</i>: Pretreating with either 20% HF solution at 70–80 °C or 40% HF solution at room temperature and 70–80 °C effectively acid etched the Y-TZP surface, resulting in more surface roughness and irregularities. Accounting for the concentration and temperature conditions of the HF solution, using 40% HF solution at room temperature will result in improvements in adhesion between resin cement and Y-TZP.