Effect of Acid Mixtures on Surface Properties and Biaxial Flexural Strength of As-Sintered and Air-Abraded Zirconia

Abstract

The aim of this work was to evaluate the effects of application time of an acid mixture solution on the surface roughness, phase transformation, and biaxial flexural strength of 3Y-TZP after sintering or air abrasion. For the biaxial flexural strength measurement, 220 3Y-TZP disk-shaped specimens were prepared after as-sintering or air abrasion. The etching solution comprised a mixture of hydrofluoric acid, sulfuric acid, hydrogen peroxide, methyl alcohol, and purified water. The samples were divided into 11 subgroups according to the etching times (Control, 1, 2, 3, 5, 8, 10, 12, 15, 20, and 30 min). The results showed that acid treatment on both as-sintered and air-abraded 3Y-TZP surfaces increased the surface roughness. However, it had no significant effects on the monoclinic phase or flexural strength of as-sintered zirconia. The monoclinic phase and flexural strength of air-abraded zirconia increased sharply after air abrasion; however, they gradually decreased after acid treatment, to a similar level to the case of the untreated surface. Surface treatment with acid mixture increased the roughness, but the lack of increase of monoclinic phase is thought to be because the loose monoclinic particles remaining on the surface were removed through the etching process.

Adhesive Cementation of Zirconia Based Ceramics-Surface Modification Methods Literature Review

“…Overly intensive blasting can lead to an increase in the monoclinic phase, surface roughness, the formation of microcracks and gaps in the material structure, and the sticking of alumina particles into the surface. Incorrectly performed sandblasting weakens both the mechanical properties of the material, and adversely affects the quality of the bond between the resin cement and zirconium ceramics [10,27,28]. Therefore, the literature recommends sandblasting with aluminum oxide.…”

“…However, attempts are made to etch zirconia ceramics. Zirconium ceramics were subjected to etching with solutions of acids and acid mixtures, including hydrofluoric acid, hydrochloric acid (HCl), sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) at various concentrations, temperatures and application times [22,28,34]. In their research, Kim et al assessed the effect of the application time of a solution containing a mixture of 25% hydrofluoric acid, 16% sulfuric acid, hydrogen peroxide, methyl alcohol and purified water on the surface properties and the biaxial flexural strength of sintered 3Y-TZP not previously treated and 3Y-TZP after sandblasting.…”

“…The probable cause was the formation of critical cracks in the material and the generation of hydroxyl groups (OH), which accelerate the low-temperature degradation (LTD) of zircon. Researchers suggested that the application of an acid mixture to the surface of zirconia ceramics could be an effective conditioning method, as it increases the surface roughness of the zirconia ceramics without compromising its original flexural strength [28]. In another study, Kim et al proved that pre-treatment with 20% HF solution at 70-80 • C or 40% HF solution at room temperature and 70-80 • C effectively etches the surface of Y-TZP with acid, providing improved bonding.…”