Korean J Dent Mater.  2022 Sep;49(3):87-96. 10.14815/kjdm.2022.49.3.87.

Effect of various surface treatments by the sol-gel method on the bond and flexural strengths of zirconia-porcelain

• Shim JH
• Hong MH

• KMID: 2534138
• DOI: http://doi.org/10.14815/kjdm.2022.49.3.87

Abstract

This study investigates the effect of a silica coating using the sol-gel method on the bonding between zirconia and porcelain. The specimens were manufactured by precise machining in accordance with the international standard (ISO 9693:2019) using commercially available zirconia (IPS-E-max-ZirCAD). The specimens were then classified into an untreated group (control), and 50 µm sandblasted, 110 µm sandblasted, 0.5 mol% sol-gel, and 0.25 mol% sol-gel treated groups. The control group was subjected to grinding treatment only, the sandblasted group used aluminum oxide, and the sol-gel group was impregnated with the test solution, dried, and sintered according to the manufacturer’s instructions. The sintered specimen underwent a grinding process, and after being layered on the zirconia specimen using a dedicated mold, it was fired according to the manufacturer's instructions. In this study, the strength was measured using a universal testing machine by applying a load until fracture occurred at the center of the specimen. Comparison of the results for the poor bonding between the initial zirconia and porcelain revealed that the sol-gel groups showed the highest bonding strength. In the absence of silica treatment, the control and 110 µm sandblasted groups showed a significantly lower bonding strength that that of the sol-gel treated groups. The 50 µm sandblasted group showed a slightly higher bonding strength than the control and 110 µm sandblasted groups owing to the rough surface of the 50 µm sandblasted specimens. When a load was continuously applied and the zirconia was finally destroyed, the sol-gel group showed lower flexural strengths (different from the initial strength) owing to the change in the elastic modulus due to silica penetration. The flexural strengths exhibited by the sol-gel treated groups were statistically significantly lower than those of the control and 110 µm sandblasted groups. The remaining three groups showed flexural strengths that did not significantly exceed the manufacturer’s strength value. Thus, when zirconia and porcelain were combined and silica was penetrated by the sol-gel method, the bonding strength increased, but the final flexural strength of zirconia was lowered due to the change in the elastic modulus.

Keyword

Sol-gel; Zirconia; Porcelain; Bond strength; Flexural strength