Influence of Zirconia Surface Conditioning on Shear Bond Strength Between Zirconia and Dental Resin Cement

Objectives: The purpose of this study was to evaluate the effect of surface treatment on the shear bond strength of zirconia ceramic to resin cement.

Methods: A total of 80 disc-shaped zirconia plates (15.0mm in diameter and 2.75mm thick) were prepared and divided into four groups. : 1) airborne particle abrasion treatment (A) : 2) Rocatec^TM (3M ESPE) treatment after airborne particle abrasion(R) : 3) nano-structured alumina coating treatment after polishing (PC) and 4) nano-structured alumina coating after airborne particle abrasion (AC). Alumina coating was formed by the hydrolysis of aluminium nitride (AlN) powder and heat treatment at a temperature of 900 °C. Coating patterns were observed with Field-emission Scanning Electron Microscopy (FE-SEM). Resin blocks were fabricated with Filtek Z250 (3M ESPE), and each was bonded to its respectively treated surface of zirconia ceramics using Rely-X Unicem (3M ESPE) resin cement. The shear bond strengths of the four groups were measured before and after thermocycling (TC). The statistical analysis was performed using SPSS version 18.0 program. In order to compare the shear bond strength between groups, the data were analyzed using analysis of variance (ANOVA).

Results: The FE-SEM images show a dense and uniform nano-structured alumina coating structure, which enhances shear bond strength by increasing micro mechanical interlocking to resin cement. PC and AC groups showed higher shear bond strengths than A and R groups before and after thermocycling. In addition, A and R groups displayed significant drops in shear bond strength after thermocycling, compared to before thermocycling. However, PC and AC groups did not show any meaningful decreases in shear bond strength after thermocycling, compared to before thermocycling.

Conclusions: In this study, it was found that treatment of Y-TZP ceramics with nano-structured alumina coating could increase their shear bond strength by a significant degree. It is believed that this method is a relatively easy and efficient way of treating the surface of zirconia ceramics.