Effects of airborne-particle abrasion protocol choice on the surface characteristics of monolithic zirconia materials and the shear bond strength of resin cement

Abstract

This study evaluated the effect of several airborne-particle abrasion protocols on the surface characteristics of monolithic zirconia and of protocol choice on the shear bond strength of resin cement. 375 bar-shaped (45×4×3mm3) and 500 disk-shaped (Ø9×1mm2) monolithic zirconia specimens were divided into 25 groups. All specimens were abraded with one of three different sizes of alumina particles (25, 50 or 125μm), two different pressures (2 or 4bar), two distinct application times (10 or 20s) and two distinct incidence angles (45° or 90°). The bar-shaped specimens were used for 3-point bending test; Weibull parameters were calculated and transformed monoclinic phase (XM), surface characteristics were examined. The disk-shaped specimens were used to determine the shear bond strength of resin cement before and after thermocycling. All data were analyzed using 4-way ANOVA and a multiple comparison Scheffé test (α=.05). The particle size, pressure and time significantly affected the flexural strength, while the incidence angle was insignificant. The XM and surface roughness were proportional to the size, pressure, time and incidence angle. The Raman spectrum analysis showed a higher proportion of the monoclinic phase as the depth of the specimen was closer to the abraded surface. In bonding with resin cement, the highest shear bond strength after thermocycling was obtained by the abrasion with 50μm particles at 4bar for 20s, regardless of incidence angle. Surface treatment of monolithic zirconia with 50μm particle at 4bar for 20s at either 45° or 90° incidence angles is recommended.