Does the zirconia cleaning protocol followed by vitrification increase the resin-bond strength to zirconia?

Abstract

Evaluate the influence of cleaning protocols on vitrification patterns, contact angles, and bond strength between zirconia and resin cement. 48 zirconia discs were sectioned, polished, and sintered (15 × 2 mm). The discs were randomized into four groups according to the zirconia cleaning protocol (n = 12), following: CJ (positive control)-sandblasted with 30-µm particles of alumina coated by silica (Cojet/3M); AV (negative control)-cleaning with alcohol + vitrification (glaze); PV-37% phosphoric acid + vitrification; and HFV-10% hydrofluoric acid + vitrification. Next, the surfaces were conditioned with hydrofluoric acid and then silanized. The samples from the CJ treatment group were silanized to proceed with the cementation stage. Resin cement cylinders were built on 10 specimens from each group (ϕ = 3mm, height = 5mm), following the manufacturer’s instructions, and next they were subjected to thermocycling (5000 cycles at 5 °C and 55 °C for 30 s) followed by the shear test (1 mm/min) and failure analysis. Two discs of each group were subjected to contact angle evaluation and surface analysis under SEM. One-way ANOVA (α = 0.05) and Tukey’s test (p < 0.05) were used to analyze the data (MPa). Weibull analysis was performed to evaluate the shear bond strength test data. Our results revealed that the shear bond strength varied among our experimental groups (p < 0.0001). AV=9.5 (0.5)B presented lower bond strength than CJ=10.8 (0.2)A, PV=10.9 (0.2)A, and HFV=10.9 (0.3)A experimental groups. The predominant mode of failure was the adhesive between the resin cement and glaze. Surface treatments have influenced the contact angles (p < 0.0001), following: CJ=41.6 (0.9)C; AV=52.1 (0.7)A; PV=46.8 (0.5)B; and HFV=46.0 (0.9)B. Zirconia cleaning protocols using 37% phosphoric acid or 10% HF followed by glaze application demonstrated to modify the ceramic surface and to increase the bond strength to resin cement after its etching with HF followed by silanization.