Effects of Various Acid-Silane Surface Treatments on Bond Strength of Metal Brackets to Porcelain Crowns

The combination of hydrofluoric (HF) acid and silane can provide sufficient bond strength for porcelain crowns. However, it requires careful isolation to prevent hurting soft tissue. Phosphoric (H3PO4) acid is safe for porcelain surface treatment, but the bond strength of its combination with silane agents as an orthodontic adhesive to porcelain has seldom been reported. This study evaluates the bond strength obtained using various acid-silane agents and porcelain fracture after debonding. One metal bracket, one orthodontic adhesive (Enlight), two etching agents (37 % H3PO4 and 9 % HF), three silane agents (Ormco Porcelain Primer, Ultradent Silane, and Jeneric/Pentron Silane), and 50 porcelain crowns were tested. The shear bond strengths were determined and the porcelain surfaces were observed using scanning electron microscopy after debonding. One-way analysis of variance (ANOVA) was used to analyze the shear bond strengths and the inter-group comparison was conducted using the Tukey test. Cross-matching of two types of acid and two types of silane (Ultradent and Jeneric/Pentron Silane) was compared using two-way ANOVA. Fisher's exact test was used to analyze the porcelain fracture index (PFI) scores. The Porcelain Primer group had the lowest bond strengths and the H3PO4-Jeneric/Pentron silane group had the highest bond strengths (p < 0.0005). Cross-matching of acid and silane showed that acid had a statistically significant effect on bond strength. There was a statistically significant difference in adhesive remnant index scores between Porcelain Primer and the other groups (p < 0.005). There were no statistically significant differences in the PFI scores among all silane groups. The H3PO4-Jeneric/Pentron silane group had the highest bond strength among all acid-silane groups and its risk of porcelain fracture was not higher than that of other acid-silane groups.