Effect of Combined Application of Hydrofluoric and Phosphoric Acids and Active Irrigation with a Microbrush on Shear Bond Strength of Lithium Disilicate Ceramics to Enamel.

BACKGROUND: This study assessed the effect of combined application of hydrofluoric (HF) acid and phosphoric acid (PA) and active irrigation (AI) with a microbrush on shear bond strength (SBS) of lithium disilicate (LDS) ceramics to enamel.

MATERIALS AND METHODS: This in vitro study was conducted on 40 extracted teeth that received enamel preparation with a #12 cylindrical bur. Forty IPS e.max LT rods (3mm diameter, 6mm height) were fabricated and randomly assigned to four groups (n = 10) for surface treatment with 5% HF (group 1), 5% HF and AI with a microbrush for 20 seconds (group 2), 5% HF and 32% PA (group 3), and 5% HF and 32% PA plus AI with a microbrush for 20 seconds (group 4). Silane and Choice 2 cement were used for bonding rods to enamel. The SBS was measured by a universal testing machine. Data were analyzed by two-way analysis of variance (ANOVA), Bonferroni, and Chi-square tests (alpha = 0.05).

RESULTS: Group 4 had the highest SBS, and group 1 had the lowest SBS ( P < 0.05). Group 2 had a significantly higher SBS than group 1, and group 4 had a significantly higher SBS than group 3. AI with a microbrush significantly increased the SBS ( P < 0.05), but the application of PA caused no significant change in SBS ( P > 0.05). The interaction effect of PA and AI on SBS was not significant ( P > 0.05).

CONCLUSION: The application of PA in addition to 5% HF acid caused no significant change in the SBS of LDS ceramic to enamel. However, AI with a microbrush significantly increased the SBS.