Effect of Calcium Hydroxide on Bonding Performance of an Experimental Self-etch Adhesive

To investigate the effect of Ca(OH)2 concentration on pH neutralization, degree of conversion (DC%), and bonding performance of experimental self-etch adhesives (SEAs).

Four different concentrations of Ca(OH)2 (0 wt%, 1 wt%, 2 wt%, and 4 wt%) were added to the bond of an experimental two-step SEA consisting of primer (10-MDP [30 wt%], TEG-DMA [30 wt%], ethanol [35 wt%], water [5 wt%], camphorquinone [0.5 wt%], and tertiary amine [0.5 wt%]) and bond (bis-GMA [50 wt%], TEG-DMA [30 wt%], HEMA [20 wt%], camphorquinone [0.5 wt%], and tertiary amine [0.5 wt%]) to form four groups: E0, E1, E2 and E4. pH neutralization was evaluated until it reached equilibrium, and DC% within the hybrid layer was analyzed by micro-Raman spectroscopy. Human molars were wet ground until the occlusal dentin was exposed, SEAs were applied, and composite buildups were constructed. After storage in distilled water at 37°C for 24 h, the teeth were cut into composite-dentin beams. Microtensile bond strength (µTBS) was evaluated after 24 h of water storage at 37°C. Nanoleakage was evaluated by SEM. Data were analyzed using ANOVA and Tukey's HSD test (a = 0.05).

All the SEAs reached pH equilibrium after thirteen days, with E1 and E4 presenting the highest pH (p < 0.05). E0 and E1 presented lower DC% than did E2 and E4 (p < 0.05). All the SEAs showed statistically similar mTBS and nanoleakage (p > 0.05).

The incorporation of Ca(OH)2 endowed the SEAs with pH-neutralization ability and improved their DC%, without interfering with the bond strength to dentin or nanoleakage extent.