Effect of Infiltrating a Commercial Etch-and-Rinse Bonding Agent with Bioactive Nanoparticles on the Degree of Conversion of Adhesive and Flexural Strength of Dentin

Abstract Background: The aim of this study was to compare the degree of conversion of adhesive and the flexural strength of dentin after adding calcium silicate (CS) and amorphous calcium phosphate (ACP) nanoparticles (NP) to an etch-and-rinse bonding system and the application of these materials on dentin. Methods: ACP and CS nanoparticles with an average size of 100 nm were synthesized and added to Tetric N-Bond two-step etch- and- rinse adhesive. To check the flexural strength, dentin samples (n=60) were divided into two groups based on immersion time (24 hours and 2 months), and each of these two groups was divided into 3 groups (n=10) including bonding agent containing ACP and CS nanoparticles and pure bonding agent. In order to measure the degree of conversion (DC), bonding agent containing ACP and CS and pure adhesive were evaluated by Fourier Transform Infrared (FTIR) spectroscopy. Results: Stepwise comparison of the bonding agent was carried out. The results revealed that the flexural strength in the group containing ACP is significantly higher than the pure bonding agent (P=0.02) regardless of the time, while the adhesive containing CS nanoparticles did not show a significant increase (P=0.74). The average flexural strength was lower in bonding agent containing ACP and CS nanoparticles two months after immersion compared to 24-hour period, but this difference was not significant in the pure type. Conclusions: According to the results of the present study, the addition of ACP nanoparticles to the dentin bonding system increased the flexural strength of dentin, while the addition of CS nanoparticles did not lead to a significant increase in flexural strength. On the other hand, the degree of conversion of adhesive increased with the addition of nanoparticles.