Bond Strength of One-step Bonding Agent to Dentin Measured by Scratch Test

Abstract

Purpose: Many studies have been conducted to examine the bond strength of bonding agents to dentin using shear and tensile bond strength measurements. However, the fracture patterns in these bond strength tests showed different failure modes, such as adhesional failure between the bonding agent and the dentin, cohesional failure within the dentin and resin composite, and mixed failure modes. Therefore, these bond strength tests did not solely reflect adhesional failure between the bonding agent and dentin. In this study, a scratch tester was used to examine the thin-film bond strength between the bonding agent and human dentin, and the characteristics and accuracy of measurement were clarified. Methods: Four one-step bonding agents were investigated: BeautiBond, Bond Force, Adper Easy Bond, and Clearfil tri-S Bond. The relationship between the thin-film bond strength (by scratch test) and the tensile bond strength of the bonding agents was evaluated. In addition, the influence of the contact angle to the dentin surface and the surface tension of the bonding agents on the thin-film bond strength were evaluated. Results: As a result, the thin-film bond strength of the bonding agent (Clearfil tri-S Bond) on various film thicknesses ranged from 5.29 to 8.50 N, meaning that the strengths of the bonding agents were significantly influenced by the film thickness. The thin-film bond strength of the four bonding agents ranged from 5.63 to 7.19 N and the standard deviation (SD) was less than 1.00 N. The tensile bond strength of the bonding agents ranged from 6.27 to 15.59 MPa and the SD ranged from 1.95 to 4.49 MPa. The recurrence coefficients showed a significant correlation (r=0.82) between the thin-film bond strength and the tensile bond strength of the bonding agents. The measured contact angle on the dentin surface of the bonding agents decreased with time, and water, ethanol, and acetone as solvents of the bonding agents showed the same trend. The contact angle of each bonding agent was approximately related to that of the solvent. The measured surface tension of the bonding agents, water, ethanol, and acetone did not change with time. The recurrence coefficients did not show a significant correlation between the thin-film bond strength and the contact angle or the surface tension. Conclusion: These results suggest that the thin-film bond strength test was successful in testing the bonding agent's ability to bond to dentin surfaces. The contact angle and surface tension were influenced by dilution in water, ethanol, and acetone solvents, however, the wettability of the bonding agents to dentin did not influence the thin-film bond strength.