The aim of this study was to determine how the method of applying a universal adhesive affects bonding performance to dentin, based on shear bond strength (SBS) tests and surface free energy (SFE) characteristics. The universal adhesive used was Scotchbond Universal Plus Adhesive. Bovine dentin specimens were divided into four groups of ten, and SBS and SFE were determined after the following surface treatments: 1) self-etch (SE) mode with immediate air-blowing after adhesive application (IA), 2) SE mode with the manufacturer’s recommended application method (MA), 3) etch & rinse (ER) mode with IA, and 4) ER mode with MA. Bonded specimens were subjected to SBS testing. SFE of dentin surfaces treated with adhesive was measured after rinsing with acetone and water. Although no significant differences in SBS were observed between SE and ER modes regardless of the application method, SBS was significantly lower in IA than in MA in both etching modes. The universal adhesive showed significantly higher total SFE (γS) values in SE than in ER mode. The results of this study showed that reduced application time in both etching modes influenced dentin SBS and SFE for the universal adhesive, and negatively affected its performance.

The aim of this study was to evaluate tensile strength, the waterproofing, and wear-resistance of an experimental resin composite with a filler surface treated with silane comprising hydrophobic phenyl group3-(3-methoxy-4methacryloyloxyphenyl) propyltrimethoxysilane (p-MBS). Additionally, a tensile test, two types of wear tests, and electron spin resonance (ESR) spectroscopy were conducted. The results were analyzed using one-way analysis of variance and Bonferroni’s post-hoc tests; Pearson’s correlation coefficient as used to compare the results of the two types of wear tests. The tensile strength of the experimental resin composite was not affected by immersion in water due to the improved effect of the coupling layer treated with silane. The wear resistance of the experimental resin composite was comparable to that of a commercial resin composite. No difference in the separation width of the absorption spectrum or signal intensity was observed between the conventional silane coupling agent and p-MBS. Likewise, no change in the separation width of the absorption spectrum or signal intensity of the ESR spectrum of p-MBS was observed before and after the thermal stress. These findings indicated that the water resistance of the resin was improved following the treatment of the coupling layer with silane.

The long-term dentin bonding effectiveness of a newly developed two-step bonding system, consisting of a primer designed based on technology used in one-step bonding systems and a hydrophobic bonding agent, was examined. The dentin surfaces of extracted human molars were treated with the new two-step bonding system (BZF, GC), G-Premio Bond (GPB, GC) or CLEARFIL SE Bond 2 (MB2, Kuraray Noritake Dental), and CLEARFIL AP-X (Kuraray Noritake Dental) was built up. Micro-tensile bond strength (μTBS) was measured after storage in water for one year. The BZF and SE2 groups showed significantly higher μTBS than the GPB group (p<0.001). Dominant failure patterns were cohesive failure for the BZF group, while the MB2 and GPB groups showed mixed failure and interface failure, respectively. TEM observation of the bonding interface showed a tight and sustainable interaction for the BZF group. In conclusion, the new two-step hydrophobic bonding material, BZF, showed superior long-term bonding durability.