The aim of this study was to examine defect depths and volumes at the resin composite-dentin (R/D) interface after air polishing with different particles and spray angles. Samples were 54 dentin specimens that were formed in saucer-shaped cavities filled with resin composite. Each specimen was air polished with either sodium bicarbonate (NaHCO3) or one of two glycine (Gly) powders. The air polisher was set at angles of 90° to the interface and at 45° to the interface from both the dentin and resin composite sides. Air polishing with Gly powder produced defects with less depth and volume than NaHCO3 powder (p < 0.05). Air polishing with a spray angle of 45° to the interface from the resin composite side produced fewer defects (p < 0.05) than polishing from the dentin side. Air polishing to the R/D interface from the resin composite side produced fewer defects to the interface because the hardness of the resin composite was higher than that of dentin.

The purpose of this study was to evaluate the microtensile bond strength (µTBS) to human dentin of an experimental bonding agent containing calcium phosphates experimentally developed for direct pulp capping. Different concentrations of four types of calcium phosphates were added to an experimental bonding monomer, and six experimental bonding agents were thus prepared. Clearfil SE Bond/Bond was used as the control. Flat dentin surfaces of human molars were assigned to the experimental adhesive systems and the control. After Clearfil SE Bond/Primer was applied to the dentin surface, each experimental bonding agent was applied and photopolymerized, and then a resin composite paste was placed and photopolymerized. The specimens were subjected to µTBS testing. Results revealed that there were no significant differences among the µTBS values of the experimental bonding agents and the control. In other words, the calcium phosphate-containing experimental adhesives did not adversely affect the µTBS to dentin.

The purpose of this study was to evaluate the effects of dentin attrition, phosphoric acid etching, and cyclic loading on the microtensile bond strength (μTBS) of a self-etching adhesive system to dentin. Flat dentin surfaces of human molars were assigned to eight experimental groups based on those with or without attrition, prior acid-etching, and cyclic loading. Resin composite paste was placed and polymerized after the bonding procedure according to manufacturer's instructions. The specimens were subjected to μTBS testing at a crosshead speed of 0.5 mm/min. Results showed that the minimum mean value of μTBS was 14.9 MPa in the group without attrition and acid-etching but with loading, while the maximum mean value of μTBS was 40.0 MPa in the group without attrition and loading but with acid etching. Therefore, the value of μTBS to dentin without attrition was significantly decreased by cyclic loading but that to dentin with attrition was not affected.