Adhesive layer properties as a determinant of dentin bond strength.

The goal of this study is to evaluate the hypothesis that the properties of the resin adhesive might affect the microtensile bond strength (MTBS) of multibottle dental adhesive system. In order to alter the properties, the experimental resin adhesives containing 2,2-bis (4-2-hydroxy-3-methacryloyloxypropoxyphenyl)propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) at various ratios were prepared. Degree of conversion immediately after curing (DC-immed), degree of conversion at 48 h after curing (DC-48h) of a thin coat of the experimental adhesives, the flexural strength (FS) of the bulk specimens made of the experimental adhesives, pH, viscosity at shear rate of 1 S(-1), and the microtensile bond strength (MTBS) values of the adhesives to dentin were investigated. The maximum MTBS and FS values of the resin adhesives were observed when the ratio of Bis-GMA/TEGDMA was 60/40. However, pH and viscosity values increased with increasing Bis-GMA content in the adhesives. When Bis-GMA content was more than 60 wt %, the viscosity increased exponentially and restricted the DC and FS, and accordingly decreased the bond strength. The stronger the resin adhesives were, the higher the bond strength to dentin could be obtained.