[Novel method to observe the interface between adhesive resin and dentin by staining Fe3+ with tannic acid]

The reaction of Fe3+ and tannic acid was used in a new visual method to confirm the Fe3+ incorporated with dentin during the pretreatment with a 10% citric acid-3% ferric chloride solution or EDTA ferric ammonium salt solution. The combination of Fe3+ and tannic acid was also effective to investigate the state of incorporated resin (resin tags and resin reinforced dentin) with the dentin. The adhered dentin treated by staining with tannic acid was examined. The incorporation of Fe3+ with dentin enhanced the monomer infiltration and resulted in a high bond strength. Addition of 4-META into the MMA-TBB resin increased the resin content in dentin by promoting the rate of monomer diffusion.