A study on the microstructure of resin-dentin interface

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Micro structure at the interface between adhesive resin materials and dentin was studied using the argon ion etching technique, which enabled the clear observation of resin impregnated layer under SEM, relating with TEM study and the bond strength.Resin impregnated layer at resin-dentin interface was confirmed to vary when the dentin bonding system, dentin(i.e. aging, caries, abrasion, and type of tooth) were different. The resin impregnated layer was also different between in vivo and in vitro study.Type of pretreatment solution for dentin, time of application and primer application were the significant factors which affected the depth of decalcification and the property of the collagen fibers exposed on dentinal surface. Penetration of the bonding resin into dentin may be controlled by these factors. The property of dentin to be bonded was also very important factor in creating resin impregnated layer. That is, type of tooth, site of dentin, distance from the pulp, phisiological or pathological changes in dentin caused by aging,caries and abrasion, and direction of the dentinal tubules at the surface were the factors affecting dentin bonding. Also, the dentinal fluid coming up from the tubules was considered to induce the decrease in the mechanical strength of a layer of bonding resin, resin impregnated layer and resin tags.The existence of a layer in which bonding resin did not penetrated, was observed, and the layer may act as a micro channel for microleakage.It was clarified that the width of the resin impregnated layer is not important for creating good bonding, but the bonding resin should be reached to dentin which is not affected with the acidic pretreatment solution, through the decalcified layer.