Abstract: Objective To study the micromorphological characteristics of dentin bonding interface in 5 different self-etching systems and a total-etching system.Methods Extracted human molars were bonded with all kinds of adhesives according to the manufacturers' instructions,and a thin layer of composite applied.The teeth were sectioned parallel to the bonded surface to obtain a bonded dentin disc.All the ultrastructures of dentin bonding interface were observed with SEM.Results All teeth showed hybrid layer formation.However,the thickness varied depending on the adhesive systems and the total-etching(Prime & Bond NT) showed the thick hybrid layer whereas SE bonded to dentin exhibited the thinner hybrid layer.Moreover,in the teeth which were used total-etching,the composite did not penetrate to the depth of the zone of demineralized dentin,leaving a substantial area of exposed dentin matrix at the dentin/cement interface.In contrast,there was substantial composite diffusion throughout the demineralized dentin when the self-etching primer was used without acid etching pretreatment.Conclusion Good obturation appeared in self-etching groups.The resin tag was broken and the dentinal tubules were open in total-etching group,however.Postoperative sensitivity of SE is less than that of TE.

Key words: adhesive, dentin, etching, postoperative sensitivity