SEM evaluation of the interaction between a three-step adhesive and dentin

Interaction between resin tags and microtags of adhesive systems and dentin al collagen fibrils is a poorly understood aspect of adhesion. This study e valuated this interaction in 25 recently extracted human third molars. Each tooth was embedded in an epoxy resin and cross-sectioned to obtain two 1-m m-thick dentin disks. The outer dentin surfaces were polished with wet 600- grit sandpaper to create a uniform smear layer. After etching with 35% phos phoric acid for 15 seconds, the primer and adhesive of Scotchbond Multi-Pur pose and the resin composite Z100 (3M Dental Products, St Paul, MN 55144, U SA) were placed on the dentinal surfaces according to the manufacturer's in structions. The disks were left in distilled water at 37 degreesC for two w eeks, then fractured perpendicular to the bonded surfaces in order to obtai n two hemi-disks. The fractured surfaces were treated with 2N-chloridric ac id and processed for scanning electron microscopy. Gold-coated specimens we re examined with a JEOL 6100 scanning electron microscope. Results showed a hybrid layer with resin tags of approximately 100 mum in length and numero us and fine branching resin microtags. The tags and microtags created by th is three-step adhesive system were observed in intimate contact with the co llagen fibrils of dentin, even in deeper zones which were not affected by a cid etching. It suggests that adhesion to dentin may include both micromech anical and chemical aspects.