Scanning electron microscopy evaluation of the interface of three adhesive systems

The objective of this research was to investigate the resin-dentin interface of three adhesive systems, Scotchbond Multi-Purpose, Optibond and Denthesive Bond II by scanning electron microscopy. The adhesives and their respective composite resins were applied inside the cervical root canal of human incisors and canines according to manufacturer recommendations. The teeth were embedded in acrylic resin and sliced transversally to the root canal and perpendicularly to the resin-dentin interface. The adhesive systems Scotchbond Multi-Purpose and Optibond had a homogenous hybrid layer and similar characteristics, involving resin penetration of peritubular and intertubular dentin matrix. Morphological differences of resin tags were seen; Scotchbond Multi-Purpose had more and longer tags than Optibond. Denthesive Bond II did not have the same consistency of bonding. Tubular orifices were not opened and the smear layer was not removed. This was due to the absence of previous acid conditioning of dentin that damages hybrid layer formation. Analysis of the hybrid layer revealed different patterns, suggesting that the attachment was influenced by many factors and a standardization of dentinal substrate was impossible.