Morphology of coupling sites between bonding agents and dentine in vivo and in vitro

In spite of the unclear relationship between in vitro and in vivo conditions, the majority of dentine bonding agent investigations are carried out in vitro. The purpose of this SEM study was to compare micromorphologically the bonding sites between dentine and seven resin bonding systems, which were applied either in vivo or in vitro on freshly cut dentine in similar locations on contralateral premolar teeth scheduled for extraction for orthodontic reasons. The morphology of the bonding sites was investigated on samples fractured perpendicularly to the bonding interface following superficial decalcification and deproteinization of the dentine. For six of the seven systems studied a resin-impregnated dentine layer was identified. This hybrid zone was very similar on specimens prepared in vivo and in vitro.