LAUSR

The aims of the study were to characterise the resin-resin interface when a universal bonding agent (UBA) was used in two different strategies in direct composite repair and to evaluate the bonding capacity of UBA by microleakage assessment. In study groups a micro-filled hybrid and a nano-filled hybrid composite resins were aged in order to simulate an old restorations. As a repair material was chosen the same micro-filled hybrid composite resin that was used as an old restoration. UBA was applied in etch-and-rinse and self-etch strategies and was used as an intermediate layer in repair procedure. After the repair the samples were aged again. In control groups were included non-aged, repaired composite resins samples. The resin-resin interface was characterised on SEM images and the microleakage at the interface was evaluated by dye penetration assessment. Universal bonding agent used in direct composite resins repair showed a very good adaptation to non-aged micro-filled hybrid and nano-filled hybrid composite resins. Aging by saliva storage of repaired composite resins leaded to an enlargement of resin-resin junction and a increased microleakage irrespective of the strategy (etch-and-rinse or self -etch) used for bonding agent application. Etch-and-rinse strategy for universal bonging agent application determined a better interface bonding when compared to self –etch strategy.