BONDING MECHANISM OF 3 ONE-BOTTLE SYSTEMS TO CONDITIONED AND UNCONDITIONED ENAMEL AND DENTIN

Purpose: This in vivo study investigated the formation of hybrid layer , resin tags and adhesive lateral branches, by use of the latest gener ation of enamel-dentin bonding systems (''one-bottle'' systems) on con ditioned and unconditioned enamel and dentin. Materials and Methods: T he dentin adhesives were tested on 24 flat dentin preparations made on facial surfaces of vital, periodontally compromised teeth. The experi mental teeth were randomly divided in six groups of four samples each. Group 1: Prime & Bond 2.1 (conditioned dentin, CD); Group 2: Single B ond (CD); Group 3: Syntac Sprint (CD); Group 4: Prime & Bond 2.1 (unco nditioned dentin, UD); Group 5: Single Bond (UD); Group 6: Syntac Spri nt (UD). In the first three groups, the ''one-bottle'' systems were ap plied following the manufacturers' instructions, while in the other th ree groups the dentin and the enamel were not treated with phosphoric acid and the primer was applied directly on the prepared surfaces. On top of the primer-adhesive, a thin layer of resin was applied and ligh t-cured for 20 seconds. The sample teeth were extracted immediately af ter the adhesive material was light-cured. All the samples were split- fractured along their long axis. Half of the samples were deproteinize d and decalcified at the interface in order to visualize the hybrid la yer and the other halves were completely dissolved in order to observe the morphology of resin tags by use of scanning electron microscopy. Results: Groups 1-3: All the tested products showed the same micromech anical bonding mechanism to conditioned dentin with phosphoric acid: t hey formed hybrid layer, resin tags and adhesive lateral branches. In the samples of the first three groups, characteristic reverse cone-sha ped tags with their corresponding adhesive lateral branches were evide nt. At the enamel site, traditional pattern of etch enamel was always observed. Groups 4-6: When the bonding systems were applied on uncondi tioned dentin, hybrid layer was not formed, resin tags were rarely not ed and their shape was narrow and they did not completely seal the tub ular orifices. The tubules remained mainly closed by smear plugs. At t he enamel site, the unetched surface showed absence of characteristic etch pattern and of resin tags.