Deproteinization and tubular occlusion influence on dentin bonding: SEM evaluation

Objective: to evaluate the effect of NaOCl and an oxalate desensitizer (BisBlock, BB, Bisco), applied after acid etching, on the morphology of dentin and resin-dentin interface. Methods: For dentin morphological analysis 5 dentin disks were flattened on a #180-grit sandpaper. They received the following treatments: PT, none; A, acid etching (Uni-etch, Bisco, 15 sec); AH, acid etching and collagen removal (10% NaOCl, 1 min); AB, acid etching and tubular occlusion (BB, 30 sec); ABH, acid etching, tubular occlusion and collagen removal. Dentin disks were then prepared for SEM. Surface and fractured dentin morphology were analyzed. Sixteen dentin specimens were used for resin-dentin interface analysis. They were ground flat on a #180-grit sandpaper and received the same treatments as described for A, AH, AB and ABH, added by the application of One Step Plus (Bisco) and composite restoration (AElite All-purpose Body, Bisco) according to manufacturer's instructions. Slices of the bonded specimens were prepared for SEM evaluation. Results: The oxalate desensitizer caused subsuperficial tubular occlusion with no interference on dentin surface. NaOCl treatment seemed to remove exposed collagen. Association of etching, BB and NaOCl resulted on a dentin surface without collagen and with visibly occluded dentin tubules. Resin-dentin interfaces of BB-treated dentin showed short resin tags, while NaOCl-treated specimens did not show a visible hybrid layer. Conclusions: Dentin morphology and resin-dentin interfaces are altered by deproteinization and tubular occlusion. Combination of these techniques may render a dentin surface without collagen and with lumen-blocked dentin tubules. Studies on the bonding mechanism to this kind of dentin surface are encouraged.