Influence of Different Dentin Finishing Protocols After Prosthetic Preparations

Objectives: To evaluate the effect of different dentin finishing protocols following prosthetic preparations on the surface roughness, smear layer formation, and bond strength to CAD/CAM resin-matrix glass-ceramic blocks.
Methods: Sound human molars, had the occlusal surface removed, exposing dentin, prepared with SiC papers (#600) and standard diamond burs, simulating preparations. The specimens were divided according to finishing protocols: FB (fine and extra-fine diamond burs), MB (12 and 30 blades carbide burs), UT (ultrasonic CVD diamond tips), MS (SiC and SiO₂ stones), SB (sintered diamond burs), AP (Al₂O₃ blasting), RC (resin coating). Specimens were analyzed by scanning electron microscopy (n=4) and confocal laser microscopy (n=4) to evaluate surface roughness and morphology, and smear layer formation. Indirect restorations (blocks) were prepared and luted with dual cure resin cement under controlled pressure (n=10). The specimens were stored in absolute humidity for 24 h and sectioned perpendicularly to the adhesive surface, obtaining sticks with approximately 1 mm² adhesive area. The sticks were fixed and subjected to tensile stress, and failure modes were determined.
Results: Significant differences were found for bond strength among the finishing protocols (p<.001). The highest bond strength values were observed for RC, followed by MS, AP, and FB. No significant differences were verified between AP and FB. The lowest bond strength values were found for MB, followed by SB and UT. Adhesive failures between resin cement and dentin were predominantly observed. Surface roughness showed significant differences among the protocols (p<.001), with FB, AP, and RC showing increased roughness, differing from other groups, but not among them. The smear layer thickness showed significant differences among the finishing protocols (p<.001), with FB showing the highest thickness of smear layer deposited on the dentin surface, followed by AP and MB. Reduced smear layer thickness was found for UT, MS and SB, without significant differences among them, but differing from the other groups.
Conclusions: Different dentin finishing protocols after prosthetic preparations influenced the surface roughness, smear layer formation, and bond strength to resin-matrix glass-ceramic blocks, with resin coating showing satisfactory results.