Evaluation of dentin desensitization protocols on the dentinal surface and their effects on the dentin bond interface

To evaluate the effect of desensitizing agent containing calcium phosphate nanoparticles on the bond strength of etch-and-rinse adhesive system (Scotchbond Multi-Purpose), presence of precipitate, dentinal tubule obliteration and hybrid layer formation in dentin in comparison with potassium nitrate plus sodium fluoride or strontium chloride compounds.

150 bovine incisors were treated with (n = 10): G1, Desensibilize Nano P (Ca₃(PO₄)₂+5%KNO₃+0.9%NaF); G2, Desensibilize (10%SrCl₂+5%KNO₃); G3, Desensibilize KF2% (5%KNO₃+0.2%NaF); G4, Ultra EZ (3%KNO₃+0.25%NaF) and G5, no treated (control). Scanning electron microscopy was used to assess the incidence of precipitates (500×) and obliterated dentinal tubule counts (1.000×). The adhesive system was used after all desensitization treatments. The bond strength (n = 40) and the fracture pattern were evaluated. Confocal laser microscopy was used to quantify the hybrid layer formation in dentin.

G1 and G2 presented higher adhesive system bond strength (MPa) than G4 and G5, however no significant differences were observed in comparison with G3. Cohesive fracture was frequently found: G1 (58.5%), G2 (51.3%) and G3 (43.8%). G1 showed the highest incidence of precipitates and the highest number of blocked dentinal tubules. G1 and G2 presented similar hybrid layer formation and the highest hybrid layer formation values.

Desensibilize Nano P (G1) favored the bond strength of the adhesive system to dentin, increased the precipitation of residues, obliteration of dentinal tubules, and hybrid layer formation in comparison with other agents.

Desensitizers promote dentin obliteration, however, may affect dentin bonding.