Effects of Desensitizing Agents on Dentin Bond Interface

Objectives: To evaluate the effect of desensitizing agent containing calcium phosphate nanoparticles (Ca₃(PO₄)₂) 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 (KNO₃) plus sodium fluoride (NaF) or strontium chloride (SrCl₂) compounds.
Methods: Groups 1, 2, 3 and 4 were treated with 3% KNO₃+0,25%NaF, 5% KNO₃+0,2%NaF, Ca₃(PO₄)₂+5% KNO₃+0,9%NaF and 10% SrCl₂+5% KNO₃. No treatment was performed in the control group (G5). Scanning electron microscopy was used to assess the incidence of precipitates (500X) and obliterated dentinal tubule counts (1.000X). 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.
Results: As regards bond strength (MPa): G3=G4=G2 and G2=G1=G5, however G3=G4>G1=G5. Cohesive fracture was frequently found: G2 (43.8%), G3 (58.5%) and G4 (51.3%). Presence of precipitates on dentin: G3> G4 = G2 = G1, G4> G5 and G2 = G1 = G5. Dentinal tubule obliteration: G3> G4 = G2, G1 = G2 = G5 and G4> G1 = G5. As regards hybrid layer formation: G3 = G4> G1 = G2 = G5.
Conclusions: Ca₃(PO₄)₂ 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 KNO₃ + NaF compounds.