Effect of primer solvent and curing mode on dentin shear bond strength and interface morphology

There is a need to study the main and interactive bonding effects of differences in solvent and curing mode used for adhesive monomers in dentin bonding systems. Objective: Two solvents (acetone and ethanol) and curing methods (light cure, dual cure) were evaluated on their effects on bond strength and interfacial morphology. Method and materials: The adhesives studied were based on two monomers, pyromellitate of glyceryl dimethacrylate (PMGDM) and 2-hydroxy ethyl methacrylate (HEMA). Four groups of eight teeth each were cut to expose planar dentin sections and treated with (a) light-cure system with acetone as solvent (LCA group); (b) light-cure system with ethanol as solvent (LCE group); (c) dual-cure system with acetone as solvent (DCA group); and (d) dual-cure system with ethanol as solvent (DCE group). The treated sections were tested for shear bond strength to composite discs and interfacial morphology. Results: The mean (standard deviation) of shear bond strength values (MPa) for the different groups were: LCA: 11.8 (2.3); LCE: 12.7 (2.7); DCA: 24.9 (9.3); and DCE: 21.6 (9.6). All bonded sections were characterized by a similar hybrid layer, resin tags, and overall interfacial morphology. Conclusion: There was a significant difference in shear bond strength as a function of cure mode, but not of solvent. The mean bond strength was higher for dual-cure systems studied. Oxygen inhibition effects may account for the difference between light-cure and dual-cure types.