Dental adhesives and strategies for displacement of water/solvents from collagen fibrils

ObjectivesTo evaluate the influence of temperature of evaporation in adhesive systems with different solvents on the apparent modulus of elasticity and mass change of macro-hybrid layers modified by proanthocyanidins (PACs).MethodsAdhesive resin beams (A) from Single Bond Plus (SB), Excite (EX) and One Step Plus (OS) were prepared after solvent evaporation at 23 °C or 40 °C (n = 12). Macro-hybrid layers (M) (n = 12) were prepared using demineralized dentin beams sectioned from extracted human third molars. The demineralized dentin specimens were infiltrated with each one of the three adhesive systems at 23 °C or 40 °C; with or without prior dentin treatment with PACs for 10 min. The apparent modulus of elasticity (E) and mass change (Wmc, %) of adhesives beams and resin-infiltrated specimens were assessed in dry and wet conditions after immersion in water (24 h, 1, 3 and 6 months). The E was statistically analyzed by Tukey–Kramer test and the Wmc, % by Kruskal Wallis, and Dunn (α = 0.05).ResultsSolvent evaporation at 40 °C resulted in higher E values for adhesive resin beams at all storage conditions, regardless of the adhesive system (p < 0.05). Increased mass loss (3 months: −0.01%; 6 months: −0.05%) was observed in One Step resin beams (p ≤ 0.05). In the macro-hybrid layer models the pretreatment with PACs along with solvent evaporation at 40 °C increased E and decreased the Wmc, % (3 months: −2.5; 6 months: 2.75%) for adhesives evaluated over time (p < 0.05). No significant differences in ratio (resin/dentin) were found for the macro-hybrid layers (p > 0.05).SignificanceImproved solvent evaporation at higher temperature, and increased collagen cross-linking induced by PACs, enhanced the mechanical properties resulting in highly stable macro-hybrid layers over 6 months storage.