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

Objectives. To 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). Methods. Adhesive resin beams (A) from Single Bond Plus (SB), Excite (EX) and One Step Plus (OS) were prepared after solvent evaporation at 23 degrees C or 40 degrees 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 degrees C or 40 degrees C; with or without prior dentin treatment with PACs for 10 min. The apparent modulus of elasticity (E) and mass change (W-mc, %) of adhesives beams and resin-infiltrated specimens were assessed in dry and wet conditions after immersion in water (24h, 1, 3 and 6 months). The E was statistically analyzed by Tukey-Kramer test and the W-mc, % by Kruskal Wallis, and Dunn (alpha = 0.05). Results. Solvent evaporation at 40 degrees 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 degrees C increased E and decreased the W-mc, % (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). Significance. Improved 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. (C) 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.