The Influence of Solvent Evaporation on the Ultimate Tensile Strength of Contemporary Universal Adhesives

This study investigated the influence of solvent evaporation on the ultimate tensile strength (UTS) and water-related weight changes in contemporary universal dental adhesives. Two two-step universal adhesives (OptiBond eXTRa Universal and G2-BOND Universal) and two one-step universal adhesives (OptiBond Universal and BeautiBond Xtreme) were evaluated. Adhesives were used either under normal storage conditions or after active solvent evaporation by removal of the bottle caps and storage at 37 °C for 2 weeks. Hourglass-shaped specimens were prepared, light-cured, and stored in water at 37 °C for 1 h or 7 days prior to UTS testing (n = 10). Specimen weights were measured before and after water storage. For OptiBond eXTRa Universal, no significant difference in UTS was observed between the original and desiccated groups after 7 days of water storage (p > 0.05). In contrast, G2-Bond Universal exhibited significantly higher UTS values in the desiccated group compared with the original group (p < 0.05). In the original group, the one-step universal adhesives failed to polymerize under the original (non-evaporated) conditions, whereas adequate polymerization was achieved following active solvent evaporation. Weight changes after water storage varied depending on the adhesive composition. These results suggest that residual solvent may influence the polymerization behavior, mechanical performance, and water-related properties of universal dental adhesives, emphasizing the importance of adequate solvent evaporation before light curing.