Warm Air Delivery in Adhesive Application: Effect on Bonding Performance and Morphological Outcomes

Solvent evaporation within an adhesive layer is a crucial step during a bonding process. The aim of this current research was to test whether the use of different air temperatures (20 °C, 40 °C, and 60 °C) for solvent evaporation improves the performance of four adhesive systems to dentin. Sixty non-carious human molar teeth were randomly prepared for micro-tensile bond strength (μTBS) tests. Four different adhesive systems, Prime&Bond Universal (PBU), OptiBond Universal (OBU), OptiBond FL (OBFL), and Clearfil SE (CSE), were applied following the manufacturer's instructions. Three groups based on the air-drying temperature were used: solvent evaporation was performed with either of warm (40 °C), (60 °C), and cold air as control group (20 °C) for 10 s at a distance of 5 cm. In all bonded surfaces, three resin composite (Reflectys, Itena Clinical, Paris, France) layers of 2 mm thickness were built up. The resin-dentin samples were kept in distilled water at 37 °C for 24 h and 6 months, respectively, before μTBS testing. Failure analysis, scanning electron microscopy of resin-dentin bonded interface, and solvent evaporation rate were tested as secondary variables. All analyses were conducted using a significance level of α = 0.05. Bond strength (BS) values were similar among all the adhesive systems used (p > 0.05). Also, the aging factor did not affect the BS (p > 0.05). Only the factor of temperature used for solvent evaporation resulted in a statistically significant effect (p < 0.05), with the temperature of 60 °C being the highest value (p < 0.05). A failure mode evaluation revealed mostly adhesive or mixed modes of failures in all the different temperatures of air used for the solvent evaporation of each adhesive system. The thickness of the adhesive layer and the creation of resin tags varied amongst the temperatures evaluated. For all adhesive systems tested, the use of 40 °C or 60 °C air for solvent evaporation led to an increased mass loss. Warmer temperatures for solvent evaporation contributed positively to bonding performance, enhancing both the quality of the adhesive layer and its interaction with the dentin tissue. Optimizing solvent evaporation with warmer air temperatures (40 °C and 60 °C) significantly improved µTBS, offering a practical means to enhance the quality and longevity of adhesive restorations in esthetic dentistry.