Evaporating solvents with a warm air-stream: effects on adhesive layer properties and resin-dentin bond strengths

This study evaluated the effect of a warm or cold air-dry stream for solvent evaporation on the microtensile resin-dentin bond strength (muTBS), nanoleakage pattern (SEM), degree of conversion (DC) and solvent evaporation rates (SE) of an ethanol/water- (Adper Single Bond, [SB] 3MESPE) and an acetone-based (Prime & Bond 2.1, [PB] Dentsply), two-step etch-and-rinse adhesive system.

Adhesives were applied on demineralized dentin surfaces. For SE, a warm or cold air-dry stream (10 s) was applied prior to light-activation (10 s). Bonded sticks (0.8mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in a 50% (w/v) solution of silver nitrate (24 h), photodeveloped (8 h) and analyzed by SEM. The DC and solvent evaporation rate of the adhesives were evaluated under FTIR and analytical balance, respectively. Data were analyzed by two-way ANOVA and Tukey test (alpha=0.05).

Higher muTBS and lower nanoleakage were observed when the SE step was performed with warm air-dry stream. However, the DC of the adhesives was not altered by the use of a warm air-dry.

The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength and the quality of the hybrid layer (less nanoleakage infiltration), since it might reduce the number of pores within the adhesive layer.