Adhesive temperature: effects on adhesive properties and resin-dentin bond strength

To evaluate the effect of adhesive temperature on the resin-dentin bond strength (μTBS), nanoleakage (NL), adhesive layer thickness (AL), and degree of conversion (DC) of ethanol/water- (SB) and acetone-based (PB) etch-and-rinse adhesive systems.

The bottles of the two adhesives were kept at each temperature (5°C, 20°C, 37°C, and 50°C) for 2 hours before application to demineralized dentin surfaces of 40 molars. Specimens were prepared for μTBS testing. Bonded sticks (0.8 mm(2)) were tested under tension (0.5 mm/min). Three bonded sticks from each tooth were immersed in silver nitrate and analyzed by scanning electron microscopy. The DC of the adhesives was evaluated by Fourier transformed infrared spectroscopy.

Lower μTBS was observed for PB at 50°C. For SB, the μTBS values were similar for all temperatures. DC was higher at 50°C for PB. Higher NL and thicker AL were observed for both adhesives in the 5°C and 20°C groups compared to the 37°C and 50°C groups. The higher temperatures (37°C or 50°C) reduced the number of pores within the adhesive layer of both adhesive systems.

It could be useful to use an ethanol/water-based adhesive at 37°C or 50°C and an acetone-based adhesive at 37°C to improve adhesive performance.