The Use of Warm Air Stream for Solvent Evaporation: Effects on the Durability of Resin-dentin Bonds

Abstract

This study evaluated the effect of a warm (W) or cold (C) air-dry stream for solvent evaporation on the immediate (IM) and six-month (6M) resindentin bond strength (µTBS) and silver nitrate uptake pattern (SNU) of two-step etch-and-rinse adhesive system (Adper Single Bond [SB] and Prime & Bond 2.1 [PB]). The adhesives were applied on demineralized dentin surfaces and a warm or cold air-dry stream (10 seconds) was applied followed by light-activation (10 seconds). After 24-hours of water storage, the specimens were serially sectioned in the "x" and "y" directions to obtain bonded sticks around 0.8 mm 2 to be tested immediately or after six months of water storage. The specimens at each period were immersed in a 50% solution of silver nitrate, photodeveloped and analyzed by SEM for SNU. Clinical RelevanceIn terms of silver nitrate uptake, the use of a warm air stream may improve bonding interface resistance to degradation over time. In terms of bond strength values, a warm air stream only improved the resin-dentin bond strengths of the ethanol/water-based system. Laboratory ResearchHigher IM µTBS values were observed for SB under W conditions. Both adhesives showed reductions in µTBS after 6M in both air temperatures. Regarding SEM, a low silver nitrate uptake was observed in the W groups either in IM or 6M for both adhesives.

Influence of a heating device and adhesive temperature on bond strength of a simplified ethanol-based adhesive system

“…No significant differences in microtensile bond strength were found among the groups tested in the present study. This finding contradicts some reports indicating that increased adhesive temperature immediately improves bond strength, regardless of the heating device or protocol used 18,19 . This discrepancy may be explained by the possibility that the temperature increase promoted by the light-curing unit itself could have been enough to improve the physicochemical reactions and enhance monomeric permeation into the etched dentin 16,[20][21][22] .…”

“…A warming protocol presented in the literature as an option for in vitro tests has been found to increase bond strength values 24 . Since heating promotes a forced evaporation of the solvent, it can alter the stoichiometric balance of the adhesive, thus affecting its permeation capability into the etched dentin 10,19 . However, despite these advantages, warm air applied to heat up adhesives up to 20°, 30°, and 50°C has failed to increase bond strength values in a previous study 19 .…”

“…Since heating promotes a forced evaporation of the solvent, it can alter the stoichiometric balance of the adhesive, thus affecting its permeation capability into the etched dentin 10,19 . However, despite these advantages, warm air applied to heat up adhesives up to 20°, 30°, and 50°C has failed to increase bond strength values in a previous study 19 . This latter finding corroborates that of the present study, mainly when considering some of the intrinsic characteristics of Adper Single Bond 2: (a) it is a one-bottle etch-and-rinse adhesive system wherein the solvent contains water and ethanol, rendering the adhesive less viscous, already favoring monomeric permeation, and (b) the 37% phosphoric acid etching prior to adhesive application completely removes the smear layer and promotes changes in the surface energy of the dentinal substrate.…”

Effect of air-drying dentin surfaces on dentin bond strength of a solvent-free one-step adhesive

“…Ideally, all solvents should be completely removed from the dentin surface prior to polymerization. One clinical approach to obtaining stable dentin bonding and relatively higher bond strengths is to employ warm air-drying of the adhesives 4,5) . However, complete evaporation using with dental air syringe in clinical situations is diffi cult to achieve and is dependent on the properties of the solvents 6) .…”

Effect of Eugenol Exposure Time and Post-removal Delay on the Bond Strength of a Self-etching Adhesive to Dentin

“…2-3 Over the last decade, a number of investigations have reported that several factors might interfere with the bonding ability of adhesive systems to enamel or dentin, including the adhesion strategy, 4 conditioning time, 5 solvent removal method, [6][7] thickness of the adhesive layer, 8 substrate structure 9 and even the provisional restorative material previously used. [10][11][12][13][14][15] Among the provisional restorative materials, zinc oxide eugenol (ZOE) is widely used as a temporary material during endodontic treatments and restorative dentistry due to its sedative effect on sensitive teeth, its low cost, ease of removal and proper seal against leakage.…”