Effect of air-drying on the solvent evaporation, degree of conversion and water sorption/solubility of dental adhesive models

Abstract

This study evaluated protocols to eliminate acetone from dental adhesives and their effect on the kinetic of water sorption and percent of conversion of these adhesives. Experimental methacrylate-based adhesives with increasing hydrophilicity (R2, R3, R5) were used as reference materials. Primer-like solutions were prepared by addition of 50 wt% acetone. Acetone elimination was measured gravimetrically before and after: a spontaneous evaporation, an application of air-drying at room temperature or application of 40°C air-drying. Protocols were performed from 15 to 60 s. Specimens of adhesive/acetone mixtures were photo-activated and tested for degree of conversion, water sorption and solubility. Data were analyzed by ANOVA and Bonferroni's tests (α = 0.05). Complete acetone elimination was never achieved, but it was significantly greater after the 40°C air-drying application. Higher acetone elimination was observed for the least hydrophilic adhesive. Longer periods for acetone evaporation and heated air-stream can optimize polymerization and reduce the water sorption/solubility of adhesive system models.

Effect of caries-affected dentin on one-step universal and multi-step etch-and-rinse adhesives’ bond strength

“…The low vapor pressure of acetone promotes alterations in the chemical composition of adhesives after application on dentin. The delicate balance of the components might be altered may be reflected in the bond performance 21,22 . In particular, prolonged application time may improve the bond performance of acetone-based adhesives on normal dentin.…”

Effect of agitation and storage temperature on water sorption and solubility of adhesive systems

“…Simplified etch and rinse adhesive systems are composed of a mixture of hydrophilic and hydrophobic monomers, solvents, stabilizers, initiators and filler particles 2) . Increasing the concentration of hydrophilic monomers allows these systems to infiltrate and diffuse into the collagen network, forming a hybrid layer [3][4][5][6][7][8] . Hydrophilic systems have an affinity for water, which enables permeation through dentin but may also promote the formation of a polymeric structure more susceptible to hydrolysis 4,9) .…”

“…Hydrophilic systems have an affinity for water, which enables permeation through dentin but may also promote the formation of a polymeric structure more susceptible to hydrolysis 4,9) . The solvents included in the composition of adhesive systems act in the dissolution of hydrophobic and hydrophilic monomers, and in the displacement of water from the acid etched surfaces, ensuring proper monomer infiltration into the porosities of enamel and dentin 8) . The commonly used solvents in dental adhesives are water, ethanol and acetone, which vary in accordance to their polarity 2) .…”

“…The quality of the hybridization process is highly dependent on the optimal monomer infiltration and on the removal of as much water and organic solvents as possible from the surface prior to curing 6) . The higher hydrophilicity and possible presence of residual solvent in the simplified adhesive agents means that care is needed to ensure the bonding layer has optimum mechanical properties 8) . A frequent recommendation is to store the adhesives at room temperature since changes in temperature may influence bonding 10) .…”

Does Maintaining a Bottle of Adhesive Without the Lid Significantly Reduce the Solvent Content?

“…Interfibrillar spaces in the collagen mesh are maintained by water, while organic solvents in the adhesive displace this water from the demineralized dentin to allow the infiltration of resin monomers (5,6). Furthermore, these solvents also help the water evaporation from dentin allowing a proper adhesive polymerization (7)(8)(9). Thus, a reduction in the solvent content can compromise the infiltration of adhesive resin and the effectiveness of the dentin bond (10).…”