One-step self-etching adhesive polymerization: influence of a self-curing activator.
OBJECTIVE
The objectives of this work were to study the spatially resolved extent of photopolymerization and the final volumetric contraction of the self-etching adhesive Xeno IV (Dentsply/Caulk, Milford, DE, USA) in association with the self-curing agent Aurora (Dentsply/Caulk, Milford, DE, USA), using (1)H Stray-Field magnetic resonance imaging ((1)H STRAFI-MRI).


METHODS
One-dimensional (1)H STRAFI-MRI images (projections along an axis, profiles) were acquired from the adhesive with and without Aurora, before and after solvent removal. Specimens were observed after the irradiation period recommended by the manufacturers and new profiles were recorded. Extent of polymerization and volumetric contraction were obtained by subtracting the profile of the cured adhesive from the profile of the liquid; the profiles were previously normalized using an external reference signal and the highest magnetization intensity recorded from the cured adhesive, respectively. Data were obtained in the presence of oxygen. Solvent evaporation was measured by gravimetry.


RESULTS
High volumetric contraction was observed for Xeno IV and Xeno IV and Aurora mixture mainly related to solvent evaporation. A drying period favourably influenced the extent of photopolymerization of Xeno IV, which did not increase in the presence of Aurora.


CONCLUSIONS
The incorporation of Aurora reduced the extent of polymerization of the one-step adhesive, probably due to the increase in the solvent content of the mixture. It may be that enhancing solvent evaporation is important in order to reach a higher extent of polymerization during the bonding procedure.
Nunes
Teresa G
TG
Centro de Química Estrutural, Complexo Interdisciplinar, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal. Teresa.Nunes@ist.utl.pt
Erhardt
Maria Carolina G
MC
Toledano
Manuel
M
Osorio
Raquel
R
D020770:Compomers / Q000737:chemistry* / Q000528:radiation effects; D001840:Dental Bonding; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D004338:Drug Combinations; D009682:Magnetic Resonance Spectroscopy; D044367:Phase Transition; D012997:Solvents / Q000737:chemistry; D014835:Volatilization
D020770:Compomers; D017220:Dentin-Bonding Agents; D004338:Drug Combinations; D012997:Solvents