title: Effect of solvent type and content on monomer conversion of a model resin system as a thin film.
abstract: OBJECTIVE
  The purpose of this study was to examine the effect of solvent concentration on the degree of conversion of a model photo-activated resin formulation when placed as a thin film in ambient air.
  
  
  METHODS
  A photo-activated co-monomer mixture (ethoxylated bis-GMA/TEGDMA) (Bisco Inc.) was diluted into six concentrations (from 1.0 to 13.0M) with either acetone or ethanol. A controlled volume of diluted, uncured resin was placed on the horizontal surface of an attenuated reflectance unit and the infrared (IR) spectrum obtained. A light emitting diode light-curing source (Bluephase, Ivoclar/Vivadent) then immediately irradiated the specimen for 10s (n=5). Five minutes after exposure, IR spectra of the cured material were obtained, and monomer conversions were calculated using standard methods that monitored changes in aliphatic-to-aromatic CC absorbance ratios in the uncured and cured states.
  
  
  RESULTS
  In the acetone/model resin system, maximum conversion occurred with 2.5-5.0M solvent. In the ethanol/model resin system, conversion peaked at 2.5M solvent. Above 5.0M solvent, conversion values declined rapidly for both solvents. A 13.0-M solution resulted in near 0% conversion for both solvents. At 2.5 and 5.0M acetone, conversions exceeded those of equivalent concentrations of the ethanol-based system.
  
  
  CONCLUSIONS
  For both an acetone- and ethanol-solvated model resin system, conversion did not immediately decrease with addition of solvent, but instead increased over that of the model resin alone. At higher solvent content (greater than 2.5M ethanol and 5.0M acetone), conversion rapidly declined, with ethanol causing less conversion at equal-molar solvent concentrations.
authors: Department of Oral Rehabilitation, Medical College of Georgia, School of Dentistry, Augusta, GA 30912-1260, USA. rholmes@mail.mcg.edu
authors: Robert G
authors: RG
authors: Holmes
authors: Frederick A
authors: FA
authors: Rueggeberg
authors: Richard S
authors: RS
authors: Callan
authors: Frank
authors: F
authors: Caughman
authors: Daniel C N
authors: DC
authors: Chan
authors: David H
authors: DH
authors: Pashley
authors: Stephen W
authors: SW
authors: Looney
mesh_terms: D000096:Acetone; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D000431:Ethanol; D008027:Light; D008422:Materials Testing; D008567:Membranes, Artificial; D044367:Phase Transition; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents; D013055:Spectrophotometry, Infrared; D018709:Statistics, Nonparametric; D014835:Volatilization
chemical_list: D017220:Dentin-Bonding Agents; D008567:Membranes, Artificial; D019279:Resin Cements; D012997:Solvents; D000096:Acetone; D000431:Ethanol