title: Polymerization- and solvent-induced phase separation in hydrophilic-rich dentin adhesive mimic.
abstract: Current dental resin undergoes phase separation into hydrophobic-rich and hydrophilic-rich phases during infiltration of the over-wet demineralized collagen matrix. Such phase separation undermines the integrity and durability of the bond at the composite/tooth interface. This study marks the first time that the polymerization kinetics of model hydrophilic-rich phase of dental adhesive has been determined. Samples were prepared by adding varying water content to neat resins made from 95 and 99 wt.% hydroxyethylmethacrylate and 5 and 1 wt.% (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl1]-propane prior to light curing. Viscosity of the formulations decreased with increased water content. The photopolymerization kinetics study was carried out with a time-resolved Fourier transform infrared spectrometer. All of the samples exhibited two-stage polymerization behavior which has not been reported previously for dental resin formulation. The lowest secondary rate maxima were observed for water contents of 10-30 wt.%. Differential scanning calorimetry (DSC) showed two glass transition temperatures for the hydrophilic-rich phase of dental adhesive. The DSC results indicate that the heterogeneity within the final polymer structure decreased with increasing water content. The results suggest a reaction mechanism involving both polymerization-induced phase separation and solvent-induced phase separation for the model hydrophilic-rich phase of dental resin.
authors.affiliation: Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA; Bioengineering Graduate Program, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
authors.forename: Farhana
authors.initials: F
authors.lastname: Abedin
authors.affiliation: Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA. Electronic address: yeq@ku.edu.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ye
authors.affiliation: Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
authors.forename: Holly J
authors.initials: HJ
authors.lastname: Good
authors.affiliation: Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
authors.forename: Ranganathan
authors.initials: R
authors.lastname: Parthasarathy
authors.affiliation: Bioengineering Research Center, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA; Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
authors.forename: Paulette
authors.initials: P
authors.lastname: Spencer
mesh_terms: D002152:Calorimetry, Differential Scanning; D003738:Dental Cements; D003804:Dentin / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D011108:Polymers / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*
chemical_list: D003738:Dental Cements; D011108:Polymers; D012997:Solvents
keywords: Dental adhesive; Hydrophilic-rich phase; Phase separation; Polymerization