title: Effect of Partition of Photo-initiator Components and Addition of Iodonium Salt on the Photopolymerization of Phase-Separated Dental Adhesive.
abstract: The polymerization kinetics of physically separated hydrophobic- and hydrophilic-rich phases of a model dental adhesive have been investigated. The two phases were prepared from neat resin containing 2-hydroxyethyl methacrylate (HEMA) and bisphenol A glycerolate dimethacrylate (BisGMA) in the ratio of 45:55 (wt/wt). Neat resins containing various combinations of popular photo-initiating compounds, e.g., camphoquinone (CQ), ethyl 4-(dimethylamino)benzoate (EDMAB), 2-(dimethylamino)ethyl methacrylate (DMAEMA) and diphenyliodonium hexafluorophosphate (DPIHP) were prepared. To obtain the two phases 33 wt% of deuterium oxide (D2O) was added to the neat resins. This amount of D2O exceeded the miscibility limit for the resins. The concentration of each component of the photo-initiating system in the two phases was quantified by HPLC. When combined with CQ, DMAEMA is less efficient as a co-initiator compared to EDMAB. The addition of DPIHP as the third component into either CQ/EDMAB or CQ/DMAEMA photo-initiating systems leads to comparable performance in both the hydrophobic- and hydrophilic-rich phases. The addition of the iodonium salt significantly improved the photopolymerization of the hydrophilic-rich phase; the hydrophilic-rich phase exhibited extremely poor polymerization when the iodonium salt was not included in the formulation. The partition concentration of EDMAB in the hydrophilic-rich phase was significantly lower than that of DMAEMA or DPIHP. This study indicates the need for a combination of hydrophobic/hydrophilic photosensitizer and addition of iodonium salt to improve polymerization within the hydrophilic-rich phase of the dental adhesive.
authors.affiliation: Bioengineering Research Center, The University of Kansas, Lawrence, KS; Bioengineering Graduate Program, The University of Kansas, Lawrence, KS.
authors.forename: Farhana
authors.initials: F
authors.lastname: Abedin
authors.affiliation: Bioengineering Research Center, The University of Kansas, Lawrence, KS.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ye
authors.affiliation: Bioengineering Research Center, The University of Kansas, Lawrence, KS.
authors.forename: Linyong
authors.initials: L
authors.lastname: Song
authors.affiliation: Bioengineering Research Center, The University of Kansas, Lawrence, KS.
authors.forename: Xueping
authors.initials: X
authors.lastname: Ge
authors.affiliation: Department of Chemical and Petroleum Engineering, The University of Kansas, Lawrence, KS.
authors.forename: Kyle
authors.initials: K
authors.lastname: Camarda
authors.affiliation: Bioengineering Research Center, The University of Kansas, Lawrence, KS; Department of Mechanical Engineering, The University of Kansas, Lawrence, KS.
authors.forename: Paulette
authors.initials: P
authors.lastname: Spencer
keywords: co-initiator; dentin adhesive; hydrophilic-rich phase; iodonium salt; photopolymerization; photosensitizer