Effect of photoinitiators on the in vitro performance of a dentin adhesive exposed to simulated oral environment.
OBJECTIVE
Our previous study showed poor mechanical durability and nano-sized heterogeneities in cross-linked dentin adhesives cured in the presence of water. To further explore the relationship between nano-scale heterogeneities and the long-term mechanical properties of dentin adhesives, the properties of model dentin adhesives polymerized using hydrophilic photoinitiators were compared with those of adhesives polymerized using hydrophobic camphorquinone-based photoinitiators.


METHODS
The model adhesives consisted of HEMA and bisGMA with a mass ratio of 45/55 and were photopolymerized in the presence of 8.3 mass% water. The photo-polymerization of the model adhesives during irradiation was monitored in situ using a Perkin-Elmer Spectrum One FTIR in the ATR sampling mode. The tensile properties were determined for all samples after dry storage at room temperature, or after aqueous storage in distilled deionized water.


RESULTS
There was a continuous decline of mechanical properties for the specimens cured in the presence of water during 3 months aqueous storage, especially for the specimens that contained hydrophobic photoinitiators. The multi-component systems containing hydrophilic photoinitiators were shown to produce superior model dental adhesives when these materials are cured in the presence of water.


CONCLUSIONS
Designing initiator systems to perform in this heterogeneous environment may improve the mechanical performance of dentin adhesives, as the results presented here indicate.
Ye
Qiang
Q
Bioengineering Research Center, The University of Kansas School of Engineering, Lawrence, KS 66045-7609, USA.
Park
Jonggu
J
Topp
Elizabeth
E
Spencer
Paulette
P
D000268:Adhesiveness; D001713:Biphenyl Compounds / Q000494:pharmacology; D017438:Bisphenol A-Glycidyl Methacrylate; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000737:chemistry; D055119:Elastic Modulus; D006244:Hardness; D057927:Hydrophobic and Hydrophilic Interactions; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008689:Methacrylates / Q000494:pharmacology; D053758:Nanoparticles; D009861:Onium Compounds / Q000494:pharmacology; D044367:Phase Transition; D055668:Photochemical Processes / Q000187:drug effects*; D019279:Resin Cements / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013718:Tensile Strength; D013729:Terpenes / Q000494:pharmacology; D014867:Water
D001713:Biphenyl Compounds; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D009861:Onium Compounds; D019279:Resin Cements; D013729:Terpenes; D014867:Water; C031291:diphenyliodonium; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; C005044:hydroxyethyl methacrylate; C049840:2-(dimethylamino)ethyl methacrylate