Effects of a solubility enhancer on penetration of hydrophobic component in model adhesives into wet demineralized dentin.
OBJECTIVE
The purpose of this study was to evaluate the effects of a polymerizable solubility enhancer, poly (ethylene glycol) dimethacrylate (PEGDMA) in BisGMA/HEMA model adhesives on adhesive phase separation, adhesive penetration and structural integrity of adhesive/dentin (a/d) interfaces.


METHODS
The occlusal one-third of the crown was removed from 10 unerupted human third molars, each tooth was separated in half by cutting perpendicular to the acid conditioned dentin surface and treated with BisGMA/HEMA model adhesives with and without PEGDMA. Five-micron-thick sections of adhesive/dentin interface specimens were cut and stained with Goldner's trichrome for light microscopy. Companion slabs were analyzed with micro-Raman spectroscopy and scanning electron microscopy (SEM). The macrophase separation in the model adhesives with/without PEGDMA was also detected using cloud point measurements in the presence of water.


RESULTS
The addition of PEGDMA enhanced the water solubility/compatibility of the BisGMA/HEMA model adhesives. Micro-Raman spectral analysis of the dentin/adhesive interface indicated that there was a gradual decrease in penetration of BisGMA component for model adhesive without PEGDMA, while homogeneous distribution of the hydrophobic BisGMA component was noted in the interface with adhesive containing PEGDMA. The addition of PEGDMA dramatically facilitated infiltration of the hydrophobic monomers into the wet demineralized dentin. The SEM and staining results showed that the addition of PEGDMA would also improve the integrity at the interface between pure adhesive and hybrid layers.


CONCLUSIONS
The addition of PEGDMA could reduce phase separation, enhance the infiltration of BisGMA-based adhesives into the wet, demineralized dentin substrates, and promote homogeneous distribution of the hydrophobic component throughout the interface.
Guo
Xinglin
X
Department of Oral Biology, University of Missouri-Kansas City School of Dentistry, 650 E. 25th St., Kansas City, MO 64108, USA.
Spencer
Paulette
P
Wang
Yong
Y
Ye
Qiang
Q
Yao
Xiaomei
X
Williams
Karen
K
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D001840:Dental Bonding; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D012995:Solubility; D013059:Spectrum Analysis, Raman; D017001:Tooth Demineralization
D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C421283:poly(ethylene glycol)-dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C005044:hydroxyethyl methacrylate