Unpolymerized layer on autopolymerizing, hard reline materials.
OBJECTIVE
The purpose of this study was to clarify certain properties of the resulting unpolymerized surface layer on 6 hard, autopolymerizing reline resins.


METHODS
Two of the resins examined were the conventional type with a base monomer composition of mainly methyl methacrylate, and the other four were cross-linked reline materials containing difunctional monomers. For curing, the materials were polymerized in air at 24 and 37 degrees C, and in distilled water at 37 degrees C. The powder-to-liquid ratio was changed by +/- 20 wt% of the manufacturer's specified ratio. The inhibition depth processed under these conditions was measured with an optical microscope. Each sample was then immersed in methylene blue dye bath for 3 weeks before its surface was observed.


RESULTS
Especially on cross-linked reline materials, the unpolymerized layer was significantly reduced with higher temperature, lower oxygen presence, and lower powder-to-liquid ratio (P < 0.01). The unpolymerized layer was stained in all materials. There were tiny, stained voids in the polymerized region on the conventional type of reline resins, whereas no staining was found in the polymerized region on the cross-linking reline resins.


CONCLUSIONS
The inhibition depth was strongly affected by the temperature, the presence of air, and viscosity. The unpolymerized layer was easily contaminated in all materials. However, the highly polymerized, cross-linked reline materials might be harder to contaminate than the conventional type of reline resins.
Yatabe
M
M
First Department of Prosthodontics, Faculty of Dentistry, Tokyo Medical and Dental University, Japan. masapro1@dent.tmd.ac.jp
Yasuda
N
N
Ai
M
M
Okabe
Y
Y
D000704:Analysis of Variance; D003432:Cross-Linking Reagents / Q000737:chemistry; D003822:Denture Liners; D003823:Denture Rebasing; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D016062:Porosity; D013499:Surface Properties; D014783:Viscosity
D003432:Cross-Linking Reagents; D008768:Methylmethacrylates; D011108:Polymers; C009931:poly(ethylmethacrylate); D019904:Polymethyl Methacrylate