[ESR study on self-curing resin for rebasing during polymerization].

Abstract

The effects of temperature, concentrations of activator (N, N-dimethyl-p-toluidine) and inhibitor (hydroquinone), atmosphere, liquid powder ratio and mixing time on polymerization process of self-curing resin for rebasing were studied by electron spin resonance. When powder and liquid were mixed at a ratio commercially recommended at a physiologic temperature of 37 degrees C, the propagating radical was first detected 5.5 minutes later, of which time interval corresponds to induction time for polymerization. After the induction time, the concentration of propagating radicals increased rapidly with time and reached the maximum level at 27 minutes. The radicals thus formed remained stable for more than 2.5 days when stored in air at 37 degrees C, though their concentration diminished gradually. With increasing temperature for curing, the maximum level of the radical concentration decreased and the propagating radicals disappeared more rapidly, indicating recombination reactions to be perferentially occurring at higher temperatures. Increase in the amount of activator of N,N-dimethyl-p-toluidine resulted in increase in the radical concentration. When powder was mixed with a liquid containing less inhibitor of hydroquinone, the radicals were found to remain stable longer. In air, propagating radical was detected faster and free radical was concentrated more rapidly than in the water and nitrogen gas. The fluidity of self-cured resin for rebasing as measured by use of spin probe TEMPO disappeared rapidly with increasing temperature for curing, decreasing the amount of liquid and shortening the mixing time. When curing temperature was raised to 37 degrees C from 22 degrees C at minutes after mixing, the fluidity disappeared 2.5 minutes later, i.e., at 5.5 minutes after mixing. To investigate the effects of the MMA-derivative radicals on growth of HeLa cells, HeLa cells were cultured on resins containing MMA-derivative radicals. The number of HeLa cells on resins containing MMA-derivative radicals was 7/10 of that of HeLa cells on resins containing no radicals.