Comparison of physical properties of light-curing and self-curing dental impression materials.

A light-curing polyether urethane dimethacrylate impression material was recently developed. Its polymerization reaction is activated by intensified visible light; therefore, the on-demand set allows operators to work at their own pace. Furthermore, its constant viscosity provides a constant flow rate at the critical stages of taking impressions. The purposes of this study were to evaluate the physical properties and accuracy of this light-curing impression material and to compare it with those of self-curing impression materials currently used in our dental clinic. Physical properties such as strain in compression, compression set, dimensional stability, and tear strength of the impression materials were measured according to test methods stipulated in ADA Specification No. 19 for elastomeric impression materials. The template-coping method developed by Lewinstein and Craig was used to evaluate the accuracy of the impression materials. It was found that the strain in compression of the polyether urethane dimethacrylate was higher than that of the condensation silicones, but lower than that of the addition silicones. The compression set of the condensation silicones was more than that of the polyether urethane dimethacrylate, but much less than that of the polysulfides. The dimensional stability showed that all of the impression materials, except the polyether urethane dimethacrylate, had a negative dimensional change 24 hours after mixing. The sequence is: polysulfide < condensation silicone < addition silicone. The expansion rate of the light-curing material was measured under 0.07% one day after curing. The polyether urethane dimethacrylate had extraordinary tear resistance compared to the other impression materials.(ABSTRACT TRUNCATED AT 250 WORDS)