Effect of contact time between alginate impression and type III dental stone on cast model properties

ABSTRACT

Objective: To measure the effect of different contact time between the alginate impression and type III dental stone on cast model properties in the terms of dimension stability, hardness and surface details reproduction. Material and methods: Sixty-seven cast models were obtained from stainless steel cylinder using alginate impression material and type III dental stone. Thirty-seven cast models were separated after one hour (control group) and 30 cast models were separated from impressions after 9 hours. The samples were evaluated under light microscope for surface details, measured by digital caliper for dimension stability and hardness was tested by making indentation on the cast then measuring the depth using digital caliper. Results: The dimension stability of cast models was not affected by increasing contact time between type III dental stone and alginate impression while surface details decreased. In the meanwhile, hardness was improved with increasing contact time. Conclusion: According to the results of this study, pouring of impression up to 9 hours can negatively affect the cast model properties in the term of details richness.