Investigation of preferred viscosity of irreversible hydrocolloid on preliminary impression for edentulism.

This study aims to investigate the preferred viscosity of irreversible hydrocolloid used in the preliminary impression for edentulism. Thirteen modalities of irreversible hydrocolloid were prepared by changing the W/P ratio. Discrimination test for the preferred viscosity was performed on 11 prosthodontists (10.4+/-5.3 years of prosthetic experience). The parameter of discrimination test (P%) was calculated as the ratio of the number of adequate tests to the total number of tests. The P% and apparent viscosity coefficient (eta a) values measured by rheometer demonstrated good correlation (Y = -35.8X2 + 118.4X - 22.8, r=0.86, p<0.01). Prosthodontists could judge the preferred viscosity based on their clinical experiences. On the preliminary impression for edentulism, the preferred viscosity demonstrated in vitro using a polyurethane maxilla model was 1.21 x 10(3) Pa x s.