Affect of storage humidity on accuracy of silicone rubber impression materials

JIE Hui-fei; XIE Chao; HE Hui-ming; ZHAO Yin-hua

Abstract：AIM: To evaluate the dimensional deviations of three recently marketed silicone rubber impres-sion materials during storage at different humidities (30%, 50%, 75%, 96% and in water). METHODS: A total of 75 impressions were made using silicone rubber impression materials-Silagum-light (DMG), EXAFINE-light (GC) The impressions were set in the environmental test chamber of different humidity. Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression to the same line on the metal die, by use of a measuring microscope with an accuracy of 0. 001 mm. RESULTS: Among the three impression materials, GC showed the smallest linear shrinkage under humidity of 30%, 50% and 75%. However, DMG showed the smallest lin-ear shrinkage under humidity of 96% and in water. KT showed the biggest change of linearity size under all tested hu-midity. CONCLUTION: Humidity significantly affects the precision of impressions. Relative higher humidity was useful for the precision of imoression. The affect of humidity on DMG material was less significant than the other two impression materials. When environmental humidity is higher, it is more suitable to use DMG as impression material. However, when humidity is relatively lower, it is more suitable to use DMG as impression material.