[Factors affecting the setting time of zinc oxide-eugenol impression materials--the influence of humidity and temperature to the reaction velocity].

Zinc oxide-eugenol paste are widely used in clinical dentistry, principally for impression of non-undercut edentulous ridges, or bite taking materials. However it has been realized by those who use these paste that different products, direction for mixing, or different conditions for mixing, have different characteristics. An experiment have been made to observe the influence of different conditions for mixing to the setting time. Zinc oxide-eugenol impression pastes were mixed in accordance with the manufacturer's instruction when supplied. The condition for mixing was at temperature of 15 +/- 1, 20 +/- 1, 25 +/- 1, 30 +/- 1 degrees C and at humidity of 40 +/- 5, 70 +/- 5, 90 +/- 5%. The setting time (a initial setting time, a final setting time) was defined in the A.D.A. specification No. 16. The following results were obtained. 1. A higher temperature and humidity shortened the initial setting time of all paste. 2. A higher temperature and humidity shortened slightly the time interval between a initial and a final setting time of all paste. 3. In clinical use, sample C is better than other ones, so that a setting time of the sample is property for impression making.