Abstract
The hardening characteristics of zine oxide eugenol (Ha, Me), polysulfide rubber (Su) and silicone rubber (Co, Xa, Ex, Pr, Si) as impression materials for ridges with flabby tissue, were measured at 23℃ and 37℃, or only 23℃ by loads using glass plates (0.5, 1.0, 1.5 kgf), a reciprocating rheometer and stress relaxation apparatus.
The measurements in three types of materials were different from each other, but those in the same type were considerably similar to each other and indicated that Ha and Pr respectively were softer than the others.
So the measurements of Ha, Su and Pr were evaluated.
1. Hardness just after completion of mixing: Pr was softest.
2. Duration of softness: Ha>Su>Pr
3. Working time and setting time: Pr was shortest.
4. Rapidity of the hardening reaction: Ha>Pr>Su
5. Dependence on load just after completion of mixing: Ha>Pr>Su
6. Dependence on temperature: Ha>Su>Pr
The impression materials for flabby ridges should be selected with consideration of these hardening characteristics. The order of preference might be strongly influenced by the experience of the dental practitioner (e.g.: time required for impression procedure, settling force of impression tray).
