Polymerization time compatibility index of polyvinyl siloxane impression materials with conventional and experimental gingival margin displacement agents

Abstract

Statement of problem: No consensus exists as to the compatibility of chemical agents used with gingival displacement methods with different impression materials.

Purpose: The purpose of this study was to investigate the effect of conventional and experimental gingival displacement agents on the polymerization time of polyvinyl siloxane impression elastomers.

Material and methods: The study comprised 10 gingival displacement agents, including 5 conventional astringents (10%, 20%, and 25% aluminum chloride, 25% aluminum sulfate, and 15.5% ferric sulfate) and 5 experimental adrenergics (0.1% and 0.01% HCl-epinephrine, 0.05% HCl-tetrahydrozoline, 0.05% HCl-oxymetazoline, and 10% HCl-phenylephrine). The polymerization time of 240 specimens (weight 3.3 g) of 4 polyvinyl siloxane (PVS) impression elastomers, type 3 (Colorise Thermochromic, Hydrorise, Express, and Take 1 Advanced), after mixing with 20 μL of each displacement agent, was measured with a viscometer. The 24 specimens from the control group were polymerized without contact with the displacement agents. The studies were performed at 23°C and 37°C (± 0.1°C).

Results: A polymerization time compatibility index (PTCI) was devised, where the polymerization time of PVS mixed with the displacement agents was expressed as the percentage of the standard polymerization time of the impression material. The PTCI values at 23°C were higher than those at 37°C for both groups of displacement agents. At 37°C, the experimental displacement agents achieved higher PTCI values than the conventional agents.

Conclusions: All of the evaluated displacement agents at laboratory and intraoral temperatures induced changes in the polymerization time of PVS. Therefore, chemical displacement agents should not come into direct contact with PVS impression materials.