Influence of prolonged setting time on permanent deformation of elastomeric impression materials

Statement of problem

Upon removal, tear forces occur in various areas of an impression. As a result, thin sulcus details may be permanently deformed, affecting the impression's accuracy.

Purpose

The purpose of this study was to investigate the effect of the chemistry and prolonged setting time on the permanent deformation of light-body impression materials after stretching.

Material and methods

A dumbbell-shaped mold (2 mm × 4 mm × 75 mm) was used to prepare specimens (n=20) of 6 different impression materials (Affinis Light Body, Aquasil Ultra XLV, Express 2 Light Body Flow Quick, Flexitime Correct Flow, P2 Polyether Light, and Impregum Garant L DuoSoft). After water storage (35°C), either for the manufacturer's suggested setting time or for 5 minutes, specimens were stretched by 80% using a universal testing machine at a crosshead speed of 200 mm/min. The permanent deformation (Δl (%)) was determined after 2 hours of storage in ambient conditions. A 2-way ANOVA followed by a Games-Howell test was used to analyze the influence of material and storage time (α=.05).

Results

Polyether materials showed a significantly higher permanent deformation (Δl>4% to 5%) than vinyl polysiloxane materials (P<.05). Extending the manufacturer's suggested setting time resulted in clinically relevant improvements in elastic recovery for products with a polyether backbone only.

Conclusions

Increasing the setting time might be necessary for impression materials with a polyether backbone to improve elastic recovery.