New Testing Method for Seating Rigidity of PVS Impression Materials

Objectives: Currently, no test is available to evaluate/compare seating forces among impression materials. This research compared impression material rigidity among commercial products when simulating the time impressions are seated, using a new test method.
Methods: Seven commercial fast-setting polyvinyl siloxane (PVS)-based impression materials were tested: Aquasil Ultra Rigid Fast Set and Aquasil Ultra Heavy fast set (Dentsply Sirona), Imprint 3 quick step and Imprint 4 super quick (3M/ESPE), Take 1 Advanced (Kerr), Exafast NDS (GC America), and FlexiTime Extreme 2 (Heraeus Kulzer). Specimens were dispensed into a stainless steel cylinder mold (Φ30mm x 20 mm depth) by using an air-driven gun to extrude samples from impression cartridges, and then transferred to a temperature-controlled environmental chamber (23°C±0.5). After 35s from the start of mix, a stainless steel probe (Φ15mm x 15 mm height) was vertically lowered into the specimen, at a rate of 5 mm/s, and the maximum force was recorded as the probe moved to a depth of 10 mm. The maximum probe force was compared among materials using a 1-way ANOVA based on ranks, followed by the Tukey post-hoc test. All statistical testing was performed at a pre-set alpha of 0.05. Four specimens per test condition were made and tested.
Results: Table presents results. Values ranged from a high or 1059g to a low of 265g. There was a great variety of values among products, indicating a range of “stiffness values” (measured as “rigidity”) 35 seconds following mixing: the time when the impression tray is ready to be seated.
Conclusions: This new test for examining the rigidity of fast-setting PVS impression materials proved to be discriminating among a wide range of commercial products, and may provide clinicians with additional knowledge of how rigid a freshly mixed material will be when it is ready to insert in the mouth.