Effect of Pressure Dynamics of Impression Materials for Selective-pressure Impression

Objectives: The aim of this study was to investigate the influence of the thickness of relief in tray and characteristics of the impression material on impression pressure for an edentulous model.
Methods: Two silicone impression materials (Exadenture; ED and Examixfine; EM), polyether impression material (Impregum soft medium body; IG), and a maxillary edentulous model were used. The tray relief consisted of no relief, 1.40-mm-thick base-plate wax, and 2.80-mm-thick base-plate wax. Miniature pressure sensors were embedded at the incisive papilla, the anterior point and the deepest point of the mid-palatal suture. These measurement points were included within the relief area. The mixing time prior to the experiment was set at 60 s for each material. The measurement of impression pressure started immediately after loading. The duration of the measurement was 150 s, and the sampling rate during all measurements was 10 Hz. The static load to the trays during measurements was set at 2 kgf. Five measurements were taken for each material using three types of customized trays.
Results: The average pressure at each point in three trays were calculated. The mean impression pressures of ED, EM, and IG in the incisive papilla were 7.75 ± 2.23, 7.59 ± 2.21, and 7.79 ± 0.96 kPa, respectively. The mean impression pressures of ED, EM, and IG in the anterior point were 6.02 ± 0.39, 5.56 ± 0.53, and 5.62 ± 0.31 kPa, respectively. The mean impression pressures of ED, EM, and IG in the deepest point were 4.57 ± 0.50, 4.55 ± 0.60, and 4.86 ± 0.11 kPa, respectively. The impression pressures at each measurement point were significantly dependent on the impression materials (P < 0.05) and tray relief (P < 0.05).
Conclusions: Impression pressure is dependent on the thickness of the relief and the characteristics of the impression material.