Dimensional Accuracy of Two Impression Materials Regarding Impression Technique and Pouring Time Using Cone Beam Computed Tomography Analysis

Abstract

An ideal impression material should present with dimensional stability over long periods, allowing the precise production of cast models at any time. However, the materials commonly used in dental impressions present alterations in their dimensional behavior. This study amid to evaluates the effect of the Impression technique, Single step, two steps, and Impression pouring time on the dimensional accuracy of two different impression materials; polyvinyl siloxane impression material, and polyether impression material, using Cone Beam Computed Tomography (CBCT) analysis. Two commercially available impression materials were used in this study Polyvinyl siloxane (PVS)- Polyether (PE),30 standardized metal custom-made dies representing full veneer all ceramic crown preparation, and 30 perforated custom-made trays fabricated that be placed in the same position on the master die for each impression, each material divided into two groups each group (n 15)one group using two-step technique the other group one step technique For each group, specimens were subdivided according to the pouring time into three subgroups (5 samples); 1hour, 24hour, 7days. All samples submitted for CBCT for evaluation of their dimensions. There were no significant differences with PVS and PE, but the single step showed a significant difference in highest mean high compared to two steps. 1 hr. (4.96±0.01 μm) showed an insignificant difference on mean height compared to 24 hours (4.96±0.01 μm) and 7 days (4.90±0.01 μm) at p=0.791 for Single step.1 hr (4.86±0.01 μm) showed insignificant difference on mean height compared to 24 hours (4.85±0.01 μm) and 7 days (4.81±0.01 μm) at p=0.960 for Two steps for PVS. 1 hr (4.95±0.03 μm) showed insignificant difference on mean height compared to 24 hours (4.94±0.01 μm) and 7 days (4.89±0.01 μm) at p=0.100 for Single step. 24 hours (4.85±0.02 μm) showed significant difference on mean height compared to 1 hr (4.84±0.01 μm) and 7 days (4.80±0.01 μm) at p≤0.001 for two steps for PE. Polyvinyl siloxane and poly ether materials give high accurate stone dies. One-step impression taking technique give more accurate stone dies than the two-step technique. pouring time is very critical for PE impression materials.