Updated: Jul 21, 2026

Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision
Published on: April 29, 2014
1Division of Operative Dentistry, Department of Restorative Dentistry, Tohoku University Graduate School of Dentistry, Japan.
This study compared the dimensional accuracy of stone dies made from impressions using a new polyether material, a conventional polyether, and a polyvinyl siloxane reference. Impressions were made at two different temperatures and stored under varying humidity conditions. The researchers measured base-diameter deviations to assess accuracy. They found that the new polyether (P2) performed similarly to the conventional material after short-term storage but showed significant dimensional changes at high humidity. Polyvinyl siloxane remained stable under all conditions. The results suggest that environmental factors like temperature and humidity strongly influence impression material performance. The study highlights the importance of controlling storage conditions to ensure accurate dental restorations.
You might also read
Articles linked to this work by shared authors, journal, and citation graph.
Area of Science:
Background:
Dental impressions require high dimensional accuracy to ensure proper restoration fit. Conventional polyether materials have been widely used, but newer formulations may offer similar or improved performance. Prior research has shown that temperature and humidity influence material behavior during storage. However, the specific impact of these variables on dimensional stability remains unclear. This gap motivated a detailed comparison of a new polyether material with a conventional one and a polyvinyl siloxane reference. No prior work had resolved how different storage conditions affect long-term accuracy. The study aimed to address this uncertainty by testing materials under controlled temperature and humidity conditions. It was already known that polyethers may absorb water, but the extent of this effect on die accuracy had not been fully explored. This study sought to clarify the role of environmental factors in material performance.
Purpose Of The Study:
The study aimed to compare the dimensional accuracy of stone dies produced from impressions made with a new polyether material, a conventional polyether, and a polyvinyl siloxane reference. The researchers focused on how temperature and humidity influence dimensional changes over time. They wanted to determine whether the new material performs similarly to the conventional one under various storage conditions. The motivation came from the need to evaluate new dental materials for clinical use. The study also sought to assess how environmental factors affect material behavior during storage. By measuring base-diameter deviations, the researchers aimed to quantify accuracy differences. They hypothesized that temperature and humidity would significantly impact dimensional outcomes. This work could inform material selection and handling protocols in dental laboratories.
The study found that a new polyether material (P2) had similar dimensional accuracy to a conventional polyether after short-term storage but showed significant deviations at high humidity.
Impressions were made using a truncated steel cone in cylindrical steel trays with a 4-mm impression layer thickness at the prominence line.
Humidity was tested because polyethers may absorb water, which could compromise dimensional accuracy during storage.
Impressions made at 37°C showed higher base-diameter deviations than those made at 23°C, indicating temperature affects material behavior.
Accuracy was measured by calculating base-diameter deviation (deltad) using axial discrepancies between a steel ring and the die surface.
Main Methods:
The study used a truncated steel cone as a standardized model for impressions. Impressions were made with two polyether materials—P2 and Impregum—and a polyvinyl siloxane material, Flexitime. Impressions were produced at either 23°C or 37°C in cylindrical steel trays. The impression layer thickness was standardized at 4 mm at the prominence line. Stone dies were poured after 1 or 24 hours of storage at ambient conditions. Additional impressions were stored at varying humidity levels (0%, 33%, 50%, 75%, or 100%) for 24 hours before die pouring. The dimensional accuracy was measured using axial discrepancies between a steel ring and the occlusal die surface. The base-diameter deviation (deltad) was calculated to quantify accuracy differences.
Main Results:
After 1 hour of storage, similar increases in deltad were observed for all materials when poured at the same temperature. Impressions made at 37°C showed significantly higher deltad than those made at 23°C. Light-bodied P2 exhibited the largest increase in deltad after 24 hours of storage. Flexitime showed moderate deltad differences between the two pouring times. The deltad of polyether materials decreased significantly with increasing humidity. In contrast, polyvinyl siloxane was not affected by humidity changes. P2’s dimensional accuracy was comparable to the conventional polyether material after short-term storage. However, polyethers may absorb water, which compromises die accuracy at high humidity.
Conclusions:
The study found that the new polyether material P2 performed similarly to the conventional polyether after short-term storage. However, dimensional accuracy declined significantly with prolonged storage at high humidity. Polyvinyl siloxane remained stable under varying humidity conditions. The researchers propose that polyethers may absorb water, which affects die accuracy. The results suggest that storage conditions influence material performance. The authors note that temperature and humidity are critical factors in impression material handling. They emphasize the importance of controlling environmental variables in dental laboratories. The findings support the need for further research on material-water interactions.
The authors found that polyvinyl siloxane was not affected by humidity changes, suggesting it maintains dimensional stability under varying conditions.