Dimensional accuracy of dental impression materials evaluated using a standardized CAD based method across materials...

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Prosthodontics

Background:

• Accurate dental impressions are crucial for fabricating well-fitting restorations.
• Dimensional stability of elastomeric impression materials is a key factor in clinical success.
• Existing standards, such as DIN EN ISO 4823, define acceptable dimensional changes.

Purpose of the Study:

• To establish a CAD-based workflow for evaluating the dimensional accuracy of dental impression materials.
• To compare the dimensional stability of vinyl polysiloxane (VPS), polyether (PE), and vinyl siloxanether (VSE) materials.
• To assess the influence of impression techniques (guided vs. freehand) and tray types (stock vs. custom) on accuracy.

Main Methods:

• An in vitro study utilizing a rigid metal reference arch with four spheres.
• Ninety double-mix impressions were made using VPS, PE, and VSE materials with stock and custom trays in guided and freehand techniques.
• Impressions were cast in Type IV dental stone, digitized, and analyzed by comparing linear inter-sphere distances to the reference model.

Main Results:

• VPS and PE materials exhibited significantly lower global deviations than VSE materials.
• No significant difference in accuracy was found between VPS and PE materials.
• Impression technique (guided vs. freehand) and tray type (stock vs. custom) showed no significant impact on dimensional accuracy under the tested conditions.
• All tested materials demonstrated deviations below the 1.5% linear-change threshold specified by DIN EN ISO 4823.

Conclusions:

• Material selection is the primary determinant of global dimensional accuracy in dental impressions.
• VPS and PE are superior to VSE in terms of dimensional stability for conventional dental impressions.
• The established CAD-based workflow provides a reliable method for evaluating impression material accuracy.