Dimensional accuracy of dental impression materials evaluated using a standardized CAD based method across materials tray types and techniques.

In this in vitro study, a CAD-based test workflow was established to evaluate the dimensional accuracy of conventional dental impression materials under standardized laboratory conditions. Ninety double-mix impressions were made from a rigid metal reference arch with four reference spheres using three elastomeric materials: vinyl polysiloxane (VPS), polyether (PE), and vinyl siloxanether (VSE). Guided impressions and freehand impressions were performed with both stock and custom trays. Impressions were cast in type IV dental stone, digitized with a laboratory scanner, and analyzed by comparing four linear inter-sphere distances with the reference model. Non-parametric statistics were applied. VPS and PE showed significantly lower global deviations than VSE, while VPS and PE did not differ significantly from each other. No significant differences were found between guided and freehand impressions when using stock trays. In the freehand-only comparison, stock and custom trays did not differ significantly; a borderline difference in the full cohort should be interpreted cautiously because of the partially crossed design. All measured deviations remained below the 1.5% linear-change threshold specified in DIN EN ISO 4823. This is the German adoption of a European and international standard for dentistry, specifically elastomeric impression materials. Within the limitations of this in vitro stone-cast workflow and linear-distance analysis, material selection had the strongest effect on global dimensional accuracy.