Evaluation of the Accuracy of Digital Impression Techniques Based on an Integrated ADA Model

The purpose of this in vitro study was to assess and compare the accuracy of three digital impression techniques based on an innovative integrated model.

The integrated model was created by incorporating crown, inlay, and long-distance specimens from the American Dental Association (ADA) Standard No. 132. Digitized files of the model were acquired using three distinct impression techniques: intraoral scanner (IOS), extraoral scanner with negative cast (EOS_N), and extraoral scanner with positive cast (EOS_P). A coordinate measuring machine (CMM) was employed to establish the gold standard. The digital files of the model obtained via the extraoral scanner were designated the reference set for 3D fitting. Statistical analysis was performed using a one-way analysis of variance and Tukey's posthoc test.

For the crown specimen, the relative error of EOS_N for indices d₁ and d₂ was higher than that of IOS and EOS_P. For the inlay specimen, IOS showed the highest trueness for d₃ and h₂. For the long-distance specimen, IOS exhibited superior trueness for indices l₁ and l₃. EOS_N displayed the lowest trueness for l₂. For l₄, IOS had the largest relative error. No significant differences were observed among the three groups for l₅ and l₆. Notable deviations were evident in the 3D fitting maps at various locations in three experimental groups.

The three digital impression techniques exhibited varying capacities for capturing features of the integrated ADA model. For crown preparations, IOS and EOS_P are recommended, while for inlay preparations, no technology meets the standard requirements. IOS is recommended for partial impressions, while both EOS_N and EOS_P are suited for full-arch impressions.