In vitro accuracy of digital and conventional impressions in the partially edentulous maxilla

Objectives This in vitro study compared the dimensional accuracy of conventional impressions (CI) with that of digital impressions (DI) in a partially edentulous maxilla. DIs were made by two intraoral scanners, Omnicam (OC) and Primescan (PS). Materials and methods CI and both intraoral scanners were used to take 30 impressions of two identical reference models. CIs were poured with type 4 gypsum and the saw-cut models were digitized. The reference models simulated a maxilla with six prepared teeth that accommodated a cross-arch fixed partial denture. Center points of five precision balls and center points at the margin level of each prepared tooth were used to detect changes in dimensions and tooth axis between the reference model and the scans. Results For DI, the largest deviations (176 mu m for OC and 122 mu m for PS) occurred over the cross-arch. For CI, the largest deviation (118 mu m) occurred over the anterior segment. For shorter distances up to a quadrant, DI was superior to CI. For longer scan distances, DI was comparable (2 sextant and anterior segment) or inferior (cross-arch) to CI. Vertical and tooth axis deviations were significantly smaller for CI than for DI (p < 0.001). Conclusions The impression method affected the impression accuracy of a partially edentulous maxilla with prepared teeth. DI is recommended for scans up to a quadrant. Larger scan volumes are not yet suitable for fabricating a fixed partial denture because of the high scatter of accuracy values.

Automated summary

This in vitro study compared the dimensional accuracy of conventional impressions with that of digital impressions in a partially edentulous maxilla. Digital impressions showed better accuracy in shorter scan distances, while conventional impressions performed better in longer scan distances. The vertical and tooth axis deviations were significantly smaller for conventional impressions than for digital impressions.