Intraoral optical impression versus conventional impression for full edentulous maxilla: an in vivo comparative study.

AIM: The aim of this in vivo study was to compare the clinical trueness of primary mucostatic impressions obtained either by a classical alginate technique or by an optical intraoral scanner of fully maxilla edentulous patients.

MATERIALS AND METHODS: 30 patients with fully edentulous maxilla were included and underwent conventional impressions as well as intraoral optical impressions (TRIOS 3®, 3Shape®). The conventional impressions were casted and the resulting stone models were digitized using a desktop scanner (Iscan D104i®, Imetric®). These digitized impressions were superimposed over the optical impressions to compare differences between the two datasets. Statistical analyses were performed to identify relevant deviations.

RESULT: For the 30 intraoral impressions, 80.88% of the surface areas were below the tolerance threshold of 25 μm and thus considered similar to the area scanned with the desktop scanner from the reference stone model. Interestingly, the differences (19.12% of the surfaces) were localized in depressible areas like vestibule, soft palate, incisal papilla and flabby ridge. These locations were coherent with the positive mean of differences of +22.8μm, indicating deformation or less compression using the intraoral scanner.

CONCLUSION: Digital primary impression of the fully edentulous maxilla can be considered as similar to the conventional alginate impression, except in the depressible areas. Considering the mucostatic objective of such a primary impression, one may consider optical impression as more accurate than the conventional one.