In Vivo Evaluation of Inter-operator Reproducibility of Digital Impression Technique

Objectives: The aim of this study was to evaluate and compare inter-operator reproducibility of digital impression and silicone impression techniques in vivo.
Methods: Five subjects who have no missing teeth were included in this study. Impressions of mandibular molars of these subjects were made by 2 impression techniques, which used intra-oral scanner (Lava COS, 3M ESPE) and silicone impression material (Imprint3, 3M ESPE). Both impressions were made by two operators with different clinical experience (3 and 15 year clinical experiences). The Standard Tessellation Language (STL) data was directly exported from the COS system, while that of gypsum model made from silicone impression was obtained by 3D lab scanner (D810, 3shape). The STL datasets recorded by two different operators were loaded into 3D evaluation software and superimposed using the best-fit-algorithm method (least‐squares method, PolyWorks, InnovMetric Software) for each impression method. Inter-operator reproducibility as evaluated by averaged discrepancies of corresponding 3D data were compared between 2 methods (paired t test, p<0.05).
Results: Twenty-four thousands polygon points and 11,000 points were obtained from the STL data for the digital and silicone impressions, respectively. The visual inspection of superimposed inter-operator datasets revealed smaller discrepancy for the intra oral scanner, which was confirmed by the statistical analysis that revealed significantly smaller averaged discrepancy for digital impression method (19.4±4.3 µm) than that for silicone impression (35.0±3.7 µm, p<0.05).
Conclusions: The results of this in-vivo study suggest that the intraoral scanner has better reproducibility in comparison with conventional silicone impression technique, which is independent upon the clinical experience of the operator.