Accuracy of full-arch digital impressions: an in vitro and in vivo comparison

Abstract

Objectives: Comparison of full-arch digital impressions to conventional impressions in vitro and in vivo.

Materials and methods: A straight metal bar was fixed between the second upper molars as a reference structure in the mouth of a voluntary patient and a corresponding polymer model. The following digitalization methods were applied: (1) the maxilla was digitized in vivo 12 times with the iTero Element (P-SCAN); (2) the maxilla was captured in vivo 12 times by conventional impression and the impression was digitized by a desktop scanner (P-IMP); (3) the impressions were poured and the 12 referring gypsum master-casts were scanned with the same desktop scanner (P-CAST); (4) the polymer model was digitized in vitro 12 times with the iTero Element (M-SCAN); (5) the polymer model was captured in vitro 12 times by conventional impression and the impression was digitized by a desktop scanner (M-IMP); (6) the impressions were poured and the 12 referring gypsum master-casts were scanned with the same desktop scanner (M-CAST). Datasets were exported and metrically analyzed (Geomagic Control X) to determine three-dimensional length aberration and angular distortion versus the reference structure. Mann-Whitney U test was implemented to detect differences (p < 0.05).

Results: For multiple accuracy parameters, P-SCAN and M-SCAN showed similar or superior results compared to the other digitalization methods. The following length deviations were found: M-SCAN (- 55 to 80 μm), M-IMP (110 to 329 μm), M-CAST (88 to 178 μm), P-SCAN (- 67 to 76 μm), P-IMP (125-320 μm), and P-CAST (92-285 μm).

Conclusions: Within the limitations of this study, the iTero-scan seems to be a valid alternative to conventional impressions for full arches.

Clinical relevance: Intraoral scanners are more and more used in daily routine; however, little is known about their accuracy when it comes to full-arch scans. Under optimum conditions, the direct digitalization using the iTero Element intraoral scanning device results in the same and for single parameters (arch width and arch distortion) even in higher accuracy than the indirect digitalization of the impression or the gypsum cast using a desktop scanner.

Keywords: Accuracy; Digital impression; Full-arch impression; Metrology analysis; iTero Element.