Impact of Scan Strategies on the Accuracy of Digital Impressions

Objectives: An increasing number of dentists are using digital intraoral scanners in their daily work with limited clinical experience. Little information is available on the impact of different scan strategies on the accuracy (trueness and precision) of full-arch scans. Thus, the aim of this in-vitro study was to quantify virtually the accuracy of full-arch maxillary digital impressions comparing three scan strategies.
Methods: A cobalt-chromium alloy model of a maxillary dentate jaw was fabricated and scanned with an industrial reference scanner. This full-arch data record was digitally superimposed with the test scans (trueness) and within-group comparison was performed for each group (precision). The TRIOS^® Pod scanner (3shape, Copenhagen, Denmark) with a color detector was used for the digital impression. Three scan strategies were applied each five times (A: first buccal surfaces, return from occlusal-palatal / B: first occlusal-palatal, return buccal / C: S-type one-way). The absolute values within the 90/10 percentiles from the digital superimposition were used for calculation. Nonparametric tests (ANOVA, post-hoc Bonferroni) were used for group comparisons.
Results: The trueness (mean ± standard deviation) was 17.9 ± 16.4 μm for scan strategy A, 17.1 ± 13.7 μm for B, and 26.8 ± 14.7 μm for C without statistically significant difference (A vs. B, p=1.000; A vs. C, p=0.457; C vs. B, p=0.363). The deviations between the scans were highest within the scans A (35.0 ± 51.1 µm) and significantly different to B (7.9 ± 5.6 µm, p<0.001) and C (8.5 ± 6.3 µm, p<0.001).
Conclusions: While the three scan strategies had no statistically significant impact on the trueness of the full-arch digital impressions, scans C showed the poorest trueness. The precision was highest for scan strategy B and lowest for A. Scan strategy B may provide the highest trueness and precision minimizing inaccuracies in the final reconstruction.