Influence of intraoral scan extension on the accuracy of impressions with 3d-printed identical single tooth preparations

Abstract

Objectives: This study investigated whether the accuracy of the digital impression of identical single-tooth preparations is influenced by the size of an intraoral scan.

Materials and methods: The intraoral scans of 30 subjects with identical preparations for a molar and a premolar were digitally processed, 3d-printed and rescanned in different scan extensions. The scans of the entire dental arch, the half arch and the sequence from the preparation with adjacent teeth were examined. The approximal and occlusal distances between the preparation and the adjacent teeth were measured, as were the volumes of the prepared teeth. For statistical analysis, A Friedman test was performed for the precision measurements and a Wilcoxon signed-rank test for the trueness measurements.

Results: The original planning differed significantly from the measurements of the volumes (p < 0.001) and the occlusal distances of the molar and premolar (p ≤ 0.003). The sequence scan differed significantly when comparing the volumes of the molar (p < 0.001), the approximal distance measurement of the premolar (p < 0.001) and the occlusal distance measurement of the premolar (p < 0.001). The measurements of the half arch had the smallest median deviations (approximal ≤ 26 μm, occlusal ≤ 102 μm) from the original planning, compared to the sequence (approximal ≤ 26 μm, occlusal ≤ 131 μm) and full arch scan (approximal ≤ 27 μm, occlusal ≤ 122 μm).

Conclusions: Small scan extensions can provide more accurate results than larger scan sizes, whereby approximal distances are recorded more precisely than occlusal ones.

Clinical relevance: 3d-printing and intraoral scanning with small scan sizes can reproducibly achieve clinically acceptable accuracies with high consistency.