Influence of material surface on the scanning error of a powder-free 3D measuring system

Abstract

Objectives: This study aims to evaluate the accuracy of a powder-free three-dimensional (3D) measuring system (CEREC Omnicam, Sirona), when scanning the surface of a material at different angles. Additionally, the influence of water was investigated.

Materials and methods: Nine different materials were combined with human tooth surface (enamel) to create n = 27 specimens. These materials were: Controls (InCoris TZI and Cerec Guide Bloc), ceramics (Vitablocs® Mark II and IPS Empress CAD), metals (gold and amalgam) and composites (Tetric Ceram, Filtek Supreme A2B and A2E). The highly polished samples were scanned at different angles with and without water. The 216 scans were then analyzed and descriptive statistics were obtained.

Results: The height difference between the tooth and material surfaces, as measured with the 3D scans, ranged from 0.83 μm (±2.58 μm) to -14.79 μm (±3.45 μm), while the scan noise on the materials was between 3.23 μm (±0.79 μm) and 14.24 μm (±6.79 μm) without considering the control groups. Depending on the thickness of the water film, measurement errors in the order of 300-1,600 μm could be observed.

Conclusions: The inaccuracies between the tooth and material surfaces, as well as the scan noise for the materials, were within the range of error for measurements used for conventional impressions and are therefore negligible. The presence of water, however, greatly affects the scan.

Clinical relevance: The tested powder-free 3D measuring system can safely be used to scan different material surfaces without the prior application of a powder, although drying of the surface prior to scanning is highly advisable.

Keywords: Accuracy; CAD/CAM; Digital workflow; Impression technique; Intraoral scanning.