We describe the development and verification of an optical, powder-free, intraoral scanner based on a chromatic confocal imaging system, which has been realized in a single-shot multifocal approach. The system is based on a combination of micro-optical and dispersion optical elements. The methodology of recording and analyzing the acquired data are discussed in detail. A proof of concept with the application in intraoral scanning is provided. According to the current findings, the measurement uncertainty, scan speed, and overall performance of the device can well compete with the state-of-the-art of commercially available intraoral scanners.
The presented work describes the development and verification of a novel optical, powder-free intra-oral scanner based
on chromatic confocal technology combined with a multifocal approach. The proof of concept for a chromatic confocal
area scanner for intra-oral scanning is given. Several prototype scanners passed a verification process showing an
average accuracy (distance deviation on flat surfaces) of less than 31μm ± 21μm and a reproducibility of less than 4μm ±
3μm. Compared to a tactile measurement on a full jaw model fitted with 4mm ceramic spheres the measured average
distance deviation between the spheres was 49μm ± 12μm for scans of up to 8 teeth (3- unit bridge, single Quadrant) and
104μm ± 82μm for larger scans and full jaws. The average deviation of the measured sphere diameter compared to the
tactile measurement was 27μm ± 14μm. Compared to μCT scans of plaster models equipped with human teeth the
average standard deviation on up to 3 units was less than 55μm ± 49μm whereas the reproducibility of the scans was
better than 22μm ± 10μm.
Various test objects, plaster models, partially equipped with extracted teeth and pig jaws representing various clinical situations of tooth preparations were used for in-vitro scanning tests with an experimental intra-oral scanning system based on chromatic-dispersive confocal technology. Scanning results were compared against data sets of the same object captured by an industrial μCT measuring system. Compared to μCT data an average error of 18 – 30 μm was achieved for a single tooth scan area and less than 40 to 60 μm error measured over the restoration + the neighbor teeth and pontic areas up to 7 units. Mean error for a full jaw is within 100 – 140 μm. The length error for a 3 – 4 unit bridge situation form contact point to contact point is below 100 μm and excellent interproximal surface coverage and prep margin clarity was achieved.
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