Accuracy of a Laser-Scanner Using Innovative Three-Dimensional-Evaluation

Methods: Three dies of a prepared maxillary molar were made in presintered Y-TZP (yttria-stabilized tetragonal zirconia). The three dies were all digitized in the laser-scanner (3Shape A/S D200) 11 times. The dies were also scanned three times using a touch-probe-scanner (Nobel Biocare M50). The first scan from the laser-scanner of each die was used as CAD-reference-models. Alignment of each scan to the corresponding model was performed by a matching-software, using least square minimization of the distance between the surfaces. The distance from the points in the model to the surface in each laser-scanner model was calculated to evaluate the reproducibility of the laser-scanner. The same three models were used to compare the accuracy against the touch-probe-scanner.

Results: The reproducibility of the laser-scanner for each die was 0.4µm ±6.8µm, -0.2µm ±4.9µm and 0.1µm ±5.7µm (mean±SD), respectively. The accuracy of the laser-scanner compared to the touch-probe-scanner for each die was -2.5µm ±15.6µm, -11.0µm ±20.0µm and -4.4µm ±16.8µm, respectively.

Conclusions: The reproducibility of the laser-scanner was high. The accuracy of the laser-scanner was three-dimensional evaluated compared to the touch-probe-scanner. Larger deviations were located at edged surfaces and caused a negative mean value. A dissimilar inaccuracy in both scanners and the insecurity of the matching-software resulted in discrepancies. The obtained result showed that a non-touching system has a good potential to serve as input in a manufacturing system for fixed dental prostheses.