Method for Analyzing Probe Scanned Surfaces

Paper in proceeding, 2008

Probe scanning is widely used in modern dental industry, which is why it is important for the scanning process to be accurate for both hardware and software. Due to the wide range of scanner manufacturers with different types of surface registration algorithms it is of interest to in an analytical way evaluate the successfulness of the scanning. If the surface is registered in a successful way it also increases the probability of fortunate re-engineering of the intended object based on the scanning. The rationale of the study is that a well represented scanning result is essential for the manufacturing, internal fit and strength of a coping. The purpose of this paper is to propose a general method that enables analysis of the successfulness of the representation of probe scanning, and an optimization of the scanning. Twenty-four scans of a premolar preparation die were made in order to demonstrate the cause and effect relationship between alignment, central revolution axis of the probe and the representation of the result. Three scans were made for each of 8 alignments of the die. First the central revolution axis of the scanner was set in the concavity between the 2 convexities of the die. In the second scan, the central revolution axis of the scanner was set slightly to the left of the higher convexity of the die. For the third scan, the central revolution axis was set on the maximum of the higher convexity. The fundamental idea of the method is that, by confining a triangulated surface representation, from the scan and the scanned object, to surfaces based on the probe tip geometry, a value for the accuracy of each triangle can be determined. When the position of the central revolution axis and the alignment were optimized the poor areas with a predefined tolerance between 0.05 mm and 1.25 mm than were reduced by a factor of 14. By optimizing scanning, better scan results can be achieved, which is desirable for the internal fit, strength and manufacturing of the coping.