Statement of problem
The fit of a dental restoration depends on quality throughout the entire manufacturing
process. There is difficulty in assessing the surface topography of an object with
a complex form, such as teeth, since there is no exact reference form.
Purpose
The purpose of this study was to determine the repeatability and relative accuracy
of 2 dental surface digitization devices. A computer-aided design (CAD) technique
was used for evaluation to calculate and present the deviations 3-dimensionally.
Material and methods
Ten dies of teeth prepared for complete crowns were fabricated in presintered yttria-stabilized
tetragonal zirconia (Y-TZP). The surfaces were digitized 3 times each with an optical
or mechanical digitizer. The number of points in the point clouds from each reading
were calculated and used as the CAD reference model (CRM). Alignments were performed
by registration software that works by minimizing a distance criterion. In color-difference
maps, the distribution of the discrepancies between the surfaces in the CRM and the
3-dimensional surface models was identified and located.
Results
The repeatability of both scanners was within 10 μm, based on SD and absolute mean
values. The qualitative evaluation resulted in an even distribution of the deviations
in the optical digitizer, whereas the dominating part of the surfaces in the mechanical
digitizer showed no deviations. The relative accuracy of the 2 surface digitization
devices was within ± 6 μm, based on median values.
Conclusion
The repeatability of the optical digitizer was comparable with the mechanical digitization
device, and the relative accuracy was similar.
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Article Info
Publication History
Karolinska Institutet, Institute of Odontology, Huddinge, Sweden; Nobel Biocare AB, Gothenburg, Sweden
Footnotes
Presented in part at the 83rd General Session of the International Association for Dental Research, March 2005 (Arthur R. Frechette Research Award finalist).
Supported by Nobel Biocare AB and grants from Karolinska Institutet.
Identification
Copyright
© 2006 The Editorial Council of The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
