A three-dimensional evaluation of a laser scanner and a touch-probe scanner.
BACKGROUND
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.


OBJECTIVE
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.


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 microm, 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 microm, based on median values.


CONCLUSIONS
The repeatability of the optical digitizer was comparable with the mechanical digitization device, and the relative accuracy was similar.
Karolinska Institutet, Institute of Odontology, Huddinge, Sweden. anna.sk.persson@ki.se
Anna
A
Persson
Matts
M
Andersson
Agneta
A
Oden
Gunilla
G
Sandborgh-Englund
D017076:Computer-Aided Design / Q000295:instrumentation*; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design / Q000295:instrumentation*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D003765:Models, Dental; D055095:Optics and Photonics / Q000295:instrumentation; D015203:Reproducibility of Results; D012984:Software; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
D003764:Dental Materials; D015019:Yttrium; D015040:Zirconium; C028541:zirconium oxide