Measurement of the margins of partial-coverage tooth preparations for CAD/CAM.
OBJECTIVE
This study tested the hypothesis that a scanning laser 3-dimensional digitizer is a precise and accurate instrument to measure chamfered and beveled margins of partial coverage tooth preparations for computer-aided design/computer-aided manufacturing (CAD/CAM).


METHODS
The margins were measured by the digitizer on stone dies and calculated by triangulation into a 3-D representation. Instrument precision was defined as the ability to reproduce the same margin in repeated measurements and expressed as the coefficient of variation as a percentage. Instrument accuracy for chamfered and beveled margins was estimated by correlating their measurements to the measurement of the margin of a spherical calibration "phantom" with known dimensions. Accuracy was expressed as the standard deviation.


RESULTS
The precision errors for the box- and cusp-chamfered margins and cusp-beveled margins were 3.9%, 3.4%, and 2.4%, respectively. With regard to accuracy the standard deviations of the measurements of the box- and cusp-chamfered margins and cusp-beveled margins were 19 microns, 21 microns, and 24 microns, respectively, compared to 15 microns for the phantom.


CONCLUSIONS
Measurements of chamfered and beveled margins by a scanning laser 3-D digitizer for CAD/CAM are (1) precise (error < 4%) and (2) accurate, with a standard deviation of less than 9 microns compared to optimal measurements of the spherical margin of the phantom.
Denissen
H W
HW
Department of Oral Function and Prosthetic Dentistry, Academic Center for Dentistry Amsterdam, The Netherlands.
van der Zel
J M
JM
van Waas
M A
MA
D000703:Analog-Digital Conversion; D017076:Computer-Aided Design; D003442:Crowns; D017267:Dental Prosthesis Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D003765:Models, Dental; D008963:Molar; D009811:Odontometry / Q000295:instrumentation*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D019231:Tooth Preparation, Prosthodontic