Accuracy of dental digitizers.
The need for proper validation and verification methodology for CAD/CAM systems is imminent. CAD/CAM systems consisting of an optical impression system, design software and a fabrication machine have to perform to a certain level, whereby manufacturers need to prove the effectiveness of the system as a whole. However, especially when dental surface digitization devices are used as open, stand-alone applications in dental outsourcing, a reliable standard test for comparison is necessary.


OBJECTIVE
This study evaluates a proposed test method to be used to quantify "digitizing quality" with respect to accuracy and reproducibility of two dental surface digitization devices. Comparability of the characteristics should be ensured.


METHODS
Two laser light section scanners: DentaScope II and D200 were evaluated by means of the 'Sphere Test', that involves repeated measurements of a precision ball (radius: 6mm) according to a pre-defined protocol. The surface information was received as unmatched, overlapping point clouds and statistically processed with a newly developed software package. The standard deviation of all points as well as a measure for undercutting the equator were determined.


RESULTS
The standard deviation for the radius for D and S were 7.7 (+/-0.8) and 13.9 (+/-1.0) microm respectively. The equator undercut elevations were -2.0 degrees and -0.25 degrees for scanner D and S respectively.


CONCLUSIONS
Scanner D had a significantly higher accuracy than S (p<0.05), corresponding with the smaller pixel distance of the sensor. Both devices show adequate accuracy and reproducibility and have an adequate ability to detect the equator. The test is also suitable for calibration purposes.
Vlaar
Simon T
ST
Department of Computerized Dentistry Academic Centre for Dentistry Amsterdam, Universiteit van Amsterdam and Free University Amsterdam, The Netherlands. simon.vlaar@quicknet.nl
van der Zel
Jef M
JM
D017076:Computer-Aided Design; D017267:Dental Prosthesis Design / Q000592:standards; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D021621:Imaging, Three-Dimensional / Q000295:instrumentation; D003765:Models, Dental; D009811:Odontometry / Q000295:instrumentation*; D015203:Reproducibility of Results