An in vitro investigation into the accuracy of CAD/CAM digitizing devices for measurement of tooth wear

Student thesis: Master's ThesisMaster of Dental Science


Aim: To investigate the accuracy and precision of measurement of extra-oral and intra-oral digitizing devices and to carry out a ‘proof of concept’ evaluation following a previously published profilometric tooth wear measurement technique using a calibration model. Methodology: Engineering slip gauges of known dimensions were scanned and measurements were compared to the gold standard measurement device (a triangulation laser profilometer). Inlay- and bridge-shaped artifacts were used to assess precision (repeatability and reproducibility) and accuracy (trueness) of the test devices. Each device recorded sixty scans and the variance of the height and angle measurements of the artifacts were calculated to assess repeatability and reproducibility. Accuracy was then calculated by measuring the difference between the mean repeatability measurement of the reference device and the mean repeatability measurement of the test device. Finally, tooth wear calibration models that had previously used to evaluate a method of profilometric tooth wear measurement were scanned by the test digitizing devices and compared to the reference profilometer. In all instances the scans were analysed using Geomagic® Qualify 11 computer software and parametric statistical analyses were performed. Results. All digitizing devices demonstrated good correlation in measuring slip gauge widths of 400 μm and above. However, below this value the test devices were unable to provide accurate readings, while the reference scanner was able to measure to 100 μm. Repeatability and reproducibility for both the extra-oral and the intra-oral scanners was found to be statistically significantly increased than that of the reference profilometer when measuring either the height or the angle of both the inlay specimen and the bridge specimen (p<0.05). Both the 3Shape® extra-oral scanner and the 3M™ True Definition intra-oral scanner were able to follow the previously published profilometric tooth wear measurement process however they showed a mean volume error of ± 0.2 mm3. Conclusions. The optical resolution and precision of the test scanners was inferior to the reference profilometer however the trueness of measurement between the test devices was not statistically significant (p>0.05).
Date of Award2014
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorDavid Bartlett (Supervisor)

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