Measurement of the margins of partial-coverage tooth preparations for CAD/CAM.
PURPOSE: 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). MATERIALS AND 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. CONCLUSION: 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.[1]References
- Measurement of the margins of partial-coverage tooth preparations for CAD/CAM. Denissen, H.W., van der Zel, J.M., van Waas, M.A. The International journal of prosthodontics. (1999) [Pubmed]
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