Occlusal Mapping by Optical or Contact Scanning?

Objectives: Occlusal mapping and wear measurements are powerful tools advancing differential diagnoses in dentistry.  This report compares two digitizing methods (Optical [O] and Contact stylus line-of-sight [Co]) and two graphical software packages (AnSur© [A] and Cumulus© [Cu]) in their ability to map and measure the progression of clinical long term occlusal wear.  Methods: High quality models of occlusal surfaces over a period of 16 years were digitized by [O] with 13 merged views, and [Co] with 1 view.  The raw digital data were rendered and measured for volumetric wear in the following 3 combinations: O/Cu, Co/Cu and Co/A (O/A is not an option).  Because occlusal wear expressed as volumetric loss is a materials property, it is largely linear with time, unlike other occlusal measures.  Linear regression lines were fitted to the data and the slopes as mm³ loss/year were recorded:

Digitizing Method/Software	O/Cu	Co/Cu	Co/A
Slope of Wear Loss (mm3/yr)	0.351	0.418	0.422
R squared	0.703	0.881	0.871

Results: Values of R² and the slope show that the linearity of and agreement between Co/Cu and Co/A were quite good, confirming the agreement of the rendering software packages.  O/Cu appeared to underestimate the wear, expressed as a lower rate of wear and greater divergence from linearity.  Second order polynomials did not significantly improve the agreement.  The difficulty may be traced to the lower resolution of the optical scanner, which could be improved by a higher resolution camera.  Conclusions: Currently, a good contact stylus digitizer is still the gold standard for accuracy, but not for all-round visibility and ease of operation. (Supported by NIH/NIDCR grant R01-DE12225 and the MDRCBB.)