Geometrics of tooth wear

Wear measurement implies the need for comparative measurements based on a reference frame. In this study, part of a tooth surface (common area) is proposed to be a reference frame for the comparative measurement. A registration procedure applies an iterative closest point algorithm for the least square best fit of the two surfaces on this common area. When the common area matches the best fit condition, the difference at the remaining part of the tooth surface represents changes between the two surfaces; in this case signifying tooth wear. The minimum requirements to verify tooth wear results are a three quadrant spherical surface of a molar tooth to be common area, and the fit of the common area needs to be less than 10 μm, to achieve the sensitivity of wear measurement up to the 100 μm level on the occlusal tooth surface. Incise apparatus was used for the digitisation of the tooth surface. Cloud, a 3-D image analysis software package was utilised for visualisation, registration and image analysis. A mathematical scrutiny was applied to validate the findings in theory. The proposed methodology is proven to be adequate to quantify tooth wear.