TABLE 1.
Dental topographic metrics currently in use
| Metric | Paper introduced | Computational meaning | Biological meaning | Computer programs | Notes |
|---|---|---|---|---|---|
| Relief index (RFI, OR) | 35 , 37 | Ratio of 3D surface area to 2D projected area | Relative crown height | Morphotester, 45 molaR, 46 Avizo + ImageJ, ArcGIS | RFI 36 when the EEC cropping method is used, OR 35 when BCO 1 , 47 is used |
| Slope | 35 | The average change in elevation | ArcGIS | Similar to inclination | |
| Angularity | 35 | The average change in slope | Tooth sharpness | ArcGIS | Similar to curvature |
| Shearing crest length (2D and 3D) | 28 , 48 | Length of border between patches that faces primarily buccal to primarily lingual | Shearing crest | GRASS GIS | |
| Orientation patch count (OPC) | 49 | Sum of the changes in triangle patch direction | Complexity; number of “tools” on the occlusal surface | Surfer, Morphotester, 45 molaR 46 | OPC/OPCR metrics calculated from 2.5 and 3D scans are not comparable |
| Dirichlet normal energy (DNE) | 39 | Variability in surface curvature | Tooth curviness or sharpness | Morphotester, 45 molaR, 46 Teether | |
| Orientation patch count rotated (OPCR) | 50 | Average OPC over eight orientations | Complexity; number of “tools” on the occlusal surface | Surfer, Morphotester, 45 molaR 46 | A way of normalizing OPC for tooth orientation |
| Elevation | 41 | z‐coordinate corresponding to each polygon | Absolute tooth height | R | |
| Inclination | 41 | The angle between the vector normal to the polygon's surface in the z‐direction and the horizontal xy plane | R | Similar to slope | |
| Curvature | 41 | Deviation of flatness of the tooth surface | Tooth sharpness | R | Similar to angularity |
| Orientation | 41 | Direction of the polygon normal vector | Complexity; number of “tools” on the occlusal surface | R | Similar to OPC/OPCR |
| Ambient occlusion (portion de ciel visible, PCV) | 40 , 42 , 51 | Estimation of how much light is shining on a point on the surface | Morphological wear resistance | CloudCompare |
Note: Others (e.g., cusp and basin volume) have been, but are no longer used. An additional program, Dental Toolkit, will soon be available for dental topographic analysis.