Returns the occlusal orientation (exposure in GIS)
Usage
orient(mesh)
Value
A numeric vector of occlusal orientation values in degrees for all
the polygons of the mesh.
Let the orientation from above be depicted as a trigonomical circle,
then for a tooth positioned as in Guy et al. (2015) an orientation of 0 (mesial) would
be located at an angle of pi/2, and an orientation of 90° (buccal) would
be located at an angle of 2*pi.