X: axial distance from {HEAD ~ the origin} at {TAIL ~ the tooth surface} at the center of the tooth thickness, 
at
X : axial distance from { HEAD ~ the origin } at { TAIL ~ the tooth surface } at the center of the tooth thickness ,
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH