///<summary>Pri or perm tooth numbers are valid.  Only locations of perm teeth are stored.  This also converts mm to screen pixels.</summary>
        private float GetTransX(string tooth_id)
        {
            int toothInt = ToothGraphic.IdToInt(tooth_id);

            if (toothInt == -1)
            {
                throw new ApplicationException("Invalid tooth number: " + tooth_id); //only for debugging
            }
            float xmm = ToothGraphic.GetDefaultOrthoXpos(toothInt);                  //in +/- mm from center

            return((WidthProjection / 2f + xmm) * Width / WidthProjection);
        }