PA is taken after a 2.2 mm drill reaches depth of 11.5 mm with 10.5 mm offset at #29 to confirm that the curved apex of the neighboring tooth is not violated (Fig1 * (red line: Mental Loop)). 

Curved Apex Last Next

Xin Wei, DDS, PhD, MS 1st edition 07/16/2019, last revision 07/16/2019