If the trajectory is off (Fig.4), withdraw the drill (Fig.5 black long arrow), find a new starting point, change the trajectory and finish osteotomy depth (red long arrow) if the new trajectory is deemed correct.  Take more X-ray if necessary.

Septum Placement

Xin Wei, DDS, PhD, MS 1st edition 04/15/2015, last revision 04/15/2015