In resection the tip of root in Apicoectomy.. Perpendicular to the long axis of tooth

In resection the tip of root in Apicoectomy, the cut should be:

OR

Resection of root end surgery must be:

a- Perpendicular to the long axis of tooth.***

b- Parallel to long axis

c- Acute angle.

d- Obtuse angle.

The cut in Apicoectomy should be perpendicular to long axis or 45 degree (ideally 90 degrees)

latest studies suggested to cut 3mm of the apex perpendicular to axis, retrograde preparation of the canal using ultra sound tips and retrograde obturation with MTA.