Bacteria invades the root canal system because of missing the defense inside the root canal system and sometimes the calcified coronal root canal change the treatment to be impossible or it needs a lot of time by ultrasonic tips and now a days the minimal invasive endodontics and to be more conservative so we need orientation to drill as fast as we can accurate especially for general practitioners. For specialists in endodontics sometimes the retreatment couldn’t achieve the success so we need to do apical surgery and even with cbct with no fenestration in buccal bone so achieve the good bone and rebuild the buccal plate we need a conservative surgical access by guided trephination so we cover a research we made this research which covers as well using the membranes in apical microsurgery under microscope The lecture covers the clinical and evidence based steps for the guided access to root canal system and in apical surgery with or with no membranes and discuss the success and limitations.