root canal and crown

The step back procedure, also known as adjustable or serial root canal preparation, is isolated in two phases: in the main, the working length is established and then the apical part of the canal is delicately shaped since a size 25 K-record reaches the working length; in the second, the remaining canal is prepared with manual or rotating instrumentation. For the eponymic third time the dentist "arrives at the apex" and, if necessary, prepares the foramen with a size 25 K-document; the last phase is isolated in two refining passages: the first with a 1-mm staggered instrument, the second with 0.5-mm staggering. All of these procedures involve visit irrigation and recapitulation with the master apical document, a small record that reaches the apical foramen. High recurrence ultrasound based systems have also been portrayed. These can be valuable in particular for cases with complex anatomy, or for retained foreign body retrieval from a failed earlier endodontic procedure. 

There is a hybrid procedure combining step back and crown down: after the canal's patency check, the coronal third is prepared with hand or Gates Glidden drills, then the working length is determined and finally the apical portion is shaped using step back strategies. The twofold flare is a procedure introduced by Fava where the canal is investigated using a small document. Then canal is prepared in crown down manner using K-documents then pursues a "step back" preparation with 1 mm increments with increasing record sizes. With early coronal enlargement, also depicted as "multiple times system", apical canals are prepared after a working length assessment using an apex locator; then dynamically enlarged with Gates Glidden drills.