Authors: Mullaney TP.
Title: Instrumentation of finely curved canals.
Journal: Dent Clin North Am
Date: Oct 1979
Citation: 23(4):575-92
Category: Access and Canal Instrumentation
Evidence-based Ranking: 5
Discussion: The step-back or telescoping instrumentation technique was developed as a hand-instrumentation process for enlarging root canals with the purpose of enlarging the apex of a finely curved canal to a no.25 file size and subsequently stepping back in 1mm increments to produce the necessary coronal funnel to allow fitting of a No.25 gutta percha point and facilitate the lateral condensation of gutta percha. Phase I: Apical Enlargement. Enlarge apex at working length to a no.25 by starting with a small file (no.10) to working length and working sequentially to a no.25, being sure to recapitulate or reuse the file one size smaller than the last one to working length following each file. Phase II: Step-back. Shorten the no. 30, 35, 40 files by 1, 2 and 3 mm to produce a coronal taper. Recapitulate with the no.25 file at working length after each step-back. Refining Phase II – A. Use Gates Glidden no.2 and no.3 to further funnel the preparation more coronally. Refining Phase II- B. Recapitulate with the no.25 to working length in order to maintain the apical preparation and short of working length to smooth and refine the “steps” created through the step-back process.

Also, three types of deviations of apical instrumentation were described. Perforation results when the root surface is perforated at a point other than the anatomic apical foramen. A ledge is created when a path other than the original root canal is formed, this is usually tangent to the original wherein no perforation has occurred. Finally, a zip is described as an everwidening continuous area at the apex.

Reviewer’s comments: A classic article describing a classic instrumentation technique.