Authors: Morgan LF, Montgomery S.
Title: An evaluation of the crown-down pressureless technique.
Journal: J Endod
Date: Oct 1984
Citation: 10(10):491-8
Category: Access and Canal Instrumentation
Evidence-based Ranking: 5
Purpose/Objectives: The purpose of the study was to determine whether ledging, zipping, and perforation occur more frequently in curved canals using the crown-down pressureless technique (CDPT) compared with a traditional filing method.

Materials & Methods: 40 single-canal-human teeth with curvature between 10 and 35 degrees were evaluated. Half the teeth were cleaned using the CDPT, the other half using a circumferential step-back filing technique. After instrumentation evaluations were made by 4 endodontists and one general dentist.

The CDPT includes placing a straight #35 file to the point of first resistance without using apical force to 16mm or where a curve began. Next a number 2 and 3 Gates were used to complete the radicular access. A provisional working length (PWL) was established at a point 3 mm from the radiographic apex. A #30 file, then a #25 file were introduced to resistance, rotating two revolutions without pressure in between, and then successively smaller files were repeated until the provisional working length was reached. The file reaching the PWL was x-rayed to determine the true working length (1mm short of the radiographic apex). If it was short, successively smaller files were introduced until they reached 1mm from the radiographic apex. This was the first instrumentation sequence. The second and third began with a #35 and #40 file respectively and progressed similarly as above until a satisfactory apical preparation was obtained (this was a file size that was two sizes larger than the one that first reached the true working length, or a minumum of size #25).

Results: The CDPT was rated excellent significantly more often than the conventional and un-instrumented control teeth. The comparison of ledging and perforation were excluded from statistical evaluation because of poor rater agreement; however 5 CDPT and 7 conventional teeth were ledged, while 8 CDPT and 5 conventional teeth were zipped.

Author’s Conclusion: The crown-down pressureless technique received more excellent ratings than conventional filing methods. The occurrence of zipping was similar in both techniques, but the occurrence of ledging and perforation was questionable in either technique. The CDPT was less fatiguing and faster than conventional instrumentation methods.

Reviewer’s Comments: The problem, as addressed by the authors, is the subjective nature of the study. The review of what the CDPT is valuable, and most closely resembles the approach used by many of today’s rotary systems.