Many endodontists have spent a great deal of time deciding on the file sequence that serves them best and would prefer not to have to learn a new technique. For those, we would recommend no technique change since the One Endo file was designed to give better results with any technique simply by using One Endo files approximating the sizes of the files of your technique.
On the other hand, we have had requests for specific technique recommendations of how we would recommend the One Endo file should be used. Practitioners should keep in mind the purpose of any recommendation is to provide a means for maximizing efficiency for enlarging the canal space while minimizing instrument failure—not to advocate a particular canal size or taper.The final canal dimensions should be adjusted to conform to the judgment of the operator and the requirements of the obturation technique used.
1 – No Change:
The One Endo file was designed to be used without changing the operator’s preferred technique. The fact is, if the One Endo file performs better than other files of the same approximate size, they can be used exactly in the same way and achieve better results.
2 – Same Technique with added Parameters:
This step requires no technique change but does make the following recommendations during the procedure:
•Advance into the canal using no more pressure than was required to advance the first 1mm. If more pressure is required, change files.
•Engage no more than 6mm of a file if it is engaged in a curvature (the exception would be a size 20-.02 or smaller). If engagement is greater than 6mm, change files.
•Advance a file into the canal with no more than 1mm increments with insertion/withdrawal motions.
•Advancement into the canal should be able to occur at a rate of approximately 0.5mm/s without increasing the pressure of insertion.
•Withdrawing at a rate greater than the rate of insertion improves debris removal.
•Follow the use of one file with a file having a different taper.
Even though more files may be used in following these parameters, the total cumulative time can be less when compared to other techniques. Each step of instrumentation can occur quickly without repetitive non-productive attempts.
3 – Technique Change:
We recommend a technique change to incorporate the findings of our research to maximize efficiency while avoiding probable risks. We refer to this technique as the zone technique in which we divide the canal into two zones, the coronal zone or the portion of the canal coronal to a curvature, and the apical zone or the portion of the canal apical to a curvature.The zone technique was designed with two objectives for minimizing file stress: One, the canal diameter should be large enough coronal to a curvature to prevent any stress due to engagement in that portion of the canal when any file is being used apical to the curvature. Two, the file diameter is not too large to rotate safely in a curvature; the file diameter is sufficiently small in a curvature to avoid excessive cyclic stress.
The first step is to determine if there is a curvature of any significance and how far the curvature is from the apex. Withdrawing the file used to establish the working length, and passively re-inserting will indicate a curvature if it meets any resistance short of the working length since the canal is now larger than the file. The canal portion short of the resistance defines the coronal zone and the portion beyond the resistance defines the apical zone. The length of the canal to the curvature, the coronal zone, is measured and recorded with the same importance as determining the working length. The working length minus the coronal zone length provides the distance the curvature is from the apex, the apical zone length.
The second step is to determine the distance each of the files having different sizes and tapers can safely be advanced around the curvatures and which size file will need to be used in the coronal zone to prevent any subsequent file from binding in the apical zone. At the point of curvature in the, the file diameter should be no greater than .60mm for a .02 taper, .55mm for .04 taper, .50mm for .06 taper, and .35mm for a .08 taper. (This consideration is the result of testing for 45-degree curvatures having 8 mm radii and applies only to these dimensions for rotary NiTi files. File diameters should be smaller for more severe curvatures and can be adjusted larger for less severe ones.) By using the parameters suggested above for diameter limitations, we can calculate if the diameter of a selected file would exceed our limitations.
Example: If the point of curvature is 6mm from the working length and we are considering using a .25/.06 file. The parameters above state that a .06 tapered file should not have a diameter greater than .50mm at the point of curvature and that diameter for a .25/.06 file is at 4mm from its tip. Therefore, in this situation the .25/.06 should only be advanced 4mm into the apical zone and if it is carried to that point, the terminus of the coronal zone should previously be prepared to a size .50mm. Following this procedure at first may seem complicated but it can be learned quickly. The result is a very expeditious and relatively worry free of threat of breakage.