Jay Vuong

The Oscillation Technique

LET ME DESCRIBE one technique that has helped me negotiate a presumably calcified canal once an accurate stick of the explorer is found.  I call it the file size oscillation technique.  The technique uses larger file sizes to facilitate the movement of smaller files deeper, and then uses a smaller file to facilitate the movement of the previous larger files.  The technique assumes that you can make an access to the anticipated level of the orifices, that an accurate feel for a stick is present, and that you can judge and memorize the penetration angle into the orifice.  You also have to be patient enough to use light apical pressure in a simple watch-winding, back-and-forth rotational movement of the file or reamer.
     After accessing to the floor of the tooth, I immediately use the double sided endo explorer, usually a sharp Dg16.  The explorer helps me feel for the catch of the orifice.  More importantly, the explorer, once it is engaged in the orifice, imparts an angulation that one can use to enlarge the access at strategic points.  Also, this angulation is the very important angle that you need to place your initial file.  In this oscillation technique, I use #10, 15, and 20 files or reamers.  I initially begin with a #15, inserting it at the same penetration angle as the explorer.
     A rule to remember is that you should always allow the file to “go where it wants to go.”  Never force a file in a preconceived direction that you want the file to take; forcing the file is a precursor to ledging.  An easy way to counteract the tendency to force the direction is to check and allow the file to “flutter” every once in a while.  Fluttering involves engaging your file or reamer into the canal, letting go of the instrument, and then flicking the handle and seeing how the file angles.  It is at this angle that you want to apply all your forces and motions.
     I move the #15 file or reamer apically with a light watch-winding movement, fluttering the handle, checking the angle, and applying my apical force in the direction that the file wants to go, not where I want the file to go.  I continue in that manner until I encounter a binding point at which two watch-winding cycles combined with light apical pressure will not advance the file further.  When the binding point has been reached for the #15 file or reamer, it is necessary to use the #10 or the #20 file or reamer in the same way.
     If my initial #15 binds halfway into the canal or deeper, I tend to “oscillate up” in file size, to the #20.  Using the #20 in the same way as I used the #15, I will usually encounter resistance at a shorter length than that to which the #15 had penetrated, or, sometimes, at the same length.  I then “oscillate down” in file size, using the #15 again with the same watch-winding apical movement.  Because of the “crown-downing” effect of the # 20, the #15 will now usually reach the apex.
     If my initial #15 binds less than half way down the canal, I tend to “oscillate down” in file size, using #10 next.  The slimmer #10, used in the same way as the #15, will slide into the canal deeper than the depth created by the #15.  Oscillating back and forth between these two instruments, #10 and #15, I can gain enough apical depth to allow the #15 to reach halfway down the canal—that is, past the first curve of the canal.  The #20 is then introduced as in the first scenario described above, and the #15 is then used to approach working length.
     The oscillating approach relies on the use of use of larger instruments to facilitate the apical movement of smaller instruments.  Unlike a pure crown-down approach, however, it uses smaller instruments to facilitate the apical movement of larger instruments, then vice versa, until the entire length of the canal is negotiated.  One is never in a rush to reach the apex, and no one instrument is ever used longer than necessary in the canal.  Each instrument is allowed to penetrate at a passive angle, “where it wants to go.”  A light touch is essential.  Learn to avoid “picking” at the binding point in the canal.  Instead, allow the “endodontic game” to come to you.
     I have found that using three file sizes, #10, #15, and #20, switching among them as I have described, has allowed me to negotiate most fine and otherwise calcified canals.  Keep in mind, however, that this oscillating approach is not rigid; you can develop your own sequence, incorporating other tools such as Gates Gliddens or Peesos, to meet your needs more effectively.  Personally, I have found that once the canal is negotiated to the apex at a size 20, then incorporating the practical measures that the SafeSider and EZ-Fill techniques allow for becomes very easy.
     I urge you to try.  If you encounter difficulties or want more information, contact us.  Better yet, sign up for our free continuation course in which you can explore this and other topics more thoroughly.  You’ll find registration information here.