Peeso and Gates Glidden Drills

Allan S. Deutsch, D.M.D.
Peeso and Gates Glidden Drills:
They’re Not Just for Post-Hole Preparation!

Allan Deutsch

bet that if you look on your bur stand you will find either a Gates Glidden drill or a Peeso reamer there. If you are like most of us, you have used them to make your post-hole preparations for years. These burs cut well, are reliable, and are relatively inexpensive. If they break, they break high up on the shaft next to the part that fits into the slow hand piece. Because they break so high up on the shaft they are usually very easy to remove from the tooth. Gates Gliddens and Peesos are not end-cutting, making them by definition reamers not drills. There is a nipple at the end of these instruments that prevents them from cutting at their tip. When the nipple engages the wall of a curved canal, the drill just spins and does not cut apically (see Figure 1).

FIGURE 1: Gates Gliddens and Peesos do not cut at their tips.

FIGURE 2: A Gates Glidden drill on the left and a Peeso on the right.

    Consequently, Gates Gliddens and Peesos will not perforate the canal in an apical plane. All in all they are very good instruments.
    Figure 2 shows a Gates Glidden drill on the left and a Peeso on the right.
    In Figure 3, we show an illustration of the main parts of each instrument. The differences are:

The cutting head is much smaller on the Gates vs. the Peeso.
The shaft is thinner on the Gates vs. the Peeso
The diameters of the heads are different for the same number instrument.

For example, the numbers on both the Gates and the Peeso are denoted by the number of circumferential grooves located on the shaft just below the cutout for the latch.

Usefulness in Preparing Root Canals
Not only are these instruments good for making post-holes but they are exceptionally good for preparing root canals in an easy and reliable manner. They are especially good to use in a modified crown-down technique.
Several years ago the “crown-down” method of root canal preparation was introduced. It stated that you should not prepare the apical end of the canal first, but rather that you should prepare the coronal end of the canal first. The dentist should use a large diameter instrument to go only 2-3 mm into the coronal end of the canal. Then the dentist should switch to a slightly smaller instrument and go a little deeper into the canal. This sequence is repeated until the apical terminus of the canal is reached with a small instrument.
Over the years we have found this to be a very time consuming, not very predictable, and a fairly difficult technique to master. However, we did notice that Peeso and Gates reamers do offer a terrific way to use the crown-down technique to speed up instrumentation for the rest of the canal.

FIGURE 3: The main parts of the Gates Glidden drill (left) and the Peeso (right).

FIGURE 4: A typical mesial canal of a mandibular molar.

The Crown-Down Technique in S.E.T.
In other words, we use the crown-down technique as just one part of the overall S.E.T (Simplified Endodontic Technique). In essence, the Peeso and Gates Glidden drills represent the rotary instrumentation sequence in the Simplified Endodontic Technique.
In the S.E.T. sequence, we first clean and shape the apex to a size number 20 (yellow) stainless steel instrument. If we would continue instrumentation without altering the canal at this stage, it would become more and more difficult to manipulate the larger number files or reamers in the canal. This would occur because the coronal end of the canal would still be narrow, and the larger files would bind and work along their entire length, both at the apical and coronal ends.
Figure 4 shows a typical mesial canal of a mandibular molar. It has a 60° curve within a very short or small radius. Figure 5 demonstrates a larger file in that canal. You can see that the file binds over almost the entire length of the canal and it is very bent or curved in that canal. Binding and bending are two situations that lead to instrumentation breakage. To lessen the chance of breakage, the file should only “work” or bind in the apical 2-3 mm of its flutes at any one time and the straighter the canal the better. This can easily be accomplished by using the Peeso or Gates to open up the coronal end of the canal to let the subsequent endodontic instruments do their job more easily. In essence we are doing a modified crown-down technique, using the Peeso or Gates.

FIGURE 5: A larger file in a typical mesial canal of a mandibular molar.

FIGURE 6: Peeso and Gates instruments cut better and more easily when used wet.

Straightening the Canal
Once the apex has been instrumented to a size # 20 stainless steel instrument a number 2 Peeso or number 3 Gates is introduced into the canal. These instruments cut much better and more easily when used wet (Figure 6). If you do not have a slow speed with water spray use xylocaine, water from the triple syringe, or even irrigating solution.
The instrument is introduced into the canal while it is spinning in the handpiece. Cut only 2-3 mm in depth, then remove the drill from the canal. Once the drill is out of the canal, clean the flutes of the drill with a wet gauze pad to remove the cut dentin.
Now go back into the canal and cut another 2-3 mm deeper, as shown in Figures 7 and 8.

FIGURE 7: Cutting deeper into the canal.

FIGURE 8: Cutting deeper still.

FIGURE 9: Decreased curvature and a straighter canal.

Continue in this manner until you have gone one-third to one-half of the way down the canal wall. The result will be that you have done two very good things:

You have lessened the curvature of the canal, usually from a 60° curve to roughly a 45° curve (see Figure 9).
You have straightened out the canal, so there is less of a radius and the endodontic instruments do not have to bend as much.

    The # 2 Peeso or number 3 Gates is equivalent to a # 90 instrument (0.90 mm). Therefore using these instruments opens the coronal 1/3 to 1/2 of the canal to 0.90 mm. This will easily let any stainless steel instrument from # 25 to # 45 into the canal without binding in the coronal section of the canal.
    Figure 10 illustrates a larger instrument in the canal that is loose in the coronal 1/2 of the canal. Because these larger stainless steel instruments now only bind in the apical 1/3 of the canal they can and do cut much or easily and with much less chance of breakage. Because they cut more easily, the instrumentation of the canal goes much faster. The instrumentation in general becomes much more predictable and easy. Predictable behavior and ease of use: a very good combination.
    Once the canal is instrumented in a step-back fashion (see “Introduction to Simplified Endodontic Techniques”) to a # 40 or # 45, the Peeso or Gates can be re-introduced into the canal to deepen the coronal flare closer to the apex by 1 to 2 mm if desired. The dentist can even widen the coronal flare at this point by using a # 3 Peeso or # 4 Gates if so desired.
    Figures 11 and 12 represent the canal in the before and after stages of Peeso or Gates preparation.

FIGURE 11: The canal before prepartation.

FIGURE 12: The canal after preparation.

In Conclusion . . .
The use of these drills results in several good things:

easier preparation of the coronal half of the canal
easier preparation of the middle third of the canal by larger-diameter instruments.
overall, a more predictable endodontic preparation

in a shorter length of time
more easily and with less hand manipulation and fatigue.

So many positives—no negatives—what are you waiting for!

FIGURE 10: Wider canal results in less binding.

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