Gates Glidden Drill – Guide

Written & Reviewed by Dr David Chen

A gates glidden drill is a stainless steel instrument that is used in endodontics and restorative dentistry. It is often called a gates glidden bur or GG drill since it is operated by a latch type slow speed handpiece.

gates glidden - size 3

Today we’ll tell you everything about this bur and what it is used for as well how to use it. Despite its flexibility of use over multi-specialties there are limitations for what it can do. You can also run into complications due to its design.

Now without further ado, shall we begin?

Technical specifications

The gates glidden drill is a stainless steel RA (right angle) latch style bur that inserts into a slow speed handpiece. There is no FG (friction grip) variation of this bur and consequently does not fit into high speed handpieces.


The head of the drill is flame shaped and as its name implies, it is similar to the shape of a candle flame. It is an elongated oval with a tip that is blunted. Picture of a candle flame below to show you what we mean.

candle flame shape

Sizes are numbered

The gates glidden comes in various sizes and are numbered accordingly.

The size can refer to the total length of the bur from the tip to the end. It comes in three different lengths.

  • 28 mm
  • 32 mm
  • 38 mm

Aside from the length, the GG drill also has six different sized drill heads. The drill tip is literally just the small flame shape portion that is about 3-4 mm in length. This is the park that does all of the cutting. The GG drill is usually numbered with markings near the latch end, which is denoted by the number of horizontal lines.

Horizontal lines and the size of the drill head:

  • #1 size head = 1 horizontal line (smallest)
  • #2 size head = 2 horizontal lines
  • #3 size head = 3 horizontal lines
  • #4 size head = 4 horizontal lines
  • #5 size head = 5 horizontal lines
  • #6 size head = 6 horizontal lines (biggest)
gates glidden drills - sizes 3-6
Gates glidden sizes 3-6

The bigger the size, the larger the drill head. What that means is it has a bigger cutting surface and will make a bigger hole if you drill with it. The smaller the size, the smaller the hole it would make. You typically start with a smaller sized drill and progressively move to a bigger one to enlarge the prepared space.

Where is the cutting edge?

The cutting edge is present at the tip of the drill, which is only 3-4 mm in length. However only the sides of the head are the cutting surfaces because the tip or apex is blunted. The very tip of it does not cut at all. All of the cutting comes from the side which is parallel to the length of the entire drill.

What is it used for?

The gates glidden drill is often used during root canal treatments and also post and core procedures (prefab and cast posts). That means it is used by both endodontists and general dentists.

For root canals, it is used during the very beginning of the procedure to flare the coronal third of the canal. Essentially it makes the opening of the canal wider so that the hand files and rotary files can go in easier.

For post and cores, it is used to prepare the post space so that you can fit a post into the canal. Drilling with the gates will remove the root canal filling material (gutta percha). It will also widen and enlarge the canals so that you can fit the size of the post of your choice.

How to use a gates glidden drill

The GG drill doesn’t have a cutting edge at the tip because only the sides can remove tooth structure. The tip is blunted so it doesn’t cut if you simply stick it into the canal or gutta percha.

In order to use it properly you must apply downward or apical pressure while stepping on the rheostat. That creates frictional heat that helps to soften the gutta percha and it allows the drill to move apically. The sides then start to cut away at the filling material.

Interestingly enough once it starts cutting, it will often try to “pull” your bur further down the canal. This is both a good thing and a bad thing.

  • The good thing is that it is automatic and it helps you remove the filling material. You no longer have to apply apical pressure.
  • The bad news is that it can pull your gates glidden so far down that it can get stuck. If it gets stuck you will have to try to reverse it out. The worse case scenario is if it the drill breaks at the neck.

Tip for preventing complications

In our experience, you shouldn’t let the gates glidden drill pull you into the canal. You should be vigilant and as soon as it pulls you in about 3-5 mm you must resist it and pull it back out.

After you clean out the orifice and the drill, you can go back in and make a second pass. Repeat this until you get to the desired length. Doing it this way is more conservative and will prevent mishaps like the gates glidden drill breaking at the neck. The first time it happened to us, we were panicking!

Potential complications

The gates is a necessary dental product that is used in endodontics and restorative procedures but it is not flawless. A couple of well known complications can arise when using it during treatment.

  • Breaking at the neck. The drill is very long, some of them are 38 mm in length. Due to the design, the weak part is the neck which is very thin and prone to breakage. You will break a lot of these during your career!
  • Perforating the tooth. The very tip of the bur is blunted in order to prevent perforations. However accidents can still happen and you may perforate the tooth and create a brand new canal!

Single use or multi-use?

GG drills can be used multiple times and doesn’t have to be single use. It is made of stainless steel so it can be disinfected and sterilized in the autoclave without any warping.

However after a couple of uses you’ll notice that it’ll start dulling. Sometimes the bur can even bend which makes it not spin straight. If either of these two scenarios are observed, you should throw it out and use a new one.

The product was purposefully designed to be removed and retrieved easily if it does break. It will always snap at the neck which leaves a long piece for you to grab with a hemostat to remove.

Gates glidden vs Peeso reamer

A peeso reamer looks very similar to a gates glidden. Both of them have a blunted tip in order to prevent perforations. Their cutting edges are all along the long side of the drill.

gates glidden vs peeso reamer
Top is gates; Bottom is peeso

The difference between them is that the peeso has a longer head or cutting edge. The drill head is roughly about 3x the length as the gates. The photo above shows you the difference between them. The overall length for both are the same but its the cutting head which is different.

The gates glidden is meant to be used to make your way down into the canal. It is more conservative since it has a shorter cutting head. It’ll cause less damage if an accident happens.

The peeso reamer is meant to be used to flare out the walls of the canal after the gates. The reason is because it has a longer cutting edge so it can do so more effectively.

Limitations and Alternatives

The biggest disadvantage for using a gates glidden drill is that it is made of stainless steel. That makes it more robust but it also means that it is not flexible unlike nickel titanium.

This is a limitation because when you use it, you can only drill straight down or make straight line space preparations. This is a problem if you have a tooth with a lot of curved canals. The GG drill cannot navigate through these curvatures since it can’t bend.

If you try to force a gates glidden through a curved canal it will either break or cause a perforation. Both of which are NOT results that you want.

An alternative would be to use a nickel titanium (niti) rotary file. These instruments are much more flexible that will bend and adapt to curves in the canal.

  • As of right now, a 17.06 niti rotary file is the preferred orifice opener. This is the first step of a root canal where you use it to enlarge the opening of the canal.
  • However for post space preparation, the gates is still the first choice since posts are straight so you do want a straight preparation!


The gates glidden is a stainless steel bur that is used by both endodontists and general dentists alike. It can be used to flare the coronal third of the canal orifice or it can be used to prepare the post space.

It comes in three different lengths and different head sizes so you have plenty of options to choose from. It is a necessary instrument in the armamentarium for dentists.


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