The First Time I Broke A Gates Glidden Drill

Written & Reviewed by Dr David Chen

This is my most vivid memory of breaking a gates glidden drill inside of a molar canal while preparing a space for the post. Of course I’ve broken many more after this but this was the first time that it happened and I had no idea how to troubleshoot the situation.

x-ray of a post
X-ray of a post

It also didn’t help that it occurred during the first three months of my first job after graduating. I was so fresh out of school that I was fresh out of ideas…

Well without further ado, I’ll tell you everything about how it happened, what I ended up doing, and what I learned from it. To this very day I still haven’t forgotten it even though it has been many years since then.

The Context

This happened when I was fresh out of school after finishing my general practice residency and it was three months into my first real world job. At that time I was working up in Westchester, NY.

It was the last patient of the day and they were scheduled for a post and core procedure. This treatment needs to be done after a root canal and before a crown can be placed.

After three months of practicing, I was getting comfortable… albeit a little TOO comfortable. I had already done this procedure multiple times and I was finishing it faster and faster. That day felt like the day that I would set a new record and finish it in record time.

Oh how wrong could I have been because everything that could go wrong did go wrong. I suppose I did set a new record… but for the longest post and core procedure that I’ve ever done.

How the gates glidden bur broke

The post and core procedure is done after a root canal but before the crown. What needs to happen during this procedure are two things:

  1. Prepare a post space.
  2. Cement a post into the prepared post space.

For the post space preparation, you need to remove a portion of the root canal filling material (gutta percha). That is to create enough space so that you can fit a post into the canal. The concept is similar to how you need to dig up dirt so that there is space to plant a tree, except in our case it is to plant a dental post.

x-ray - four nerve molar root canal
X-ray of completed root canals. The filling material are the white lines inside of the canals.

The removal process uses the gates glidden drill first and then followed by the peeso reamer You need to drill straight down into the root canal filling by applying downward pressure to remove it. As you drill down, a lot of the pink gutta percha will come flying out.

You’re supposed to do it in multiple passes by pushing the gates glidden down further and further with each pass. Eventually you reach the desired depth inside of the canal and then you’re finished.

However since I was so comfortable with the procedure, complacency turned into arrogance. I wanted to finish this appointment in record time. Instead of making multiple passes with the gates glidden and removing it bit by bit, I plunged the entire drill straight down to the desired depth.

Unfortunately the entire drill breaks and snaps at the neck while leaving the rest of the gates glidden stuck inside of the canal. When I saw that, sweat started dripping down my forehead and panic was starting to set in. You cannot leave the patient with a stainless steel drill stuck inside of their tooth!

This has never happened before so I had no idea what to do with this broken instrument…

How I removed the broken gates glidden drill

The first thing I tried to do was grab it with a hemostat. Since there was still a piece that was sticking out of the canal, I figured maybe I can grab it and pull it out.

Unfortunately that did not work because the gates glidden was embedded very deep into the canal and completely locked in by the surrounding gutta percha. I grabbed and pulled multiple times but it never budged once. There was too much surface friction from the filling material holding it in. I even tried twisting in a counter clockwise position but it just wouldn’t budge.

The second thing that I tried was to take a second gates glidden and drill down parallel to the broken one that was stuck. I took a second bur and drilled down bit by bit. Eventually I got it down to the same depth as the first one and the broken one began to loosen. Then I was finally able to use the hemostat to grab it and retrieve it.

Thankfully the second method worked. The reason that it did was because the broken one was still nonetheless embedded within gutta percha. I just had to pretend like it wasn’t there and remove the filling material as usual. That was quite the learning experience which I’ll never forget for the rest of my professional career.

What I learned from this experience

Of course the first thing that I learned was to never do that again. Never again will I try to skip steps and rush it by plunging the gates glidden all the way down to depth. Slow and steady wins the race right?

Ever since that day, even though it may take longer I would always do small passes with the drill first. Remove about 3-4 mm of gutta percha, come back out and then do another pass. Keep repeating this conservative tempo until you reach the desired depth for a post.

Doing small passes are safer because if the gates glidden does break, it will ONLY be embedded within 3-4 mm of gutta percha. For these situations you can still grab it with a hemostat and twist it out.

How do I know? Well that is because I’ve broken more of the burs in the same manner. However the difference is that it takes less than a minute to remove it.

These drills will break no matter how careful you are because of the way that they are designed. The drill bit only comprises 3-4mm of the tip which is attached to a VERY LONG THIN neck. That length and thinness is the achilles heel that makes it prone to snapping. (Although Dentsply says that it was meant to break at the neck to facilitate retrieval.)

gates glidden - size 3
Size #3 – gates glidden bur

It’s not a problem as long as you don’t break it while it is nearly completely submerged within the canal. That makes it difficult to remove because that means most of the length of it is being locked in with gutta percha. It is significantly easier to remove if only about 3-4 mm of it is being locked in with the filling material.


The moral of the story for me was to keep my hubris in check along with these key points for the post and core procedure.

  • Remove 3-4 mm of gutta percha at a time.
  • Repeat that multiple times.
  • The gates glidden can still break but retrieval is easier than if you plunged the whole drill bit down to the entire depth of the canal.
  • If you really can’t remove the broken instrument, you can take a second gates glidden and drill parallel down into the canal.
  • That should loosen it enough for you to grab with a hemostat.

Hopefully my folly was at least enlightening to you. What you should do and what you shouldn’t do… however pain is often one of the best teachers. It was truly an unforgettable experience.

Although I do have to say that after I opened my own practice, I’ve sort of moved away from doing post and core procedures. As of the moment I’m only doing core build ups because the bonding technology have just about rendered the posts irrelevant.


David Chen, DDS


1311 Jackson Ave
Long Island City, NY 11101

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