I used to have a real love/hate relationship with my endodontic apex locator.
This electronic device can be so dang helpful to find the position of the apical constriction and successfully complete a root canal.
But I know I’m not alone in this: there’s a lot to know when it comes to using one of these bad boys. And if you’ve struggled with yours—well, there could be user error issues, or you might be missing out on some key information.
I’m here to set you straight so you can use this awesome tool successfully.
True Story: I Bought Every Endodontic Apex Locator on the Market
For a long time, I truly believed that any difficulties I was running into had to do with the machine itself—not my own lack of experience with it.
So I bought every last one on the market: yep, you read that right. I’m the proud owner of the traditional Root ZX, the Root ZX2, the PAL by Brasseler, the Promark by Dentsply, and the Apex Find by Ultradent. And as I tested out every last one of these machines, I found I’d still run into issues.
Here’s what I learned (so you can save some money when you invest in your next apex locator): they all had identical drawbacks. Why? I’m going to be real honest. It was a user error.
But now that I know my way around these machines and have clocked many, many hours of experience, I want to share what I’ve learned so you can skip the learning curve and go straight to using your endodontic apex locator with greater efficiency.
Knowing Where You Need your Instrumentation to Stop
Every time I talk or teach about the apex locator, someone asks me, “Well, where do I need my instrumentation to stop?” It’s a question I’m glad to answer because for every single millimeter that you’re off—you decrease your success rate by 14%. Yikes! Those are some pretty crucial millimeters.
As a teacher of mine long ago put it, “You gotta get to zero-zero. That’s it! It’s simple!”
These are words to live by, my friends.
Getting to 0.0—which your apex locator will alert you on the screen and usually by sound when you’re there—confirms you are patent in your canal. That is your proper working length, and it will help you clean and shape properly.
Want to see it in practice?
I recorded a quick two-minute video on how I use my endodontic apex locator to get to 0.0.
A Few Troubleshooting Tips
There are some things you just don’t know about using an apex locator until you’ve been around the block a few times. If you’re relatively new to using these tools—don’t worry! I’ve got some of the insight you need right here.
First of all, make sure you’re starting with a dry canal. A dry canal is going to give you a way more accurate reading and it will keep your apex locator from constantly chirping at you when you’re trying to concentrate. Simply take some paper points and dry the canal thoroughly, making sure it is free of sodium hypochlorite, EDTA, and pus while you’re there.
I also suggest using a large file. I typically use my 10 file to get my initial working length. If the canal is too big, though, this file will give me an inaccurate read. Typically this will make the machine bounce all over the place—but a 15 or even 20 file will typically get a more steady reading that will provide the accuracy that I need.
Another tip: Just take a radiograph if you need to.
Old school isn’t always bad. And typically, I end up doing both—that is, using an endodontic apex locator and taking a radiograph. This way, I can truly understand the anatomy of what I’m working with and see where canals join and where they separate.
The Benefits of the Apex Locator
The apex locator is so fast and so easy to use (once you’ve gotten the hang of it) and it can be used repeatedly without any fear of exposure to radiation. They are truly such useful pieces of equipment to have in your office.
And when we can determine the apical position with such accuracy, we can avoid over enlargement and even retreatment.
Want more quick and easy-to-digest endo insight and advice? Find me on Instagram at @soniachopradds for more content like this!
In the meantime, let me know in the comments if this opened your eyes to anything regarding apex locators! What did you learn? What will you do?
Thank you so much . That was so formative. I am old school and am usually reluctant to use my apex locator.. this helps alot
I’m so glad this was helpful for you! -Sonia
Hi, Dr Sanket here
Endodontist from mumbai..
As per literature there is no difference between 0.5 and 0.0 but for all practical purpose, keep rotaries till 0.5 ( recommend on root zx by their manual) but take hand files till 0.00..
This is what most recommend..
Taking rotaries till 0.0 often leads violation of AC..
Dr Riccuci recommends to stop till end of blue zone.
Kindly share your your email id.. I would be happy to share cases done till 0.5 with rotaries and 0.0 for handfiles in between
Hi Dr. Sanket, thanks for your comment. The apical constriction is a histological location, and so deriving the clinical significance for this can be an ambiguous location sometimes. I am a big believer in patency, and I have found that many cases don’t heal if your are not at 0.0. Hope this helps. -Sonia
Very clear explanation
I’m grateful this was helpful for you, Vivian! -Sonia
Does the zero reading on apex locator show the major apical foramen?
Since this is really a histological landmark, I think it is hard to say. I just prefer to go to 0.0 since I have seen less failures by following this rule.
Awesome! Do you have a course on endo dontic retreatment?
In my Eschool with Coaching course, we can talk about whatever you want. However, I do feel that retreatment is more of an advanced endo topic and it is not covered in the base curriculum. But, the beauty of the coaching hours is that you can take the conversation wherever you want to take it.
Hello Dr. Chopra
I have great passion for Endodontics and your channel is very helpful.
You mentioned about taking X-rays if we need to. What is the rule when using apex locator? Do we need to obtain an image confirming the length or in cases that looks straightforward we can skip confirming the length?
There are many times when I skip the WL radiograph. Instead, I use my conefit radiograph for that purpose and trust my apex locator as much as possible. I hope that helps.
I have only used the Root ZX ever since it originally came out. I don’t know how old mine are but they must be approaching 12 years (I know because we lost everything in the 2011 Joplin Tornado), an excellent investment I believe. I have done root canals for 49 years and learn something with every single one. I never try and think that this is going to be an “easy one” because that always gets me in trouble. In my experience, I have found that using RC-Prep in the chamber and canals has given me the most accurate readings. This is before I have used any hypochlorite as I find that hypochlorite greatly interferes with accurate readings. That being said I am going to use your advice on dry canals and compare. Thanks for your wonderful information!!!
Thank you for sharing!
I totally agree with you. In fact Apex locators reach the 0.0 point when the file touches the PDL which is after the apical constriction and minor apical foramen. This is the perfect location to end our instrumentation, although our professor says it’s a good practice to decrease 0.5 milimeters after we reach 0.0 for safety purposes.
Thank you for your comment.