All About the Radix Root

Root canal anatomy is one of those tricky, complex things that will get you every time when you are doing a root canal. No matter how many times you’ve done root canals in your career—things inevitably pop up that take you totally by surprise. For example, the radix root.

As I continue to teach dentists through E-School: Everyday Endo Made Easy, I have realized something important as an educator: that some knowledge that I find to be common sense in endodontics may not be so obvious to others who don’t get as much exposure to endo as I do. After all, most dentists don’t spend all day every day peering into canals! 

So I wrote this blog to simply bring awareness to one important bit of anatomy: the radix root. Let’s dive in!

Radix Root Basics

The radix root is a third root that exists primarily in mandibular first molars. This root can be located buccally (AKA the radix paramolaris) or lingually (AKA the radix entomolaris). Interestingly, this anatomical anomaly has a higher prevalence in Caucasian populations than others. 

When it comes to a radix root, step one is just to know it’s there. Be aware and on the lookout! 

Check out the radiograph—what do you see?   

Something looks funny on that distal root, right?

A different angle radiograph may also help you decipher what’s going on … 

Luckily, nowadays we have our handy dandy CBCT that allows us to catch this kind of unusual anatomy before we start treatment. 

The possibility of a radix root being present is just another good reason why I like to take a preoperative cone beam. To me, it’s pretty important to know what I am getting into before I open up a case. We have a responsibility to our patients’ wellness!

Using CBCT to Account for a Radix Entomolaris vs. Radix Paramolaris and More

A cone beam is also a good way for you to do some risk assessment. Do you even want to take on this case? If you feel like you could be more productive banging out two crowns instead of struggling with a radix root, then I would suggest taking the time to perform this kind of risk assessment up front, which, incidentally, is just a straight up smart business move. (That tip’s for free!)

The access shape of a tooth with a radix root is always a bit different than your typical textbook rectangular shape. Instead, it tends to have a bit of a rhomboid shape in order to capture the root within your access. A cone beam is also pretty essential for determining if you’re working with a radix entomolaris (that is, on the lingual side) or a radix paramolaris (the buccal side). 

You can see here in the axial view that this particular radix is more lingual, therefore it’s plainly a radix entomolaris, and you can really appreciate just how kicked out of the original access it is.  

Do you see how this could be easily missed without a cone beam? 

This shot is of the tooth in a more coronal slice of the cone beam.

This is an axial shot that is more apical in the cone beam…

And here is the radix in the coronal slice. You can appreciate how it kicks out a bit towards the lingual here.

On to the Finer Points of the Radix Root 

Next it is time to gather a little more information on the radix root.  

They are typically very skinny and curvy, with a bend typically occurring in the coronal part of the tooth. Check out the image above to see what I’m talking about. 

What is the clinical significance of that? Well, there is a higher chance of file separation that can occur. That means you must take extreme care during the instrumentation process.  

These cases have often given me a hard time with patency and achieving proper working length  due to their intricacy. 

Remember the cardinal rules of endodontics: 1) you need to find all those canals and 2) get to the end of every single one every dang time. Or else that root canal just ain’t going to work!

The key here is to be aware that your chair time will be a bit longer with these cases—so schedule accordingly! 
I mean, just look at how skinny this tooth’s radix root is (the obturation aspect can be hard to spot, too).

Not to mention, the mesial roots were not that straightforward either. I had to trough a good bit down that mesial root to pop into the second mesial canal. Let’s just say, I clocked some extra time on this particular case. 

The Key to Success when it Comes to a Tooth’s Radix Root

First of all, these are not the easiest cases, my friends, so give yourself a little bit of a break if you’re worried right now. 

The presence of a radix root tends to be a little bit of an anomaly so you might not get a lot of cases like this to begin with—which can mean that experience is hard to come by. 

But it’s definitely best to be prepared! So my first bit of advice would be to get out your CBCT and get a clear understanding of your patient’s anatomy before you get started. 

Getting the lay of the land can help you decide if you even want to commit to doing a root canal like this. And hey, if you don’t, that’s fine. But be prepared either way. 

When it comes to a radix root, it’s not just important to have a cone beam to determine the viability of the case for you as a clinician. It can also help you plan for the procedure. You can get a handle on this curvy canal and determine its location as either a radix entomolaris or a radix paramolaris. 

Lastly, you have to mentally prepare! These are tricky cases that require some extra time and attention. Pad your schedule when you’re working on a radix root to accommodate some twists and turns during the root canal. 

– Sonia