Do lateral canals really matter? Part 6

Dr. John West explores the significance of the lateral canal

This question has been asked of endodontists as long as I can remember. Many of us remember spirited 1970s debates between Dr. Herbert Schilder and Dr. Frank Weine. When I went to dental school, we were taught that if we “instrument and fill the mother canal” we could expect a 95% success rate. Dr. Schilder, however, taught his students “all foramina are potentially significant.” Which thinking is right? Do lateral canals matter? And what is a lateral canal anyway?

Is it biology or just “the look?”
First, in order to determine the biologic determinants of endodontic predictability, there is the biologic question. Am I willing to leave that answer to our scientists and academicians? Second, I do not distinguish “lateral canal.” Nature doesn’t either. Nature simply creates root canal “systems” with portals of exit (POEs). What if a canal divides into two apical POEs of equal length in the last 2 to 4 mm? Which one is the lateral canal? Which one don’t you want if lateral canals do not matter? As endodontic clinicians, we want them both. We want them all. In my experience the “lateralness” of a lateral canal does not matter since even furcal “lateral” canals can cause and/or prevent lesions of endodontic origin.⁴

Even if clinicians do not think lateral canals matter, they are always excited and proud if they pack one. I remember a colleague showing me a radiograph of a central incisor with his filled lateral canal using lateral condensation. It was the first demonstrable lateral canal he filled in over 15 years! Really, that’s what it’s all about. Demonstrating multiple radiographic POEs is a signature outcome. We know from studying all the teeth in the ToothAtlas.com that there are approximately 2.5 POEs on average for every canal.¹ Getting them means the clinician has usually accomplished most, if not all, of the following:

1. Unrestricted access, dentin triangles removed while safeguarding precious restorative ferrule dentin
2. Appropriately shaped canals with smooth walls and a continuously tapering funnel design where the clinician has preserved the original position and size of the shaped canal, i.e., FLOW
3. The root canal system has been cleaned of necrotic debris, detached pulpal tissue, dentin shavings and mud, biofilm, and smear layer
4. Proper conefit
5. Vertical compaction of warm gutta percha or carrier-based obturation, thereby delivering heat and pressure at the foraminal sites. It means you have created the possibility to seal multiple POEs where they exist. The clinical does not find the “lateral” canal; the obturation hydraulics system finds the lateral canal, which could be in any position along the tunnel geometry of the shaped canal itself.

As a clinician and educator for over 35 years, I am often asked by students if I have a patient where I could demonstrate that a lateral canal matters. Actually, all endodontists can produce these examples if the patients are carefully followed.

Lateral canal matters: case report
In this issue of Anatomy Matters, I report on a 25-year posttreatment where a “lateral” canal matters. In 1988, the patient presented with soreness over facial of the maxillary left central incisor (Figure 1). A radiograph demonstrated the patient had experienced previous nonsurgical endodontics followed by a surgical endodontic retreatment. In addition, a lateral radiolucency incisal to the apparent lateral canal surgical seal was observed. After reviewing treatment options, the patient, referring restorative dentist, and I choose to nonsurgically attempt to seal the root canal system with the anticipation of an underfilled or unfilled lateral canal. After gutta-percha removal with heat and solvents, I was able to slide into a lateral POE with a No. 6 manual file, which can be seen approximately 2 mm incisal to the amalgam retrofilled apparent lateral canal (Figure 2). The root canal system was cleaned and shaped incisal to the apical amalgam, which tested solid and sealed. Vertical compaction of warm gutta-percha was performed with clear obturation of lateral canal that had been cleaned to size 10 manual file (Figure 3). Twenty-year posttreatment validates radiographic healing of the lesion of endodontic origin with reconstitution of the attachment apparatus and the lamina dura (Figure 4).

In 2010, the patient returned with a fractured crown but without endodontic symptoms (Figure 5). Dr. John Kois, a superb clinician and educator in Seattle, Washington, restored the crown with a robust post/foundation, and 3 years later, in 2013, the tooth continues to “feel good,” is asymptomatic, and “looks good” to the patient (Figures 6 and 7).

For me, endodontics has a golf metaphor. The golf pro tells me that in order to finish the golf swing properly, I need to be “scratching my back” with the club and facing the ball path. That finish position means all the right things had to happen properly: position to desired path and stance relative to the ball, proper grip, back swing and nice flat plane, the swinging club forward through the same plane, proper body position of swing from beginning to end, and then the finish or follow-through. Endodontics is the same way. If you consistently visibly obturate multiple POEs, you have disciplined yourself, just like the golf pro, to do all the right things that increase your Endodontic Seal probability and performance.

And remember, some clinicians that may be a little heavy-handed discover that their first lateral canal may actually be their first canal!

So, do lateral canals matter? For this patient it did. And while we do not have scientific control to prove the importance the lateral canal plays in endodontic predictability, there are most certainly cause and effect documentations. The cause for the patient in this report was an undersealed root canal system causing a symptomatic tooth with a lateral radiolucency. The root canal system was treated and 25 years later shows that sustained healing has occurred by all biologic and radiographic standards. The only difference in the before and after: a sealed lateral canal. Anatomy Matters once more.