The location of calcified canals

The primary goal of root canal therapy is to create an environment in which the root or roots of a tooth are maintained in a healthy periodontium. This, in turn, allows the tooth to be restored to normal function.

To achieve this objective it’s important to minimize or eliminate microorganisms and pathologic debris in root canal systems. This becomes more challenging when we are presented with teeth having calcified canals.

Much has been written about achieving a proper glide path from the canal orifice to the root terminus. With the advent of nickel titanium rotary files, proper glide path becomes essential. However, all of this becomes a moot point if we cannot locate a calcified canal within a root canal system, as we cannot clean a canal that we cannot find.

Typically, root canals calcify from the coronal portion down apically. Root canal calcification can occur as a natural process of aging. In addition root canals will calcify as a result of decay, restorative treatment, gingival recession and trauma.

Finding and treating teeth with calcified canals is an orderly progression of important steps, each one’s success dependant on how well the previous one has been carried out.

THE SET-UP
“Root canal success or failure can depend on the location and negotiation of calcified canals. This article describes a proven technique on how to help locate these elusive canals. Use of these methods will allow the clinician to locate canals that might have previously been left untreated.”- Dr. Garry Bey, Team Lead

Pre-treatment radiograph
Careful attention to our pre-treatment radiograph is important to not only give us an idea of how calcified a particular root canal system may be, but also to give us initial information on how many canals there are in a tooth. The severity of any root curvatures also can become apparent.
It’s important at this time to decide on whether this is a tooth we want to attempt to treat, or might this be one we should consider referring to an endodontist.

Isolation
After proper diagnosis, examination of the pre-treatment radiograph and administration of adequate local anesthesia, isolation of the tooth to be treated is accomplished.

I routinely place the rubber dam clamp on a tooth posterior to the tooth I will be treating. I then extend the rubber dam one or two teeth anterior to the tooth to be treated, making sure the rubber dam fits tightly enough around the isolated teeth so as not to allow an instrument to be aspirated or swallowed.

Unfortunately, single tooth isolation doesn’t give the clinician a good 3-dimensional feel for root anatomy and angulation. The problem is further compounded when there’s a full crown present and the original anatomic landmarks are gone. The clamp also can impede handpiece orientation, which further steers the clinician astray.1

Access
When I was a dental student at NYU College of Dentistry, I was taught that proper access was the cornerstone of successful endodontics. That’s as true today as it was then. An access opening that’s too small or misdirected can not only affect canal location, but also can affect proper instrumentation, irrigation and obturation. Possible iatrogenic complications such as perforation also can occur.

I usually begin access with a surgical length FG-557SL (SL557) bur from SS White (sswhiteburs.com) in a highspeed handpiece when no crown is present. I prefer the use of a surgical length bur because it moves the head of the highspeed handpiece away from the tooth’s occlusal surface. This allows visualization of the proper apical angulation of the bur during initial access preparation.

After my initial access with a SL557 bur to approximately the level of the pulp chamber, I then flare the walls of the access preparation in a coronal direction. Although I use a SL557 to flare the walls, there are a myriad of access burs on the market that can be used for this purpose.

They range from flared diamond stones with safety tips, to conical shaped carbide burs. I will then stop and flush out any accumulated debris.

Instrumentation
Once my initial access is accomplished, my next step is to use surgical length round burs of varying sizes in a slowspeed handpiece. For example, in molars, I will start with either a surgical length #8 (RA-8SL) from SS White or a surgical length #6 (RA-6SL) round bur also from SS, White, to gently remove the pulpal roof. In vital cases where there is bleeding, I will extirpate as much tissue as possible and begin instrumentation of the canals that have been located.

I will then carefully look for any microscopic canal openings. If only one canal can be located, I will instrument that canal until I am able to get the orifice to the size of a #4 Gates-Glidden drill from DENTSPLY Maillefer (maillefer.com). This allows me a better orientation of where the other canals are located. If any or all of the canals are calcified to the degree where they cannot be located, the next step I will describe will be a game changer!

Transillumination
Transillumination is the technique of sample illumination by transmission of light through the sample. Transillumination is used in a variety of methods of imaging.

In medicine transillumination generally refers to the transmission of light through tissues of the body. In dentistry, bright transilluminated light through the tooth can highlight dental caries, show signs of dental trauma such as coronal fractures and assist in the location of calcified canals.

As we progress through an orderly sequence of treatment, we begin to see how each previous step makes our next step more easily accomplished. Recall during isolation that we isolated the tooth at least one tooth posterior to the tooth being treated. This now allows us to use transillumination without interference from the rubber dam clamp.

With my microscope in focus, I turn the microscope light off, and then use a transillumination light from Welch Allyn (welchallyn.com). By moving the transilluminator around the neck of the tooth, both a calcified pulp chamber and calcified canals can be visualized. After visualizing where the calcified canal is, I incrementally progress apically with progressively smaller surgical length round burs, stopping from time to time and flushing away any dentinal debris.

Surgical length round burs allow me to search for canals by smoothing out calcified tooth structure. This is done without gouging, keeping the landmarks intact. The surgical length of the burs allows me to see the head of the bur as  I advance apically, keeping me on the proper path.

Placing sodium hypochlorite into the chamber and letting it soak for about one minute also can help in canal location by bleaching secondary dentin. It’s best to dry out the chamber before canal location is continued.

If you have never attempted this technique, it will open your eyes to a whole new world.

Piezoelectric technology
The first piezoelectric ultrasonic was introduced into the market by Satelec in the late 1970s. Since that time, there has been an evolution in the technology, operation, ergonomics, and the design of the machines.2 For both general practitioners and endodontists, the ultrasonic is a valuable tool to treat calcified and difficult to find canals, as long as it is complemented by the proper tip, and sufficient magnification and light.2

In our practice we have a P5 Newtron, Satelec piezoelectric unit from Acteon North America (acteongroup.com) available in every operatory. They are invaluable for isthmus and pulp stone removal, coronal shaping and finding hidden canals such as MB2 canals in upper molars.
In addition, when searching for a calcified canal, once we approach the middle third of the root, the continued use of surgical length round burs becomes complex. It’s in these cases that I will then switch to piezoelectric ultrasonics, as the tips are thin allowing better visibility and more precise dentin removal.

Conclusion
It’s quite evident that today many different modalities exist to help increase our current rate of endodontic success. If we all believe that the best dental implant is a natural tooth, then it behooves us to do all in our power to save as many teeth as we can for our patients.
When it comes to increasing our success rates, it’s universally accepted that canals have to be instrumented, irrigated and obturated as best as possible. Before that can be accomplished, canals have to be located and negotiated to their terminus. This becomes more difficult to achieve when we are presented with moderate to severe calcifications.

With the aforementioned technologies and techniques I have presented a blueprint on how to locate these types of canals. Consider using these strategies and both you and your patients will benefit. 

References
1. Dave Clark DDS, Inside Dentistry, April 2011, pg. 40.
2. Gary Glassman, DDS and Sam Kratchman, DMD, Dentistry Today, September 2011, pg. 114.