Cleaning and Shaping Calcified Canals

I wanted to thank Dr. Dabuleanu for authoring the audiovisual presentation on treating calcified canals¹ on the JCDA.ca website. It was very informative and clear. I am a recent graduate who can make use of those great tips!

One problem I run into when doing difficult endodontic treatment for very calcified canals is that I want to use lots of irrigation. However, I feel that during my initial gaining of length, when the canal is quite narrow, a flush with irrigant doesn’t remove the debris from the apical portion I am filing. To solve this problem, I had been trying to do an initial coronal opening with Gates Glidden burs. However, I have gotten away from this because I feel that the initial preparation with the burs projects debris apically, which makes the initial gaining of working length down a calcified canal more difficult. Now I am using a rotary orifice opener initially, which I don’t think forces debris apically as much. I just worry that the orifice opener rotary file may separate. Basically, I want to create a coronal flare (crown-down technique?) so that I can better negotiate the apical portion and gain working length, as well as have an area for irrigant to pool.

Do you have any thoughts on this?

Response from the Author

Cite this as: J Can Dent Assoc 2011;77:b37

Thank you for your questions and comments about my audiovisual presentation on managing calcified canals.¹

Generally, most canals have various degrees of calcification where access is limited. If instrumentation proves difficult in parts of a canal system, then irrigation of these hard-to-reach areas will also be a challenge. Khademi and colleagues² found that a canal system should be shaped to a 6% taper with an apical diameter of 0.3 mm (size 30 file) to remove bacteria and the smear layer from the apical third of canals. Moreover, Boutsioukis and colleagues³ found that a 30-gauge, side-vented needle needs to be placed at 1 mm from the working length in a canal with a 6% taper and 0.45 mm (size 45 file) apical diameter to get adequate irrigant replacement at working length. Having said this, the closer the needle is to the apex, the greater the apical pressure, which increases the risk of irrigant extrusion. A safer compromise in view of the results of their study is to limit apical placement of such a needle to 2–3 mm from the established working length.

It has thus been proven that proper canal geometry leads to more effective cleaning and shaping of the critical apical third of canals. The challenge is to quickly gain access to the apical system to expose it to irrigants for a sufficient amount of time to be considered ‘clean.’ Giardino and colleagues⁴ found that even a 5-minute exposure of 5.25% sodium hyphochlorite (NaOCl) can disgregate and dissolve biofilms of Enterococcus faecalis generated on cellulose nitrate membrane filters. A 5-minute exposure is enticing given the time constraints of everyday practice. However, direct exposure of irrigants to canal biofilms is often the challenge, so a longer soaking time would be more prudent.

Researchers are constantly investigating various delivery methods to make irrigants more effective. These include the novel negative-pressure irrigation system (EndoVac, Discus Dental, Culver City, CA) to better expose the apical third of the canal system to irrigation.⁵ Others have set out to prove the added antibacterial benefit of passive ultrasonic agitation, with or without pulsation, to expedite the removal of dentinal debris.⁶ Still others have found that subsonic agitation of 5% NaOCl with Ruddle’s EndoActivator (Dentsply Tulsa Dental, Tulsa, OK) for 30 seconds will significantly reduce bacterial loads when compared to soaking alone.⁷

Calcified canals are not only difficult to locate, but their negotiation and the creation of a glide path takes considerably more time. Creating coronal flare with an orifice shaper is a great way to gain further access into a calcified system. Nickel-titanium rotary instruments can be safely taken into the portion of a calcified canal where a glide path has been created with a size 15 or 20 K-file. The coronal flare created will certainly allow for a greater volume of irrigant deeper into the canal system. Usually, if you use small hand files such as a size 6, 8 or 10 K-file you will then be able to negotiate further into a system once some coronal pre-flaring has taken place. Alternating between rotary and hand instrumentation while constantly bathing the pulp chamber of the tooth can expedite negotiation to the apex. Now PathFile rotary nickel titanium instruments (Dentsply Maillefer, Tulsa, OK) are available with tip diameters of 0.13 mm, 0.16 mm and 0.19 mm and 0.2 (2%) taper. These rotary files are extremely flexible and a safe alternative to hand instrumentation of a glide path once a size 10 K-file has negotiated the canal to the apex.⁸

In understanding the principles of cleaning and shaping, which are based on clinical and scientific research, we can better tackle both the mechanical and biological challenges we face with calcified canals.