Category Archives: Techniques

Inseparable Teeth, Unconventional Access!

Sometimes when the conventional endodontic access is not possible, the unconventional approach can save the day.

A clinician should always aim at establishing a straight line access (SLA) in order to properly instrument, irrigate and obturate the canal system.  Depending on the initial challenges, establishing a SLA could mean accessing an anterior tooth through its buccal surface [example below], accessing an anterior tooth through its incisal edge, or accessing a molar tooth through its mesial marginal ridge or its MB cusp.

 

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Not Every Hole is a Canal!

Sometimes when we try locating canals during access preparation stage, we may accidentally exit the pulp chamber in the wrong spot and create perforations.  Perforations or accidental communications need to be repaired as soon as possible in order to achieve the best possible prognosis.  The choice of repair material depends on the location and the size of perforation. MTA is still one of the best materials that can be used to seal the pulp floor perforations as long as it is not communicating with the sulcus.

To Prevent Perforations:
1. The pulp chamber floor is always at or slightly below the level of CEJ and the canals are located at the periphery of the pulp chamber floor.  Any attempt to locate canals farther apically may result in perforation.
2. The chamber floor colour is always greyish. If the colour during locating canals is turning dentin-colour, that would be the best time to stop and reorient ourselves.
3. Always probe around the CEJ to gain a better appreciation the outline of the root trunk, as the chamber floor is at the center and concentric to the CEJ outline.
4. When in doubt, stop and take an X-ray to confirm that treatment is progressing in the right direction.

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To Treat Perforations:
1. If facing significant difficulty with locating canals, the procedure should be stopped, the tooth should be medicated with CaOH, and patient should be referred out for proper care.  More digging may result in multiple perforation sites, further weakening of the tooth structure and enlargement of the existing perforation site, which ultimately results in an unfavorable outcome.
2. If canals are already located, ignore the perforation site, complete the root canal treatment and repair the perforation site with MTA.  Attempting to repair the site before obturating the canals may result in the repair material occluding the shaped and cleaned canals.
3. When dealing with established infection in the canal system which benefits from the utilization of short term CaOH medicament, the perforation site can be repaired and sealed before final obturation. In this case, the other canals need to be protected by paper points while the site is being repaired (the above case).


Middle Mesial canal: can it be any more complicated?

As if dealing with MB2 canals in upper molars was not complicated enough (see my previous post on MB2 canals), here is another thing to consider when doing root canals on lower molars:

The presence of an independent Middle Mesial (MM) canal has been reported for decades in endodontic literature.  Owing it to technological advancements, it appears that the incidence rate for these extra canals is on the rise: Skidmore & Bjorndol 1971 (0%), Pineda & Kuttler 1972 (0%), Vertucci 1984 (1%), Fabra-Campos 1989 (2.6%), Goel et al. 1991 (15%).  I even hear incidence rate of up to 60% based on the more recent micro-CT studies.  This may be pushing it though!

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It is really important to realize that MM canal could exist and therefore, the area between MB and ML canals in lower molars should be explored thoroughly during accessing, locating canals and instrumenting.


How do you “seal” the deal?

After we’ve spent so much time doing great endodontic treatment – with rubber dam isolation, perhaps gingerly applying OraSeal or Kool-Dam to make sure everything is water tight, carefully instrumenting, copiously irrigating, and then obturating with great style – how can we protect our painstaking work?

Here is a case where the root canal has been completed, but unfortunately, the final restoration – a ceramic restoration – has been made without replacing the cotton pellet and temporary base material. Even though the periapical lesion has healed nicely, the risk of coronal leakage, and thus the need for retreatment in the future again, is great.

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One nice way to prevent coronal microleakage is to definitively restore the teeth after root canal treatment. If you want to go one step further, you might consider an intra-orifice barrier. This is simply a (bonded) restoration that involves removing approximately 2 mm of gutta percha from the orifice of the root canal. Then, a material, such as glass ionomer, or composite, or MTA can be placed into the orifice. I also prefer to cover the furcation floor. I have been placing an intra-orifice barrier of glass ionomer (and often a 1 mm intra-canal barrier when I prepare post spaces), and then restoring the rest of the access with a bonded core material when indicated. The glass ionomer can be placed with a small plugger, or a Centrix Accudose needle tube.

I have also been trying a neat product as an intra-orifice barrier, PermaFlo Purple, which is simply a flowable composite that is colored purple. You can place a tooth-colored material on top, in the bulk of the access. I suppose the rationale of a purple-tinted flowable composite is to make any future treatment easier, since you’ll be looking for purple composite, instead of B2 composite! The case below shows a 2 mm intraorifice barrier of glass ionomer, extending below the floor of the root canal chamber.

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MB2: a Pain in the Neck.

When I went through my undergraduate dental training, I was taught that MB2 canals in upper molars are there 60-70% of the time.  Newer tools and techniques show us that MB2’s are always there whether or not we can get to it.  As a matter of fact I tell our endodontic residents at UBC that “if you haven’t found it, you have missed it“.

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Here are some pointers on how and where to find the canal that can potentially result in endodontic failure if left untreated, specially if the tooth is necrotic to begin with:

  1. MB2 is always there!
  2. It is always located palatal to MB1.
  3. It is always mesial to the line running between MB1 and P canals. This is the only safe area to trough.
  4. A good magnification and illumination is necessary.
  5. The access should be big enough to allow for adequate visualization of the pulp floor colour and map.
  6. Only instruments/burs (such as Munce Discovery Burs) that produce smooth troughing surface should be used. This is a more conservative and much cheaper option than using ultrasonic tips.
  7. There is absolutely no need for using explorer to poke and create misleading holes on the pulp floor.
  8. If there is no indication of the canal initially just start by troughing from MB1 mesio-palatally.
  9. Use copious irrigation to remove all debris created during troughing.
  10. The troughing should continue until a small size file can easily drop into this canal. This point of entry could sometime be 2-4 mm below the pulp chamber floor.
  11. Do not trough and hope you can find the canal. Always observe the colour changes on the floor and look for the clues.
  12. Know your limits and when you hear the whisper in your ears asking you to stop, listen to it!

Micro-surgery Works, Macro-surgery Doesn’t.

When endodontic surgery (a.k.a. apico, apicoectomy) is indicated, certain steps must be followed in order to ensure a successful outcome.  Skipping any of the steps below, specially steps 4 AND 5, may result in failure:

  1. Proper flap design.
  2. Adequate magnification and use of proper instruments.
  3. Root-end resection: to expose the uncleaned isthmi between the canals and to eliminate portal of exits/apical deltas which are more frequently seen in the apical 2-3mm.
  4. Retro-preparation: to create a class I cavity prep for placement of retro-filling material.
  5. Retro-filling: to seal the canal at the apical end, which is ABSOLUTELY NECESSARY for the apical surgery to be successful. Without this seal, the surgery is bound to fail as the root-end resection (Macro-surgery) alone cannot prevent the bugs from coming out of the canal system and causing the periapical lesion.
  6. Primary flap closure: in order to allow the stabilized clot that forms in the surgical site turning into bone in the absence of micro-organisms.

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Your Tooth Broke My File!

“A dentist who has not separated a tip of a file, reamer, or broach has not done enough root canals.” — Louis Grossman

There are essentially 2 reasons for rotary rotary instrument separation inside a canal:

1) Cyclic fatigue (file rotating inside a curved canal for extended period of time):
Factors contributing to cyclic fatigue are: overuse of rotary NiTi files, spending too much time inside the canal during instrumentation, canal curvature (degree and abruptness of the curvature), improper speed setting for the handpiece and the file tapers (larger tapers break faster).

2) Torsional fatigue (too much friction between the rotary file and the canal wall):
Factors contributing to torsional fatigue are: improper endodontic access, using too much apical pressure during instumentation, not following the proper sequence for a particular file system, not using lubricating agent/irrigants, using greater tapered files inside a tight/calcified canal and using handpieces with no torque control or auto reverse option.

Attempting to control the factors above will greatly minimize the risk of file separation.  But even in a perfect situation, a patient’s canal anatomy can bring the man-made technology to its knees.

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What to do if a file breaks inside a canal?

1. Stay calm. It is not the end of the world.

2. Try to remove it only if the separated portion is in the coronal segment of the tooth and not past the root curvature. This step also requires good magnification, illumination and proper tools (such as different ultrasonic tips).

3. Bypass it if the separated segment is apical to the curvature of the root using hand-instruments and finish the shaping of that canal with hand-files. Sometimes the separated file comes loose and can be easily flushed out.

4. Make it part of the filling if the file has completely blocked the canal. This may not affect the prognosis negatively [Crump and Natkin 1970, Spili et al. 2005] depending on the initial status of the pulp and whether or nor the separation happened towards the beginning or the end of cleaning and shaping stage.

5. Follow up the healing and the resolution of symptoms. Endodontic surgery may be needed if symptoms persist or the PA lesion does not heal.


The Pink Tooth

One of the reasons for a tooth appearing pink is the presence of External Cervical Resorption (ECR) or Invasive Cervical Resorption.  This type of resorption has been described and classified by Heithersay.

Some of the predisposing factors for ECR include: trauma, orthodontics, periodontal therapy, surgical procedures, intracoronal bleaching/restorations, etc.  For the reasons that are poorly understood, odontoclastic activity below the epithelial attachment would cause resorption that advances inwardly and, if untreated, eventually result in significant loss of crown and root structure. Resorptive process does not usually involve the pulp tissue and in most cases the tooth stays vital.  Teeth with Class 3 or 4 resorption have poor prognosis.  So, the key to saving these teeth is to catch the resorptive defects early on.

One of the telling signs is the presence of pinkish discolouration in the cervical area of vital teeth.  A resorptive defect harbouring a very touch-sensitive granulation tissue can be detected easily by running the sharp, curved end of the explorer below the level of CEJ.  The treatment of the resorptive defect is open-flap restoration.  The tissue residing inside the defect is usually very easy to remove as it appears detached.  As mentioned before, the pulp tissue is unaffected by this resorptive process and therefore, root canal therapy is not needed.

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One Cone Fits All, or Does It?

“After about ten years of first appearing on the market, currently Thermafil obturators are completely modified and form an integral part of a complete and sophisticated system of root canal obturation that, when used correctly, can give optimal results.   — W. Ben Johnson”

The reported advantages of Thermafil include: shortness of learning curve, speed of clinical application, apical control of fill, conservative enlargement of root canal (when compared to other warm gutta percha compaction techniques), three-dimensional obturation and apical sealing ability, etc.

In my opinion, shorter treatments do not allow for adequate disinfection of the canal system, speed compromises the quality, apical control of fill is nonexistent with this technique, and conservative enlargement of root canal is not always beneficial since some degree of apical enlargement is necessary to allow for proper disinfection by irrigants.

If used correctly (proper size obturator in a single, adequately-instrumented canal and following the manufacturer’s recommendations), 3-D obturation and apical sealing ability are the major advantages of this obturation technique.

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Inappropriate case selection for the use of Thermafil obturation technique is demonstrated above.  This case shows how Thermafil would give us a false sense of achieving an “optimal” obturation in challenging cases such as this.  There was only one obturator used in the canal system that splits into three apically.

As I mentioned in my previous post I Love Sealer Puffs!, extrusion of obturation material into the uncleaned and unshaped portion of the canal system (lateral canals, fins, isthmus, irregular areas, etc.) does not translate into success.  The prerequisite for any obturation technique is adequate shaping and cleaning of the entire system, and the only reason for endodontic failure is the presence of micro-organisms.


Alcohol Will Set Things Straight!

During re-treatment procedures, removing the gutta-percha dry (if possible) is preferred.  Simply because it is less messy.  But I often find myself use a bit of C-form (what we call chloroform in the office) specially when I have to negotiate the very last part of the gutta-percha close to the apex.  I also use it quite often when I re-treat cases with carrier-based obturation material.  And, what a mess that creates!

softened gutta-percha by chloroform

To get rid of this “soup” of gutta-percha from the access cavity and to continue working in a very clean and controlled environment, alcohol should be used as the next irrigant.  It clumps up all the softened gutta-percha to the point that it can easily be rinsed off by water spray or picked off by instruments.

Once the gross removal of gutta-percha from the canals is complete with alternating use of C-form and alcohol, I usually use EDTA as it will continue to clean the remaining of the softened gutta-percha from the canal system.

 


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