The Dental Operating Microscope Prevents Procedural Errors in Challenging Teeth

In case you are a new reader, it merits repeating that the dental operating microscope is the most valuable tool available for providing endodontic care.  The light and magnification provided are critical to success.  With this post, I will present two recent cases where two different clinicians had difficulty locating canal anatomy and perforated the root structure.  Each case was originally treated by a general dentist within the last year or two. With the use of a dental operating microscope, I was able to locate the missed canals and repair the perforations.  Hopefully, our clinician readers who are not microscope trained will become motivated to invest in one.

Case 1

This patient described an on and off awareness of her tooth since root canal treatment by her general dentist.  Her symptoms began to worsen, and she noticed a bump on the gums that drained.  Her general dentist had admitted to difficulty locating a challenging ML canal.

Preoperative Distal Shift
Note the ML canal is obturated a few millimeters below the orifice.

Preoperative Straight
Note the furcation radiolucency and absence of apical problems.

There was no clinical sign of swelling or of a sinus tract at our appointment.  The tooth was tender to percussion and uncomfortable to palpation in the furcation area.  Probing depths were 2-3mm with some bleeding and serous drainage on probing in the furcation area on the buccal.

A diagnosis of previous root canal treatment with a chronic furcation abscess was made.  I discussed the findings and treatment options at length with the patient.  When a perforation exists for a long time and then becomes infected, our success rate with retreatment drops by some indeterminate margin, and the treatment was not without risk.  The patient opted to take a chance on saving her tooth.

Upon access, purulent drainage was found pushing up from the gutta percha in ML area.

Upon removal of the gutta percha, a perforation was found that drained. 

After irrigating the perforation site with saline, and drying, the ML canal was located lingual to where the previous clinician had been looking.  It was high on the wall.

I was surprised to find the ML canal to not merge with the MB canal.

The location of ML was confirmed.  (ML not MB2!)

After two weeks of calcium hydroxide treatment, the patient returned symptom free and with improvement in the periodontal health.  You can see on our post op radiographs just how large the perforation was.

At a second visit two weeks later, the canal was obturated and the perforation repaired with MTA.
While the MTA extruded into the furcation is not ideal, the area should continue to heal.

Post operative image distal shift.

At a follow up visit, the patient remained symptom free and the periodontal health continued to look good.  The extruded MTA does not appear to have affected the outcome, which is consistent with the findings of others. For example, see this case of a large furcation perforation repair by Dr. Hales: http://www.theendoblog.com/2008/06/herodontics.html

Case 2

This patient initially presented with a chief complaint of minor soreness to bite forces and an intermittent dull pressure ache that she described as emanating from between the teeth #13 and #14.  Her symptoms were described as unchanged with root canal treatment by her general dentist within the last six months.  She described an improvement in symptoms when flossing and flushing between her teeth with Peridex.

Preoperative image.

The tooth was slightly tender to bite forces and percussion, but there was again no signs of swelling or a sinus tract. The probing depths were 2-3mm with a 7mm pocket on the MB and a 6mm pocket on the DB.  Because of the bilateral probing and bone loss, and the symptoms unchanged with root canal treatment, I recommended a periodontal evaluation.  I knew that there was an untreated MB2, but the periodontal symptoms did not match up.  After periodontal treatment, the pocket on the distal resolved, and there was a short-term improvement in symptoms, but they soon returned.  At this point, I was suspicious of a perforation.  A CBCT would certainly help confirm the diagnosis and be of value, but a decision was made to access and investigate.

Upon access, gutta percha was found in the location of the MB2.  Beneath, a perforation was found, just as in the previous case.

A file was inserted and a radiograph taken to confirm the perforation location.

Here you can see a 6 file entering the true MB2 canal.  It was located angling toward the mesial and buccal from the perforation.

The canal opened up a little.

A file inserted confirms the MB2 location.

Now, the MB2 can clearly be visualized after proper orifice shaping.

A gutta percha cone was inserted into the canal, and the others blocked with cotton while MTA was used to repair the perforation.

At the first visit, the patient was made aware of a fracture from the mesial to the distal that dramatically decreased the prognosis for the tooth.   After the first visit, the patient's symptoms resolved, and she could chew comfortably.  A case could be made to have the tooth immediately extracted, but the patient opted to finish the treatment even with the uncertainty involved.

Unfortunately, this tooth also exhibited a fracture across the floor of the pulp chamber.  These fractures are  very bad for the longevity of the tooth. 

Post operative radiograph

In each of these cases, it is clear from the preoperative radiographs, that the clinicians who originally treated these teeth had good command over the processes of instrumentation and obturation.  Both cases are instrumented to length (with the exception of the DB of #14), and appear well obturated with Thermafil carriers.  Both clinicians were aware of the missed anatomy, but could not locate the ML and MB2 canals respectively.  They were certainly difficult ones to find; they were not immediately obvious upon access, and while I do have extra training in endodontics, the microscope is what enabled these teeth to be saved.  The long-term prognosis of either tooth is not great, especially the fractured #14, which could fail in the short-term, but the patient's were well educated and appreciate the risks involved.  The patient with tooth #14 is now prepared for the eventuality of a dental implant in that site.

The success of perforation repairs depends on many factors, such as the time since perforation, the location within in the tooth, the size of the perforation, and the materials used for repair.  The smaller and more recent the perforation, the better the chance of success.  The farther apical the perforation, the generally better success with repair, as long as the true canal path can be recaptured.  Furcation perforations are the easiest to access for repair, and have the best surrounding tooth structure.  Perforations in the gingival attachment level have a decreased prognosis due to difficulty controlling materials and the increased risk of a periodontal defect.  In the Toronto studies (Friedman 2004), a prospective longitudinal study of the success of endodontic retreatment, of the 8 cases, roughly half of the retreatments with perforation exhibited healing.  However, the materials used for repair in this this study were glass ionomers.  In another study, 16 out of 16 cases repaired with MTA exhibited healing at a minimum of 1 year (Torabinejad 2004).

For tips on the placement of MTA, see this other post by Dr. Hales: http://www.theendoblog.com/2008/04/placement-of-mta.html

Example of a case of perforation repair in the lateral gingival attachment.  I used MTA for this case, and the perforation was repaired non-surgically.  The patient's restorative dentist used glass ionomer as a restoration on top. A case for a different treatment plan involving crown lengthening could be made.

All three teeth in this posted here I consider to have guarded long-term prognosis.  However, all three patients continue to chew and function in the absence of disease.  If you have any questions or input, please let us know.

Any suggestions for future topics or posts are also welcome!



Farzaneh M, Abitbol S, Friedman S. Treatment Outcome in Endodontics: The Toronto Study.  Phases 1 and 2: Orthograde Retreatment. J Endod. 2004;30: 627-33.

Main C, Mirzayan N, Shabahang S, Torabinejad M. Repair of root perforations using mineral trioxide aggregate: a long-term study.  J Endod. 2004;30: 80-83.

Value and Limitations of CBCT in Endodontics-Case Report

For the longest time, I have been skeptical of the ability of the CBCT to detect vertical root fractures. Especially in previously treated teeth, where scatter radiation produces artifacts in the image. There has been research(mostly in vitro) supporting CBCT imaging for detecting fractures(Hassan 2009), and there is no doubt that the technology shows exciting promise for use in our field. This case demonstrates both the value and limitations of this exciting imaging system.

The patient first presented six months ago with new crowns on teeth #30 and #31. His symptoms were described as a spontaneous ache and a soreness to mastication that started with the new crowns and felt localized to #31. Diagnostic testing revealed percussion sensitivity and a lingering dull ache to cold on #31, as well as a mild soreness to bite forces on #30. The original root canal treatment and post on #30 were over 15 years old. A diagnosis of irreversible pulpitis was made for #31 and treatment was completed. The mild bite soreness on #30 was attributed to a heavy occlusion and/or some referred pain from #31. Here is our post op radiograph:

The patient reported an episode of severe spontaneous pain lasting one day in the area that started four days after the first visit for #31 and resolved prior to his second visit. This odd experience certainly raised some alarms for me, but when he returned, a new exam and series of diagnostic tests produced nothing of note.

At three months following treatment, the patient reported continued discomfort to mastication in the region. An exam and diagnostic testing produced some continued bite soreness on #30. A new periapical radiograph revealed a possible missed DB canal:

I also speculated on what appeared to be the early formation of a lateral radiolucency on the mesial root that could be the result of a vertical fracture:

However, there were no significant probing depths, only mild symptoms, and no obvious signs of an apical radiolucency. At this point, to aid in our diagnosis, I recommended a CBCT. I reviewed the scan at length individually, and with a periodontist and with an expert from the company. I immediately confirmed the missed DB canal, but also noticed an obvious radiolucency associated with the distal root. What we could not find, independantly or together, was any sign of a fracture in the mesial root or of any lateral bone loss along the root.

It's remarkable the accuracy with which we can pick up the missed DB canal and see the periapical radiolucency (PARL) that was not evident on the periapical radiographs above.

With the new diagnostic information, the decision was made to retreat #30. Of course, I still warned the patient about the risk of losing the tooth if a fracture is found in the root structure. Upon access, I was greeted with the familiar sight of purulent drainage pulsing up the distal with each heartbeat:

Below you can see the missed DB canal before and after post removal: Unfortunately, upon cleaning up the mesial, two fractures were found leading to the MB canal. One along the mesial wall:Another fracture was found along the MB wall: These large fractures probably form a wedge out of the MB root. Unfortunately, they severely compromise the prognosis of our treatment. I cleaned and disinfected the untreated DB canal before placing calcium hydroxide. I then closed the tooth and recommended extraction to the patient. Because of our diagnostic efforts involving a lengthy consult with clinical and radiographic images, the patient was understanding of his situation and appreciative that every effort was taken to diagnose his problem and save his tooth.

In this case, I had high hopes that the CBCT might confirm my suspicion of lateral bone loss around the mesial root. The CBCT was excellent, as it has been in the past, at confirming missed canals. However, it has still not demonstrated to early detect a vertical root fracture prior to an obvious clinical and periapical radiographic presentation.

If anyone has any questions or input, or has had different experiences with the CBCT. Please share them! Also, check out our office's facebook page at www.facebook.com/alpharettaendo where I post new cases regularly.

Evaluation of #2 for Retreatment, CBCT Revisited.

I want to thank Dr. Hales for the introduction and for inviting me to contribute here on the Endoblog. I've been following and learning from the Endoblog for some time. It's my hope that I can not only share some of my knowledge, but also receive some valuable feedback from others who read this blog with other experiences and points of view.

Many interesting cases, treated by myself and Dr. Stephen Parente, can be found on the Facebook page for our practice: http://www.facebook.com/pages/Alpharetta-Endodontics/137382942943581 I would urge those interested in endodontics to check us out there as well.

This past week, I evaluated a patient who's tooth reminded me of the case previously presented here on June 7th by Dr. Hales. Since it was so similar, I thought it would be a perfect follow up and first post. This patient had #2 treated with root canal therapy 1 year ago by another endodontist. I am familiar with this endodontist's work from other patients requiring retreatment and know that he does not use a microscope. He also tends to limit most treatments to one visit.

The patient described symptoms as an occasional spontaneous dull ache of varying intensity that has persisted since initial root canal treatment. At worst, the symptoms are moderate with some pulsing or throbbing. At the time of evaluation, the patient was experiencing a mild awareness of the tooth, a common description of symptoms from a failing root canal. Prior to root canal therapy, symptoms were similar, but more intense, and the patient has no recollection of any hot or cold sensitivity at that time period. From this information, we learn the tooth was likely necrotic prior to treatment, which is relevant when understanding possible challenges to disinfection. The symptoms are well localized, and the patient points directly at tooth #2. The tooth has been reevaluated by the previous endodontist and by the referring dentist. They adjusted the the occlusion and prescribed antibiotics.

The relevant medical history consists of prior dual knee replacement surgeries in 2009 and 2010 necessitating antibiotic prophylaxis. The patient is currently taking clarithromycin (Biaxin) for a sinus infection, but the tooth symptoms predate the sinus problems by many months.

Extraoral exam revealed no relevant findings. Intraoral exam revealed normal tissue contour and consistency with no swelling or sinus tracts. All probing depths were 2-3mm and percussion and bite tests produced only a mild discomfort on #2.

In addition to the above two radiographs, I also examined a bitewing and two traditional film radiographs which I chose not to include here. One thing that stands out is that the crown margin is placed on the buildup, not an ideal situation. You can see only two canals treated and an in tact PDL. The orifices of the canals are clearly overenlargedand the obturation does not appear to follow the root anatomy.

Drawn below is what I drew for the patient, predicting the true root and canal anatomy of the tooth and showing where I speculated there to be an untreated distal buccal canal.

It appeared as if the previous operator perforated during instrumentation, not only between the mesial and distal roots, but also at the apex. In addition to these root perforations, the coronal tooth structure is clearly compromised. The patient was anxious to save the tooth since she invested in root canal treatment and a crown within the last year. I did not feel retreatment would have a good prognosis and recommended extraction. The patient was understandably reluctant about this option, and so I opted to image the tooth with CBCT for more information and better patient education.

In the below left image, I circled the missed DB canal. The below right images (one is reversed, please forgive me) display the missed DB root in the sagittal plane as well as the apical perforation and over enlargement (strip perforation) of the MB root.

The below horizontal slice displays the previous instrumentation into the furcation between the MB and DB roots. I question if the radiolucent line mesial to the radiopacity is a fracture.

The left and below images show a palatal radiolucency forming as well as the off center and possibly apically perforated palatal obturation.

This last image to the left is a horizontal slice in the apical third of the root again displaying the palatal radiolucency forming.

The CBCT shows this tooth has many problems that are not reliably correctable with endodontic retreatment. Finding the missed DB canal and even repairing the MB perforation in the furcation will not help recapture the correct path of the MB or P canals.

The CBCT confirmed with certainty what was highlighted in the periapical radiograph above. With these images, the patient was better able to visualize the root anatomy and obstacles to repairing this tooth. Consequently, the patient was much more accepting of the treatment plan of extraction.

We are increasingly using the CBCT as a diagnostic tool in our practice, specifically in complex retreatment cases or in vague diagnostic situations. In this specific case, the CBCT images confirmed suspicions about root perforations and missed anatomy. They also displayed a palatal radiolucency that was not evident on the periapical radiographs. Lastly, and not to be overlooked, the images were invaluable for patient education and treatment plan acceptance.

All CBCT images provided by Dr. Colin Richman and his Kodak 9000.

3D Evaluation of Root Canal Morphology (Cone Beam Computed Tomography)

At Superstition Springs Endodontics, the use of cone beam computed tomography (CBCT) is a valuable tool in endodontic diagnosis and treatment. This technology is used on a case by case basis, following the guidelines specified in the joint position statement by the AAE and AAOMR.

The joint position statement by the AAE and AAOMR regarding the use of CBCT in endodontics states that "The patient’s history and clinical examination must justify the use of CBCT by demonstrating that the benefits to the patient outweigh the potential risks. Clinicians should use CBCT only when the need for imaging cannot be answered adequately by lower dose conventional dental radiography or alternate imaging modalities."

A significant concern noted in this position statement is the added radiation dosage to the patient. In our practice, using the J. Morita Veraviewepocs 3De, the patient is exposed to the lowest radiation dose on the market. A single 40 x 40mm 3D scan exposes the patient to 0.029mSv. This is approximately the same amount of radiation a patient would receive with 9 digital periapical films (0.003mSv).

The volume of data acquired in a single scan allows us to look at that tooth from any coronal, sagittal or axial view, and the ability to re-slice the volume at any slice thickness. This volume of data can be manipulated over and over to gather unlimited amount of information about the tooth and it's periapical tissues.

A CBCT scan, provides visualization of root number & anatomy, canal number & morphology, much more accurate evaluation of peripical tissues. Understanding the advantages of CBCT, the limited radiation and limited liability associated with a focus field CBCT, I would suggest that the benefits routinely outweigh the potential risks. Unfortunately, there are often benefits of a CBCT scan that are not apparent unless the scan is taken. The following case is an example.

This patient presented with complaint of pain in lower left quadrant. Recent crown prep on #19. Regular diagnostics were inconclusive as to the source of this pain (#19 was testing normally to vitality, probing and percussion testing) A short obturation of #18 was noted, but this tooth was asymptomatic. After short period of time waiting to see if symptoms localized, and failure to do so, a CBCT scan was acquired to evaluate if there was apical bone loss associated with one of these teeth that would help in the diagnosis.

CBCT did not show any radiographic lesions on #18 or #19. The temporary crown #19 was removed for additional pulpal testing. Tooth #19 gave no response to cold on the buccal side and a vital response on the lingual side. It was decided that endodontic treatment should be initiated on #19 with a probable "partially necrotic" pulp.

The CBCT gives us valuable information about tooth #19. For example, following CBCT, prior to starting RCT #19, we know that the mesial root is a single root with 3 canals that merge. We also know that distal root has a single canal.

3 canals found in a single, mesial root. This was identified prior to treatment with CBCT. In this particular case, the 3rd (middle) canal would likely not have been found due to its location.

In this case, the CBCT identified a variation in the mesial canal morphology. Knowing that the mesial root was a single root and that it had 3 canals, gave me the ability & confidence to explore the ML-MB groove to a greater depth than would have normally been done for fear of perforation. This is a perfect example of radiographic information that is not available through traditional 2D imaging. This information allowed us to provide better cleaning, shaping and obturation, which will lead to a better RCT.

Herodontics? - Revisited

In Aug 2009, an American Academy of Implant Dentistry press release stated, "...times have changed and patients should forego prolonged dental heroics to save failing teeth and replace them with long-lasting dental implants". While it universally accepted that implants are a great way to replace missing teeth, a more controversial topic is when to replace a diseased tooth with an implant. In my opinion, those promoting dental implants have become increasingly more aggressive about replacing natural teeth.

As a specialist, I am occasionally called upon to perform "heroic" procedures. This may be following some iatrogenic damage or by a patient who wishes to retain a natural tooth at any cost. While I would much rather treat a normal, straightforward endodontic case, the use of microscopes, ultrasonics and MTA have allowed us to preserve teeth that many would consider "hopeless". I am often amazed at the success that we have with some of these "heroic" cases.

The following case was previously posted, but the patient returned for a 4 year recall last month. Unfortunately, the patient was returning for another root repair perforation following endodontic access on a different tooth. This case would be considered a "heroic" case by anyone's standard! In this particular case, this patient has been pleased with his decision to retain the tooth.

Original Post
This root canal was done just over four years ago. The patient presented with pain to percussion, and an 8 mm buccal probing was present. The RCT had been completed 2 years previously and recently became symptomatic.
DX: Prior RCT w/ Symptomatic Apical Periodontitis.
Treatment recommended: Non-surgical retreatment, perforation repair with possible need for endodontic surgery. Prognosis: guarded.

As you can see, the MB canal is very calcified. Calcification of this kind would make this case a very high level of difficulty. The MB canal was missed and the furcation was found, instrumented & obturated. Proper case selection can help prevent this type of complication. However, if this does occur, one would expect to find bleeding and the tactile sensation of the pdl/cortical bone is very different from the canal. Length determination films, working films or final films should also identify the perforation. I would recommend immediate referral to an endodontist for treatment of an iatrogenic event such as this.

Retreatment completed. MB canal located and treated. Furcal perforation repaired with MTA. Patient placed on recall to watch the area and see if endodontic surgery will be required.

Recall at 2 years & 3 months. Patient reports complete function and no symptoms. The 8mm periodontal probing has dissappeared. This tooth is considered "healing", and scheduled for a 1 year recall.

You can call it "herodontics", but that tooth is functional, apical bone looks good, periodontal pocket has disappeared. This will be a fun case to watch over time.

4 Year Recall

Asymptomatic & fully functional.

NOTE: I have never said this is pretty. Actually, its pretty ugly. However, retaining the natural tooth has preserved the crestal bone, provided normal function, and cost much less in time and money than any replacement option available.

Root Perforation causing Tooth Loss

This patient came to our office for evaluation of tooth #3. He reported having a recent root canal and crown done by a general dentist. Since the time the work was completed, he was experiencing "burning & itching in the gums around that tooth". The patient was concerned that he was having an allergic reaction to the cement or materials of the crown.

Our examination found #3 sensitive to palpation, moderately sensitive to percussion. (Adjacent teeth WNL) The radiopacent material in the furcation area of the tooth was noted.

Retreatment was initiated to evaluate the area.


The crown was first removed. Upon first look, there appears to be mesial decay still present and an obvious void between the tooth and the post/core material.

Additional removal of the buildup material shows a surprise underneath.

It become obvious that the distal wall of the MB canal has been perforated.

At this point, we can understand where the symptoms have been coming from. An attempt could be made to try and repair this defect (with MTA), however, the long term prognosis would be guarded to poor. Considering the the cost of initial treatment, the cost of retreatment which would then require post & build-up and new crown, this patient elected to extract the tooth.

This then becomes an appropriate time to replace this missing tooth with an implant or bridge. I recommended an implant consultation.

Endodontic treatment did not fail on this patient. The treating doctor failed to put his patient's best interest first and failed to inform the patient of the treatment complication (perforation) that occurred during treatment.

In a case like this, the patient referred himself to our office for evaluation. Had his dentist properly evaluated the case difficulty and referred him to an endodontist for treatment, this tooth would likely not have been lost.

This is not endodontic failure. This is failure to do good endodontics. This failure to do quality endodontics may be part of the reason that some clinicians are questioning the success of endodontic treatment.