Preventing Root Canal Perforation by Case Selection

This patient came to Superstition Springs Endodontics in June 2009.  Her general dentist had started RCT on #3 but was unable to locate the MB canal(s).  A perforation was made during the efforts to find the MB canals.  We have taught the generalists in our community that the most successful and fulfilling way to practice endodontics depends upon careful case selection.  Proper case evaluation can:

1.  prevent lost chair time without reimbursement
2.  prevent loss in patient confidence
3.  prevent clinician frustration

The Endodontic Case Assessment Form from the AAE, can help clinicians determine the difficulty level of treatment - before therapy is started. This is how this case should have been classified - prior to starting treatment. 

 

 

 The treatment for this tooth was RCT completion and repair of the iatrogenic damage using Mineral Trioxide Aggregate (MTA).

Fortunately, with good repair materials, the prognosis for a tooth like this is still good.  A 7 year recall finds the tooth in full function and asymptomatic.

However, proper case selection will make your practice of endodontics more fulfilling, less stressful and ultimately, more successful.

Successful Endodontics in Your General Practice

Successful endodontic treatment in the general dentist's office is based upon proper case selection.

Proper case selection will allow endodontics to be a profitable, enjoyable procedure and provide a valuable service to your patients that will build your practice.

Failure to perform proper case selection will result in:

1. Frustration

2. Loss of patient confidence

3. Loss of practice revenue

4. Additional costs incurred with retreatment or repair of iatrogenic damage

The American Association of Endodontists has prepared an assessment form to help clinicians evaluate the level of difficulty associated with endodontic treatment to help the clinician decide when to refer. (click here)

To summarize this assessment form, here's a breakdown of the type of cases that are considered minimal, moderate and high difficulty level.

MINIMAL DIFFICULTY

1. Pt is healthy, cooperative, minimal pain and/or swelling

2. Diagnostics are clear and pulpal/peripaical diagnosis made without complication

3. Tooth is easily accessible for treatment. (anteriors/premolars w/ slight inclination or rotation)

4. Canal is open, not calcified, mature apex, no resorption

5. No previous RCT

6. Root has slight curvature

7. Periodontium is healthy

MODERATE DIFFICULTY

1. Pt has minimal health issues, anxious - but cooperative, moderate pain and/or swelling

2. Diagnostics requiring additional evaluation (sinuses, TMD, electric pulp testing on calcified teeth)

3. Tooth accessibility is difficult - 1st molars, moderate inclination, rotation, crown, bridge, extensive decay

4. Canal is reduced in size, pulp stones, wide apex

5. Prior RCT without complication

6. Root has moderate curvature

7. Moderate periodontal disease

HIGH DIFFICULTY

1. Complex health issues, difficulty cooperating, severe pain and/or swelling

2. Diagnostics difficult - confusing complex signs & symptoms, chronic oro-facial pain

3. Tooth accessibility is difficult - 2nd & 3rd molars, severe inclination, severe rotation, crown/bridges with alignment irregularities

4. Canal is calcified (not visible), S or C-shaped, canal divides in middle or apical thirds, additional roots (3 rooted bicuspid), apex is open

5. Prior RCT with complication

6. Root has severe curvature

7.History of traumatic injury (avulsion, horizontal fracture, luxation)

Each clinician must evaluate the difficulty level and select cases that match his/her skill level and cases for which they have adequate instrumentation.  Pick cases that you can do in a timely manner, without complications.  As you become more and more comfortable, select slightly more difficult cases to challenge you, always being aware of that some cases are better managed under the microscope and with the aid of CBCT.

 

 The following case demonstrates the benefit of proper case selection.

Root Canal on a C-shaped, 2nd molar, through a crown with mild angulation and calcified canals makes this root canal a "HIGH DIFFICULTY" level.  The clinician performing this treatment had challenges due to these issues.  Access was difficult, interpreting the c-shaped canal was difficult and C-shaped canal all led to the mesial perforation.  The calcified canals also made it difficult to instrument/fill to the apex.  The perforation was improperly managed by sealing with gutta percha and patient was not informed of the complication.

CBCT view of the issues

Retreatment completed with MTA repair of mesial perforation.

  Prognosis: Fair

Proper case selection also helps you to build relationships with your endodontist.  When you have a good working relationship with your endodontist, you can rely on him/her to help you advance your endodontic skills and experience as well as help in difficult case management.

Root Canal Surgery to Repair Post Perforation

#6 Post perforation on a long span (7 unit) bridge. Pt is insistant that she does not want to lose this tooth or bridge at this time.  Lateral radiolucent lesion is present adjacent to the perforation.

CBCT taken to evaluate the position and extent of perforation, bone loss and possible surgical intervention. Given the treatment options, the patient wishes to try and maintain the tooth with surgical repair of post perforation. Pt understands that post repair will not improve coronal margins, but does not wish to replace bridge at this time.

Surgical flap reflected, post perforation located, 2-3mm post resected, lateral root preparation created.

Geristore used to repair root.

Lateral root restoration contoured to adjacent root.

Post Op radiograph showing perforation repair.

6 month recall showing initial healing. Pt is asymptomatic and fully functional.

At 18 month recall, bone has healed completely, tooth #6 is asymptomatic and fully functional.  Tooth #4 is now testing necrotic w/ asymptomatic apical periodontitis. RCT has been recommended.

 This case demonstrates how a skilled endodontist's surgical abilities can save what would seem like non-restorable, iatrogenic damage.

Microscopes & Management of Root Canal Perforation

As discussed in Dr. Justin Parente's previous post, dental operating microscopes can prevent procedural error in endodontic treatment.

There are those who may debate this, but in my opinion, microscopes are the standard of care in endodontics. Molar endodontics should be done using a microscope. In our practice, we use microscopes on every case. Perforations happen, missed canals happen, but with a microscope (and other advanced imaging systems - but that is another post) they are much less likely to occur.

The following case is that of a root perforation, it's microscopic retreatment, repair using MTA and the 6 month recall showing healing.

This patient was referred to Superstition Springs Endodontics with the complaint of "constant pain on lower right". Our diagnostics found #30 with Prior RCT and symptomatic apical periodontitis (SAP). He reports that this root canal was done 1.5 yrs earlier by a general dentist.
As you can see in the radiograph, there is a large pa lesion on the distal root and a radiolucency in the furcation area - likely caused by furcal perforation.
We discussed options and recommended retreatment with probable perforation repair in the pulpal floor.

Upon access, we found a furcal perforation that had been covered with resin buildup material.

RCT retreatment was completed. By using a microscope, we were able to locate a 4th canal that had previously been left untreated in the distal root. We also repaired the pulpal floor perforation using MTA.

At 6 month recall, you can see that the periapical lesion has healed very nicely. The bone loss in the furcation area has also improved. The patient is functioning on this tooth and is asymptomatic. He occasionally reports some swelling adjacent to the tooth, but upon our clinical exam today, probings are normal and there is no sign of irritation or infection.

Prevention of root perforation is always better for the long term prognosis than perforation repair. Use of magnification and lots of light (microscope), understanding pulp & canal anatomy, proper use of high & slow handpieces and ultrasonics, recognizing buildup material from dentin of the pulpal floor are all important factors to help prevent root perforation. With that said, if perforation occurs, the patient should be informed and the perforation should be repaired immediately with MTA. Proper management following root perforation can allow the tooth to be retained. Endodontists are specialists in saving teeth.

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.

Consult Along: A Day at Alpharetta Endodontics

Rather than try to have an overarching theme to this post, I will present each of today's patients as each case was complex and each illustrate rather important points. For the sake of brevity, I will only post significant findings (and I apologize for poor consistency and errors in grammatical tense) . Unless otherwise stated, assume medical history is non-contributory. I would love for readers to post feedback, alternate treatment plan ideas, or other approaches to these cases.

Patient 1:

This patient presented with a history of root canal treatment on #20 by an endodontist 1-2 years ago. #19 was treated by her general dentist ~8 months ago, and #18 was fractured and replaced with an implant within the last two years. The crown came loose and was replaced with a post 1 month ago. Following this treatment, she described severe pain upon chewing and swelling on her tongue side of the tooth. There is no extraoral sign of swelling or lymphadenapathy. No intraoral swelling or sinus tract. Around #19, the gingiva is edematous and inflamed with bleeding on probing. The crown margins are open and overextended. The probing depths on #19 are 3 mm interproximally and 8-9mm mid buccal and mid lingual. The radiograph reveals a laterally widened PDL with a hint of an apical radiolucency. The restoration on the mesial is into the furcation and associated with horizontal bone loss. #20 displays an apical radiolucency as well. The implant on #18 is bulbous and overcontoured to the mesial with some signs of horizontal bone loss.

Unfortunately, I recommended extraction of #19 due to the likelihood of a vertical root fracture and a poor restorative prognosis. I recommended she return to her previous endodontist for reevaluation/recall of #20. I also provided her some proxibrushes to maintain oral hygiene around #18. Would you rather have that root canal/crown or that implant...or neither?

Patient 2:

This patient is referred by her general dentist for evaluation of #3 and initially presented two weeks ago. She reports having root canal therapy a year and a half ago by another local endodontist, no microscope. Since the time of treatment, she has had spontaneous "shooting" pain that is localized to tooth #3. It is worse in the morning and with mastication. A history of symptoms indicates that the tooth was likely vital preoperatively and so persistent bacteria is not a feasible etiology. No extraoral swelling or lymphadenopathy. No intraoral swelling or sinus tract. Probing depths 2-3mm, crown margins are in tact. Occlusion is light in MI with no interferences. No palpation tenderness, no swelling, no sinus tract, no percussion tenderness, no mobility. Slight bite pressure tenderness on the MB cusp and P cusp only.

Preop, no radiolucency, slight ligament widening in the palatal, short palatal obturation, overenlarged mesial obturation in the cervical third, undermined/weakened mesial tooth structure. Diagnosis: previous treatment/acute apical periodontitis. Possible etiology: restorative recontamination, root fracture, strip perforation of MB/MB2. I recommended retreatment but cautioned that a finding of a root fracture would indicate a need for extraction.

Upon access, blood was found on the palatal canal, and, in spite of anesthesia, the GP was tender to pressure with fluid built up around it. No fractures were found. Additionally, a strip perforation was found in the cervical third of MB2. It was repaired with MTA and the palatal canal was retreated. The patients symptoms resolved immediately, and the case was finished this morning.

Patient 3:

This patient went to her new dentist for a broken restoration on #30. Decay was found encroaching on the pulp chamber and she was referred for root canal therapy. She is asymptomatic. #31 was treated 2 years ago by another endodontist, no microscope. The anatomy appears to be very challenging. A history of symptoms of cold sensitivity and throbbing pain prior to the previous treatment indicate that #31 was likely diagnosed as irreversible pulpitis preoperatively.

Treatment on #30 was completed at today's visit and treatment options for #31 were discussed. Restoratively, the case is compromised with a crown on a buildup with voids. Additionally, retreatment of the mesial root is going to be challenging if not impossible. If, as it appears, the distal root is the primary source, retreatment may be successful. One alternative, if retreatment is not successful, is to place spacers to loosen the tooth and then try an intentional reimplantation. Apical surgery is difficult to impossible in this location with such long roots (25mm working length on #30).

Patient 4:

Asymptomatic, original treatment over 15 years ago. Her crown and posts came off and extensive recurrent caries was found beneath. Her dentist cleaned the area and placed a temporary crown before referring her for evaluation. While radiographically, the ligament is in tact, her history indicates bacterial contamination and retreatment was recommended.

Case #5:

This patient is asymptomatic. She recently moved here and her new dentist noted a parulis buccal to #30. She is ~85 years old. Probing depths were 2-3mm with bleeding on probing and a class 1 furcation involvement. The margins on the composite were open. Due to the compromised restorative prognosis and the furcation radiolucency, I recommended extraction. She does not wish to replace this tooth at this time, but an FPD is likely her best option. She is fortunate to have full molar occlusion on her left side.

I hope that our readers learned something from these cases. You will probably realize that I started no new root canal treatment today, and that all our cases were complex diagnostically and involved molars. This is typical for our practice.

If you have any input or questions, please voice them in the comments, but please remain constructive. As always, I invite readers to see more cases posted regularly on our facebook page at www.facebook.com/alpharettaendo.

If you have any suggestions or requests for future posts, please leave them in the comments!