Lateral Portals of Exit

As clinician readers know, the canal anatomy of teeth is rarely simple. Lateral portal of exits (lateral canals) are a significant challenge to clean and are present in many of the teeth we see for root canal therapy. In a previous post, I discussed the use supplemental irrigation and ultrasonic instrumentation to clean isthmus tissue. That post can be found here: http://www.theendoblog.com/2012/07/the-isthmus.html I use these same techniques to address lateral portal of exits. These lateral exits are very common, but with proper irrigation, they can be predictably addressed.

Sometimes, as in this #19 below, the exit can be found at the apex in the form of a sharp distal turn or delta. Direct instrumentation may or may not be possible with small, pre-bent files (6 or 8).

These exits can also be found in the furcation region. If untreated and contaminated with bacteria, they can feed furcation radiolucencies and cause attachment loss (probing). Here is a straightforward #30.

 

 

Untreated, you will see radiolucencies centered on the exit as in this #9 retreated below. I measured to the depth of the lateral canal and focused my irrigation and irrigant activation at that level.

 

 

 

 

Always be aware that the potential for more anatomy exits. With this #28, I found 3 canals splitting at midroot and thought I had found all the anatomy. Fortunately, extensive irrigant activation picked up a lateral exit off the mesial buccal canal in the apical third. Tooth #29 is scheduled for retreatment.

 

In summary, do not believe for a second that sticking a file in a canal completely cleans a canal system.

 

Merry Christmas!

 

Justin Parente

Alpharetta Endodontics

www.Alpharettaendo.com

www.facebook.com/alpharettaendo

 





Why Is It Better to Save a Natural Tooth?

A patient recently asked...

 I'm a healthy 47 year old male. My upper central incisor (#9) was struck (trauma). It cracked vertically to the gum line, and then cracked horizontally to the lateral edge (resulting in an inverted "L" shaped fracture).

My general dentist first tried applying a layer of bonding, which appeared to be acceptable both aestetically and structurally.

6 weeks later, severe pain started to develop. I went back to my dentists and he said that there is no sign of infection, but that the pain is likely from the nerve dying. We agreed that we should go with either a root canal + crown, or implant + crown.

As a mechanical engineer, I'm leaning towards the implant, because it seems more "fool proof", especially considering that the existing tooth has been structurally compromised down to the gumline.

But the one thing that still has me second-guessing the implant option is that endodontists and periodontists both seem to universally agree that "It's better to save the tooth whenever possible."

So I have to ask: WHY???

Why is it "better to save the natural tooth" if it is subject to future decay (in particular at the base of the crown) and is also subject to brittleness following the root canal?

As a mechanical engineer, I like the prospect of an inert metal or zirconium implant that is not subject to these potential future modes of failure.

Please share your insights in the context specific to my situation described above. Much appreciated. Thank you. 

While it may seem a simple solution to replace a tooth with an implant and then avoid future issues like decay or root fracture, there are some important reasons why the specialists are recommending preserving the natural tooth if possible.

Periodontal Ligament attaches the root to the bone

Teeth and implants are not the same. The main difference between a tooth and an implant is that a tooth has a periodontal ligament. This ligament attaches the root to the bone and acts as a shock absorber for the tooth.  Without a periodontal ligament, when you touch, tap or chew on the tooth, you cannot feel the tooth or how hard you are biting.

The sensory function of the periodontal ligament helps you know when something is wrong with your tooth. If the tooth is hitting too hard, the ligament senses it. If there is infection around the tooth, the ligament senses it. The sensory function of the periodontal ligament is very important to dental health.

The periodontal ligament also supports the surrounding bone. When the ligament (tooth) is removed, bone loss naturally follows. The periodontal ligament also is a home to multiple cell lines which support the bone such as: osteoclasts, osteoblasts, fibroblasts, cementoblasts, cementoclasts, and stem cells. The periodontal ligament allows the tooth to be moved through the bone (orthodontics).

The periodontal ligament has an important role with esthetics.  When the ligament is removed, and bone loss naturally occurs, gingival recession follows. This can change the esthetics of the tooth, especially in the anterior esthetic area.

The periodontal ligament also has an immunological purpose. The ligament and the gingival connective tissue fibers form a barrier to protect the bone from bacterial invasion.

There are times when the natural tooth cannot be saved.  If the root is fractured, then the tooth is not savable.  The endodontist is the most qualified specialist to determine if a root is fractured.  At Superstition Spring Endodontics, we use microscopes and focused field, high resolution CT scans to aid in the diagnosis of root fracture.

The periodontal ligament is the difference!

In these particular cases, a dental implant may be the ideal way to replace a missing tooth.  Marketing of dental implants by manufacturers has made this treatment options well known to the public, however, dental implants are not free of complications or need for revision (additional) treatment over time. By understanding the complications that can occur with implants, it will help to understand why specialists recommend, "saving the tooth if possible".

The ligament is a shock absorber

Many of the complications with dental implants can be associated with the lack of a periodontal ligament. Here are a few of the ways the lack of periodontal ligament can cause complications with dental implants.

The periodontal ligament is the shock absorber for your tooth.  Can you imagine driving a car without shocks? An implant, without a ligament, has no proprioception (sense of feeling). This means it is difficult for you to "feel" how hard the teeth are hitting together. Porcelain chipping, cracking and loosening of implant screws are all common complications with implants, mostly due to the lack of a periodontal ligament and the proprioception it provides.



Fortunately, with implants adjacent to natural teeth, you maintain proprioception from the adjacent natural teeth so your chewing can still feel the same. However, it is difficult to feel if the implant crown is hitting too hard, like you would with a natural tooth. Your dentist must be careful to get the implant crown adjusted just right, and will often times flatten the crown to prevent excessive force on the implant or make the biting contact light.

Bone loss over time is expected

The periodontal ligament transfers the force from the tooth to the bone. That constant transfer of force to the bone, keeps the bone functioning around the root.  When the periodontal ligament is gone, bone loss naturally follows. Some studies say that up to 0.2mm/yr of bone loss can be expected. There are theories as to why this occurs. Some think its simply the mechanical forces on the implant transferred to the bone that causes the recession.

Bone loss in anterior can cause esthetic defects

Loss of bone around an implant can cause unsightly changes in the anterior esthetic zone. While the implant may be functioning, esthetic failure is a well known complication with anterior implants.

Peri-implantitis is the growth of bacterial biofilms on the implant surface, causing chronic inflammation leading to bone loss.  Many people are not aware that an implant can get peri-implantitis, just like a tooth can get periodontitis, both of which can eventually lead to the loss of the implant/tooth.   The periodontal ligament plays an important role in the preservation of the bone around a tooth.

Historically, implants have been classified as "surviving" or "failed" based upon mobility of the implant. New implant studies have suggested that implant intervention may need to be done at earlier stages before too much bone loss has occurred.  It was proposed that surgical intervention may need to be done when an implant is considered "ailing" or "failing" rather than waiting until enough bone loss has occurred to consider it "failed".

In a recent study published in the Journal of Oral and Maxillofacial Implants, a comparative study between the success rates of implants and root canals revealed no significant difference in the two options and emphasized that treatment decisions should be made on factors other than outcomes.  In other words, neither of these treatment options can claim to be more successful than the other.  These treatments are different, and each has its own pro's and con's.

Implants have an important role in dentistry.  I routinely recommend implant placement for missing teeth or teeth that are too damaged to save. However, implants are not teeth and we should try to preserve our natural teeth if possible.

For more information on the longevity of implants vs. natural teeth, click here or here.

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.

Apical Surgery for Complete Endodontic Healing

Sometimes endodontic surgery (apicoectomy) is required for complete periapical healing - even on teeth with ideal (or close to ideal) non-surgical treatment.  We are not always able to identify the reason that apical surgery is required. Perhaps it is complex apical anatomy and the inability to completely clean, shape & fill it.

The apical third of the root tends to have the most anatomical variation.  For a greater appreciation of the complex anatomy of the apical canal, check out the anatomy shown by Dr. Ronald Ordinola Zapata and others published at the cleared teeth blog.

 The following case demonstrates the occasional need for endodontic surgery, despite adequate non-surgical treatment and retreatment.

Tooth #14 was asymptomatic, but a large pa lesion was noted. Tooth was diagnosed as necrotic pulp with chronic apical abscess (sinus tract present). Note the size of the lesion and its elevation of the floor of the Mx sinus. RCT was recommended.

RCT was completed.

 At 1 yr recall the tooth was still asymptomatic and functional, but the lesion does not appear to be improving as expected and a sinus tract has again appeared.

ReTx completed. No cracks or fractured seen. No additional canals located. No sign of the cause of initial failure.

7 month recall after Retx. Tooth still asymptomatic and fully functional, but sinus tract returned.  Apicoectomy recommended.

 

 

 

 

Apicoectomy completed under microscope with MTA retrofill

6 month recall following apico finds the tooth asymptomatic, fully functional, periapical bone healing.

 The patient was pleased to be able to save the tooth. The periapical bone has healed nicely and the anatomy of the sinus floor once again looks normal.

In this particular case, non-surgical RCT and retreatment - both done with use of operating microscope, failed to resolve the infection.  Apical surgery was required. At Superstition Springs Endodontics, we are committed to saving teeth and have all treatment options available to help people save their natural teeth.

Apexification using Pulpal Regeneration - 2 Yr Results

At Superstition Springs Endodontics, we are leaders in novel endodontic treatments including pulpal regeneration. The traditional treatment for immature roots of CaOH apexification fails to strengthen the root of the tooth and leaves the root more prone to fracture over the lifespan of the tooth. 

Pulpal regeneration allows "pulp-like" tissue to re-grow into the immature root and continue the development of the root. This provides the root with stronger, thicker root walls. Here's another successful case of pulpal regeneration.

 

This young patient had a traumatic incident to tooth #9 5 months earlier. At our initial evaluation, the tooth responded normal to thermal testing. We decided to monitor the tooth over time. At a follow up visit, #9 exhibited no response to thermal testing with an open apex.

Pulpal regeneration was started. Complete pulpectomy was performed with minimal instrumentation to the apex, and irrigation with 5.25% NaOCl. A blood clot was initiated into the canal, a collagen plug was placed and an (white) MTA coronal barrier was placed below the level of the CEJ.

At six month recall, the tooth is asymptomic and functional. The radiograph shows dentinal bridging apical to the MTA placed intracoronally.

 

A sagittal view using CBCT also clearly shows the dentinal bridging below the MTA plug.

At the 2 yr recall of #9, the tooth is asymptomatic, fully functional and orthodontic treatment has been completed.

Root Canals Heal Dental Abscesses

This small video shows three necrotic teeth with apical abscesses that are all completely healed within 1-2 years. This video clip can be used to help your patients understand how endodontic therapy can save their natural teeth. It is posted on our YouTube channel. Feel free to use it for your patient education.



YOUTUBE LINK: http://www.youtube.com/watch?v=CKPRcc6MBAU

CBCT Reveals Root Resorption Unseen in Regular Radiography

The following case shows the advantage of CBCT in endodontic diagnosis.


The following patient returned to our office today for re-evaluation of #14. We previously looked at #14 which had some gingival swelling, yet we could not definitively diagnose the tooth as necrotic. We assumed the swelling was a periodontal abscess and had given him an antibiotic. He returned reporting no relief with the antibiotic and short, spontaneous episodes of severe pain. Once again our diagnostics were inconclusive. Normal to palpation, normal to percussion, normal to probing, responsive to cold on the lingual and unresponsive on the buccal, normal response to EPT. The canals were obviously calcified and the pdl looked normal around the roots. We decided we would take a CBCT to see if we could see any additional radiographic changes.

The CBCT clearly shows a resorptive defect on the palatal. The CBCT also tells us the location (mesio-palatal), the size of the defect which allows us to make a restorative call.

Look again at the initial film. There is no sign of this resorption with traditional 2D imaging. CBCT continues to surprise me.

The Importance of Quality Initial Root Canal Therapy

It is fair to say that endodontic retreatment has a lower success rate than initial endodontic therapy. This highlights the importance of good INITIAL endodontic therapy.

In a study by Boucher et. al. (2002) to evaluate the quality of endodontic treatment in a French subpopulation of 204 patients, looking at approximately 2,010 obturated canals, found that canals were filled to an acceptable standard 21% of the time.

Chueh et. al. (2003) in a similar study in Taiwan to evaluate root canal filling for length and fill density in 1085 RCT cases found similar results. Their study found that RCT fill and/or length was inadequate 70% of the time.

Gumru et. al. (2011) in a similar study, using a Turkish subpopulation, looked at 459 root filled teeth and found the technical quality inadquate 60.1% of the time.

After looking at the data reproduced by these studies, it would be reasonable to say that the number of endodontic retreatment cases could be reduced by improving the quality of initial endodontic therapy. If we know that initial endodontic therapy has higher success rates than endodontic retreatment, it is our duty to make good treatment decisions and give our patients the best chance for successful initial endodontic therapy. This may mean referral to a specialist on more difficult cases such as molars, RCT through crowns/bridges or cases with calcified canals. Deciding when to refer to an endodontist can be a difficult decision. The AAE has published a case difficulty assessment form to help dental professionals with that decision making process.

With all that being said, there has been a lot of misinformation regarding endodontic retreatment. While success rates for retreatment are lower than initial endodontic therapy, at Superstition Spring Endodontics, we have excellent success with retreatment. The case below demonstrates that when retreatment is able to correct the issue causing initial failure, success is achievable.



To find out an accurate success rate of endodontic retreatment, click here or come to our upcoming Inner Space Seminar.

SOURCES:

Boucher et. al. "Radiographic evaluation of the prevalence and technical quality of root canal treatment in a French subpopulation". Inter Endod Journ 2002; 35:229-238.

Chueh, L.H. et. al. "Technical quality of root canal treatment in Taiwan". Inter Endod Journ 2003; 36:416-422.

Gumru et. al. "Retrospective radiological assessment of root canal treatment in young permanent dentition in a Turkish subpopulation". 2011;44:850-856.

The Isthmus

Devoted readers and astute clinicians know of the importance of the isthmus.  I found this definition for isthmus online on dictionary.com:  a connecting, usually narrow, part, organ, or passage, especially when joining structures or cavities larger than itself.   In the case of canal anatomy, we're referring to a narrow band of tissue connecting two canals.  These isthmus areas can occur in any tooth with multiple canals, and can be seen all the way back in the images published by Hess in 1925.

Recently, researchers are using micro-ct imaging to have a more accurate map of the anatomy.  The next image is from http://rootcanalanatomy.blogspot.com/, a great resource for understanding canal anatomy.  We can see the red color representing the preparation of the canals by rotary files, and the green area of unprepared canal space in the isthmus areas.  It is evident from this image that our rotary instrumentation alone does not address but a small percentage of the canal anatomy.

Between the two mesial canals of a mandibular molar is a very common area to find isthmus tissue.  Traditionally ignored by clinicians without a microscope, the isthmus has become a recent target for canal disinfection.  I typically reserve cleaning the isthmus as a final step in my cleaning and shaping process.  Once both canals have been cleaned, I can zoom in with the microscope and examine the area between them.  The coronal third of a canal isthmus can be troughed with a small abrasive ultrasonic tip like these from Tulsa/Dentsply: 

I prefer the 3 or 4.

The middle and apical third are trickier to access.  Often we are relying on our irrigation techniques to flush debris from the isthmus in the bottom third of the root.  There are many supplemental disinfecting protocols on the market.  Techniques range from the simplest plunging with a gutta percha cone (manual dynamic agitation) to using a complex vacuum system (apical negative pressure).  I highly recommend readers familiarize themselves with Gu's excellent review of irrigant agitation techniques found online here: http://www.endoexperience.com/userfiles/file/review_of_irrigation_agitation.PDF.  In a research project at MCG, we found apical negative pressure (using the Endovac) to be slightly more effective than manual dynamic agitation at removing isthmus debris (Susin 2010).  More importantly, we found neither technique could consistently produce clean isthmus histology slides like this one reproduced from this article by Gutarts, Nusstein, Reader, and Beck (reprinted here: http://www.endoexperience.com/userfiles/file/unnamed/Ultrasonic%20irrigation%20%20Gutarts%20et%20al%20JOE%202005.pdf): 

Clinically, I have experience using many of the techniques described in Gu's article, and, after using passive ultrasonic agitation for years, I have recently switched to the Endoactivator's sonic agitation.  I am not convinced whether one technique is strictly superior to another, but I highly recommend you use some form of advanced irrigation in your practice, especially in necrotic cases.

These retreatment images by Dr. Stephen Parente show debris and necrotic tissue within the coronal third of the canal isthmus of a mandibular first molar.  The original root canal treatment was performed outside of our practice several years ago by a different dentist.  An ultrasonic tip described above was used to clean the area.

Preop.  There was some concern of finding a vertical root fracture, but there was no detectable attachment loss.

Contaminated debris within access.

Mesial isthmus exposed full of debris.

Cleaned of all debris using an ultrasonic tip.  No fractures evident.

With the previously described limitations to our cleaning of the canal isthmus, we may conclude that we are occasionally "entombing" some bacteria or necrotic tissue within the isthmus area with our obturation materials.  In those cases where bacteria persist through all our advanced cleaning and find a portal of exit, we must rely on a different approach to resolve apical inflammation and infection.

These next images, captured from a recent mandibular molar apicoectomy of mine, demonstrate an unclean isthmus from the apical view.  The original root canal treatment was performed outside of our practice several years ago by a different dentist. 

Preop 1.  Apical radiolucency on mesial root.

Upon root resection, we see a stained black isthmus area between the canals.

A contra-angled surgical ultrasonic tip was used for the retroprep and to clean the isthmus area.

MTA was used for the retrofill.

Immediate post op radiograph.

These two case images illustrate approaches to correct unclean isthmus areas that can contribute to treatment failure.  With good magnifcation, and with advanced irrigation, we can clean the isthmus and avoid having to recommend retreatment or apicoectomy procedures.  If you have any questions or comments, please let us know.  


As always, more cases and thoughts on endodontics can continually be found on our practice's facebook page, www.facebook.com/alpharettaendo.  

Thanks to Dr. Stephen Parente for supplying the retreatment images.  

Thanks to The Root Canal Anatomy Project for supplying the micro-ct image.

Gu L, Kim J, Ling J, Choi K, Pashley DH, Tay FR. Review of Contemporary Irrigant Agitation Techniques and Devices. J Endod 2009; 35: 791-804.

Gutarts R, Nusstein J, Reader A, Beck M. In vivo debridement efficacy of ultrasonic irrigation following hand-rotary instrumentation in human mandibular molars. J Endod 2005;31:166–70.

Susin L, Liu Y, Yoon JC, Parente JM, Loushine RJ, Ricucci D, Bryan T, Weller RN, Pashley DH, Tay FR.  Canal and isthmus debridement efficacies of two irrigant agitation techniques in a closed system.  Int Endod J 2010; 43: 1077-90.

Use of CBCT to Detect Small Apical Lesions & Length Determination in Endodontics

Two recents studies published highlight some of potential applications of CBCT in endodontics.

The first study by Tsai et. al. supports our clinical experience with CBCT, that it is more effective than traditional periapical films at detecting small lesions.

This study was designed to test the effectiveness of CBCT in detecting very small apical lesions created using small burs on human cadavers. It also compared the Kodak 9000 3D (now called Carestream with the demise of Kodak) and the J. Morita Veraviewepocs 3De. This study showed that both CBCT units were fair-good at detecting simulated lesions with a diameter between 0.8-1.4mm and excellent accuracy with simulated lesion >1.4mm diameter. Traditional periapical films were poor at best, in detecting lesions of these sizes. Another interesting find in this study was that there was no statistically significant difference between the two CBCT units evaluated. These two CBCT units are by far the most common in use by endodontists because of there focused field size, lower radiation dosage and high resolution.

The second study by Jeger et. al. indicate that CBCT may be an effective tool for measuring working length in anterior teeth compared to electronic apex locators. The patients in this study had previously received a CBCT and then required endodontic treatment on an anterior tooth included in the scan. The root canal length was measured by an endodontist using an apex locator. This length was compared with a measurement taken from the CBCT in a vestibulo-oral and mesio-distal CBCT slices by an examiner not involved in the endodontic treatment.

The Pearson correlation coefficient (r) comparing the the CBCT measurements with the apex locator was 0.97. The CBCT also showed higher intrarater reliability 0.99.

With the incorporation of CBCT into our practice of endodontics at Superstition Springs Endodontics, we have found many uses for CBCT that we did not initially plan on. Length determination using CBCT prior to treatment is just another potential application of CBCT in endodontics.

For a clinical example, let me share one of my cases that demonstrates both of these applications.

Tooth #29 has what looks like a fairly normal pdl. Whild some condensing osteitis is noted, without symptoms, I would consider this WNL.

CBCT clearly show periapical lesion on #29 with cortical plates in tact. A clear example of ability of CBCT to show more accurately the minor changes in the bone.

With this added radiographic evidence, the tooth was diagnosed as necrotic pulp and endodontic treatment was completed. My working length was 20.0mm.

After completion of RCT, I went back to CBCT and measured length, from coronal height to radiographic apex in a coronal and sagittal views. The length determined by CBCT was 20.5mm and my working length as determined by Root ZX - 0.5 mm short of apex - was 20.0mm.

This particular case shows the ability of CBCT to help detect small lesions and determine working length.

CBCT is the future of endodontics!

Sources:

Tsai P, Torabinajad M, Rice D, Azevedo B. "Accuracy of Cone-Beam Computed Tomagraphy and Periapical Radiography in Detecting Small Peripaical Lesions". JOE 2012, 38:7, p 965-970.

Jeger F.B., Janner S.F.M., Bornstein M.M., Lussi, A. "Endodontic Working Length Measurement with Preexisting Cone-Beam Computed Tomography Scanning: A Prospective, Controlled Clinical Study". JOE 2012, 38:7, p 884-888.