Is Endodontic Retreatment Passé?

INTRODUCTION
The definition of passé means to be no longer current or out of date. With the fast rise of dental implants now being done by almost any dental provider, endodontic retreatment has been slowly waning. So, who’s at fault for this dilemma? Is it the dentist, the endodontist, or the dental companies? I believe everyone plays a part in this issue. However, it is our duty as dental professionals to give the most current recommendation to our patients based on evidence-based research. Unfortunately, this has not been practiced lately, especially during this time of economic uncertainty.
In 2007, I attended a practice management seminar in Las Vegas. The practice management guru told me if I was not placing implants within the next 2 to 3 years, my endodontic practice would be in jeopardy. This alarmed me, so I decided to do some soul searching. I had to ask myself, “Should I learn to place implants as an endodontist to sustain my practice for several years to come?” Well, I had another thought; therefore, I asked myself another question: “If it were my tooth, who would I want to perform the implant surgery?” The answer was simple: The one who is most qualified to perform the procedure (based on successful completion of an accredited residency program) and can handle any complications, should they arise. Based on this thought process, I decided to stay in my lane and to focus on being the best endodontist I can possibly be. As a result, my practice has been sustained during these economic times because people still want to save their natural teeth!
As with anything “new,” the “hotness” has to die off before we can look at the cold, hard facts. Similar to when the original root canal filling material was gutta-percha and then it changed to silver points, or a combination of both, about 46 years ago. After some time, we realized silver points leak and corrode contributing to apical periodontitis.¹ Now, years later, we are back to using gutta-percha (or some form thereof) as the root canal obturation material of choice. Perhaps we may see this cycle repeat itself again when comparing true success rates or “retained rates” of endodontic retreatment versus implants long-term.
According to the American Association of Endodontist (AAE) in 2010, there are more than 15 million root canals performed in the United States each year. In addition, according to the AAE, dentists refer an average of 46% of their root canal patients to an endodontist. This means more than one half of root canal therapies are performed by the general dentist (GP).
Studies have shown that success rates of conventional endodontic treatment can be upwards of 95%.² In a survey of survivability of endodontically treated teeth completed by endodontists and GPs, endodontists experienced significantly greater success (98.1%) than did general dentists (89.7%).³ New techniques, in-depth training, microsurgical instruments, new materials, microscopes, and understanding biological principles inside and outside the root canal system have greatly enhanced the endodontist’s ability to successfully treat and/or retreat endodontically involved teeth.
Although initial root canal therapy success rates are very high, patients can experience “post-treatment disease,” as coined by Dr. Shimon Friedman in 2002.4 When this happens, conventional endodontic retreatment has been suggested as preferable to surgical intervention.5 “Endodontic retreatment has been defined as a procedure performed on a tooth that has received prior attempted definitive treatment, resulting in a condition requiring further endodontic treatment to achieve a successful result.”⁴ According to Bergenholtz et al,⁵ overall average retreatment usually results in successful outcomes of 75%. However, successful retreatment can be as high as 98% in teeth without apical periodontitis (no lesion present), according to Sjogren et al⁶ in a 10-year follow-up; and as high as 86% in teeth with apical periodontitis (lesion present), according to Farazneh et al⁷ in a 4-year follow-up.⁸ This article is an introduction to nonsurgical retreatment, and it will also highlight some of the issues that cause root canal failure. There will be 5 mini case examples presented and discussed. The purpose of this article is to: (1) Discuss reasons for endodontic failure; (2) Discuss when retreatment should be considered; and (3) Demonstrate that endodontic retreatment has a high rate of success and long-term predictability.

WHY DOES ROOT CANAL THERAPY FAIL?
There are a number of common causes for endodontic failure. Among these are: leaky restorations, root fractures, untreated canals, inadequately cleaned canals, operative errors (such as errors in placing posts), separated instruments, blocks, ledges, perforations, zips, and transportations.⁹ We need to keep all these considerations in mind when performing root canal therapy. There are no 2 cases, nor 2 patients, exactly alike.

Case 1
This patient presented with spontaneous pain associated with tooth No. 30. He said his root canal was performed more than 10 years ago. The diagnosis was previous endodontic treatment with acute apical periodontitis. The tooth was restored with 2 posts and a crown. There was no probing, swelling, or significant mobility (Figures 1a to 1e).
Tooth No. 30 had to be extracted, and then the patient later received an implant in the site from an oral surgeon. This was a case that, although the final case looked acceptable in the postoperative radiographs at the time of treatment, the patient unfortunately had developed post-treatment disease 2 years later, resulting in an extraction and implant placement.

Case 1 Figure 1a. Tooth No. 30; previously treated with a periapical lesion. Figure 1b. Tooth No. 30 was disassembled utilizing ultrasonics to remove the posts. No apparent crack was noted using the surgical microscope. Calcium hydroxide was placed for 3 weeks. Figure 1c. Case completed with gutta-percha, and the patient was asymptomatic. Figure 1d. Patient returned 2 years later with a buccal sinus tract associated with tooth No. 30. Figure 1e. Exploratory surgery revealed a vertical fracture in the mesiobuccal root.

When Should Retreatment be Considered?
Biological, aesthetic, clinical, functional, and financial factors must be considered.

1. The periodontal status is of the utmost importance: (a) Periapical and bite-wing radiographs must be evaluated to make sure the tooth has a solid foundation; (b) The attachment apparatus must be intact; (c) Periodontal probing must be within normal limits unless a sinus tract is draining from the sulcus; (d) Good crown-to-root ratio.
2. Evaluate tooth restorability: (a) Strategic value; (b) Remaining tooth structure; (c) Periodontal support.
3. Access patient concerns: (a) Cost; (b) Expectations; (c) Motivation.
4. Communicate clearly to the patient before retreatment: (a) Diagnosis; (b) Prognosis; (c) Treatment options just in case the tooth can’t be saved.

Case 2
The patient’s chief complaints were as follows: tooth No. 19 hurt sometimes; his crown kept falling off; and, in addition, there was a “bump” on his gum (Figures 2a to 2h). Upon clinical evaluation, it was noted that there was a buccal sinus tract associated with tooth No. 19 that could not be traced. There was no mobility and probing was 3.0 mm circumferentially. As demonstrated in the radiographs, the tooth had been previously obturated with silver points, and there was a large periapical lesion associated with the distal root of tooth No. 19. The diagnosis was previous root canal treatment with an associated chronic apical abscess.

Case 2 Figure 2a. Tooth No. 19 with crown removed and buccal sinus tract. Figure 2b. Tooth No. 19 pre-op showing silver points and a periapical lesion on the distal. Figures 2c and 2d. Ultrasonics (ENAC [Osada USA]), on low power under the surgical microscope, was used to remove the silver points. It was very important not to hit the silver points with the ultrasonic tips because it could have broken the silver points more apically inside the canals, making retrieval more difficult. Calcium hydroxide paste was placed for 2 weeks. Figures 2e and 2f. Four corroded silver points were removed with a pair of Stieglitz forceps. Figure 2g. Obturation was completed with gutta-percha, with Cavit (3M ESPE). Figure 2h. Tooth was restored; this is a 4-year recall showing healing.

Case 3
This patient presented with a chief complaint of pain when biting on tooth No. 15 (Figures 3a to 3c). She reported that her root canal therapy had been completed more than 20 years ago. There was no evidence of mobility, and probing was within normal limits. Radiographically, there was a silver point in the distobuccal canal. The mesiobuccal and palatal canals appeared to be underfilled with a pastelike material. The diagnosis was previously treated with acute apical periodontitis.

Case 3 Figure 3a. Tooth No. 15 preoperative radiograph. Figure 3b. Ultrasonics was used to remove the silver point in the distobuccal canal. Chloroform was used with a combination of Gates Glidden drills and Hedstrom (SybronEndo) files to remove the paste. Figure 3c. Located an MB2 with the surgical microscope; all canals were then obturated with gutta-percha.

Case 4
In this case, the patient presented with pain and swelling associated with tooth No. 3 (Figures 4a to 4d). She said a GP had completed the root canal procedure about 5 years previously. The tooth had a crown, a large post, and a large periapical lesion. The diagnosis was previous endodontic treatment with an acute apical abscess.

Figure 4a. Preoperative radiograph revealed a large periapical lesion. Figure 4b. Tooth was disassembled and calcium hydroxide placed for 2 weeks. Figure 4c. MB2 was located and canals were obturated with gutta-percha. Figure 4d. Six-month recall showing healing.

Case 5
The final case example is shown in Figures 5a to 5e. Patient “x” presented with pain upon biting. She reported her root canal procedure was completed by her GP about 6 months previously. Her chief complaint included sharp pain and that it felt like there was something in her right jaw bone.

Figure 5a. Patient “x.” Figure 5b. Preoperative radiograph of tooth No. 30, showing previous endodontic treatment with overfill in the mesial and a separated instrument in the distal. Figure 5c. Tooth No. 30 was disassembled. Thermofil was used to obturate the tooth. Thermofil was removed using a Touch’n Heat tip (Sybron Endo) and a Hedstrom file (Sybron Endo) screwed into the remaining material. The separated file was removed using ultrasonics after staging with a cut-off tip No. 4 Gates Glidden Drill. Figure 5d. Overextended Thermofil material was removed, including a separated rotary file tip (first object). Figure 5e. Final obturation with gutta-percha (done in one visit).

DISCUSSION
Clinicians should look at the overall case before choosing to retreat a tooth themselves. Ethical questions should arise as to who is best qualified to produce the desired result. In addition, the clinician must consider balancing desire and monetary issues with what is best for the patient. Ask yourself what you would want if it were your tooth. In most instances, a referral to an endodontist is prudent.

Figure 6. Global Surgical Microscope (Global Surgical Corporation).	Figure 7. Mineral trioxide aggregate (ProRoot MTA [DENTSPLY Tulsa Dental Specialties]).

Dental implants are excellent treatment options in cases when natural teeth cannot be saved. However, an implant should never be used as the “gold standard” when a previous root canal-treated tooth has failed to heal. The erroneously perceived high rate of treatment success and “ease” of procedure when inserting single-tooth implants, compared with endodontic treatment, has often biased the GP’s objectivity in recent years when selecting treatment options. As a result, the endodontist usually gets isolated from the patient’s overall treatment plan. This definitely needs to be reconsidered, especially since the advent and advancement of new materials and technologies in endodontics (such as mineral trioxide aggregate [a “miracle” material] and surgical microscopes) are increasing the success rates even more (Figures 6 and 7).
According to Doyle et al,¹⁰ restored endodontically treated teeth and single-tooth implant restorations have similar failure rates. However, the implant group was reported to have more maintenance issues and postoperative complications. The postoperative complications were confirmed by the research of Goodacre et al¹¹ at Loma Linda University and included: hemorrhage, neurosensory disturbances, adjacent tooth devitalization, mandibular fracture, air emboli (sometimes fatal), and implant abutment screw loosening/breakage.

CLOSING COMMENTS
This article is an attempt to persuade and convince all dental professionals not to give up on an endodontically treated tooth that may be a candidate for retreatment. In most cases, nonsurgical retreatment is performed to reduce the need for surgery, or to increase the prognosis for a future surgery. In addition, it is more effective from a cost and biological perspective to maintain a person’s natural tooth. With the latest advances in technology (magnification, illumination, ultrasonics, apex locators, rotary instrumentation, advances in intracanal irrigation and medicaments, and devices to remove or bypass intracanal obstructions), nonsurgical retreatment is very often possible and highly successful.

References

1. Brady JM, del Rio CE. Corrosion of endodontic silver cones in humans: a scanning electron microscope and X-ray microprobe study. J Endod. 1975;1:205-210.
2. Torabinejad M, Anderson P, Bader J, et al. Outcomes of root canal treatment and restoration, implant-supported single crowns, fixed partial dentures, and extraction without replacement: a systematic review. J Prosthet Dent. 2007;98:285-311.
3. Alley BS, Kitchens GG, Alley LW, et al. A comparison of survival of teeth following endodontic treatment performed by general dentists or by specialists. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004;98:115-118.
4. Cohen S, Burns RC. Pathways of the Pulp. 8th ed. St. Louis, MO: Mosby; 2002:791-834.
5. Bergenholtz G, Lekholm U, Milthon R, et al. Retreatment of endodontic fillings. Scand J Dent Res. 1979;87:217-224.
6. Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod. 1990;16:498-504.
7. Farazneh M, Abitbol S, Friedman S. et al Treatment outcome in endodontics: the Toronto study. Phases I and II: orthograde retreatment. J Endod. 2004;30:627-633.
8. Friedman S, Mor C. The success of endodontic therapy—healing and functionality. J Calif Dent Assoc. 2004;32:493-503.
9. Lin LM, Skribner JE, Gaengler P. Factors associated with endodontic treatment failures. J Endod. 1992;18:625-627.
10. Doyle SL, Hodges JS, Pesun IJ, et al. Retrospective cross sectional comparison of initial nonsurgical endodontic treatment and single-tooth implants. J Endod. 2006;32:822-827.
11. Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JY. Clinical complications with implants and implant prostheses. J Prosthet Dent. 2003;90:121–132.

Dr. Short is a board-certified endodontist in private practice near Atlanta in Smyrna, Ga. He also serves as an expert consultant to the Georgia Board of Dentistry, and is an assistant clinical professor at the Medical College of Georgia School of Dentistry. Dr. Short is also a published author (including the Journal of Endodontics) and a featured national lecturer. He can be reached at dr.short@yahoo.com.

Disclosure: Dr. Short reports no disclosures.