The Importance of Increasing the Success Rate: A Look at Procedures, Factors, and Clinical Practices

INTRODUCTION
When I first started to practice dentistry, I asked myself what is im­portant when treating patients. My answer was: “a high clinical success rate.” Not only is it important to make sure that what you do for your patients will actually work, but the clinical success rate can also be used as a benchmark to measure what techniques and products will directly benefit your practice and your patients. If the clinical success rate reported is the same for similar products or techniques, then one can fall back on Dr. Gordon Christensen’s criteria for evaluation: Is the technique or product “easier, cheaper, faster and/or more predictable to use”? If the answer is yes, then switch to the new technique or product. If the answer is no, then stay with what you are currently using.

To measure how I was actually doing clinically, I needed to compare my clinical success rate in the office with what was being reported in the literature. This required some work. That work was published in 2001.¹ It showed that my clinical practice had a 94.1% clinical success rate for its patients. No one gets a 100% success rate because, postoperatively, approximately 4% of the teeth fail and are extracted due to vertical root fractures.² During the years before we published the success rate data, I had been keeping a list of the endodontic failures in our practice for each year. When I first started practicing endodontics in 1976, my recorded success rate was approximately 90%. At that time, I thought that my success rate would get better the longer I was in practice. In other words, as my clinical skills improved (finding canals, instrumentation, obturation), my success rate would also improve (Figure 1).

Figure 1. Graph showing factors that increase our practice clinical success rate.

It turned out that I was wrong; the increase in my success rate had very little to do with my clinical skills. The red line in Figure 1 represents what I thought would be the correlation between improvements in my technique throughout time and an increase in the success rate of my endodontic treatments. A slow but gradual increase in endodontic success was realized as time progressed. The reality was that the success rate increased in discrete increments after each introduction of a new technique, method, factor, or clinical practice into my endo­dontic treatment protocol. For instance, when we started to enlarge the apex to a greater diameter, the success rate increased. When I first started doing endodontics in dental school, it was normal protocol to finish a canal to a 20 or 25 stainless steel instrument with a .02 taper. When we started to take into account the published literature on the anatomic sizes of the different canals on various teeth, we realized that we needed to enlarge the anatomic apex to a larger size. We are currently enlarging most canals to either a 30/.04 or 35/.04. With the larger apical preps we noticed our first jump in the success rate.

OPTIMIZING OPTICS
In the early 1980s, a dental school classmate of mine, Dr. Thomas Frankel (Miami, Fla), convinced me that I would do much better endodontics if loupes were used (Figure 2). Of course, he was right. With loupes, I could see where the canals were with much greater acuity and accuracy. Therefore, I found more canals, and my success rate, once again, jumped up. Naturally, with more magnification and the introduction of the operating microscope, things got even better (Figure 3). The direct light going through the Seiler microscope (Seiler Instrument) and shining on the tooth anatomy greatly sped up the finding of canals and the procedure itself. In the mid-1980s, the first report of the existence of the mesiobuccal 2 (MB2) made its appearance in the dental literature. Since I had been using optics to improve my technique already, it became fairly easy to find these extra canals, thereby increasing the success rate once again.

Figure 2. Seiler 2.5x loupes (Seiler Instrument).	Figure 3. Seiler operating microscope (Seiler Instrument).

ONE-VISIT ENDODONTICS
Once more, one of my classmates came to the rescue. Dr. Sheldon Nadler (New York, NY) suggested that I should be doing single-canal vital cases in one visit. He used this treatment protocol to be able to schedule his patients more quickly, and then to finish their cases faster and with fewer complications. At this point, I researched the literature and found that there were a myriad of studies indicating that there was no difference in clinical success rate between one- versus multiple-visit root canal and the clinical success rate is the same for vital and nonvital cases done in one visit versus multiple visits.^3-9 Quite a shock, since most schools still teach multiple-visit endodontic protocol. Usually, the limiting factor is the speed of the operator doing the root canal treatment. Students are novices in all areas of dentistry; hence, most will take a longer amount of time to treat their patients. And perhaps consequently, the procedure is artificially broken up into multiple visits to address this issue.

In private practice, I look for techniques that will speed up my treatment and allow me to complete the endodontics in one visit if possible. Recently, we sped up the instrumentation portion of the procedure with the use of the Tango-Endo instruments (Essential Dental Systems). Tango-Endo is a tough and reusable 2-instrument reciprocal system that contains a unique patented “flat” along the entire length of the reamers. This flat permits faster engagement with less resistance, increased flexibility without sacrificing strength, and nearly eliminates instrument separation. By using only 2 instruments subsequent to the creation of the glide path, the clinician can cut down the patient chair time substantially.

Figure 4. Demonstration of factors that influence higher endodontic success rates.10

One of the more interesting articles that I have read evaluated the clinical success of 2,000 endo­dontically treated teeth¹⁰ (Figure 4). This article reported that vital teeth were more successfully treated than nonvital teeth. Teeth without lesions were more clinically successful than teeth with lesions. The study also showed that conventional endodontic treatment was slightly more successful than nonsurgical re­treatment. In summary, the study stated that single-appointment treatments were more successful than multiple-appointment treatments, and that a short filling level was more successful than filling material to the apex or in excess. We have found all these factors to be true in our practice and, by doing endodontics in one visit whenever possible, our success rate has increased and our complications have decreased.

APEX LOCATORS AND OBTURATION SHORT OF THE RADIOGRAPHIC APEX
In my practice, we noticed some very interesting correlations when we started to use more accurate multiple frequency apex locators in the mid-1990s. This type of apex locator was getting much more precise readings, and the literature confirmed this. We noticed that when we obturated to the constriction or anatomic apex, we were zero to 2.0 mm short of the radiographic apex a large percentage of the time. Initially, this was worrisome because we were taught (and this is still being taught) that endodontic beauty is achieved by filling to, or level with, the radiographic apex. However, when filled to the anatomic apex, which often was short of the radiographic apex, there were fewer postoperative problems, thus (again) increasing the clinical success rate. What was going on? In a check of the literature, we found a great many articles that reported^2,10-17 more clinically successful root canals were achieved when the obturation material was zero to 2.0 mm short of the radiographic apex. This was exactly what we found in our clinical practice. In a recent article by ElAyouti et al,¹⁸ it was reported that the anatomic apex was short of the radiographic apex in 88% of the canals and that, in 5% of the canals, the foramen was more than 2.0 mm short of the apex (Figure 5). Therefore, clinically speaking, obturations extending to the radiographic apex are actually over fillings in most of the canals. If you eliminate these over fillings, a lot of good things happen clinically. The only tool that can reliably do this is the newer apex locators.

Figure 5. Gutta-percha short of the radiographic apex but way beyond the anatomic apex. This excess gutta-percha is impinging on the periodontal ligament.

Radiographs cannot, and do not, tell you where the anatomic apex is located. The take-home lesson for that increase in success (and the lessening of post-op complications) is to fill to where the apex locator says the constriction or the anatomic apex is located, and to expect to be zero to 2.0 mm short of the radiographic apex a majority of the time. You must readjust your concept of endodontic aesthetics to achieve a better success rate.

CHLORHEXIDINE
Infection is one of the key challenges in endodontics. Unfortunately, instrumentation does not totally remove or sterilize the canal spaces. In order to remove more bacteria from the canals and tubules, we must irrigate with antibacterial agents. One of the best irrigants for this is still sodium hypochlorite, but unfortunately, not all bacteria are susceptible to it. An excellent adjunct to using sodium hypochlorite is the use of a solution of 2% chlorhexidine (CHX). A lower percentage of CHX takes a much longer time to kill bacteria and is not practical for endodontic usage. Once we started to use CHX, we again found an increase in our success rate on nonvital cases. However, in order for the CHX to reach the bacteria that are located in the dentinal tubules, the smear layer that is overlying and closing the tubules must be removed. Therefore, the canal must be rinsed with ethylenediaminetetraacetic acid (EDTA) 17% solution for at least 30 to 60 seconds before we use the 2% CHX. The CHX should be left in the canal for one to 2 minutes in order for it to work. If the canal is left slightly wet with CHX before the obturation, the CHX has the property of substantivity and will continue to kill bacteria for several more weeks. Recently, there have been a few new products on the market that combine smear layer removal and CHX disinfection. One such product is Irritrol (Essential Dental Systems), which combines an antibacterial surfactant and EDTA for smear layer removal, and CHX for disinfection. By doing so, the clinician not only saves time and money, results also show that this solution has a greater disinfection rate (Table).¹⁰

THE PULP CHAMBER SEVEN-MILLIMETER RULE
Eliminating perforations and finding canals in a quantitative fashion was another factor that helped to increase my practice’s success rate. For years, gaining access to the pulp chamber was a qualitative experience. It was all a matter of “feel,” especially in any calcified chambers. Within the last 10 to 12 years, many corroborating papers have been published on pulp chamber morphologic measurements.^18-23 All these papers verify that the distance to the middle of the pulp chamber from a cusp tip is approximately 7.0 mm. It is another 3.0 mm from the floor of the chamber to the closest furcal perforation point. As a result, I now mark my No. 4 round bur with a permanent marker at the 7.0 mm point on the bur. This lets me immediately make my access down to the 7.0 mm depth, which is in the middle of the chamber (or near the floor). No more drill, irrigate, dry with cotton, and then look to see where I am. This technique also eliminated perforations and made it much easier to find even calcified canals; easier because I was now near the level of the floor before the calcifications formed, and where the orifices for the canals originally entered the chamber.

CLOSING COMMENTS
In summary, it was not only my “mastery” of endodontic techniques that increased my endodontic success rate throughout time. It also was obvious that every time the science of endodontics advanced, and if those advances were properly implemented into our daily endodontic protocol, my team observed an increase in the success rates for our clinical results.

References

1. Deutsch AS, Musikant BL, Cohen BI, et al. A study of one visit treatment using EZ-Fill root canal sealer. Endodontic Practice. 2001;4:29-36.
2. Ricucci D, Russo J, Rutberg M, et al. A prospective cohort study of endodontic treatments of 1,369 root canals: results after 5 years. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2011;112:825-842.
3. Penesis VA, Fitzgerald PI, Fayad MI, et al. Outcome of one-visit and two-visit endodontic treatment of necrotic teeth with apical periodontitis: a randomized controlled trial with one-year evaluation. J Endod. 2008;34:251-257.
4. Sathorn C, Parashos P, Messer HH. Effectiveness of single- versus multiple-visit endodontic treatment of teeth with apical periodontitis: a systematic review and meta-analysis. Int Endod J. 2005;38:347-355.
5. Su Y, Wang C, Ye L. Healing rate and post-obturation pain of single- versus multiple-visit endodontic treatment for infected root canals: a systematic review. J Endod. 2011;37:125-132.
6. Peters LB, Wesselink PR. Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms. Int Endod J. 2002;35:660-667.
7. Fleming CH, Litaker MS, Alley LW, et al. Comparison of classic endodontic techniques versus contemporary techniques on endodontic treatment success. J Endod. 2010;36:414-418.
8. Figini L, Lodi G, Gorni F, et al. Single versus multiple visits for endodontic treatment of permanent teeth: a Cochrane systematic review. J Endod. 2008;34:1041-1047.
9. Vieyra JP, Enriquez FJ, Acosta FO. Frequency of postoperative pain in one- versus two-visit endodontic treatment. Endodontic Practice. 2015;8:34-39.
10. Imura N, Kato AS, Zaia AA, et al. Success evaluation of 2,000 endodontically treated teeth. J Endod. 2001;27:234. Abstract PR11.
11. Schaeffer MA, White RR, Walton RE. Determining the optimal obturation length: a meta-analysis of literature. J Endod. 2005;31:271-274.
12. Kojima K, Inamoto K, Nagamatsu K, et al. Success rate of endodontic treatment of teeth with vital and nonvital pulps. A meta-analysis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004;97:95-99.
13. Ng YL, Mann V, Rahbaran S, et al. Outcome of primary root canal treatment: systematic review of the literature—Part 2. Influence of clinical factors. Int Endod J. 2008;41:6-31.
14. Love RM, Firth N. Histopathological profile of surgically removed persistent periapical radiolucent lesions of endodontic origin. Int Endod J. 2009;42:198-202.
15. Peak JD, Hayes SJ, Bryant ST, et al. The outcome of root canal treatment. A retrospective study within the armed forces (Royal Air Force). Br Dent J. 2001;190:140-144.
16. Chandra A. Discuss the factors that affect the outcome of endodontic treatment. Aust Endod J. 2009;35:98-107.
17. Naito T. Better success rate for root canal therapy when treatment includes obturation short of the apex. Evid Based Dent. 2005;6:45.
18. ElAyouti A, Hülber-J M, Judenhofer MS, et al. Apical constriction: location and dimensions in molars—a micro-computed tomography study. J Endod. 2014;40:1095-1099.
19. Azim AA, Azim KA, Deutsch AS, et al. Acquisition of anatomic parameters concerning molar pulp chamber landmarks using cone-beam computed tomography. J Endod. 2014;40:1298-1302.
20. Lee MM, Rasimick BJ, Turner AM, et al. Morphological measurements of anatomic landmarks in pulp chambers of human anterior teeth. J Endod. 2007;33:129-131.
21. Deutsch AS, Musikant BL, Gu S, et al. Morphological measurements of anatomic landmarks in pulp chambers of human maxillary furcated bicuspids. J Endod. 2005;31:570-573.
22. Deutsch AS, Musikant BL. Morphological measurements of anatomic landmarks in human maxillary and mandibular molar pulp chambers. J Endod. 2004;30:388-390.
23. Velmurugan N, Venkateshbabu N, Abarajithan M, et al. Evaluation of the pulp chamber size of human maxillary first molars: an institution based in vitro study. Indian J Dent Res. 2008;19:92-94.

Dr. Deutsch co-operates an endodontic practice in New York City. He holds 18 patents for co-inventing endodontic products for Essential Dental Systems. He is one of the leading authorities in endodontics, having lectured at more than 150 worldwide locations, and has co-authored more than 200 dental articles. He can be reached at info@essentialseminars.org, (800) 223-5394, or essentialseminars.org.

Disclosure: Dr. Deutsch is executive vice president and co-owner of Essential Dental Systems. Some products in this article are manufactured by Essential Dental Systems.