March 2017
Volume 38, Issue 3

What is endodontic success? How successful is endodontic therapy?

Allen Ali Nasseh, DDS, MMSc; James Bahcall, DMD, MS; and Anne Koch, DMD

Dr. Nasseh

According to the most credible academic studies, an endodontic success rate of 89% to 94% should be expected from conventional root-canal therapy. This number varies slightly based on the pulpal and periapical statuses of the tooth at the time of treatment. For example, necrotic pulps with apical lesions have a slightly lower success rate than vital pulps. However, these definitions of success are mostly based on radiographic analysis, using the strictest criteria. In aggregate, and when tooth retention was chosen as the main criterion (similar to implant studies), large-scale epidemiologic studies have demonstrated an 8-year retention rate of 97% for endodontically treated teeth. This shows that endodontic therapy is highly effective in retaining a natural tooth. But what is success?

Clinical success is based on effective treatment of pulpal and apical diseases and preservation of the tooth versus its extraction. However, adequate restoration of an endodontically treated tooth is as important, if not more critical, to the long-term success. As a result, the quality of the restoration should also be considered in this endodontic equation, as endodontic therapy is merely a link in the endodontic-restorative chain. The most effective endodontic treatment will inevitably fail if the tooth is not correctly and efficiently restored. Therefore, while endodontic success alone is dependent on the successful cleaning, shaping, and obturation of the root-canal system, a well-sealing coronal restoration remains a critical factor for the overall success of the case in the long term. This is because endodontic therapy can effectively remove microbes from the root-canal space at the time of treatment, but prevention of recontamination of this space is only possible in the presence of a well-sealing coronal restoration. In the absence of an optimal coronal seal leading to microleakage, the recontamination failure will manifest as an endodontic failure rather than a restorative failure.

Therefore, the success of endodontic treatment is dependent on the quality of the root-canal therapy in the short run and the quality of the ensuing coronal restoration over time. Yes, minimally invasive preparations, irrigation, disinfection, restoration, and proper occlusion all play a role throughout treatment; however, in general, microbial control during and after treatment remain the main source of long-term success for endodontically treated teeth.

Insofar as how long an endodontically treated tooth can last, we can claim a root-canal–treated tooth can potentially last a lifetime, provided it is adequately decontaminated during treatment and remains clean due to the presence of a proper coronal restoration and an apical seal. Therefore, adherence to quality restorations and obturation/restorative materials that retain apical/marginal integrity are the key factors for ensuring long-term success.

We must also consider the objective of endodontics as a field. Traditionally, the main goal of endodontics has been defined as prevention and treatment of pulpal and periapical diseases to save the tooth. While improvements in the quality and efficiency of endodontic procedures have excelled, we have not focused enough on preventing pulpal disease. Prevention is clearly the best way to improve public health and should be a top priority in conjunction with improved therapies. I urge my colleagues in both the endodontic and restorative fields to focus on developing restorative solutions that are minimally invasive to the pulp and can help retain pulp vitality. We succeed as a profession when we aim to preserve the natural biologic properties of the body whenever possible. 

Dr. Bahcall

By definition, success is the accomplishment of an aim or purpose. When applied to clinical endodontic treatment, success has been discussed for more than 50 years. During this time, clinical assessment of endodontic success has been based on radiographic healing of osseous tissue and/or elimination of adverse signs and symptoms, such as spontaneous pain, sensitivity to temperature, mastication, palpation, and/or percussion. Other clinical signs of successful endodontic treatment outcomes are elimination of a sinus tract and/or periodontal pockets that are of endodontic origin. Many classic endodontic success studies published during the 1960s show the standard of success to be lower than what more recent literature suggests due to more stringent definitions. If the lack of clinical and academic knowledge in endodontics is considered, it is easy to see why reported findings during this period demonstrated lower treatment success.

In the last 20 years, the endodontic research has reported high success rates in treatment outcomes from both conventional and surgical endodontic therapies. The basis of this increased treatment success is derived from advancements in treatment techniques and materials through evidence-based practice, the usage of cone-beam computed tomography (CBCT), understanding clinical success through implantology literature, proper case diagnosis, phase treatment, and the correlation of endodontic and restorative treatment.

Evidence-based endodontic treatment is the clinical foundation of successful conventional and surgical endodontic treatment outcomes. As in any healthcare profession, advancements in science and technology continue to improve treatment outcomes. The advancements in endodontic knowledge, clinical techniques, and materials, as reported by the literature, have been associated with better treatment outcome success.

The use of CBCT in endodontics has done for endodontic radiology what the microscope and endoscope did for advancing visualization in clinical endodontics. CBCT provides the clinician with a more three-dimensional radiographic view of what was a limited two-dimensional assessment from an endodontic traditional periapical or bitewing radiograph. Recent studies have shown the use of CBCT was more effective in detecting periapical lesions than conventional periapical radiographs. This information can better enhance identifying etiology and allow for more targeted endodontic treatment, thus leading to better treatment outcomes.

Most implant literature uses survival as the sole “success” criterion. When this is applied to endodontic success, it automatically makes the stated criterion in the literature less stringent and, therefore, improves endodontic treatment outcomes.

Other factors that have increased endodontic treatment success are proper case diagnosis, phase treatment, and the correlation of endodontic and restorative treatment. Endodontic diagnosis is the starting point of achieving successful treatment outcomes. Understanding that a major factor in endodontic treatment failure is the persistence of microbial infection in the root-canal system and/or periradicular area is also important. In addition, realizing a pulpitis is inflammation and not infection is just as crucial. Through proper diagnostic information in either case scenario, a clinician can improve treatment success by choosing the correct endodontic treatment armamentarium and technique to better achieve thorough chemomechanical canal debridement along with proper obturation.

Endodontic phase treatment can consist of and progress from initial root-canal therapy to root-canal retreatment and/or apical surgery. An example is a case in which the patient presented with a necrotic pulp and preoperative periapical rarefaction. After conventional endodontic treatment, the patient returned for 6-month and 1-year recall appointments, but the radiographic lesion had not changed. Instead of deeming this a treatment failure, the patient’s dental providers performed endodontic surgery to remove the lesion. At a 6-month recall following surgery, the lesion had completely healed. Therefore, it was a successful outcome.

The connection between endodontic treatment and restorative dentistry is paramount for endodontic treatment success. Coronal leakage has been documented as a cause of endodontic treatment failure. However, the literature has also reported an endodontically treated tooth that has not been restored after root-canal therapy was four times more likely to undergo extraction than a restored tooth.

Endodontic treatment outcomes will continue to show improvement as compared with previous reports in the literature. With the advancements of new technology, materials, and treatment modalities, clinicians will be better able to clean and obturate canals along with providing better restorative materials to reduce coronal leakage, thus improving their endodontic treatment success rates.

Dr. Koch

What is endodontic success? This is the essence of what we do as endodontic specialists, and it can be answered in various ways. However, I believe endodontic success means retaining the natural dentition. This is somewhat personal for me, as I worked for 14 years in prosthodontics prior to my endodontic training. Endodontics is not about the x-ray or image; our practices should not be dictated by radiodontics. Surely, we all want our cases to “look good,” but more important is the patient’s experience and the long-term retention of the tooth. A satisfactory radiographic finding doesn’t matter if we lose the tooth a few years later to a root fracture. I have seen this so often in my career when endodontically treated teeth have been cored out in the coronal third of the root, to accommodate obturation techniques. This weakening of the tooth, due to excessive dentin removal, becomes problematic, particularly if a post is placed or the tooth is subject to heavy occlusal forces.

We must think of endodontic success as being connected to an “endo-restorative continuum,” in which an intimate relationship exists between endodontics and prosthodontics. These are not separate entities; the dentist who is placing a post in a tooth is in the same space as the person who performed the root canal. The best post drill possible, in my opinion, is the last rotary file used. This is why I am excited about the availability of new endodontic instruments, which, due to their unique design, have the ability to clean the root-canal space three dimensionally while removing a minimal amount of tooth structure. The use of the instruments, when employed with a bioceramic filling technique, is a truly biologic approach to endodontic therapy. More importantly, this combination in its simple approach will allow us to maintain and save teeth in a far more predictable manner than previously seen in endodontics.

In 1975 when I was a dental student at the University of Penn­sylvania in Philadelphia, I performed three root canals on a patient (all in a single visit). How successful were they? She retained these teeth until her death 35 years later. Well-executed endodontics most assuredly can last a lifetime. The key is to not destroy the tooth in the process of performing the root canal. Fortunately, we now have the ability to predictably maintain the dentition through use of the innovative instruments and a bioceramic filling technique. This combination will be a game changer.

Keeping a tooth instead of extracting it and placing a fixture? Now that’s what I call endodontic success.

Allen Ali Nasseh, DDS, MMSc
President, RealWorldEndo™
Wilmington, Delaware
Clinical Instructor
Department of Restorative Dentistry and Biomaterial Sciences
Harvard University School of Dental Medicine
Boston, Massachusetts
Private Practice
Boston, Massachusetts

James Bahcall, DMD, MS
Clinical Associate Professor
Department of Endodontics
University of Illinois-Chicago School of Dentistry
Chicago, Illinois
Diplomate
American Board of Endodontics

Anne L. Koch, DMD
Adjunct Assistant Professor

Department of Endodontics
University of Pennsylvania School of Dental Medicine
Philadelphia, Pennsylvania
Senior Fellow
Penn Medicine
Philadelphia, Pennsylvania

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