Dental Tribune United Kindom Edition

July 30 - August 5, 2012United Kingdom Edition12 Endo Tribune R oot-canal treatment has been shown to have a success rate of 92 per cent.1 However, as research methodologies move towards higher levels of substantia- tion, clinicians must rely on the best current evidence available to gain insight into the expected outcomes of their treatment. The highest level and best current evidence we have on the clinical success of endodontic treatment comes from a meta-analysis of the literature. A meta-analysis done in 2007 by Ng et al. provides a thorough review of endodon- tic success rates from a vari- ety of classical outcome stud- ies. They found a weighted pooled success rate of 68 to 85 per cent, with at least one year of follow-up.2 This re- view considers the strictest of criteria for determining that a tooth has healed, and includes many studies that were com- pleted prior to the clinical use of dental operating micro- scopes and other advanced ar- mamentaria. When considering treat- ment for a tooth that has not healed successfully with root- canal therapy, there are sig- nificant challenges to address to be able to attain complete healing of the diseased tooth. The armamentarium and techniques available today al- low us the ability to disinfect the root-canal system prop- erly after initial treatment has led to post-treatment disease. The success rate of retreat- ment has been shown to be in the range of 80 per cent heal- ing. Phases III and IV of the Toronto Study showed such a healing rate four to six years after non-surgical retreat- ment.3 In a systematic review by Torabinejad et al. com- paring non-surgical retreat- ment to endodontic surgery, it was demonstrated that non- surgical retreatment had a success rate of 83 per cent versus 71.8 per cent for endo- dontic surgery after four to six years.4 The presence of pretreat- ment apical periodontitis is one factor that has been shown to decrease the success rate. Without apical periodon- titis, a ten-year success rate of 92 to 98 per cent has been shown for both initial and re- treatment root-canal therapy. With the preoperative pres- ence of apical periodontitis, there is a decrease in the suc- cess rate to 74 to 86 per cent over the 10 years.5 From this, it is evident that endodontic healing is attainable through retreatment procedures, al- lowing us to maintain our patients’ natural teeth (Figs. 1a–c). Although the alterna- tive clinical treatment option of implant placement can provide an effective method for replacing a missing tooth, healthy maintenance of the natural tooth should remain the overall goal. Post-treatment disease is, inevitably, a result of bacteria and the host response of the patient to the bacteria. These micro-organisms are the most critical aetiology of post- treatment disease, as they are present within the root-canal system of a previously endo- dontically treated tooth owing to a combination of substand- ard endodontic techniques, iatrogenic treatment issues and restorative failure. Intra-radicular bacteria are the primary aetiology of post-treatment disease6 and eradication of these bacteria is the primary goal of retreat- ment procedures. The intra- radicular bacteria present in the previously treated tooth are persistent and resist re- moval methods. Bacteria are able to hide and survive in canal ramifications, deltas, irregularities (fins) and den- tinal tubules.7 Figure 28 shows the com- plex root-canal anatomy pre- operatively (green areas) and the minimal amount of canal-wall cleansing that was accomplished during canal instrumentation (red areas). The remaining green areas il- lustrate the space that might be left untreated, thereby pro- viding a source of bacteria and supporting substrate for intra- canal infection. The poten- tial substrates that are found inside the canal and help the bacteria survive can include untreated pulpal tissue, the presence of a biofilm and tis- sue fluid. This may be present in the canal owing to a poor coronal or radicular seal and microbial proliferation. The presence of a poor seal, bac- teria and substrate for their growth results in ideal condi- tions for persistent inflamma- tion and disease.9 The bacteria present in the initial infection of a root canal differ markedly from the bacteria infecting a previ- ously treated tooth. Pretreat- ment flora is polymicrobial with equal numbers of Gram- negative and -positive bacte- ria. Post-treatment bacteria are predominantly Gram-pos- itive10 and they have been shown to be able to survive in harsh environments and to be resistant to many treatment methods. There are high numbers of Enterococcus species.11 Ente- rococcus faecalis, for exam- Fig 1a: Tooth #19 shows a radiolucent periapical lesion around the mesial root apex and into the furcation Fig 1b: Post-op radiograph Fig 1c: One-year follow-up radiograph. (Courtesy of Dr Brett E. Gilbert) Fig 2: The unprepared pulpal tissue (green) and the post-op prepared or instrumented areas (red), showing the complexity of the root-canal anatomy and the difficulty in completely cleansing the root-canal system. (Courtesy of rootcanal- anatomy.blogspot.com) Fig. 3a: Tooth #30 with a radiolucent periapical lesion with evidence of incomplete cleansing, shaping and obturation Fig 3b: Post-op radiograph.Fig. 3c: Thirteen-month follow-up radiograph. (Courtesy of Dr Brett E. Gilbert) Fig. 3c: Thirteen-month follow-up radio- graph. (Courtesy of Dr Brett E. Gilbert) Fig. 4a: Tooth #3 with a radiolucent peri- apical lesion on the mesiobuccal root apex ‘The presence of pretreatment apical periodontitis is one factor that has been shown to decrease the success rate’ Dr Brett E Gilbert discusses how to achieve success the second time around Endodontic retreatment