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Background: Root canal re-treatment (RCR) cases are considered some of the most challenging cases in the field of endodontics, as they are mostly associated with various iatrogenic errors such as ledge formation, incomplete biomechanical preparation, file separation, and incomplete obturation. These iatrogenic errors lead to defective niches within root canals that may act as reservoirs for various viable microorganisms. Such residual microbial niches may cause postoperative pain even after thorough debridement and reshaping the canals, ultimately leading to a poor prognosis for the tooth. Nowadays, prevention of postoperative pain in re-treatment cases and prognosis are effectively managed by photobiomodulation therapy (PBMT)., Method: Relevant studies in the English language published before November 2022 were identified using electronic databases like PubMed, SCOPUS, and EBSCO to conduct bibliographic research. This systematic review is based on 3 studies that were found eligible as per the inclusion and exclusion criteria. This systematic review is in accordance with PRISMA guidelines., Results: The systematic review indicated a positive impact by significantly decreasing postoperative pain in RCR cases when treated with PBMT. The variation was statistically significant at 24 hours (P = .0002), 48 hours (P = .03), and 72 hours (P = .02). The mean difference at 24 hours was 0.65 (95% CI, 0.32-0.99), at 48 hours was 0.46 (95% CI, 0.05-0.87), and at 72 hours was 0.40 (95% CI, 0.07-0.74). There was no statistical heterogenicity at 24 hours (P > .05), but a medium heterogenicity was observed at 48 hours and 72 hours., Practical Implication: PBMT or low-level laser therapy has shown superior results as compared to the conventional pharmacologic approach in postoperative pain management in RCR cases., Competing Interests: Conflict of interest None disclosed., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: The success rates of NS-ReTx have varied across decades of prior research. Nonetheless, recent endodontic advances have substantially enhanced case management. This systematic review aimed to identify rigorous studies on contemporary NS-ReTx, investigating both periapical healing-evaluated strictly for complete resolution or loosely for size reduction of periapical radiolucency-and success, denoting clinical normalcy combined with periapical healing., Methods: We systematically searched MEDLINE, Embase, Web of Science, the Cochrane Library, and gray literature from January 1988 to December 2022. Article selection and data extraction were independently conducted by 3 reviewers. Selected studies underwent risk of bias assessment, and evidence quality using the Grading of Recommendations, Assessment, Development, and Evaluation approach. Meta-analysis and meta-regression established pooled outcome rates, 95% confidence intervals (CIs), and significant clinical prognostic factors (P < .05)., Results: Twenty-nine articles were included. Pooled periapical healing rates using strict and loose criteria were 78.8% (95% CI: 75.2-82.4) and 87.5% (95% CI: 83.8-91.2), respectively. Pooled success rates using strict and loose criteria were 78.0% (95% CI: 74.9-81.2) and 86.4% (95% CI: 82.6-90.1), respectively. Meta-regression analyses revealed significant influences on NS-ReTx outcomes (P < .05), including periapical status, lesion size, apical root filling extent, and follow-up duration., Conclusions: Contemporary NS-ReTx shows encouraging outcomes, achieving periapical healing and success rates ranging from approximately 78% (strict criteria) to 87% (loose criteria). The absence of or smaller preoperative lesions, adequate root filling length, and extended follow-ups significantly improve NS-ReTx outcomes. Integrating these factors into treatment planning is pivotal for optimizing the outcome of NS-ReTx., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: This study compared the clinical and radiographic outcome of endodontic retreatment of teeth with apical periodontitis using either 1% sodium hypochlorite (NaOCl) or 2% chlorhexidine digluconate (CHX) as the irrigant. The influence of residual infection detected by a molecular method on the outcome was also examined., Methods: Fifty-two root-filled teeth with apical periodontitis were randomly assigned into 2 groups according to the irrigant used during retreatment. Root canal microbiological samples taken before (S1) and after (S2) preparation using either NaOCl or CHX irrigation and after calcium hydroxide medication (S3) were subjected to 16S ribosomal RNA gene-based real-time quantitative polymerase chain reaction (qPCR) to quantify total bacteria. The periapical status was scored using the periapical index and dichotomized as healed (<3) or not healed (≥3) at the 1- and 4-year follow-up., Results: Forty-five (NaOCl, n = 20; CHX, n = 25) and 33 teeth (NaOCl, n = 16; CHX, n = 17) were available at the 1- and 4-year follow-up, respectively. After 1 year, 65% in the NaOCl group and 64% in the CHX group healed, with no differences between them (P > .05). At the later follow-up, the corresponding figures were 81% and 82%, respectively (P > .05). Canals that yielded qPCR-negative results in S3 had a higher healing rate (79%) than qPCR-positive canals (45%, P < .05). The mean bacterial load increased from S2 to S3 in half of the unhealed cases (P < .05). All S3-positive canals containing <3.12 × 10 3 bacterial cell counts healed. Increasing the apical level of the root canal filling influenced the outcome (P < .05)., Conclusions: No significant differences in the clinical outcome between 1% NaOCl and 2% CHX were found. Bacterial persistence at the time of filling as detected by qPCR significantly affected the outcome., (Copyright © 2019 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to evaluate postoperative pain after single-visit and 2-visit non-surgical endodontic retreatments with 2 different intracanal medicaments., Methods: A total of 150 patients with asymptomatic root canal-treated teeth in need of nonsurgical endodontic retreatment were randomly divided into 3 groups (n = 50). Patients were selected randomly from among those without preoperative pain. Patients in group 1 (single visit) were treated in a single visit. Patients in group 2 and group 3 were treated in different visits with calcium hydroxide and chlorhexidine (CHX) as intracanal medicaments. The presence of postoperative pain was assessed 1, 2, 3, and 7 days and 1 month after treatment. All 2-visit treatments were completed 1 week after the initial visit. Data were analyzed using the Mann-Whitney U, Kruskal-Wallis, and Pearson chi-square tests (α = 0.01, 0.05)., Results: Postoperative pain was significantly higher in the CHX group in comparison with the single-visit group (P ≤ .05) on the first day of assessment. On the second day, postoperative pain was significantly less in the single-visit group (P < .05) than in the other 2 groups. There were no significant differences among the groups on the third and seventh days of assessment. At the 1-month assessment, postoperative pain was significantly higher in both the calcium hydroxide group (P < .05) and the CHX group (P < .05) in comparison with the single-visit group., Conclusions: Single-visit nonsurgical endodontic retreatment presented fewer incidences of postoperative pain in comparison with 2-visit nonsurgical endodontic retreatment based on assessments ranging from 1 day to 1 month., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this randomized clinical trial was to evaluate the influence of rotary or reciprocating retreatment techniques on the incidence, intensity, duration of postoperative pain, and medication intake., Methods: After power analysis calculations, 65 patients who needed endodontic retreatment were randomly assigned to 1 of 2 groups according to the instrumentation system used: Mtwo (VDW, Munich, Germany) or Reciproc (VDW). Retreatments were performed in a single visit by an endodontic specialist. Participants were asked to rate the incidence and intensity of the postoperative pain on a verbal rating scale 24, 48, and 72 hours after treatment. Patients were also asked to record the number of prescribed analgesic medication tablets (ibuprofen 400 mg) taken. A logistic regression analysis was used to assess both the incidence and duration of pain. Differences in the intensity of pain were analyzed using the ordinal (linear) chi-square test, and the Mann-Whitney U test was used to assess differences in the intake of analgesic medication between groups., Results: No statistically significant difference was found among the 2 groups in relation to postoperative pain or analgesic medication intake at the 3 time points assessed (P > .05). Multivariate analysis showed a significantly higher incidence of pain after 24 hours when preoperative pain was present and a significantly longer duration of pain for men than women independently of the retreatment technique used., Conclusions: The reciprocating system and the continuous rotary system were found to be equivalent regarding the incidence, intensity, duration of postoperative pain, and intake of analgesic medication., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The infectious content of root canals, including bacteria and lipoteichoic acid (LTA), cause injuries to the periapical tissues. The purpose of this clinical study was to quantify the levels of both LTA and cultivable bacteria at the different phases of endodontic retreatment (ER) of teeth with post-treatment apical periodontitis. It also aimed to investigate the presence of gram-positive microorganisms before and after chemomechanical preparation (CMP) and intracanal medication (ICM)., Methods: Twenty infected root canals of single-rooted teeth were randomly assigned into 2 groups according to the chemical substance used for CMP (n = 10 per group): chlorhexidine (CHX) group, 2% CHX gel, and the sodium hypochlorite (NaOCl) group, 6% NaOCl. Root canal samples were taken using paper points before (S1) and after CMP (S2) and after 30 days of ICM with calcium hydroxide + 2% CHX gel (S3). Microorganisms were identified by the culture technique using biochemical tests. Cultivable bacteria were determined by counting the colony-forming unit. LTA levels were measured using the enzyme-linked immunosorbent assay (pg/mL)., Results: A total of 70 gram-positive species, out of 102 species isolated, were found in the root canals (54 in S1, 4 in S2, and 12 in S3). Enterococcus faecalis was the most frequent isolated taxon in all phases of the ER. LTA (574.0 ± 94.7) and cultivable bacteria (101.2 ± 79.2) were present in all S1 samples. CMP decreased the overall levels of cultivable bacteria by 99.4% and LTA by 24.8% (P < .05), whereas the total overall reduction level of ICM on viable bacteria was 99.5% and on LTA it was 38.6% (P < .05). CMP with 2% CHX gel (CHX group, 99.3%) was more effective (P < .05) than 6% NaOCl (NaOCl group, 92.1%) on bacterial reduction. Likewise, ICM showed a 100% reduction in the CHX group and 98.5% in the NaOCl group. Regarding the reduction of LTA, CMP with 2% CHX gel (CHX group, 26.9%) was more effective (P < .05) than 6% NaOCl (NaOCl group, 22.6%). In addition, ICM showed a 43.2% reduction in the CHX group and 36.2% in the NaOCl group (P > .05)., Conclusions: The reduction rates of bacteria were higher than the LTA. Moreover, gram-positive microorganisms were present in all phases of the endodontic retreatment., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Subcutaneous emphysema (SCE) rarely occurs from endodontic treatment. Most reported cases of iatrogenic SCE occur in the cervicofacial region. Only a few cases have been reported of SCE extending into the mediastinum or orbital spaces. In the present report, we describe a concomitant occurrence of orbital, mediastinal, and cervicofacial SCE immediately after endodontic retreatment., Methods: A 33-year-old woman presented to the hospital with acute swelling of the right side of her face and neck. Earlier in the day, she began experiencing rapid swelling while undergoing endodontic retreatment of a mandibular right first premolar by her general dentist. The dentist immediately referred the case to an oral surgeon who then ordered additional tests and radiographic studies at the hospital. From there, the patient received consultation and comprehensive treatment by a multidisciplinary team of medical and dental staff., Results: Physical examination, laboratory tests, and computed tomographic studies confirmed a diagnosis of SCE. Extensive air pockets were detected within the orbital, mediastinum, and cervicofacial spaces. The patient was admitted to the hospital and underwent treatment and observation for massive SCE with likely secondary infection. On the fifth day, she was discharged after showing dramatic improvement., Conclusions: SCE may go undetected or misdiagnosed. Complications may be fatal. Therefore, clinicians should apply preventive measures and know how to identify and manage SCE. We review reports of SCE in the last century, discuss etiology and differential diagnosis, and present recommendations for prevention and management of SCE., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Enterococcus faecalis is known to be the most frequently detected species in root canals with failed endodontic treatment. Many studies are available on biofilm formation and the expression of virulence factors such as gelatinase (gelE) in E. faecalis. However, the relationship of biofilm formation and the expression of gelE in E. faecalis recovered from root canals undergoing orthograde retreatment is not well understood., Methods: E. faecalis was isolated from clinical samples of root canal retreatment, and the expression of gelE in E. faecalis was assessed. Automatic microplate reader and scanning electron microscopy were used to investigate the biofilm formation ability of E. faecalis isolates. Real-time quantitative polymerase chain reaction was used for detecting the expression of gelE in biofilm-positive and biofilm-negative E. faecalis isolates., Results: The detection rate of E. faecalis in the root canal retreatment cases was 39.26%. An automatic microplate reader showed that most isolates were able to form biofilms, and the biofilm formation ability of strains isolated from the teeth without a sinus tract was better than that with a sinus tract (P < .05). The expression of gelE was stronger in the cases of apical radiolucency than in those without the symptom (P < .05). The expression of gelE was higher in the biofilm-positive than in biofilm-negative strains (P < .05)., Conclusions: Biofilm formation in E. faecalis was facilitated in the cases without a sinus tract. In the cases of apical radiolucency and in the biofilm-positive strains, the expression of gelE was higher., (Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Teeth undergoing initial endodontic therapy have a very high survival rate. Some teeth that continue to show signs of pathosis after the initial therapy will require nonsurgical (orthograde) retreatment. Outcome assessment of endodontic retreatment is crucial for appropriate case selection and treatment planning. However, reports on outcomes of orthograde endodontic retreatment performed by endodontists are limited in number, and the reported data vary. In this study, outcomes of orthograde endodontic retreatment performed on 4744 teeth were assessed during a period of 5 years., Methods: Data were obtained from retreatments that were performed by endodontists participating in the Delta Dental Insurance plan that insures approximately 15 million individuals in the USA., Results: Overall, 89% of teeth were retained in the oral cavity 5 years after the endodontic retreatment. Four percent of all teeth underwent apical surgery that occurred mostly within 2 years from completion of orthograde retreatment. Eleven percent of teeth were extracted at the end of the 5-year observation period., Conclusions: It appears that orthograde endodontic retreatment yields high incidence of tooth retention after 5 years., (Copyright (c) 2010 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

A light and electron microscope examination of the resected root tip of a failing endodontically re-treated lower molar was examined. The tooth had been initially treated 10 years ago and then re-treated 2 years ago. The resected root tip was sectioned axially, and thin sections were examined through the entire length of the specimen. Thin sections were examined with a transmission electron microscope. The thin sections were randomly chosen along the isthmus areas between the mesiobuccal and mesiolingual canals. Our findings suggest that a complex, variable, multispecies biofilm was present the entire length of the specimen.

This case report presents an unusual root canal system in a maxillary first molar tooth: a single canal in a single root. The endodontic access cavity displayed only 1 canal orifice. This case demonstrated that: 1) clinicians must have adequate knowledge about root canal morphology and its variations; 2) the location and morphology of root canals should be identified radiologically before the root canal treatment; and 3) careful examination of radiographs and the internal anatomy of teeth is essential.

The Editorial Board of the Journal of Endodontics has developed a literature-based study guide of topical areas related to endodontics. This study guide is intended to give the reader a focused review of the essential endodontic literature and does not cite all possible articles related to each topic. Although citing all articles would be comprehensive, it would defeat the idea of a study guide. This section will cover retreatment rationale, corrosion of silver points, retreatment techniques, removal of posts, and possible complications during retreatment.

The purpose of this case presentation is to describe nonsurgical retreatment of anterior teeth with gemination. A 21-year-old male patient was referred for endodontic treatment of his maxillary left lateral incisor. In the clinical examination, a large crown was observed in the left maxillary incisor region when compared with the right maxillary lateral incisor. In the present case, a tooth gemination of a maxillary lateral incisor has been described. A periapical radiograph showed that the tooth had partially separated two crowns having a single root and one root canal, but the access cavity of the distal crown had not been opened, and the root canal had been obturated with single cone technique. Nonsurgical endodontic retreatment was decided for geminated lateral incisor. At the 6-month follow-up, the tooth was asymptomatic and there was no radiolucency around the apical region.

The prognosis for endodontic treatment in teeth exhibiting a complex anatomy is unfavorable if clinicians fail to recognize extra root canals. This case demonstrates the presence of a second canal in the disto-buccal root of a maxillary right first molar. Conventional retreatment followed by endodontic surgery was performed and a 1-year postoperative radiograph shows apparent periapical healing.

The purpose of this investigation was 2-fold: (a) to complete a thorough search of published literature related to clinical studies on the success and failure of nonsurgical retreatment, and (b) to assign levels of evidence to these publications. Clinical studies related to success and failure of retreatment since 1970 were identified using both electronic and manual literature searches. After identification of pertinent literature, each article received a level of evidence (LOE) from one (high) to five (low). Thirty-one clinical studies and six review articles related to this subject were identified. There was no LOE 1 Randomized Control Trials (RCT). There were three LOE 2 RCTs, one LOE 2 Cohort, and two LOE 3 Case Control Studies. Thirteen Case Series (LOE 4), which comprise the most highly quoted success and failure data, were found. Twelve Case Reports (LOE 5) and six review articles (LOE 5) were found. Based on these findings, it appears that few high level studies have been published in the past 34 yr related to the success and failure of endodontic retreatment.

Objective: The purpose of this clinical study was to determine the effect of 1- or 2-visit root canal treatment on the postoperative pain in the retreatment cases., Study Design: Two hundred eighteen cases that required retreatment were included in the study. Obturated and unfilled canal space and the status of periapical tissues were evaluated according to the PAI index. The patients were subcategorized in regard to the presence or the absence of preoperative pain. Approximately half of each category was treated in 1 appointment. After removing the previous root canal obturation materials and biomechanic preparation of root canals, the teeth in the 1-visit group were obturated at the first appointment by using AH 26 sealer and laterally compacted gutta-percha, and those in the 2-visit group were medicated with calcium hydroxide-chlorhexidine combination and then closed with a temporary filling material. One week after the initial appointment, patients were asked about the occurrence of postoperative pain. The level of discomfort was rated as no pain, mild pain, moderate pain, or severe pain (flare-up). Data were statistically analyzed using the chi-squared and Fischer exact tests., Results: Eight patients from the 1-visit group and 2 patients from the 2-visit group had flare-ups. There was a statistical difference between the groups (P <.05). Two-visit root canal treatment was more effective in completely eliminating pain than 1-visit treatment of previously symptomatic teeth (P <.05)., Conclusions: Two-visit endodontic treatment with intracanal medication was found to be effective in reducing postoperative pain of previously symptomatic teeth and decreased the number of flare-ups in all retreatment cases.

Purpose: Root-filled teeth with persistant periapical radiolucencies are often classified as endodontic failures. Studies have shown that general dental practitioners (GDP) do not consistantly suggest retreatment of "failures." The "Praxis Concept" (PC) theory hypothesizes that dentists conceive periapical health and disease as different states on a continuum. This study examined endodontic retreatment concepts among 157 GDPs from Värmland, Sweden., Study Design: In 6 simulated cases the periapical condition, quality of root filling and presence of a root canal-retained post were systematically varied. Five options were offered: no therapy, wait and see, nonsurgical retreatment, surgical retreatment, and extraction., Results: The investigation showed large interindividual variation in retreatment behavior among the GDPs. Only 9 dentists (6%) where found to repeatedly suggest retreatment of endodontic failures. A majority of GDPs (79%) performed in accordance with PC., Conclusions: The data indicate that several retreatment decision rules are used by Swedish GDPs, but PC-derived strategies attract the majority.

Retreatment is common in endodontics. The purpose of this article was to classify the different clinical situations encountered in retreatment cases and relate them to the outcome after an observation period of 24 months. A total of 425 patients (452 teeth) from 451 patients, consecutively admitted for root-canal retreatment, were monitored during a 24-month period. All teeth (254 molars, 107 premolars, and 91 single-root anterior teeth) were divided into two major categories: teeth with modified anatomy from previous endodontic treatment (root-canal-morphology altered) and teeth in which no significant anatomical changes were made by the former endodontic treatment (root-canal-morphology respected). Although the overall success was 69.03%, the success in the root-canal-morphology-respected group was 86.8% and in the root-canal-morphology-altered group 47% (Mann-Whitney U test p < 0.0001). The clinical success of an endodontic retreatment seems to depend on whether alterations in the natural course of the root canals were caused by previous root-canal treatment.

With new wavelengths that allow light transmission by optical fibers, the laser is now often used in endodontics either during treatment or retreatment. The aims of this study were to (i) specify the effects of laser irradiation on restorative materials in terms of topographic effects and (ii) describe different protocols for the first steps of retreatment. The laser used in this study was an optical fiber Nd:YAP (Lokki dt, Vienne, France) with a wavelength of 1.34 microns. Samples of the following restorative materials were prepared: amalgam, composite, permanent and temporary cements, and prosthodontic alloy. The handpiece of the Nd:YAP laser was fixed perpendicular to the surface of the different preparations. All trials were performed with the fiber tip either in contact with or at a distance of 2 mm from the material. The surface effects in all cases were (i) the creation of craters in the center of the lased areas, (ii) a border of fusion material at the edge of the craters, and (iii) cracks or fractures at a distance from the target areas. For the cements, amalgam and composite, the effects included a projection of material from the center to the edge of the lased area and/or the apparent photovolatization of light particles. For all materials the laser induced deeper absorption in the areas of direct contact than when it was held at a distance. This suggests that the fiber should be in contact with the restorative material for lasing in the straight part of the canal when the objective is either to pass through the material or alongside it between material and tooth. If the practitioner cannot determine the direction of the curve of the canal, lasing should be performed at a distance to weaken the material and thus permit more efficient use of an ultrasonic device. Lasing should in all cases be performed under close X-ray monitoring. Provided that sufficient caution is used, the laser may be helpful in removing restorative materials during retreatment.

A clinical technique for using rectified turpentine oil to soften and dissolve gutta-percha to facilitate retreatment is described. Turpentine oil should be heated to 160 degrees F (71 degrees C) to increase its reactivity before delivery to the canal space.

Anatomical and morphological variations in teeth may affect the success and prognosis of endodontic therapy. The reported data regarding such variations in the maxillary central incisors are limited. This article presents a case of endodontic retreatment in unusually long maxillary central incisors.

Chloroform has been the most widely used solvent in endodontics, but due to concerns about its safety, alternatives have been sought. The purpose of this study was to compare the effectiveness of gutta-percha removal and time of retreatment between halothane and chloroform used as solvents. Thirty mandibular premolars were prepared, obturated, and stored in a humidor for 14 months, after which they were randomly divided into two groups for retreatment. The teeth were retreated using either halothane or chloroform as the solvent. The time of retreatment was measured to the nearest minute. Retreatment was deemed complete when there was no evidence of gutta-percha or sealer on the files or paper points. Teeth were split longitudinally and photographed. The resulting slides were projected, the canals traced, and the areas of the canal, gutta-percha, and sealer were measured using a sonic digitizer. The results were analyzed statistically by t test. The results showed no significant difference in gutta-percha removal between the two groups. The chloroform group took significantly less time to retreat than halothane (7.7 min. versus 10.8 min, respectively).

The purpose of this study was to quantify the amount of remaining gutta-percha/sealer after retreatment of post space prepared teeth obturated with a lateral condensation technique or with Thermafil with plastic and metallic carrier. The time required for retreatment was also recorded. Forty-five extracted mandibular premolars were prepared using a step-back flared technique and obturated. The post space was prepared and a 5-mm obturation was left in the canal. Retreatment of all groups was done using a solvent technique. The teeth were split longitudinally and photographed. The total area of the canal and the area of gutta-percha/sealer were traced on white paper. Both areas were quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Statistical analysis (analysis of variance, p = 0.01) showed no differences among the techniques when the average percentage of remaining gutta-percha/sealer was compared. Results revealed that the Thermafil metallic retreatment group consumed significantly more time than the others (analysis of variance, Scheffe p = 0.01). The metallic carriers were not easily removed from the canals, six metal carriers could not be retrieved during the retreatment routine.

A survey was conducted to determine the frequency and popularity of contemporary methods used in endodontic retreatment to remove intraradicular posts. Opinions and rationales were also sought for the choice of surgical management instead of nonsurgical retreatment. A questionnaire was sent to 571 active Diplomates of the American Board of Endodontics with 324 members responding (56.7%). Hand instruments, such as hemostats or special forceps, were the most commonly used, often in conjunction with ultrasonic or sonic vibration to loosen the post or break down the cement interface. A wide range of rationales was identified for the use of surgical retreatment methods, with failure to remove the post after reasonable nonsurgical efforts being the most often cited.

During nonsurgical endodontic retreatment, endodontic instruments are forced apically to remove the root canal filling material and regain canal patency. Undiscriminating burrowing down the canal in the apical direction may be fruitless and harmful. To avoid complications, the dentin overhanging the canal orifice must be removed and an unobstructed access established to the root filling material, so as to facilitate its removal. Reinstrumentation of the filled canal must take into consideration the nature of the filling material and the physical properties of endodontic instruments, as well as the dynamic aspects of canal preparation. This article discusses the mechanical considerations pertaining to root canal retreatment and outlines a step by step rationale approach to retreatment.

This study used a special jig system, photography, and a sonic digitizer to evaluate the change in canal size and location after retreatment in 20 teeth with small or large curved canals (greater than 23 degrees). During initial instrumentation, small canals enlarged twice as much as large canals in the coronal and middle areas. During retreatment, small and large canals showed 30 to 85% enlargement compared with that of the initial instrumentation. There was a trend, primarily during retreatment, for small canals to deviate more than large canals away from the original canal location.

The change in original canal size and location after canal preparation and after reinstrumentation using a step-back technique was studied in small and large canals with less than 20-degree curvature. Teeth were mounted in jigs and then sectioned. The jig permitted the sectioned teeth to be repositioned exactly. Slides were made of the canal in the coronal, middle, and apical at the following intervals: before instrumentation, after instrumentation, and after reinstrumentation. The increase in canal area and the direction of movement was measured. The data were analyzed by ANOVA and Duncan's multiple range test. The results showed: (a) All canal areas increased after retreatment. The retreated apical canal increased in area significantly more (25.4%) than middle (4.0%) or coronal (3.0%) regardless of whether the canal was large or small. (b) The retreated canals tended to move in the same direction they moved after first instrumentation.

The necessity to remove filling materials from the root canals is one of the major differences between primary endodontic therapy and retreatment. The obturating material has to be removed from the root canals before routine endodontic therapy can be performed. The removal of the material should not result in a change in the canal morphology, so that the objectives of endodontic therapy can be maintained. Numerous techniques may be used for removing filling materials and other obstructions from root canals. This article reviews the techniques that were suggested in the literature for this purpose and discusses their advantages and disadvantages.

Nonsurgical endodontic retreatment can be a successful treatment option, especially if the existing root canal therapy is technically deficient. It is the preferred treatment for most endodontic failures unless iatrogenic, restorative, or morphological factors dictate otherwise. A restorative post in the involved canal is usually considered an indication for apical surgery; however, in cases where nonsurgical retreatment is preferable to surgical management, many posts can be removed.

Forty extracted teeth were instrumented using a step-back flare technique and obturated with gutta-percha and either AH26 or Roth's 801 sealer. After 3 months the canals were retreated by removing gutta-percha and sealer with hot instruments followed by chloroform and files. As a final step, the teeth were instrumented using ultrasonics with either chloroform or with NaOCl. Most teeth were well cleaned. No significant differences were found between sealer groups or between the two irrigants as to the ability to remove gutta-percha/sealer.

A total of 1300 endodontic patient charts were analyzed for factors that may have contributed to the failure of the original treatment or the success of the retreatment. Of those surveyed, 667 had recall information of 6 months or more and were used to consider success rates. The remaining cases were analyzed for other information. The findings were tabulated and analyzed by computer for significant relationships. The overall success rate for retreatment was 65.6% with an additional category of "uncertain" of 18.3%. Surgical treatment was necessary to retreat 53.5% of the cases.

Objective: The aim of this study was to assess endodontic retreatment outcomes based on quality of obturation and healing., Materials and Methods: A total number of 223 radiographs of patients who had received endodontic retreatment during the period (2008-2015) at a postgraduate teaching clinic were selected. Unreadable radiographs were all excluded. From the original sample of 223 in total 24 radiographs were discarded. The final sample thus consisted of 199 root canal fillings. All radiographs were individually evaluated for the density of the root filling as well as the distance between the end of the root canal filling and radiographic apex based on a six-point scoring system. Subsequently, patients were reviewed and follow up periapical radiographs were exposed. The outcome of healing was assessed using the Periapical Index (PAI) scoring system. The data were analysed using Chi Square test (p < 0.05)., Results: The study revealed that 78.9 % of the endodontic retreatments were both homogeneity and length acceptable. The corresponding figure was only 13.1 % before endodontic retreatment. Conversely, homogeneity and length unacceptable before endodontic retreatment was 47.2 % reducing to a mere 2.5 % after retreatment. The results were statistically significant (P < 0.001). There was over 80 % improvement in periapical healing following endodontic retreatment and this was also statistically significant (P < 0.001)., Conclusion: There was a significant improvement in outcome after endodontic retreatment on the postgraduate endodontic clinic. The success rate of endodontic retreatment was over 70 % which is in line with the endodontic literature. Radiographic follow up confirmed some 81 % improvement in healing rate following endodontic retreatment., Clinical Significance: Endodontic re-treatment cases are normally categorised as high complexity and as such referral to specialist settings should be considered to help improve treatment outcomes., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Introduction: The root canal microbiota in root-filled teeth with post-treatment apical periodontitis before and after chemomechanical instrumentation and irrigation with either 1% sodium hypochlorite (NaOCl) or 2% chlorhexidine digluconate were analyzed by using the pyrosequencing method., Methods: Samples from 10 root-filled teeth with apical periodontitis undergoing retreatment were taken before (S1) and after (S2) preparation using irrigation with either NaOCl (n = 5) or 2% chlorhexidine digluconate (n = 5). DNA was extracted, and the 16S rRNA gene (V3-V5) variable regions were amplified and subjected to pyrosequencing (GS junior 454) to determine the bacterial composition., Results: Pyrosequencing yielded 43,797 sequence reads in S1 and 9196 in S2 samples. Overall, 125 bacterial species belonging to 68 genera (S1, 59; S2, 38) and 9 phyla were found. The most abundant and prevalent phyla in S1 and S2 samples were Firmicutes, Fusobacteria, Bacteroidetes, and Actinobacteria. The most represented, abundant, and prevalent genera in S1 and S2 samples were Streptococcus and Fusobacterium. The most prevalent species in S1 and S2 samples were Fusobacterium nucleatum ss. vincentii, Streptococcus oralis/mitis, Streptococcus intermedius, and Streptococcus gordonii. The mean number of species per root canal was 20 (range, 4-37) in S1 and 9 (range, 4-15) in S2, respectively., Conclusions: A high interindividual diversity was observed in both S1 and S2 samples, with no difference between the two irrigation groups. F. nucleatum ss. vincentii and some Streptococcus species were the most prevalent species in pre-preparation and post-preparation samples during retreatment of root-filled teeth with infection., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Low-level laser therapy (LLLT) is a practical, nonpharmacologic technique for reducing pain. This study evaluated the effect of LLLT on postoperative pain after root canal retreatment (RCR)., Methods: This study enrolled patients (N = 36) who required root canal retreatment (RCR) on mandibular molar teeth, presented with periapical lesions with periapical index scores of 2 or 3, and had a pain visual analog scale (VAS) <50 and a percussion pain VAS <50. The participants were divided into 2 groups: (1) patients scheduled for RCR followed by LLLT (n = 18) and (2) patients scheduled for RCR followed by a mock LLLT (placebo) (n = 18). Postoperative pain was assessed using the VAS. Data were collected and statistically analyzed with the chi-square test, the independent sample t test, and the Mann-Whitney U test (P = .05)., Results: On the first 4 days, postoperative pain significantly reduced in the LLLT group compared with the placebo group (P < .05). However, no statistically significant differences in postoperative pain were found between the 2 groups after 5 and 7 days (P > .05). The number of patients who needed analgesics was lower in the LLLT group than in the placebo group (P < .05). No patient reported pain during LLLT application., Conclusions: LLLT may reduce postoperative pain after RCR of mandibular molars., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Occlusal and percussion pain may manifest occasionally following endodontic treatment, influencing retreatment decisions. Two cases of periapical neuropathic pain, classified as post-traumatic trigeminal neuropathic pain according to the International Classification of Orofacial Pain, are presented. Although mirogabalin is effective in managing neuropathic pain, there is a lack of clinical reports on its use for occasional post-traumatic trigeminal neuropathic pain after endodontic treatment. These cases highlight clinical symptoms and successful treatment with mirogabalin for post-traumatic trigeminal neuropathic pain after endodontic treatment, providing clinicians a "take-away" lesson for improving patient condition., Methods: The patients, referred by their primary dentist due to postendodontic abnormal pain, found no relief with antibiotics or nonsteroidal anti-inflammatory drugs. Although no findings including swelling or periapical radiolucency were observed around the tooth, they experienced occlusal and percussion pain. Local anesthetic testing showed that the pain originated from the peripheral area around the tooth rather than from central sensitization. Dental radiography and cone-beam computed tomography revealed no abnormal findings. Root canal retreatment was performed by a specialist in endodontic treatment. Although endodontic retreatment drastically decreased visual analog scale pain score, pain persisted. Based on the International Classification of Orofacial Pain criteria, diseases other than post-traumatic trigeminal neuropathic pain were excluded. Mirogabalin (10 mg/d) was prescribed once daily before bedtime., Results: Visual analog scale scores gradually and drastically decreased 2 weeks after mirogabalin therapy. Several months later, no recurrence of postendodontic pain was observed after tapering off and discontinuing mirogabalin., Conclusions: These findings suggest the possibility of a new treatment method for post-traumatic trigeminal neuropathic pain after endodontic treatment., (Copyright © 2024 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This microsurgical clinical study evaluated if teeth that have undergone endodontic retreatment are associated with more dentinal defects than primary root canal-treated teeth., Methods: One hundred fifty-five patients who underwent periapical microsurgery treatment in a private practice setting were evaluated. The root ends were resected, and the roots were inspected for the presence of dentinal defects through the surgical operating microscope with the help of a 0.8-mm-diameter light-emitting diode probe light and methylene blue dye. The root canal treatment history (primary vs retreatment) of the teeth was documented and related to the presence or absence of dentinal defects. Bivariate analysis was performed using the chi-square test, and a multivariate analysis was performed using logistic regression to evaluate possible confounding effects of patient age, sex, and tooth location on the association between treatment and the presence of dentinal defects., Results: Of the 155 treated teeth, 33 were excluded (3 fractured and 30 missing treatment history). Of the remaining 122 included teeth, 73 (59.8%) had undergone primary root canal treatment and 49 (40.2%) retreatment. Sixteen teeth (22.5%) of the primary root canal group versus 33 (64.7%) of the retreatment group had dentinal defects. The proportion of retreated teeth with dentinal defects compared with primary treatment was statistically significant (P < .001) with a higher proportion of retreated teeth having dentinal defects. In the multivariate analysis, only the type of treatment was statistically significant (P < .001)., Conclusions: This clinical study showed that root canal-retreated teeth are associated with more dentinal defects than primary root canal-treated teeth., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Nonsurgical retreatment procedure involves the complete removal of the previous filling material to allow thorough instrumentation, disinfection, and refilling of root canal system. We aimed to determine the residuals of the root-filling material by using 3 different retreatment techniques with the aid of micro-computed tomography., Methods: Thirty extracted human maxillary molar teeth were included. All root canals were also obturated with F2 ProTaper single cones and AH Plus sealer. The following retreatment techniques were performed: group 1, ProTaper retreatment files; group 2, Mtwo retreatment files; and group 3, ProFile files. For the assessment of residual filling material, preoperative and postoperative micro-computed tomography scans were compared with each other, and the working time was recorded. One-way analysis of variance was used to analyze the differences between the groups. The significance level was set at P < .05., Results: None of the retreatment techniques were capable of removing the whole filling material. The percentages of the residual filling materials for groups 1, 2, and 3 were 34.45, 45.43, and 23.63, respectively. There was a statistically significant difference between groups 2 and 3 (P < .05). ProTaper and ProFile instruments required less time for the removal of filling materials when compared with Mtwo instrument., Conclusions: ProFile files revealed the best results for endodontic retreatment in terms of both removing capacity and time requirement., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to investigate changes in treatment planning decisions among different practitioner groups over 7 years for teeth with apical periodontitis and a history of endodontic treatment., Methods: A Web-based survey was sent to dentists in Pennsylvania in 2009 consisting of 14 cases with nonhealing periapical lesions and intact restorations without evidence of recurrent caries. Participants selected among 5 treatment options: wait and observe, nonsurgical retreatment (NSRTX), surgical retreatment (SRTX), extraction and fixed partial denture, or extraction and implant (EXIMP). In 2016, the identical survey was resent to the original 2009 participants., Results: In 2009, 262 dentists participated in the survey. Two hundred one participants were general practitioners (GPs: 76.7%), 26 endodontists (ENDOs: 9.9%), and 35 other specialists (prosthodontics, periodontics, and oral surgery [SPECs]: 13.4%) (n = 262). EXIMP, NSRTX, and SRTX were fairly equally selected but with great variation between practitioner groups (χ 2  = 173.49, P < .05). A subset group of 104 participants (SUB) (39.7% of the original participants) retook the survey in 2016 (69 GPs [66.3%], 15 ENDOs [14.0%], and 20 SPECs [19.7%]). Comparisons among practitioner groups were significantly different in SUB (n = 104) for 2009 (χ 2  = 95.536, P < .05) and 2016 (χ 2  = 109.8889, P < .05). Intragroup reliability between 2009 and 2016 revealed no significant differences between the overall treatment planning choices for all practitioners (GPs, ENDOs, or SPECs). Intrapractitioner reliability showed many treatment planning decision changes on an individual level. Chances that individuals changed their original decision were 47.8% (95% confidence interval, 45.2%-50.4%) and were significantly different among the 3 practitioner groups (GPs > SPECs > ENDOs [χ 2  = 11.2792, P < .05]). No significant changes were observed in the decision for tooth saving versus replacement treatment options (P = .520)., Conclusions: No significant differences were noted between current and past treatment planning decisions in regard to tooth preservation by endodontic retreatment versus tooth extraction and replacement. However, individual practitioners lacked consistency in their decision making over time., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Regenerative endodontic procedures (REP) are a promising alternative for necrotic immature teeth in adolescents and children, but very little evidence is available on this alternative in long-lasting necrotic teeth with open apices in adults. REPs are designed to replace damaged structures of the pulp-dentin complex, but no regeneration has been obtained in any of the cases described in necrotic immature permanent teeth with apical periodontitis with histologic results. The results are limited to periapical tissue repair with increasing root length, thickening of the root walls, and apical closure in young patients. In this series of cases, we report on the outcomes of the adjuvant use of autologous platelet-rich plasma (PRP) in endodontic therapy in adults by monitoring periapical tissue healing with periodic periapical radiographs and cone-beam computed tomographic scanning., Methods: Three teeth with apical periodontitis and open apices in 3 different patients from 21 to 35 years-old were evaluated. An REP was performed with the adjuvant use of PRP., Results: At controls, complete disappearance of the radiolucent lesions and the presence of calcified structures forming bridges occupying the pulp lumen were observed but not an ostensible thickening of root walls with a regeneration of pulp-dentin complex., Conclusions: The repair of periapical tissues with REPs of open apex teeth with apical periodontitis and in nonsurgical endodontic retreatment appears to be feasible in adults, but no regeneration was obtained in any of the present cases. The use of PRP may be a good choice as an autologous matrix because of its stability and induction; it contains growth factors and bioactive molecules like transforming growth factor beta, bone morphogenic proteins, insulinlike growth factors, and angiogenetic growth factors, which stimulate collagen production, angiogenesis, and cell differentiation. Anti-inflammatory and antibacterial properties have also been reported for this preparation, which are involved in all processes of repair., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the current investigation was to assess the effect of the use of a dental operating microscope on the outcome of nonsurgical root canal treatment (NS RCT) while treating the mesiobuccal (MB) root of the maxillary first molar., Methods: This retrospective investigation included endodontically treated maxillary first molars (ETMs) with apparent adequate previous NS RCT and restorations referred for endodontic retreatment at the endodontic graduate clinic. Inclusion criteria were ETMs that were diagnosed with irreversible pulpitis and normal periapical tissues before the initial NS RCT and ETMs that presented with a minimum of 1 identifiable periapical lesion (PAR) at 1 of the roots at the time of retreatment. One hundred ninety-five ETMs were included and divided into 2 groups: (1) the initial NS RCT had been performed using a microscope (n = 83) and (2) NS RCT had been performed without the use of a microscope (n = 112). Data extracted were whether the second MB (MB2) canal was located initially and the presence of an MB PAR at the time of retreatment. Data were statistically analyzed using binary logistic regression (α = 0.05)., Results: The MB root was 3 times more likely to present with a PAR at the time of retreatment if the initial NS RCT was performed without the use of a microscope (P < .05, odds ratio = 3.1). There was a significant association between a missed MB2 canal and an MB PAR in the group in which the initial NS RCT was performed without the use of a microscope (P < .05, odds ratio = 5.1). However, in cases in which the initial NS RCT was performed using a microscope, a missed MB2 canal was not associated with the presence of an MB PAR., Conclusions: With proper education, dentists can gain further insight into recognizing limitations in treating cases that require advanced training and advanced optics such as a microscope. Based on this strategy, it would appear that the outcome of NS RCT can be improved., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: There have been many recent technical advances in modern endodontics that have the potential to affect treatment outcomes. Reports on treatment outcomes using contemporary techniques are relatively scarce, especially in the field of nonsurgical retreatment. The purpose of this study was to determine the success of nonsurgical root canal retreatment in molars using contemporary endodontic techniques., Methods: Sixty-three patients referred for retreatment in first molars were enrolled in the study. The retreatment procedures were performed by endodontic residents using a semistandardized treatment protocol. Patients were followed-up at 6, 12, and 24 months. Treatment outcomes were categorized into healed, healing, or nonhealing based on clinical and radiographic criteria. Healed and healing were considered as successes, and nonhealing was considered a failure. Outcomes were also evaluated using patient-centered criteria that included oral health-related quality of life scores and subjective chewing ability., Results: Fifty-two of the 63 patients were available for final analysis. Five cases (9.6%) were determined to be nonhealing at the last follow-up with new or persistent periapical lesions. Thirty-seven (71.2%) patients had complete resolution of apical periodontitis, and the remaining 10 (19.2%) remained asymptomatic and showed radiographic evidence of healing. Oral health-related quality of life scores and chewing ability improved significantly over time (P < .05), with the biggest increase observed within the first week of treatment completion., Conclusions: This study showed that endodontic retreatment using contemporary techniques significantly improved patients' quality of life and chewing ability over time, with a success rate of 90.4% after 2 years., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this retrospective cohort study was to evaluate the incidence of missed canals in endodontically treated teeth in the Greater Philadelphia area patient population and to evaluate the effect of untreated canals on endodontic outcome., Methods: A total of 1397 cone-beam computed tomography (CBCT) volumes taken from January 2013 to July 2015 were investigated. Limited view CBCT images were taken with Kodak 9000 3D System field of view at voxel size, 76 μm or Morita Veraviewpocs 3D F40 field of view at voxel size, 125 μm. All root canal-treated premolars and molars were included in the study. Unfilled canals appearing from cementoenamel junction to apex including splitting from a main canal at coronal, mid, or apical third were defined as missed-untreated canal. A periapical lesion was diagnosed when disruption of the lamina dura was detected and the low density area associated with the radiographic apex was at least twice the width of the periodontal ligament space., Results: The overall incidence of missed canals was 23.04%. The incidence of missed canals per tooth was highest in tooth #14 at 46.5% and tooth #3 at 41.3%. The incidence of missed canals was highest in the upper molars at 40.1% and lowest in the upper premolars at 9.5%. There was a significant difference in lesion prevalence when a canal was missed-untreated (P < .05). Teeth with a missed canal were 4.38 times more likely to be associated with a lesion., Conclusions: Limited field-of-view CBCT should be examined before any endodontic retreatment to identify missed canals. This knowledge would not only help clinicians to locate missed canals clinically but would also help in deciding the surgical approach., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: The authors undertook a study involving members of a dental practice-based research network to determine the outcome and factors associated with success and failure of endodontic therapy., Methods: Members in participating practices (practitioner-investigators [P-Is]) invited the enrollment of all patients seeking treatment in the practice who had undergone primary endodontic therapy and restoration in a permanent tooth three to five years previously. If a patient had more than one tooth so treated, the P-I selected as the index tooth the tooth treated earliest during the three- to five-year period. The authors excluded from the study any teeth that served as abutments for removable partial dentures or overdentures, third molars and teeth undergoing active orthodontic endodontic therapy. The primary outcome was retention of the index tooth. Secondary outcomes, in addition to extraction, that defined failure included clinical or radiographic evidence (or both) of periapical pathosis, endodontic retreatment or pain on percussion., Results: P-Is in 64 network practices enrolled 1,312 patients with a mean (standard deviation) time to follow-up of 3.9 (0.6) years. During that period, 3.3 percent of the index teeth were extracted, 2.2 percent underwent retreatment, 3.6 percent had pain on percussion and 10.6 percent had periapical radiolucencies for a combined failure rate of 19.1 percent. The presence of preoperative periapical radiolucency with a diagnosis of either irreversible pulpitis or necrotic pulp was associated with failure after multivariate analysis, as were multiple canals, male sex and Hispanic/Latino ethnicity., Conclusions: These results suggest that failure rates for endodontic therapy are higher than previously reported in general practices, according to results of studies based on dental insurance claims data., Clinical Implications: The results of this study can help guide the practitioner in deciding the most appropriate course of therapy for teeth with irreversible pulpitis, necrotic pulp or periapical periodontitis.

Introduction: This article describes a case of recurrent post-treatment apical periodontitis and late failure after endodontic retreatment performed in a single visit., Methods: The patient presented with a tooth exhibiting inadequate endodontic treatment and a large periradicular lesion that extended laterally to the root. Retreatment was performed in a single visit and involved chemomechanical preparation using 5.25% NaOCl as the irrigant and root canal obturation by Schilder's vertical compaction technique. A large lateral canal was radiographically revealed after obturation. After 2 years, the lesion was no longer radiographically discernible, a condition that was confirmed 9 years after retreatment procedures. Nonetheless, after 12 years, radiographs revealed recurrent disease. Apical surgery was performed, and the root apex, including the area of the large lateral canal, was resected with care to maintain the lesion attached to it. The biopsy specimen was subjected to histopathologic and histobacteriologic analyses., Results: Longitudinal sections of the apical root specimen revealed a heavy dentinal tubule infection surrounding the area of the lateral canal. Bacteria were not found in any other area of the specimen. No other possible reason for the inflammatory periradicular lesion, such as root fracture, coronal leakage, or foreign-body reaction, was evident., Conclusions: A persistent intraradicular infection caused by bacteria located within dentinal tubules is the most reasonable explanation for resurgence of the apical periodontitis lesion. This case report stresses the importance of attaining proper disinfection of the root canal system for a predictable long-term outcome of the treatment., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This article describes a case of late failure after endodontic retreatment as characterized by recurrent post-treatment apical periodontitis., Methods: At the time of the initial treatment, the patient presented with acute apical abscess associated with a tooth with pulp necrosis caused by trauma. Four years later, the tooth was retreated because of persistent disease. The follow-up examination 28 months after retreatment showed complete healing., Results: The patient returned 11 years and 7 months later for bleaching of the discolored tooth, and although the periodontal tissues were clinically and radiographically normal, a fracture line was observed on the mesial aspect of the pulp chamber. Extraction was indicated, but the patient only returned 5 years and 9 months later. Then a radiograph showed recurrent post-treatment apical periodontitis. The tooth was extracted, and histopathologic and histobacteriologic analyses revealed bacterial colonies along the fracture line and colonizing ramifications and accessory canals at the apical root canal system., Conclusions: Coronal leakage can be regarded as the most reasonable explanation for resurgence of the disease. However, a predisposing overlapping condition in the form of root fracture conceivably favored the penetration of bacteria from saliva and plaque biofilm along the filled root canal., (Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to explore the influence of retreatment procedures on the appearance of defects on the root canal walls., Methods: Two hundred mandibular premolars were divided into 4 groups. One group was left unprepared. The rest of the teeth were prepared with ProTaper files up to size F4 and filled with gutta-percha and AH26. One group was left filled and received no further treatments. The filling material was removed from the remaining teeth either with ProTaper retreatment files or with Hedström files. Roots were then sectioned and inspected under a microscope. Data were analyzed with the nominal regression test (α = 0.05)., Results: No defects were observed in the unprepared group. Retreatment groups showed significantly more defects than the initial treatment group (P < .05).There was no difference between the appearance of defects after retreatment with Hedström files and ProTaper retreatment files. The remaining dentin thickness and level of the root did not significantly influence the appearance of defects., Conclusions: Retreatment procedures result in more defects than initial treatment. When assessing the outcomes of endodontic retreatment, the substantial damage to the root canal walls should be considered., (Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)