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Introduction: Endodontic treatment failures often stem from the presence of microbial pathogens, particularly Enterococcus faecalis and Candida albicans. This study systematically assesses the prevalence of E. faecalis and C. albicans in endodontic retreatment cases, aiming to explore their impact on treatment outcomes. Methods: Employing a systematic sampling approach, 30 patients with a history of previous endodontic treatment were selected. Rigorous clinical and radiographic assessments were conducted, following standardized protocols for root canal sample collection. Microbiological analysis, utilizing selective culture media, was employed to identify and quantify E. faecalis and C. albicans. Statistical analyses, including chi-square and logistic regression tests, were performed. Results: The study involved 30 patients undergoing endodontic retreatment, with comprehensive clinical and radiographic evaluations for cases with and without periradicular lesions. Microbiological analysis unveiled a significant prevalence of E. faecalis and C. albicans, establishing a robust association between these pathogens and retreatment failure. These findings underscore the critical need for targeted antimicrobial interventions to enhance the overall success rates of endodontic retreatment procedures. Conclusion: This study highlights the substantial prevalence of E. faecalis and C. albicans in endodontic retreatment cases, emphasizing the importance of identifying and effectively managing these pathogens for successful treatment outcomes. The notable association between these microbial agents and retreatment failure underscores the imperative for tailored antimicrobial strategies to enhance the efficacy of endodontic retreatment procedures.

الخلاصة: الهدف: الهدف من هذه الدراسة هو مقارنة فعالية المبارد اليدوية نوع هيدستروم و بين مبارد البروتيبر المستخدمة في علاج وإعادة علاج الجذور، في إزالة اقماع الجوتابيركا أثناء إعادة المعالجة اللبية باستخدام تقنية التصوير الإشعاعي الرقمي. الطرق: هذه الدراسة تمت خارج الأجسام الحيه / دراسية مختبريه، استخدمت تقنية أخذ العينات المتتالية غير الاحتمالية. واستُخدمت الدراسة ستين من الأسنان الأمامية الدائمة احادية الجذور ذات القنوات المستقيمة. بعد تحضير الاسنان تم حشو القنوات واروائها بأقماع الجوتابيركا ومالئ الفجوات ومن ثم تم الاحتفاظ بها لمدة اربعة عشر يوما في بيئة رطبة في درجة حرارة ٣٧ مئوية. ثم تم اختيار ثلاثة وثلاثين من الاسنان بصورة عشوائية لمجموعتي المراقبة (المجموعة الأولى) والمجموعة التجريبية (المجموعة الثانية). تمت عملية إزالة الجوتابيركا بمبارد الهيدستروم اليدوية في المجموعة الاولي ومبارد البروتيبر الممكنة المستخدمة في علاج الجذور وإعادة علاج الجذور في المجموعة الثانية. وتم الحصول على إشعاعات رقمية باستخدام برنامج كيرستريم ( كودك) إصدار رقم RVG VER.6.10.8.3-A ، وجرى تحليلها لمعرفة الفرق بين الشوائب التي تمثل بقايا الجوتابيركا. واستُخدم برنامج AutoCAD 2006 في توضيح قنوات الجذور وبقايا حشوات الجذور. واستُخدم اختبار العينة المستقلة t لمقارنة مجموع ما تبقى من الجوتابيركا في كلتا المجموعتين. النتائج: لم تتم ملاحظة أي فروق ذات دلالة إحصائية في بقايا حشو العصب باستخدام الطرق المختلفة التي تم اختبارها ومقارنتها. في كلا المجموعتين، كان الجزء المتبقي من حشو العصب محصورًا في الثلث الاسفل من الجذور. الاستنتاجات: تعد مبارد البروتيبر الممكنة ومبارد الهيدستروم اليدوية فعالة بنفس القدر لإزالة حشو العصب من الاسنان احادية الجذور ذات القنوات المستقيمة. Abstract: Objective: This research was aimed at assessing the effectiveness of manual H-files versus a combination of a Pro-Taper universal rotary canal preparation system and retreatment system in removing gutta-percha (GP) during endodontic retreatment, by using a digital radiography technique. Methods: This ex vivo study used a non-probability consecutive sampling technique. The study sample comprised 60 extracted anterior permanent teeth, each with one root with a straight root canal (RC). After preparation, RCs were obturated with GP and sealer. Subsequently, teeth were stored for 2 weeks in a humid environment at 37 °C. Thirty teeth each were randomly assigned to the control (group I), and experimental (group II) groups. GP removal was performed with H-files {group I) or a combination of a Pro-Taper universal rotary canal preparation system and retreatment system (group 2). Digital radiographs were acquired with Carestream digital radiovisiography software (Kodak; version-VER.6.10.8.3-A), and the presence of residual GP was analyzed. AutoCAD (2006) software was used to demarcate the RC and residual root filling. The residual GP in both groups was compared with independent sample t-tests. Results: The remaining root filling did not significantly differ when GP was removed with conventional Hedstrom files versus a combination of Pro-Taper Universal preparation and retreatment file systems. The residual GP was confined to the apical third of the canals in both groups. Conclusions: Pro-Taper Universal preparation and retreatment file systems have similar effectiveness to manual H-files in GP removal in straight canals.

ABSTRACT: 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.

Background: Despite the general guidelines for retreatment, differences in decision making exist for secondary endodontic treatment and may be related to many factors including education, clinical experience, dentist specialty, patient preferences and economic resources. Aim of the study was to evaluate the decision making of the Saudi Board in Restorative Dentistry (SBRD) senior residents in the endodontic retreatment of molar teeth as per the scientific guidelines of the American Association of Endodontists (AAE) and also to identify the causes of retreatment and measure how far they become deviated from their taught retreatment principles and inter-individual variability. Materials and methods: Case histories have been obtained from the files of cases treated in the SBRD Resident Comprehensive Case Archives in the SCHS from 2003 to 2015 in Riyadh region. The cases were only confined to Complex I and Complex II cases according to RDITN (Restorative Dental Index of Treatment Need), and seen by R3 and R4 residents only. Residents’ diagnosis was recorded as well as their treatment plan and any given notes regarding their decisions to retreat. Differences between the two groups (R3 and R4) residents and within the same group, regarding endodontic retreatment decisions and reasons for their treatment options were analyzed using Chi-Square test and Fisher’s Exact test. Results: The majority of residents in both R4 and R3 groups followed the recommended guidelines. R3 residents preferred to retreat all cases while R4 chose ‘no to retreat’ in few cases. Although R4 residents preferred nonsurgical retreatment more than R3 residents, the difference was insignificant. R4 residents preferred ‘no therapy’ or ‘follow up’ more frequent than R3 residents. Members of the R3 residents agreed more or less with each other as did those of the R4 residents without significant inter-individual variations within each group regarding the choice of retreatment). Conclusions: R4 residents appeared more likely, although not significant, to choose no retreatment or follow up than R3 residents. Conventional nonsurgical retreatment had the highest selection by both R3 and R4 residents. No significant inter-individual variations within each group regarding the choice of retreatment. There is a need to establish evidence based guidelines for more uniform management of failed root treated teeth.

Objectives: Non-surgical endodontic retreatment is to be a conservative option over endodontic surgery in case of recurrent infections. Root canal retreatment procedures needs to be initiated faster and proficiently with proper root canal retreatment files. The main aim of this study is to evaluate the remaining root dentin thickness post Gutta Percha (GP) retrieval from the root canal after using two different rotary instruments. Materials and methods: A total of sixty extracted single rooted teeth were chosen. Shaping and Cleaning was done Step Back (Telescopic) technique with apical preparation of size 40 k File. Irrigation was carried out using NaOCl (3 %) and Ethyelenediamine tetraacetic acid (EDTA) to clear the smear layer. The canals were dried using paper points and obturation was completed using lateral compaction technique with AH plus resin sealer. Upon completing the obturation, it was categorized into two groups: Group I- ProTaper retreatment files (PTR) and Group II- Solite RS3 (S-RS3) Retreatment files. Cone Beam Computed Tomography (CBCT) was used to assess the remaining dentin thickness post gutta-percha retrieval at 3,5 and 7 mm respectively. To test the significance between groups independent t test was used. Results: It can be noted from the results that more amount of remaining dentin thickness was seen after using Solite RS3 files at 3 mm, 5 mm and 7 mm on the mesial side compared to ProTaper retreatment files (p 0.05). Conclusion: Within the limitations of the study, it can be concluded that Solite RS3 files have the potential to preserve the remaining dentin thickness. However, more studies including various other parameters should be performed to arrive at a definitive conclusion.

Introduction: No clinical studies have examined the effect of mineral trioxide aggregate (MTA) obturation levels on the outcome of endodontic retreatment. This retrospective study examined treatment outcomes in three cohorts that compared overfilling, flush filling, and underfilling after orthograde retreatment using MTA., Methods: Two hundred fifty patients with 264 teeth diagnosed with previously treated root canals and apical periodontitis retreated in a private endodontic practice were included. All teeth received MTA obturation and the extent of the final filling level was measured in relation to the major apical foramen. After 6-month follow-ups, all nonhealing cases were treated surgically. After 24- to 72-month reviews, the effect of preoperative lesion size and the degree of MTA obturation level were assessed. Multiple linear regression and time-to-event analysis using Stata 17 software (StataCorp LLC, College Station, TX) were used to evaluate the data., Results: Within the three cohorts, 99 out of 108 overfilled teeth (91.7%), 90 out of 103 flush fills (87.4%), and 10 out of 53 underfilled teeth (18.9%) healed and were successfully retreated without surgery at 48-months. When surgical outcomes were included, the combined healed proportion was 93.2%. Preoperative lesion size was found to be an important predictor for retreatment nonhealing. A 1-mm increase in lesion size at baseline resulted in an estimated 11% (95% CI 1.04, 1.18)-38% (95% CI 1.22, 1.58) increase in the risk of surgery. Compared to overfilling and flush filling, underfilling was associated with an approximately three-fold increase in requiring surgery and characterized by delayed healing., Conclusion: MTA obturation is a viable retreatment option for teeth with nonhealing endodontic treatment. MTA overfills or flush fillings do not adversely affect healing outcomes. However, MTA underfilling increases the chances for nonhealing and surgical intervention., (Copyright © 2023 American Association of Endodontists. 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.)

Paresthesia is a potential consequence of unsuccessful root canal treatment. Persistent infection resulting in apical periodontitis may enlarge sufficiently to involve the mental neurovascular bundle. The case presented in this report was referred for endodontic evaluation with a chief complaint of discomfort on mastication and persistent numbness of the lower left lip. Clinical and radiographic evaluation revealed incomplete primary endodontic treatment of the left mandibular second premolar with complex internal anatomy. The untreated root canal system resulted in the progression of apical periodontitis involving the left mental neurovascular bundle as confirmed by cone-beam computed tomography imaging. Nonsurgical root canal retreatment was performed over 2 visits. At the 3-year follow-up visit, the paresthesia had resolved with return of normal sensation. Nonsurgical endodontic retreatment may be sufficient to allow healing of large periapical lesions and resolve complications including paresthesia without the need for surgical intervention., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: No clinical studies have examined the effect of mineral trioxide aggregate (MTA) obturation levels on the outcome of endodontic retreatment. This retrospective study examined treatment outcomes in three cohorts that compared overfilling, flush filling, and underfilling after orthograde retreatment using MTA., Methods: Two hundred fifty patients with 264 teeth diagnosed with previously treated root canals and apical periodontitis retreated in a private endodontic practice were included. All teeth received MTA obturation and the extent of the final filling level was measured in relation to the major apical foramen. After 6-month follow-ups, all nonhealing cases were treated surgically. After 24- to 72-month reviews, the effect of preoperative lesion size and the degree of MTA obturation level were assessed. Multiple linear regression and time-to-event analysis using Stata 17 software (StataCorp LLC, College Station, TX) were used to evaluate the data., Results: Within the three cohorts, 99 out of 108 overfilled teeth (91.7%), 90 out of 103 flush fills (87.4%), and 10 out of 53 underfilled teeth (18.9%) healed and were successfully retreated without surgery at 48-months. When surgical outcomes were included, the combined healed proportion was 93.2%. Preoperative lesion size was found to be an important predictor for retreatment nonhealing. A 1-mm increase in lesion size at baseline resulted in an estimated 11% (95% CI 1.04, 1.18)-38% (95% CI 1.22, 1.58) increase in the risk of surgery. Compared to overfilling and flush filling, underfilling was associated with an approximately three-fold increase in requiring surgery and characterized by delayed healing., Conclusion: MTA obturation is a viable retreatment option for teeth with nonhealing endodontic treatment. MTA overfills or flush fillings do not adversely affect healing outcomes. However, MTA underfilling increases the chances for nonhealing and surgical intervention., (Copyright © 2023 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to evaluate the effect of previous root canal treatment on dentinal tubule penetration of calcium silicate-based sealers during endodontic retreatment and to compare 2 different (commonly used and modified) tubule penetration depth measurement techniques., Methods: The crowns of mandibular premolar teeth were removed, and root canals were prepared (ProTaper Universal; Dentsply Sirona, York, PA) and obturated using AH Plus (AH; Dentsply DeTrey, Konstanz, Germany), MTA Fillapex (MTAF; Angelus, Londrina, Brazil), and WellRoot ST (WRST; Vericom, Gyeonggi-do, South Korea); 0.1% red Rhod-2 dye (Chemodex, St Gallen, Switzerland) was added to the sealers. After storage for 3 weeks (37°C, 100% humid), the following sealer combination subgroups were created (the sealer used during the primary root canal treatment/the sealer used during the retreatment, n = 8): AH/AH, AH/MTAF, and AH/WRST; MTAF/AH, MTAF/MTAF, and MTAF/WRST; and WRST/AH, WRST/MTAF, and WRST/WRST. Green Fluo-3 dye (0.1%) was added to the sealers during retreatment. Sealer penetration depths were measured at 8 points and averaged, and the ratio of the retreatment sealer to the initial sealer was recorded as the mean tubule penetration depth ratio in the first technique, whereas the percentage of the circumferential penetration area ratios of the retreatment and initial sealers was calculated in the second technique. Statistical analyses were performed using Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests., Results: The mean penetration depth of AH and MTFA was found to be higher at the coronal third region in the control groups (P < .05). Both methods showed a significant difference among the groups at the coronal and median regions (P < .05). The AH/WRST, MTAH/AH, MTAF/MTAF, MTAF/WRSTS, and WRST/WRST groups showed deeper tubule penetration (first technique, P = .01). Both techniques showed that the penetration depth of the sealers was the same at the apical region (P > .05), whereas a difference was found among the techniques at the coronal and median regions. The sealers used in the previous root canal treatment limited the penetration depth of the sealers used during the retreatment process (P < .05). When MTAF was used as the initial sealer, the penetration depth of the second sealer did not change, whereas if WRST was the initial sealer, the penetration depth of the sealers at the median and apical regions is negatively affected during the retreatment process (P < .05)., Conclusions: Previous root canal treatment affects the penetration depth of calcium silicate-based sealers. The use of AH Plus and MTA Fillapex during the retreatment process showed an advantage. Both measurement techniques showed similar performances at the apical region, whereas the results varied at the coronal and midcoronal regions; therefore, a more stable sealer penetration measurement technique is still necessary., (Copyright © 2022 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Objective: This retrospective study compared changes in periapical trabecular patterns using fractal analysis and the periapical index (PAI) on the periapical radiographs of patients who underwent multivisit nonsurgical endodontic retreatment of persistent periapical disease., Study Design: In total, 50 participants were included in the study. For each patient, baseline periapical radiographs were acquired just before retreatment and postoperative radiographs were acquired 1 year later. The region of interest, located in the abnormal tissue around the root apex, was selected from each of the paired radiographs and the fractal dimension (FD) was calculated. Periapical status was classified using the PAI as "healed" (PAI <3) or "unhealed" (PAI ≥3)., Results: According to the PAI scores, retreatment after 1 year had a healing rate of 70%. In healed cases, the FD values increased significantly (P < .001), whereas FD decreased significantly in unhealed cases (P = .021). Change in FD was significantly different between healed and unhealed cases (P < .001). However, change in FD did not have a significant correlation with PAI in either healed or unhealed cases (P > .05). There was no significant effect of sex on the change in FD values in either healed or unhealed cases (P ≥ .690)., Conclusions: The significant differences in FD suggest that this parameter may be useful in detecting increased trabeculation and estimating retreatment prognosis., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Introduction: This randomized clinical trial aimed to compare the effectiveness of endodontic retreatment of teeth with posttreatment apical periodontitis (PTAP) performed in 1 visit versus 2 visits on the reduction of cultivable bacteria (colony-forming units [CFUs]), lipopolysaccharides (LPSs), lipoteichoic acid (LTA), and the periapical lesion volume (mm 3 ) after 18 months of follow-up., Methods: Forty patients diagnosed with PTAP were selected and randomly divided into the following 2 groups: 1-visit retreatment and 2-visit retreatment with the placement of calcium hydroxide medication for 14 days. Cone-beam computed tomographic scans were performed at 2 stages: preoperatively and after 18 months of follow-up. Samples were collected before and after root canal procedures. A chromogenic limulus amebocyte lysate assay test was used to quantify endotoxins (EU/mL). LTA levels were measured using the enzyme-linked immunosorbent assay (pg/mL). Culture techniques were used to determine cultivable bacteria by counting the CFU (CFU/mL). The volume of the periapical lesions at the onset of the trial and at the 18-month posttreatment follow-up was obtained by the ITK-SNAP program (Cognitica, Philadelphia, PA)., Results: All samples showed baseline values greater than those collected after the retreatment protocol for all investigated parameters. A higher bacterial load and lower LTA level were found in the 2-visit group after the retreatment protocol (P < .05), with no statistical differences between the groups regarding endotoxin levels and periapical lesion volume (mm³) at the 18-month follow-up analyzed by cone-beam computed tomographic imaging (P > .05)., Conclusions: Endodontic retreatment in 1 or 2 visits exhibited equally favorable periapical healing at 18 months, with no statistically significant differences between groups., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background/purpose: The aim of the this study was to compare the amount of debris apically extruded during endodontic retreatment using two rotary nickel–titanium (NiTi) instruments (K3 and R-Endo) and Hedström files. Materials and methods: Forty-five extracted human mandibular premolar teeth were used in this study. Root canals of the teeth were filled before being randomly assigned to three groups. In group 1, gutta-percha was removed with K3 (SybronEndo, West Collins, CA, USA) rotary NiTi instruments. In group 2, gutta-percha was removed with R-Endo (Micro-Mega, Besançon, France) rotary NiTi instruments. In group 3, gutta-percha was removed using Hedström files (Dentsply Maillefer, Ballaigues, Switzerland). Debris extruded from the apical foramen was collected into Eppendorf tubes. The liquid inside the tubes was dried, and the debris in each group was weighed and compared. Data were statistically analyzed using one-way analysis of variance, and Kruskal–Wallis test and Mann–Whitney U test. Results: Although all retreatment techniques resulted in apical extrusion, groups 1 and 2 produced significantly less apical extrusion than group 3 (P0.05). Conclusion: All retreatment techniques produced extruded debris during endodontic retreatment; however, both rotary NiTi systems were associated with less apical extrusion than manual instrumentation with Hedström files.

Calcium hydroxide (Ca(OH)2) has been widely used as an intracanal medicament for endodontic retreatment, but very few studies used both Ca(OH)2 and 1% chlorhexidine (CHX) as intra-canal medicaments. The purpose of this study was to assess the in vivo effectiveness of a combination of Ca(OH)2 and 1% CHX as intracanal medicaments in endodontic retreatment cases with periapical lesions. Methods: Previous cases of endodontically treated teeth with periapical pathosis in 70 patients (36 men and 34 women, age range 18-60 years) were included. Of these teeth, 59 had received root canal treatment and 11 had been subjected to previous apical surgery, indicating endodontic failure. Following the routine procedures, including canal reshaping and irrigation with 2% CHX, a canal medication material containing Ca(OH)2 powder and a 1% CHX solution was placed into the root canals. Over a 6-week period, the intracanal medication was periodically changed until the teeth became asymptomatic. Patients were recalled at 3-month intervals for radiographic and clinical examination. Results: Our clinical and radiographic assessment of retreatment cases showed complete healing in 41 (64%) teeth, incomplete healing in 9 (14%) teeth, and failure in 14 (22%) teeth. For complete healing teeth, the healing time varied from 6 to 36 months. The size of the periapical lesions and previous surgical treatment had no influence on the prognosis. Conclusion: Our results suggest that a combination of Ca(OH)2 and 1% CHX can be successfully used as intracanal medicament for disinfection in endodontic retreatment cases with periapical lesions. [J Formos Med Assoc 2007;106(3):217-224]

Introduction: Dynamic navigation systems are used in dental implantology to optimize the accuracy of dental implant placement., Methods: A 30-year-old man was seen at the endodontic clinic of the Universidad Autónoma de Yucatán for pain in the left maxillary lateral incisor. A previously treated tooth with symptomatic apical periodontitis was diagnosed. The patient accepted treatment, and after signing an informed consent form, minimally invasive coronal access was performed through a zirconia crown. Then a post removal was performed with an ultrasonic tip to 2 mm before the apical gutta-percha limit, and the removal of material was completed manually with a K-file., Results: This case report demonstrates the use of dynamic navigation to remove a post from under a zirconia crown for the retreatment of a failing root canal procedure. The removal of fiber posts from endodontically treated teeth can present a unique challenge for clinicians. Numerous techniques and instrument kits are recommended for the removal of fiber posts, but the risk of excessive root structure damage is a major concern because the ability to differentiate the color difference between peripheral dentin and a bonded fiber post can complicate the accuracy of the removal., Conclusions: The dynamic navigation system enabled minimally invasive removal of the fiber post with a high degree of accuracy, thus ensuring that there was no unnecessary removal of root structure. Dynamic navigation using real-time monitoring could reduce the attendant risk of iatrogenic errors in complex treatment cases., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Nonsurgical endodontic retreatment continues to be a challenge in endodontics, particularly when dealing with a complex tooth anatomy. This study evaluated the efficacy of passive ultrasonic irrigation (PUI) and the GentleWave system as supplementary techniques to remove remaining filling materials from oval-shaped root canals., Methods: Twenty distal roots of human mandibular molars with single and oval-shaped canals were shaped with R40 (40.06) instrument and filled with gutta-percha and AH Plus sealer using warm vertical obturation. Initial filling material removal was performed with R50 (50.05) instrument, followed by the use of PUI (n = 10) or GentleWave system (n = 10). Micro-computed tomographic images were obtained after obturation, initial material removal, and after the use of PUI and GentleWave. The volume of remaining filling material was calculated for the entire canal as well as for the coronal, middle, and apical thirds. Statistical analyses were performed by using analysis of variance, Kruskal-Wallis and Mann-Whitney tests. P ≤ .05 was considered significant., Results: The use of PUI and GentleWave as supplementary techniques significantly reduced the volume of remaining filling material after initial instrumentation (P < .05). However, none of these techniques was able to render canals free from filling materials. PUI showed better performance by removing 18% of the remaining filling material, whereas the GentleWave system was able to remove approximately 10% (P = .02)., Conclusions: The use of supplementary techniques optimized filling material removal after initial instrumentation. PUI enhanced the overall cleaning of the root canal system during endodontic retreatment in oval-shaped canals., (Copyright © 2020 American Association of Endodontists. 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.)

One of the major concerns about endodontically retreated teeth (ERT) is undoubtedly its loss of remnant structure, which could lead to consequently greater fracture risk. Therefore, the objective of this systematic review is to assess the influence of endodontic retreatment on the fracture strength of the dental tooth remnant. In vitro studies assessing the influence of mechanical retreatment on the mechanical properties (static or under fatigue) of restored teeth were searched in PubMed and SCOPUS databases. Three independent reviewers screened titles/abstracts of articles and the full-text of potentially eligible studies. The risk of bias was independently assessed by one researcher and verified by another two. Comparison between the mean load to fracture of teeth after endodontic treatment and after endodontic retreatment were estimated using pairwise random effects meta-analysis to calculate pooled mean differences. Three studies were included for the systematic review and 2 for the meta-analysis. The pooled effect indicated a statistical difference (Mean difference: -121.03 95%CI: -183.02, -59.05) between conditions favoring the endodontically treated teeth. However, the low number of studies combined with their heterogeneity made it difficult to prove such phenomenon. ERT might present lower fracture strength than endodontically treated teeth. However, more coherent laboratory tests may provide better evidence and quantitative parameters on how much reliability can be attributed to an endodontic retreatment, in addition to which technique can provide more predictable results in this conservative approach., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Introduction: The aim of this study was to evaluate in vitro the performance of 3 single-file systems: WaveOne Gold Primary (WOG; Dentsply Sirona, Ballaigues, Switzerland), Hyflex EDM "one file" (EDM; Coltene/Whaledent, Alstatten, Switzerland), and XP Shaper (XP; FKG, La Chaux de Fonds, Switzerland), for nonsurgical endodontic retreatment on mandibular anterior teeth in regard to the amount of remaining filling material inside the canal, debris extrusion, and operation time., Methods: Sixty extracted standardized mandibular incisors presenting with a single oval canal were prepared to size 30.04 and obturated using warm vertical condensation. After 30 days (37°C, 100% humidity), teeth were randomly divided into 3 groups (n = 20) according to the file used for retreatment (WOG, EDM, or XP operated at 3000 rpm). During the retreatment procedures, preweighed vials were used to collect apically extruded debris, and the time required to remove the filling material was recorded in seconds. Cone-beam computed tomographic scans were taken before and after the retreatment to determine the amount of remaining filling material inside the root canal space. Statistical analysis was performed using the Kruskal-Wallis test, 1-way analysis of variance, and the Pearson test at a 5% significance level., Results: There was a statistically significant difference among the groups regarding the instrumentation time (P < .05). XP was the fastest to remove gutta-percha from the canals (40.54 ± 28.03 seconds) followed by EDM (55.77 ± 19.76 seconds) and WOG (105.92 ± 53.92 seconds). The percentage of remaining filling was significantly greater for WOG (26.65% ± 14.63%) (P < .05). No difference was found between EDM (13.51% ± 9.53%) and XP (8.60% ± 7.28%). No difference was found regarding the amount of extruded debris among the 3 groups (P > .05)., Conclusions: XP was the most efficient in gutta-percha removal from the canals when operated at a higher speed (3000 rpm) followed by EDM and WOG., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the study was to determine long-term tooth survival after endodontic retreatment and whether the presence of intraradicular posts influences the outcome., Methods: Ninety-five teeth were randomly assigned to surgical or nonsurgical endodontic retreatment. Forty-seven teeth in 45 patients were treated by conventional endodontic surgery and 48 teeth (47 patients) by nonsurgical retreatment, including the removal of intraradicular posts in 37 (77%). The outcome was tooth survival; follow-up continued until the tooth had been extracted, at least 10 years had elapsed since retreatment, the patient declined further follow-up, or the patient died. The Fisher exact test was used to analyze differences between the groups., Results: The median follow-up time was 10.1 years (range, 0.0-15.6 years). The overall survival rate was 76%, with no significant differences in long-term tooth survival between retreatment methods or the presence of an intraradicular post. The reasons for tooth extraction were related to the retreatment method. Vertical root fractures were significantly more frequent in the nonsurgical group when retreatment included post removal (P = .036)., Conclusions: There was no significant difference in long-term tooth survival after surgical or nonsurgical retreatment. The presence of intraradicular posts did not affect long-term tooth survival, but for teeth with posts, those retreated nonsurgically were more frequently extracted because of vertical root fractures than those retreated surgically (P = .036). The major limitations of the study were a smaller sample size and the use of outmoded retreatment techniques., (Copyright © 2018 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 aim of this systematic review was to answer the following clinical question: Which is the best treatment option for a pulpally involved tooth?, Methods: An electronic search was conducted in the Cochrane, PubMed (MEDLINE), and ScienceDirect databases between December 2015 and February 2016. A manual search was also performed. The inclusion criteria were randomized clinical trials, prospective or retrospective cohort studies, and cross-sectional studies performed on humans with at least 1 year of follow-up and published within the last 10 years. Two researchers independently screened the title and abstract of every article identified in the search in order to establish its eligibility. The selected articles were classified into different levels of evidence by means of the Strength of Recommendation Taxonomy criteria., Results: Sixty articles met the inclusion criteria for this systematic review. The survival rate of single-tooth implants was greater than the success rate of the distinct conservative treatments. However, among comparative studies, no important differences between both treatments were observed until at least 8 years later., Conclusions: The endodontic treatment and the implant placement are both valid and complementary options for planning oral rehabilitation. Although a level B recommendation can be stated, these results come from retrospective comparative studies because there is a lack of randomized clinical studies comparing both types of therapeutic options., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: The aim of the study was to compare the efficacy of different irrigation and irrigant activation system used as an adjuvant to retreatment rotary files in removal of gutta-percha and sealer from endodontic retreatment using Micro-CT. Method: 64 extracted permanent maxillary central incisor teeth with single canal, were collected and decoronated to standard length of 16 mm. Instrumentation was done using rotary files and obturation was performed using GuttaCore and AH plus sealer. After setting of sealer, initial removal of filling material was performed using ProTaper universal retreatment files (D1, D2, D3). All 64 sample were randomised into four groups (n = 16) Group1: Endodontic syringe irrigation, Group 2: Passive Ultasonic Irrigation (PUI), Group 3: EndoActivator, and Group 4: EndoVac. Micro-CT scanning was performed after obturation, initial removal of filling material by retreatment file and after using experimental protocols of each group, and volume of remaining filling material was calculated using Dolphin software. Statistical analysis performed with one-way ANOVA followed by Tukey's post hoc. Results: A significant reduction in the volume of residual obturation material were found between each group. PUI was superior to the sonic (EndoActivator), negative pressure irrigation technique (EndoVac) and positive pressure irrigation at the coronal, middle third and apical third of the root canal. However, none of the supplementary techniques were able to completely remove the residual obturation material. Conclusion: PUI and EndoActivator were found better in remaining filling material removal, demonstrating clinically useful as supplementary technique in removing remaining obturation material during endodontic retreatment.

Introduction: Treatment options for endodontic failure include nonsurgical or surgical endodontic retreatment, intentional replantation, and extraction with or without replacement of the tooth. The aim of the present study was to determine the impact of cone-beam computed tomographic (CBCT) imaging on clinical decision making among general dental practitioners and endodontists after failed root canal treatment. A second objective was to assess the self-reported level of difficulty in making a treatment choice before and after viewing a preoperative CBCT scan., Methods: Eight patients with endodontically treated teeth diagnosed as symptomatic apical periodontitis, acute apical abscess, or chronic apical abscess were selected. In the first session, the examiners were given the details of each case, including any relevant radiographs, and were asked to choose 1 of the proposed treatment alternatives and assess the difficulty of making a decision. One month later, the examiners reviewed randomly the same 8 cases with the additional information from the CBCT data., Results: The examiners altered their treatment plan after viewing the CBCT scan in 49.8% of the cases. A significant difference in the treatment plan between the 2 imaging modalities was recorded for endodontists and general practitioners (P < .05). After CBCT evaluation, neither group altered their self-reported level of difficulty when choosing a treatment plan (P = .0524). The extraction option rose significantly to 20% after viewing the CBCT scan (P < .05)., Conclusions: CBCT imaging directly influences endodontic retreatment strategies among general dental practitioners and endodontists., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This ex vivo study aimed to evaluate the efficacy of retreating GuttaCore (Dentsply Tulsa Dental Specialties, Tulsa, OK) and warm vertically condensed gutta-percha in moderately curved canals with 2 different systems: ProTaper Universal Retreatment (Dentsply Tulsa Dental) and WaveOne (Dentsply Tulsa Dental)., Methods: Eighty mesial roots of mandibular molars were used in this study. The mesiobuccal canals in each sample were prepared to length with the WaveOne Primary file (Dentsply Tulsa Dental). The canals were obturated with either a warm vertical approach or with GuttaCore and divided into 4 retreatment groups with the same mean root curvature: warm vertical retreated with ProTaper, warm vertical retreated with WaveOne, GuttaCore retreated with ProTaper, and GuttaCore retreated with WaveOne. The warm vertical groups were obturated using a continuous-wave technique of gutta-percha compaction, and the GuttaCore groups were obturated according to the manufacturer's instructions. After allowing sealer to set, each specimen was retreated with either the ProTaper Universal Retreatment files D1, D2, or D3 or with the WaveOne Primary file to the predetermined working length. The time taken to reach the working length was recorded. Instrument fatigue and failure were also evaluated., Results: The post hoc 2-sample t tests showed that the overall mean total time taken to reach the working length for the warm vertical groups was significantly greater than that observed for the GuttaCore groups (mean = 87.11 vs 60.16 seconds, respectively), and the overall mean total time taken to reach the working length for WaveOne was significantly greater than that observed for ProTaper (99.09 vs 48.18 seconds, respectively). Two-way analysis of variance showed a significant main effect for both the type of experiment groups (F 1,76  = 15.32, P = .0002) and the type of retreatments (F 1,76  = 54.67, P < .0001). Also, the WaveOne Primary file underwent more separations than the ProTaper files., Conclusions: The WaveOne Primary file underwent more separations and was unable to remove gutta-percha as efficiently as the ProTaper Universal Retreatment files. Also, canals obturated with GuttaCore were retreated more efficiently and with fewer file separations than the canals obturated using continuous wave of warm gutta-percha., (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 present study assessed the obturation removal and reinstrumentation working time of canals filled with Resilon/Real Seal in comparison with canals filled with gutta-percha/AH Plus. Thirty human extracted canines were instrumented. In group 1 (n = 15) root canals were filled with Resilon/Real Seal and in group 2 (n = 15) with gutta-percha/AH Plus sealer. The obturations were removed from both by using chloroform and irrigation with 2.5% NaOCl, and the canals were manually reinstrumented. The teeth were radiographically analyzed. Specimens without obturation material remnants visible in the radiographic examination were selected for analysis under scanning electron microscopy. The Resilon/Real Seal system was removed in greater quantities from the canal walls compared with the gutta-percha cones and the AH Plus cement. Time was not a significant factor. Under scanning electron microscopy analysis, the teeth presented material remnants in the 3 analyzed thirds. Resilon was better removed from the canal than the gutta-percha cones and the AH Plus.

This study evaluated the amount of apical debris during endodontic retreatment by using the ProTaper Universal Tulsa rotary files. Forty-five extracted human anterior teeth were root filled before randomly assigned to 3 groups. In group A, gutta-percha was removed by using the ProTaper Universal Tulsa retreatment system, and canals were re-prepared with ProTaper rotary files. In group B, gutta-percha was removed by using Hedström files with chloroform, and canals were reshaped with ProTaper rotary files. In group C, the same method as that in group B was used for gutta-percha removal, and canals were reshaped with K-flex files. Apical debris was collected and compared among 3 groups. Although all retreatment techniques resulted in apical extrusion, the ProTaper Universal Tulsa rotary technique in group A produced significantly less amount of apical extrusion than other 2 methods (P < .001). The ProTaper Universal Tulsa rotary technique proves to be a viable alternative method in endodontic retreatment.

Background: Iatrogenic root perforations are an unfortunate accident that can occur during dental treatment and can lead to peri-radicular damage, poor treatment outcome and extraction of the tooth. The aim of this review was to analyse the occurrence and risk factors for root perforation. Methods: A systematic search of the literature was conducted in CINAHL, Cochrane, EMBASE, Medline and SCOPUS in May 2019. Additional literature was identified through a hand search. Clinical studies enrolling adults with permanent dentition were included. Single case studies and case reports were excluded. Duplicate articles were removed, titles and abstracts were screened and studies were selected according to the inclusion criteria. Data were collected and reported in accordance with PRISMA guidelines. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Tools. Results: A total of 916 articles were screened, from which 47 full-text articles were analysed and 22 articles were finally included in the study. The data were analysed qualitatively because meta-analysis could not be conducted owing to lack of heterogeneity among the studies. Most of the articles were retrospective cross-sectional studies on root canal treatments performed by undergraduate students. The occurrence of perforation ranged from 0.6% to 17.6%. Risk factors for perforation included experience of the practitioner, tooth type, and tooth morphology. The risk of bias in most of the studies included was assessed as low. Conclusions: This systematic review suggests a need for additional studies on the risk factors associated with iatrogenic root perforation as the current literature is insufficient. Educational efforts in dental schools should address the issue of perforations and provide more clinical experience prior to graduation in order to improve the clinical skills of graduates.

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.

This study compared the remaining filling material and working time when removing gutta-percha/AH 26 and Resilon/Epiphany from root filled extracted teeth. The root fillings were removed using chloroform and two different rotary systems (K3 and Liberator files). The amount of residual filling material on the canal walls was imaged and measured using image analyzer software. The group filled with Resilon/Epiphany and retreated with K3 files demonstrated the least residual filling material on the walls (p < 0.05). There was no statistically significant difference between the gutta-percha/AH26 and Resilon/Epiphany groups when the Liberator files were used (p > 0.05). In the groups filled with Resilon/Epiphany, the filling was removed faster than groups filled with gutta-percha/AH 26 (p < 0.05). K3 rotary system was faster than Liberator to remove both gutta-percha and Resilon (p < 0.05). Resilon/Epiphany was effectively removed with K3 or Liberator rotary files.

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.

This study investigated the retreatment effectiveness of .04 Taper nickel-titanium rotary ProFiles. Thirty extracted single-rooted anterior teeth were instrumented and obturated with gutta-percha/Roth's Sealer using lateral condensation. They were distributed into three groups of 10 each. Retreatment for group A was done using Profile alone, group B using Profile and chloroform, and group C using hand files with chloroform. The teeth were then split longitudinally into halves. The remaining gutta-percha/sealer on the root canal wall in the cervical, middle, apical thirds, and the whole canals were visually scored with the aid of light microscopes. The results showed that the mean scores in groups A and B were generally lower (better) than group C. Mean scores of the apical thirds tended to be higher (worse) than the middle and the cervical thirds, except in group A. ProFile with or without chloroform seemed to be a viable alternative retreatment method.

Information of "success" rates after surgical or nonsurgical endodontic retreatment is abundant but inconclusive. Reported healing frequencies vary between 45% and 90%. The present study was designed to find any systematic difference between the methods. Nonsurgical and surgical retreatment was randomly assigned to 95 endodontically "failed" cases. The outcome of the procedures was clinically and radiographically recorded, and followed for 4 years. At the 12-month recall, a statistically significant (p < 0.05) higher healing rate was observed for cases surgically retreated. At the final 48-month examination, no such difference was found. These findings may be explained by (a) slower healing dynamics in the nonsurgical group and (b) the event of late "failures" in the surgical group. Within the latter category, four cases classified as healed after 1 yr failed at the final follow-up. Conclusively, this study failed to show any systematic difference in the outcome of surgical and nonsurgical endodontic retreatment. Surgical retreatment seems to result in more rapid periapical bone fill, but also may imply a higher risk of "late failures." From a scientific point of view, the length of the follow-up period is very important and may strongly influence the conclusions made.

Nd:YAP laser is a dental laser with a 1340 nm wavelength. The laser beam is carried by a 200 to 300 microns fiberoptic and is suitable for endodontic therapy. We used the Nd:YAP laser in an in vitro experiment to study its effectiveness in endodontic retreatment. Temperature measurements and irradiation parameters were first defined. Then Nd:YAP laser irradiation was used, alone or in combination with hand instruments, to remove various canal sealers and broken instruments. Clinical parameters were monitored and scanning electron microscopic observations were conducted. When used at 200 mJ--with a pulse duration of 150 ms, an exposure time of 1 s and a frequency of 10 Hz--Nd:YAP laser preserved the dentinal walls of the root canal and enabled root canal retreatment without thermic elevation harming periodontal tissue. It is concluded that, in combination with hand instruments, the Nd:YAP laser is an effective device for root canal preparation in endodontic retreatment.

Three randomly assigned groups of single-canaled extracted teeth obturated with gutta-percha were retreated using controlled application of one of three organic solvents: chloroform, xylene, or halothane. Two additional groups of teeth served as positive and negative controls. Residual volume of solvent expressed through the apical foramen during retreatment was determined by the difference of pretreatment and posttreatment weights of hermetically sealed receptacles attached to the root surface of the teeth. Results indicate that the amount of solvent that has been determined to have leached out through the apical foramen is several orders of magnitude below the permissible toxic dose. Thus, it is proposed that the use of any of the aforementioned solvents used in the retreatment of root canals would pose negligible risk to the patient.