|Year : 2020 | Volume
| Issue : 1 | Page : 7-14
Outcomes of nonsurgical endodontic treatment among endodontic postgraduate students at Riyadh Elm University
Hassan Muteq1, Saad Al-Nazhan2, Nassr Al-Maflehi3
1 Department of Dental, Ministry of Health, Abha, Saudi Arabia
2 Department of Restorative Dentistry – Endodontics, College of Dentistry, Riyadh Elm University, Riyadh, Saudi Arabia
3 Department of Preventive Dental Sciences – Biostatistics, College of Dentistry, King Saud University, Riyadh, Saudi Arabia
|Date of Submission||18-May-2019|
|Date of Acceptance||19-Jul-2019|
|Date of Web Publication||27-Dec-2019|
Prof. Saad Al-Nazhan
Department of Restorative Dentistry – Endodontics, College of Dentistry, Riyadh Elm University, P.O. Box 84891, Riyadh 11681
Source of Support: None, Conflict of Interest: None
Aim of the Study: This study aims to investigate the outcomes of endodontic treatments performed by endodontic postgraduate students at the Riyadh Elm University College of Dentistry.
Materials and Methods: The records of 187 patients with 432 teeth endodontically treated by endodontic postgraduate students at Riyadh Elm University College of Dentistry from February 2013 to February 2017 were randomly selected. In all, 151 patients were lost to follow-up. Clinical and radiographic examinations were performed in 135 teeth of 36 patients. Two qualified endodontists reviewed the results of clinical and radiographic examinations. Outcomes were healed, healing, or diseased. Data were coded and statistically analyzed.
Results: Overall results of endodontic treatment were healed teeth in 68.1%, healing teeth in 27.4%, and diseased teeth in 4.4%. The proportions of healed teeth in one and two visits were 64.3% and 90.5% (P = 0.083), respectively. The acceptable quality root canal filling had a higher healed rate (74.4%) than long or short root canal filling (P = 0.027). The presence of apical periodontitis significantly affected the success of endodontic treatment (P = 0.002).
Conclusion: The outcome of this study is similar to those of previous studies, despite the limited sample size.
Keywords: Endodontic treatment, endodontics, postgraduate, success, treatment outcome
|How to cite this article:|
Muteq H, Al-Nazhan S, Al-Maflehi N. Outcomes of nonsurgical endodontic treatment among endodontic postgraduate students at Riyadh Elm University. Saudi Endod J 2020;10:7-14
|How to cite this URL:|
Muteq H, Al-Nazhan S, Al-Maflehi N. Outcomes of nonsurgical endodontic treatment among endodontic postgraduate students at Riyadh Elm University. Saudi Endod J [serial online] 2020 [cited 2021 Jul 24];10:7-14. Available from: https://www.saudiendodj.com/text.asp?2020/10/1/7/274194
| Introduction|| |
The main goal of endodontic therapy is resolution and/or prevention of apical periodontitis, which can be achieved by thorough cleaning, disinfection, and filling in the three-dimensional context of the root canal system. Failure to locate all canals, incomplete instrumentation, ledge, perforation, and overfilling of the teeth during treatment can cause endodontic failure.,,,, Seltzer  analyzed local and systemic factors that might affect the endodontic repair process and suggested that endodontic failure may be beyond the dentist's control. The success of endodontic treatment is typically determined by careful evaluation of radiographic findings and clinical signs and/or symptoms of the treated tooth. The histological evaluation has also been used. Studies performed under strictly controlled parameters have reported a 92%–98% success rate in teeth without apical periodontitis or with orthograde retreatment, and 74%–84% in teeth with apical periodontitis.,,,
Few studies have been published regarding the outcomes of endodontic treatment performed by postgraduate students. Chugal et al. evaluated 200 endodontically treated teeth with 441 root canals in patients who were treated during a defined period. A pulpal diagnosis of pulpitis without periapical pathosis showed the best success rate after endodontic treatment (89.7%), whereas pulp necrosis showed the worst success rate after endodontic treatment (68.7%). In addition, the endodontic treatment of teeth diagnosed with acute apical periodontitis demonstrated excellent success (91.5%), whereas the endodontic treatment of chronic and exacerbating apical periodontitis demonstrated moderate success (63.8%); these differences were statistically significant. In a study conducted in Toronto, primary endodontic treatment revealed an excellent outcome (81% overall healed rate), which was significantly better in single root teeth without apical periodontitis or mid-treatment complications., Higher success rates of primary and retreatment endodontic therapy were reported by Touboul et al.
A systemic review by Ng et al. reported that the success rate for secondary endodontic treatment performed by specialists was lower than that performed by undergraduate or postgraduate students. By contrast, primary endodontic treatment performed by postgraduate students and specialists had higher pooled success rates than that performed by undergraduate students. Ng et al. attributed this discrepancy to the possible management of more complex biological or technical problems by specialists. Furthermore, de Chevigny et al. concluded that the outcome was better in teeth with inadequate previous root filling, but without perforation and radiolucency. Thus far, no study has been published regarding the work of endodontic postgraduate students of Saudi Universities. Therefore, this study evaluated the clinical performance of endodontic postgraduate students of Riyadh Elm University as a representative Saudi University.
| Materials and Methods|| |
The current study was approved by the Scientific Research and Ethics Committee of Riyadh Elm University (approval number: RC/IRB/2018/987). The records of 187 patients with 432 teeth endodontically treated by endodontic postgraduate students at Riyadh Elm University College of Dentistry from February 2013 to February 2017 were randomly selected. The patients' records were reviewed, and the following data were collected: age and sex; reason for root canal treatment; and history and any problems from the endodontically treated tooth in prior years. Each patient was called for a follow-up appointment. Patients were informed about the importance of the visit and the procedures to be performed. The clinical records identified in the database query were reviewed for follow-up eligibility using the following specific inclusion and exclusion criteria. Inclusion criteria were the presence of complete endodontic and radiographic records, and root canal treatment performed by an endodontic postgraduate student. Exclusion criteria were open apices; apexification, apexogenesis, and revascularization cases; missing information or an incomplete record of the case; teeth that served as a prosthesis abutment; and/or third molars and teeth undergoing active orthodontic therapy.
Each patient was clinically examined with respect to extraoral parameters (e.g., swelling of the temporomandibular joint and lymph nodes) and intraoral parameters (e.g., presence or absence of pain, swelling, sinus tract, periodontal probing, mobility, crack, fracture, tenderness to palpation, percussion, and status of coronal restoration).
Preoperative and postoperative (recall) radiographs were evaluated regarding the presence of periapical radiolucency. The periapical index proposed by Orstavik  and “healed, healing, and diseased” classifications were used for the radiographic registration of apical periodontitis.
Quality of root canal filling
The quality of root canal filling was evaluated in accordance with the method of Sjogren et al. short root canal filling was <2 mm from the radiographic apex; long root canal filling was >2 mm from the radiographic apex; flush root canal filling was placed at the radiographic apex; and acceptable root canal filling was within 0–2 mm of the radiographic apex. The root filling was considered adequate when there was no lumen apical to the filling and no void in the apical portion of the root.
Follow-up appointment procedure
A letter was sent to each subject that explained the importance of endodontic follow-up examination. Nonresponders were contacted by telephone to encourage them to attend. Each patient underwent a clinical and radiographic examination for 15–20 min. Patients with teeth that needed further treatment (e.g., endodontic retreatment, endodontic surgery, final restoration, or extraction) were scheduled for follow-up. A form was used to collect the following information: patient data, reason for root canal treatment, clinical examination, radiographic examination, quality of root canal treatment, mishaps of root canal treatment, and follow-up results.
One investigator reviewed the entire endodontic history and data record. Two qualified endodontists reviewed the results of the clinical and radiographic examinations. Each tooth was evaluated in its entirety for preoperative, intraoperative, and postoperative factors. Assessments of outcome were reviewed, and cases of disagreement were reassessed jointly in accordance with the method of Molven and Halse. Chi-square tests were conducted to compare the characteristics of teeth with successful and unsuccessful outcomes. However, P < 0.05 was considered statistically significant. Data were coded and statistically analyzed with SPSS software (IBM, New York, USA).
| Results|| |
The scores for inter-examiner agreement and intra-examiner agreement were K = 0.8 and κ = 0.9, respectively; these were considered good, according to the criteria of Landis and Koch. Of 187 patients, 36 patients with 135 endodontically treated teeth (81 men and 54 women) were evaluated in this study [P = 0.074, [Figure 1]. Most evaluated teeth were located in the maxilla, rather than in the mandible [P = 0.974, [Figure 2]. Patients 41–50 years of age with 47 teeth came for evaluations most frequently compared to other age groups (P = 0.167).
|Figure 1: Frequency of root canal treatment according to tooth type (n = 135) and gender (n = 36)|
Click here to view
|Figure 2: Frequency of root canal treatment according to tooth location (n = 135)|
Click here to view
The overall results of endodontic treatment were as follows: 68.1% of teeth (n = 92) were healed, 27.4% of teeth (n = 37) were healing, and 4.4% of teeth (n = 6) were diseased [Table 1]. Caries followed by retreatment of failed root canal therapy was the most common causative factor for endodontic treatment performed by postgraduate students. Among the 79 teeth treated with primary root canal therapy due to caries, 67.1% (53 teeth) were healed and 29.1% (23 teeth) were healing. Similarly, among the 52 teeth retreated due to failure of primary therapy, 67.3% (35 teeth) were healed and 26.9% (14 teeth) were healing. The number of recalled teeth treated in a single visit (112 teeth) was greater than the number treated in ≥2 visits (23 teeth). The proportions of healed teeth treated in one and two visits were 64.3%–90.5%, respectively [P = 0.083, [Table 2].
|Table 1: Results of endodontic treatment in relation to treatment procedure|
Click here to view
|Table 2: Results of root canal treatment in relation to number of appointments (visits)|
Click here to view
Outcomes differed according to the teeth in the maxillary and mandibular jaw, as shown in [Table 3]. Maxillary healed better than mandibular teeth (P = 0.000). The acceptable quality root canal filling had a higher healed rate (74.4%) than long or short filling [P = 0.027, [Table 4]. The absence of signs and symptoms during the recall visit revealed successful therapy; 68.7% of patients without symptoms were healed. There was a significant difference (P = 0.000) between the presence and absence of permanent restorations. Healed teeth were recorded when apical radiolucency was absent [P = 0.002, [Table 5]. Three teeth with broken instrument healed after successful management. Two teeth with perforation and one tooth with a missing canal were considered failed treatment. In all, 151 patients were lost to follow-up (90 patients have no problem, 38 did not respond, 7 moved out of Riyadh city, 6 do not like to come, 4 failed to come, 4 wrong phone number, and 2 patients extracted the tooth).
|Table 4: Results of root canal treatment in relation to quality “class” of root canal filling|
Click here to view
|Table 5: Results of endodontic treatment according to radiographic apical findings|
Click here to view
| Discussion|| |
The current study evaluated the outcome of nonsurgical endodontic treatment performed by endodontic postgraduate students at Riyadh Elm University. Patients treated between February 2013 and February 2017 were recalled. Notably, according to the American Endodontic Society  and European Society of Endodontology, root canal treatment should be assessed at least 1 year postoperatively, and as needed thereafter.
A prospective study performed by Ng et al., demonstrated that the success rate of secondary endodontic treatment performed by postgraduate students was higher than that performed by specialists; moreover, the success rate of primary endodontic treatment performed by postgraduate students' primary treatment was higher than that performed by undergraduate students. Because the evidence base for the current endodontic treatment outcome is limited to a few studies of endodontic postgraduate students,,,, additional studies, such as the present study, may add important information to the literature.
All treatment procedures and data collection in this prospective study followed a standardized protocol established before patients began treatment. The coded computerized program of clinical treatment used at Riyadh Elm University facilitated tracking of cases. Our findings showed that more teeth required endodontic treatment in the maxilla (56.3%) than in the mandible (43.7%). These results are in agreement with the findings of prior studies regarding postgraduate treatment outcome.,, Most patients were referred from the undergraduate clinic while undergoing comprehensive dental care; some patients were referred from private practice. Caries and failed root canal treatments were the main causative factor for referral for endodontic treatment in the present study. Similar findings were reported by Scavo et al. A meta-analysis revealed a high prevalence of caries in Saudi Arabia. Microorganisms from dental caries were previously identified as the most common causative factor of pulpal disease. If the disease is left untreated, the infection can eventually cause periapical disease.
The rate of root canal retreatments performed in the present study was moderate (38.5%). Patients with difficult cases were typically referred to postgraduate clinics by undergraduate students for better management, due to the postgraduate students' increased experience in avoiding complications. This was recognized by Alhekeir et al., who reported that the rate of complications was 68% at two dental schools, King Saud University and Riyadh Elm University (Former Riyadh Colleges of Dentistry and Pharmacy). This high percentage of complications was presumed to be due to the complicated root canal morphology of molar teeth. Unfortunately, the numbers of evaluated teeth overall, and molar teeth, in particular, were low in the present study. Similar findings were reported by de Chevigny et al., Touboul et al., and Chugal et al. The reduced recall rate may have affected the analyses of the treatment outcome, thus weakening the validity of the results. Furthermore, general practitioners typically avoid treatment of difficult cases; in a retrospective study, Bernstein et al. showed that the failure rate for endodontic therapy among general practitioners was high.
Premolars and molars were more frequently treated in the present study than canines and incisors (P = 0.074). These findings are in agreement with those of prior studies regarding postgraduate endodontic treatment., The inception cohort of 187 patients and 432 teeth was distributed as follows: “dropouts” comprised 288 teeth (66.7%) of 151 patients, whereas statistical analyses were performed for 135 teeth (31.3%) of 36 patients. Many dropouts either ignored the recall, had no regular relationship with the dental school, or moved out of the city; 90 dropouts did not have any signs or symptoms and apologized for not attending.
Analyses of outcome were performed considering each tooth as a unit of analysis. Accordingly, endodontic treatment outcomes were defined with reference to healing and disease. The evaluation criteria “healed, healing, and diseased” reported by Touboul et al., Orstavik, and Friedman and Mor  were used in the present study, based on the primary goal of endodontic treatment “to prevent or heal apical periodontitis.” Friedman and Mor  interpreted the criteria of evaluations from the outcomes of published reports in which combined clinical and radiographic normalcy was classified as healed; reduced radiolucency combined with clinical normalcy was classified as healing. According to these outcome criteria, 92 teeth (68.1%) were classified as healed, 37 teeth (27.4%) as healing, and 6 teeth (4.4%) as diseased. In the present study, healing was considered “successful” when the evaluated patient had no signs or symptoms, and when periapical pathosis (if present) appeared healed on the periapical radiograph. Previously published studies of endodontic therapy considered healed and healing teeth as successes., Therefore, the success rate in the current study, based on combining “healed” and “healing” cases, was 95.6%. This combined rate (95.6%) is similar to the findings of de Chevigny et al. and Touboul et al. The number of failures (diseased teeth) was insufficient for multivariable analyses.
Most of the teeth in the present study had permanent restorations; 67.9% were healed and 28.2% were healing. Ray and Trope  and Ng et al. reported a significant correlation between adequate coronal restoration and periapical normality. By contrast, Tronstad et al., Hommez et al., and Di Filippo et al. reported no association when the root canal was properly filled. According to Ricucci et al., well-prepared and filled root canals resist bacterial penetration, regardless of the duration of exposure to dental caries, fractures, or restoration loss. In general, the chance of healing apical periodontitis increases with good endodontic and restorative treatments., The presence or absence of apical periodontitis significantly affects the rate of success of endodontic treatment. In the current study, 93% of recalled cases without apical periodontitis were successful; similar findings were reported by de Chevigny et al., Touboul et al., and Chugal et al. Moreover, when periapical pathosis was present, the rate of success was lower (56.5%); this is similar to the findings of Chugal et al., but contradicts the findings of Touboul et al. Healing of apical periodontitis may require several years, and thus, additional observation time is needed.
In the present study, of the 112 teeth treated in a single visit, 72 (64.3%) were healed; of the 21 teeth treated in two visits, 19 (90.5%) were healed; similar findings were reported by Touboul et al. In the two-visit case, intracanal medicament in the form of calcium hydroxide was typically used; it aids in host defense and disturbs the dynamic of persistent microbial flora. Mechanical debridement combined with antibacterial irrigation (0.5%–6% sodium hypochlorite) can render 40%–60% of the treated teeth bacteria negative., In addition to mechanical debridement and antibacterial irrigation, the use of calcium hydroxide as intracanal medicament between visits has been shown to further reduce the bacterial count by 80%–100%., This has been the basis of the multi-visit treatment of apical periodontitis. However, many studies have questioned the effectiveness of calcium hydroxide in the healing of apical periodontitis., The achievement of adequate bacterial eradication in a single visit is the main source of controversy. Although there might be a reasonable biologic argument to prefer multiple visit root canal therapy for infected teeth with apical periodontitis, clinical research has been equivocal with regard to the usefulness of this approach., In the present study, the rates of success (healed and healing) for one and two visits were 95.53% (107 of 112 teeth) and 95.23% (20 of 21 teeth); these were not significantly different. Notably, similar findings were reported by Trope et al.
The outcome of treatment for roots with pulp necrosis and apical periodontitis was dependent on the level of root filling in relation to the root apex. Roots that could be filled to the apex or within 2 mm of the apex had 94% treatment success. Thus, the prognosis for the treatment of nonvital teeth with periapical lesions was similar to that for the treatment of vital teeth when the instrumentation and filling of the root canal could be performed at an optimal level. The healed rate was significantly higher for teeth filled to an acceptable root length (74.4%) in the current study. Sjogren et al. reported that in cases where roots were filled to excess or where fillings were >2 mm below the root apex, the lesions healed in only 76%–68% of the cases, respectively. Teeth with short fillings and periapical lesions were included among the roots that could not be instrumented to their full length. The inability to instrument a canal to its full length may have been due to preexisting obstruction of the canal or pretreatment complications. Thus, the lower success rate in underfilled roots may be due to obstruction of the apical segment of the canal by infected dentin chips, which may have caused persistent infection at the root apex.
The negative impact of root-filling excess on the healing of periapical lesions may indicate cytotoxic effects of the coated gutta-percha when combined with sealer cement. However, several studies have shown that gutta-percha is well-tolerated by tissues. The adverse effects of root-filling excess on the outcome of treatment may be due to over-instrumentation, which often precedes overfilling. This may force infected dentin chips into the periapical tissue. Yusuf  observed that periapical granulomas from cases of failed root treatment often contain foreign material, such as dentin, cementum chips, and/or residual root-filling material during retreatment. In the present study, of the 43 teeth treated without preoperative radiolucency, 40 (93.02%) remained healed. Many studies have demonstrated that the success rate in endodontic therapy is significantly influenced by the presence or absence of a pretherapeutic radiographic lesion.,,, In teeth treated without preoperative apical periodontitis, the healed rate was 94%, which was in the middle of the range (88%–97%) reported in previous studies.,,, This outcome was unaffected by any of the analyzed variables, suggesting that clinical outcome research related to initial treatment should focus on teeth with apical periodontitis.
| Conclusion|| |
Despite the limited sample size and problematic recall rate, the overall findings were as follows: (1) the success rate of root canal treatment performed by endodontic postgraduate students at Riyadh Elm University was 68.1%; (2) caries and failed root canal treatment were most commonly referred for management by endodontic postgraduate students; (3) the presence or absence of apical periodontitis significantly affected the rate of success of endodontic treatment; (4) teeth treated in ≥2 visits showed superior healing relative to those treated in one visit; and (5) short and long root canal filling resulted in poor prognosis, relative to that of adequate filling.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Strindberg LZ. The dependence of the results of pulp therapy on certain factors. An analytic study based on radiographic and clinical follow-up examinations. Acta Odont Scan 1956;14 Suppl 21:1-175.
Nair PN, Sjögren U, Figdor D, Sundqvist G. Persistent periapical radiolucencies of root-filled human teeth, failed endodontic treatments, and periapical scars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:617-27.
Siqueira JF Jr. Reaction of periradicular tissue to root canal treatment: Benefits and drawbacks. Endod Topics 2005;10:123-47.
Holland R, Mazuqueli L, de Souza V, Murata SS, Dezan Júnior E, Suzuki P. Influence of the type of vehicle and limit of obturation on apical and periapical tissue response in dogs' teeth after root canal filling with mineral trioxide aggregate. J Endod 2007;33:693-7.
Suzuki P, de Souza V, Holland R, Murata SS, Gomes-Filho JE, Dezan Junior E, et al.
Tissue reaction of the EndoREZ in root canal fillings short of or beyond an apical foramenlike communication. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:e94-9.
Seltzer S. Repair following root canal therapy. In: Endodontology: Biologic Considerations in Endodontic Procedures. Philadelphia: Lea Fabinger; 1988. p. 389-438.
Ricucci D, Lin LM, Spångberg LS. Wound healing of apical tissues after root canal therapy: A long-term clinical, radiographic, and histopathologic observation study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;108:609-21.
de Chevigny C, Dao TT, Basrani BR, Marquis V, Farzaneh M, Abitbol S, et al.
Treatment outcome in endodontics: The Toronto study – Phases 3 and 4: Orthograde retreatment. J Endod 2008a; 34:131-7.
de Chevigny C, Dao TT, Basrani BR, Marquis V, Farzaneh M, Abitbol S, et al.
Treatment outcome in endodontics: The Toronto study – Phase 4: Initial treatment. J Endod 2008b; 34:258-63.
Touboul V, Germa A, Lasfargues JJ, Bonte E. Outcome of endodontic treatments made by postgraduate students in the dental clinic of Bretonneau hospital. Int J Dent 2014;2014:684979.
Chugal NM, Clive JM, Spångberg LS. A prognostic model for assessment of the outcome of endodontic treatment: Effect of biologic and diagnostic variables. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:342-52.
Friedman S, Abitbol S, Lawrence HP. Treatment outcome in endodontics: The Toronto study, phase 1 – Initial treatment. J Endod 2003;29:787-93.
Ng YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: Systematic review of the literature – Part 1. Effects of study characteristics on probability of success. Int Endod J 2007;40:921-39.
Orstavik D. Time-course and risk analyses of the development and healing of chronic apical periodontitis in man. Int Endod J 1996;29:150-5.
Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16:498-504.
Molven O, Halse A. Success rates for gutta-percha and kloroperka N-0 root fillings made by undergraduate students: Radiographic findings after 10-17 years. Int Endod J 1988;21:243-50.
Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74.
American Association of Endodontists Communique. AAE and Foundation Approve Definition of Endodontic Outcomes. Vol. 29. Chicago, IL, USA: The American Association of Endodontists Communique; 2005.
European Society of Endodontology. Quality guidelines for endodontic treatment: Consensus report of the European society of endodontology. Int Endod J 2006;39:921-30.
Scavo R, Martinez Lalis R, Zmener O, Dipietro S, Grana D, Pameijer CH. Frequency and distribution of teeth requiring endodontic therapy in an argentine population attending a specialty clinic in endodontics. Int Dent J 2011;61:257-60.
Khan SQ, Khan NB, Arrejaie AS. Dental caries. A meta analysis on a Saudi population. Saudi Med J 2013;34:744-9.
Martin FE, Nadkarni MA, Jacques NA, Hunter N. Quantitative microbiological study of human carious dentine by culture and real-time PCR: Association of anaerobes with histopathological changes in chronic pulpitis. J Clin Microbiol 2002;40:1698-704.
Alhekeir DF, Al-Sarhan RA, Mokhlis H, Al-Nazhan S. Endodontic mishaps among undergraduate dental students attending King Saud University and Riyadh Colleges of dentistry and pharmacy. Saudi Endod J 2013;3:25-30. [Full text]
Sackett D, Haynes RB, Guyatt GH, Tugwell P. Clinical Epidemiology: A Basic Science of Clinical Medicine. 2nd
ed.. Boston: Little, Brown; 1991.
Bernstein SD, Horowitz AJ, Man M, Wu H, Foran D, Vena DA, et al.
Outcomes of endodontic therapy in general practice: A study by the practitioners engaged in applied research and learning network. J Am Dent Assoc 2012;143:478-87.
Friedman S, Mor C. The success of endodontic therapy – Healing and functionality. J Calif Dent Assoc 2004;32:493-503.
Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod J 1995;28:12-8.
Ng YL, Mann V, Gulabivala K. A prospective study of the factors affecting outcomes of nonsurgical root canal treatment: Part 1: Periapical health. Int Endod J 2011;44:583-609.
Tronstad L, Asbjørnsen K, Døving L, Pedersen I, Eriksen HM. Influence of coronal restorations on the periapical health of endodontically treated teeth. Endod Dent Traumatol 2000;16:218-21.
Hommez GM, Coppens CR, De Moor RJ. Periapical health related to the quality of coronal restorations and root fillings. Int Endod J 2002;35:680-9.
Di Filippo G, Sidhu SK, Chong BS. Apical periodontitis and the technical quality of root canal treatment in an adult sub-population in London. Br Dent J 2014;216:E22.
Ricucci D, Russo J, Rutberg M, Burleson JA, Spångberg LS. A prospective cohort study of endodontic treatments of 1,369 root canals: Results after 5 years. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:825-42.
Gillen BM, Looney SW, Gu LS, Loushine BA, Weller RN, Loushine RJ, et al.
Impact of the quality of coronal restoration versus the quality of root canal fillings on success of root canal treatment: A systematic review and meta-analysis. J Endod 2011;37:895-902.
Song M, Park M, Lee CY, Kim E. Periapical status related to the quality of coronal restorations and root fillings in a Korean population. J Endod 2014;40:182-6.
Vera J, Siqueira JF Jr., Ricucci D, Loghin S, Fernández N, Flores B, et al.
One- versus two-visit endodontic treatment of teeth with apical periodontitis: A histobacteriologic study. J Endod 2012;38:1040-52.
Byström A, Sundqvist G. Bacteriologic evaluation of the effect of 0.5 percent sodium hypochlorite in endodontic therapy. Oral Surg Oral Med Oral Pathol 1983;55:307-12.
Sjögren U, Figdor D, Persson S, Sundqvist G. Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis. Int Endod J 1997;30:297-306.
Law A, Messer H. An evidence-based analysis of the antibacterial effectiveness of intracanal medicaments. J Endod 2004;30:689-94.
Rahimi S, Janani M, Lotfi M, Shahi S, Aghbali A, Vahid Pakdel M, et al.
A review of antibacterial agents in endodontic treatment. Iran Endod J 2014;9:161-8.
Peters LB, van Winkelhoff AJ, Buijs JF, Wesselink PR. Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions. Int Endod J 2002;35:13-21.
Sathorn C, Parashos P, Messer HH. Effectiveness of single- versus multiple-visit endodontic treatment of teeth with apical periodontitis: A systematic review and meta-analysis. Int Endod J 2005;38:347-55.
Su Y, Wang C, Ye L. Healing rate and post-obturation pain of single- versus multiple-visit endodontic treatment for infected root canals: A systematic review. J Endod 2011;37:125-32.
Trope M, Delano EO, Orstavik D. Endodontic treatment of teeth with apical periodontitis: Single vs. multivisit treatment. J Endod 1999;25:345-50.
Spångberg L. Biological effects of root canal filling materials 7. Reaction of bony tissue to implanted root canal filling material in guineapigs. Odontol Tidskr 1969;77:133-59.
Yusuf H. The significance of the presence of foreign material periapically as a cause of failure of root treatment. Oral Surg Oral Med Oral Pathol 1982;54:566-74.
Farzaneh M, Abitbol S, Lawrence HP, Friedman S; Toronto Study. Treatment outcome in endodontics-the Toronto study. Phase II: Initial treatment. J Endod 2004;30:302-9.
Engström B, Hard AF, Segerstad L, Ramström G. Frostell G. Correlation of positive cultures with the prognosis for root canal treatment. Odontol Rev 1964;15:257-70.
Kerekes K, Tronstad L. Long-term results of endodontic treatment performed with a standardized technique. J Endod 1979;5:83-90.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]