Expert consensus on difficulty assessment of endodontic therapy

doi:10.1038/s41368-024-00285-0

PDF

International Journal of Oral Science ›› 2024, Vol. 16 ›› Issue (0) : 22. DOI: 10.1038/s41368-024-00285-0

Expert consensus on difficulty assessment of endodontic therapy

Dingming Huang¹, Xiaoyan Wang², Jingping Liang³, Junqi Ling⁴, Zhuan Bian⁵, Qing Yu⁶, Benxiang Hou⁷, Xinmei Chen¹, Jiyao Li¹, Ling Ye¹, Lei Cheng¹, Xin Xu¹, Tao Hu⁸, Hongkun Wu⁹, Bin Guo¹⁰, Qin Su¹, Zhi Chen⁵, Lihong Qiu¹¹, Wenxia Chen¹², Xi Wei⁴, Zhengwei Huang³, Jinhua Yu¹³, Zhengmei Lin⁴, Qi Zhang¹⁴, Deqin Yang¹⁵, Jin Zhao¹⁶, Shuang Pan¹⁷, Jian Yang¹⁸, Jiayuan Wu¹⁹, Yihuai Pan²⁰, Xiaoli Xie²¹, Shuli Deng²², Xiaojing Huang²³, Lan Zhang¹, Lin Yue², Xuedong Zhou¹

Author information +

1. State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China;
2. Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology & National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, China;
3. Department of Endodontics, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, National Clinical Research Center for Oral Diseases, National Center for Stomatology, Shanghai Key Laboratory of Stomatology, Shanghai, China;
4. Department of Operative Dentistry and Endodontics, Hospital of Stomatology, Guanghua, School of Stomatology, Sun Yat-Sen University & Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China;
5. The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) & Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China;
6. Department of Operative Dentistry & Endodontics, School of Stomatology, The Fourth Military Medical University, Xi’an, China;
7. Department of Endodontics, Beijing Stomatological Hospital, School of Stomatology, Capital Medical University, Beijing, China;
8. State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China;
9. State Key Laboratory of Oral Diseases & National Center for Stomatology & National Clinical Research Center for Oral Diseases & Department of Geriatric dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China;
10. Department of Stomatology, First Medical Center, Chinese PLA General Hospital, Beijing, China;
11. Department of Endodontics, School of Stomatology, China Medical University, Shenyang, China;
12. College of Stomatology, Hospital of Stomatology, Guangxi Medical University, Nanning, China;
13. Department of Endodontics, School and Hospital of Stomatology, Nanjing Medical University, Nanjing, China;
14. Department of Endodontics, Stomatological Hospital and Dental School of Tongji University, Shanghai Engineering Research Center of Tooth Restoration and Regeneration, Shanghai, China;
15. Department of Endodontics, Stomatological Hospital of Chongqing Medical University, Chongqing, China;
16. Department of Endodontics, First Affiliated Hospital of Xinjiang Medical University, and College of Stomatology of Xinjiang Medical University, Urumqi, China;
17. Department of Endodontics, Schoolof Stomatology, First Affiliated Hospital of Harbin Medical University, Harbin, China;
18. Department of Endodontics, The Affiliated Stomatological Hospital of Nanchang University, Nanchang, China;
19. Key Laboratory of Oral Disease Research, School of Stomatology, Zunyi Medical University, Zunyi, China;
20. Department of Endodontics, School and Hospital of Stomatology, Wenzhou Medical University, Wenzhou, China;
21. Department of Cariology and Endodontics, Xiangya Stomatological School, Central South University, Changsha, China;
22. Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine, Zhejiang Provincial Clinical Research Center for Oral Diseases, Key Laboratory of Oral Biomedical Research of Zhejiang Province, Cancer Center of Zhejiang University, Hangzhou, China;
23. School and Hospital of Stomatology, Fujian Medical University, Fuzhou, China

Show less

History +

Abstract

Endodontic diseases are a kind of chronic infectious oral disease. Common endodontic treatment concepts are based on the removal of inflamed or necrotic pulp tissue and the replacement by gutta-percha. However, it is very essential for endodontic treatment to debride the root canal system and prevent the root canal system from bacterial reinfection after root canal therapy (RCT). Recent research, encompassing bacterial etiology and advanced imaging techniques, contributes to our understanding of the root canal system’s anatomy intricacies and the technique sensitivity of RCT. Success in RCT hinges on factors like patients, infection severity, root canal anatomy, and treatment techniques. Therefore, improving disease management is a key issue to combat endodontic diseases and cure periapical lesions. The clinical difficulty assessment system of RCT is established based on patient conditions, tooth conditions, root canal configuration, and root canal needing retreatment, and emphasizes pre-treatment risk assessment for optimal outcomes. The findings suggest that the presence of risk factors may correlate with the challenge of achieving the high standard required for RCT. These insights contribute not only to improve education but also aid practitioners in treatment planning and referral decision-making within the field of endodontics.

Cite this article

EndNote

Ris (Procite)

Bibtex

Download citation ▾

Dingming Huang, Xiaoyan Wang, Jingping Liang, Junqi Ling, Zhuan Bian, Qing Yu, Benxiang Hou, Xinmei Chen, Jiyao Li, Ling Ye, Lei Cheng, Xin Xu, Tao Hu, Hongkun Wu, Bin Guo, Qin Su, Zhi Chen, Lihong Qiu, Wenxia Chen, Xi Wei, Zhengwei Huang, Jinhua Yu, Zhengmei Lin, Qi Zhang, Deqin Yang, Jin Zhao, Shuang Pan, Jian Yang, Jiayuan Wu, Yihuai Pan, Xiaoli Xie, Shuli Deng, Xiaojing Huang, Lan Zhang, Lin Yue, …Xuedong Zhou. Expert consensus on difficulty assessment of endodontic therapy. International Journal of Oral Science, 2024, 16(0): 22 https://doi.org/10.1038/s41368-024-00285-0

References

1. Buonavoglia, A.et al.Endodontic microbial communities in apical periodontitis.J. Endod. 49, 178-189 (2023).
2. Siqueira J. J.& Rôças, I. N. Present status and future directions: microbiology of endodontic infections.Int. Endod. J. 55, 512-530 (2022).
3. Tan K. S., Yu V. S., Quah S. Y.& Bergenholtz, G. Rapid method for the detection of root canal bacteria in endodontic therapy.J. Endod. 41, 447-450 (2015).
4. Lin P. Y., Chiang Y. C., Chou Y. J., Chang H. J.& Chi, L. Y. Association of unfinished root canal treatments with the risk of pneumonia hospitalization.J. Endod. 43, 29-35 (2017).
5. American Association of Endodontists. Evaluating Endodontic Treatment Risk Factors. Colleagues for Excellence Series, 1-10, 2005 (American Association of Endodontists, accessed 11 October 2021); https://www.aae.org/specialty/wp-content/uploads/sites/2/2017/07/ss05ecfe.pdf.
6. Muthukrishnan A., Owens J., Bryant S.& Dummer, P. M. Evaluation of a system for grading the complexity of root canal treatment.Br. Dent. J. 202, E26(2007).
7. Hou, Y.et al.Potential relationship between clinical symptoms and the root canal microbiomes of root filled teeth based on the next-generation sequencing.Int. Endod. J. 55, 18-29 (2022).
8. Tang L., Sun T. Q., Gao X. J., Zhou X. D.& Huang, D. M. Tooth anatomy risk factors influencing root canal working length accessibility.Int. J. Oral Sci. 3, 135-140 (2011).
9. Zhang Q., Chen H., Fan B., Fan W.& Gutmann, J. L. Root and root canal morphology in maxillary second molar with fused root from a native Chinese population.J. Endod. 40, 871-875 (2014).
10. Liu, N.et al.A micro-computed tomography study of the root canal morphology of the mandibular first premolar in a population from southwestern China.Clin. Oral Investig. 17, 999-1007 (2013).
11. Liu X., Gao M., Bai Q., Ruan J.& Lu, Q. Evaluation of palatal furcation groove and root canal anatomy of maxillary first premolar: a CBCT and micro-CT study.Biomed. Res. Int. 2021, 8862956(2021).
12. Yang, B.et al.Evaluation of the prevalence of the maxillary molars with two palatal roots by cone-beam CT.Chin. J. Stomatol. 48, 359-362 (2013).
13. Wang Y., Yin Z. Z., Nie X. K., Ma, Z. D. & Xiong, S. J. Detection of middle mesial canal in1125 permanent mandibular first molars using CBCT and related factors. J. Shandong Univ. (Health Sci.) 60, 100-108+113 (2022).
14. Chen, L. C., Li, J., Zeng, C. M., Liu, Y. W. & Jiang, H. W. Clinical outcome of using single-cone obturation technique with bioceramic sealer iRoot SP in root canal treatment: a retrospective analysis. Chin. J. Stomatol. Res. (Electron. Ed.) 14, 353-360 (2020).
15. Liang Y. H., Li G., Shemesh H., Wesselink P. R.& Wu, M. K. The association between complete absence of post-treatment periapical lesion and quality of root canal filling.Clin. Oral Investig. 16, 1619-1626 (2012).
16. Restrepo-Restrepo, F. A. et al. Prognosis of root canal treatment in teeth with preoperative apical periodontitis: a study with cone-beam computed tomography and digital periapical radiography.Int. Endod. J. 52, 1533-1546 (2019).
17. Liang Y. H., Li G., Wesselink P. R.& Wu, M. K. Endodontic outcome predictors identified with periapical radiographs and cone-beam computed tomography scans.J. Endod. 37, 326-331 (2011).
18. Zhu Q., Gan Y. H., Zhao L., Zhang S. X.& Zhang, J. Analysis of radiographic technical quality of 2306 root canal obturation performed by endodontists.J. Oral. Sci. Res. 32, 1282-1286 (2016).
19. Karhunen S.& Virtanen, J. I. Dental treatment injuries in the Finnish Patient Insurance Centre in 2000-2011.Acta Odontol. Scand. 74, 236-240 (2016).
20. Pesonen, R. et al. Usefulness of an endodontic case difficulty assessment form of root canal treatments in dental education in Finland. Dent. J. (Basel) 9, 118 (2021).
21. Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University. Procedure rules and prognostic evaluation criteria of root canal therapy.West China J. Stomatol. 22, 196-197 (2004).
22. Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University. Difficulty assessment of root canal therapy.West China J. Stomatol. 22, 381-383 (2004).
23. American Association of Endodontists AAE. Endodontic Case Difficulty Assessment and Referral, 2005 (American Association of Endodontists, accessed 7 March 2020) https://www.aae.org/specialty/wp-content/uploads/sites/2/2017/10/2006casedifficultyassessmentformb_edited2010.pdf.
24. Current Care Guidelines. Root Canal Treatment. In Working Group Set Up by the Finnish Medical Society Duodecim and the Finnish Dental Association Apollonia, 2016 (The Finnish Medical Society Duodecim, Helsinki, Finland, accessed on 26 August 2021). www.kaypahoito.fi.
25. Chung S. H.& Chang, J. Impact of endodontic case difficulty on operating time of single visit nonsurgical endodontic treatment under general anesthesia.BMC Oral Health 21, 231(2021).
26. Ree, M. H., Timmerman, M. F.& Wesselink, P. R. An evaluation of the usefulness of two endodontic case assessment forms by general dentists.Int. Endod. J. 36, 545-555 (2003).
27. Huang D. M.& Zhou, X. D. Difficulty assessment of root canal treatment. Chin. J. Dent. Sci. 41, 532-534, https://doi.org/10.3760/j.issn:1002-0098.2006.09.006(2006).
28. Tian Y.& Zhang, Y. The relationship between hypertension and physical activity in middle-aged and older adults controlling for demographic, chronic disease, and mental health variables.Medicine 101, e32092(2022).
29. Susarla S. M.& Dodson, T. B. Estimating third molar extraction difficulty: a comparison of subjective and objective factors.J. Oral Maxillofac. Surg. 63, 427-434 (2005).
30. NHS England (2019) Commissioning Standard for Restorative Dentistry (accessed 22 February 2022). england.nhs.uk/publication/commissioning-standard-for-restorative-dentistry/.
31. Chang J.Dental treatment under general anesthesia: an overview of clinical characteristics of special needs patients.J. Korean Assoc. Disabil. Oral Health 10, 61-67 (2014).
32. Ricucci D.& Siqueira, J. J. Anatomic and microbiologic challenges to achieving success with endodontic treatment: a case report.J. Endod. 34, 1249-1254 (2008).
33. Gao Y., Zhang Y., Zhou X. D.& Huang, D. M. Endodontic infection management in root canal preparation: question and solution.West China J. Stomatol. 36, 590-594 (2018).
34. Ricucci D.& Siqueira, J. J. Biofilms and apical periodontitis: study of prevalence and association with clinical and histopathologic findings.J. Endod. 36, 1277-1288 (2010).
35. Ng, Y. L., Mann, V.& Gulabivala, K. A prospective study of the factors affecting outcomes of nonsurgical root canal treatment: part 1: periapical health.Int. Endod. J. 44, 583-609 (2011).
36. Neelakantan, P., Devaraj, S.& Jagannathan, N. Histologic assessment of debridement of the root canal isthmus of mandibular molars by irrigant activation techniques ex vivo.J. Endod. 42, 1268-1272 (2016).
37. Lu, Y., Wang, R.& Huang, D. M. A study related to root canal retreatment of affected teeth with loss of crown seal.Chin. J. Conserv. Dent. 23, 136-139 (2013).
38. Kinane, D. F., Stathopoulou, P. G.& Papapanou, P. N. Periodontal diseases.Nat. Rev. Dis. Prim. 3, 17038(2017).
39. Sanz, M.et al.Scientific evidence on the links between periodontal diseases and diabetes: consensus report and guidelines of the joint workshop on periodontal diseases and diabetes by the International diabetes Federation and the European Federation of Periodontology.Diabetes Res. Clin. Pract. 137, 231-241 (2018).
40. Fezai H.& Al-Salehi, S. The relationship between endodontic case complexity and treatment outcomes.J. Dent. 85, 88-92 (2019).
41. Bruna del Cojo, M., Gallardo López, N. E., Mourelle Martínez, M. R. & De Nova García, M. J. Time and sequence of eruption of permanent teeth in Spanish children.Eur. J. Paediatr. Dent. 14, 101-103 (2013).
42. Chen X., Huo Y., Peng Y., Zhang Q.& Zou, J. Ectopic eruption of the first permanent molar: predictive factors for irreversible outcome.Am. J. Orthod. Dentofac. Orthop. 159, e169-e177 (2021).
43. Abella, F.et al.Cone-beam computed tomography analysis of the root canal morphology of maxillary first and second premolars in a Spanish population.J. Endod. 41, 1241-1247 (2015).
44. Martins J. N.R., Marques, D., Mata, A. & Caramês, J. Root and root canal morphology of the permanent dentition in a Caucasian population: a cone-beam computed tomography study.Int. Endod. J. 50, 1013-1026 (2017).
45. Kantilieraki E., Delantoni A., Angelopoulos C.& Beltes, P. Evaluation of root and root canal morphology of mandibular first and second molars in a Greek population: a CBCT study.Eur. Endod. J. 4, 62-68 (2019).
46. Shah, P. K.et al.Comparison of two case difficulty assessment methods on cohorts of undergraduate dental students—a multi-centre study.Int. Endod. J. 53, 1569-1580 (2020).
47. Tziafas D., Kodonas K., Gogos C., Tziafa C.& Papadimitriou, S. EDTA conditioning of circumpulpal dentine induces dentinogenic events in pulpotomized miniature swine teeth.Int. Endod. J. 52, 656-664 (2019).
48 48.Yong, W.et al. [X-ray evaluation of pulp calcification in adult permanent teeth after pulpotomy].Beijing Da Xue Xue Bao Yi Xue Ban. 55, 88-93 (2023).
49. Vertucci F. J.Root canal anatomy of the human permanent teeth.Oral. Surg. Oral Med. Oral Pathol. 58, 589-599 (1984).
50. Ahmed H. M.A., Versiani, M. A., De-Deus, G. & Dummer, P. M. H. A new system for classifying root and root canal morphology.Int. Endod. J. 50, 761-770 (2017).
51. Pomeranz, H. H., Eidelman, D. L.& Goldberg, M. G. Treatment considerations of the middle mesial canal of mandibular first and second molars.J. Endod. 7, 565-568 (1981).
52. Song J. S., Choi H. J., Jung I. Y., Jung H. S.& Kim, S. O. The prevalence and morphologic classification of distolingual roots in the mandibular molars in a Korean population.J. Endod. 36, 653-657 (2010).
53. Tomaszewska, I. M.et al.An original micro-CT study and meta-analysis of the internal and external anatomy of maxillary molars-implications for endodontic treatment.Clin. Anat. 31, 838-853 (2018).
54. Wu, D.et al.Root canal morphology of maxillary and mandibular first premolars analyzed using cone-beam computed tomography in a Shandong Chinese population.Medicine 99, e20116(2020).
55. Martins, J. N. R.et al. Worldwide analyses of maxillary first molar second mesiobuccal prevalence: a multicenter cone-beam computed tomographic study. J. Endod. 44, 1641-1649.e1 (2018).
56. Shah P. K.& Chong, B. S. A web-based endodontic case difficulty assessment tool.Clin. Oral Investig. 22, 2381-2388 (2018).
57. Kato, A.et al.Aetiology, incidence and morphology of the C-shaped root canal system and its impact on clinical endodontics.Int. Endod. J. 47, 1012-1033 (2014).
58. Fan, B.et al.Negotiation of C-shaped canal systems in mandibular second molars.J. Endod. 35, 1003-1008 (2009).
59. Zhang L., Luo H. X., Zhou X. D., Tan H.& Huang, D. M. The shaping effect of the combination of two rotary nickel-titanium instruments in simulated S-shaped canals.J. Endod. 34, 456-458 (2008).
60. Zhu, J. X.et al.Root canal morphology of mandibular incisors with double root canals in a Chinese population.Chin. J. Dent. Res. 23, 199-204 (2020).
61. Zheng, Q.et al.C-shaped root canal system in mandibular second molars in a Chinese population evaluated by cone-beam computed tomography.Int. Endod. J. 44, 857-862 (2011).
62. Endal U., Shen Y., Knut A., Gao Y.& Haapasalo, M. A high-resolution computed tomographic study of changes in root canal isthmus area by instrumentation and root filling.J. Endod. 37, 223-227 (2011).
63. von Arx, T. Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgery.Int. Endod. J. 38, 160-168 (2005).
64. Ahmed H. M.A. et al. Application of a new system for classifying root and canal anatomy in studies involving micro-computed tomography and cone beam computed tomography: explanation and elaboration.Int. Endod. J. 54, 1056-1082 (2021).
65. Xu T., Fan W., Tay F. R.& Fan, B. Micro-computed tomographic evaluation of the prevalence, distribution, and morphologic features of accessory canals in Chinese permanent teeth.J. Endod. 45, 994-999 (2019).
66. Dammaschke T., Witt M., Ott K.& Schäfer, E. Scanning electron microscopic investigation of incidence, location, and size of accessory foramina in primary and permanent molars.Quintessence Int. 35, 699-705 (2004).
67. Jang J. H., Lee J. M., Yi J. K., Choi S. B.& Park, S. H. Surgical endodontic management of infected lateral canals of maxillary incisors.Restor. Dent. Endod. 40, 79-84 (2015).
68. Fu, Y.et al.Coronal root canal morphology of permanent two-rooted mandibular first molars with novel 3D measurements.Int. Endod. J. 53, 167-175 (2020).
69. Hou B. X.Complications occurred in root canal mechanical preparation: the reason, prevention and management.Chin. J. Stomatol. 5, 605-611 (2019).
70. Martins J. C.L. G. D. et al. Micro-computed tomographic assessment of dentinal microcrack formation in straight and curved root canals in extracted teeth prepared with hand, rotary and reciprocating instruments.Int. Endod. J. 54, 1362-1368 (2021).
71. Schneider S. W.A comparison of canal preparations in straight and curved root canals.Oral Surg. Oral Med. Oral Pathol. 32, 271-275 (1971).
72. Chen, L., Chen, Z.& Wu, B. L. Finite element analysis of nickel-titanium rotary instrument in curved root canals with different parameters.Chin. J. Geriatr. Dent. 12, 273-276 (2014).
73. Gorni F. G.& Gagliani, M. M. The outcome of endodontic retreatment: a 2-yr follow-up.J. Endod. 30, 1-4 (2004).
74. Fonseca Tavares, W. L., Diniz Viana, A. C., de Carvalho Machado, V., Feitosa Henriques, L. C. & Ribeiro Sobrinho, A. P. Guided endodontic access of calcified anterior teeth.J. Endod. 44, 1195-1199 (2018).
75. Roane, J. B., Sabala, C. L.& Duncanson, M. G. J. The “balanced force” concept for instrumentation of curved canals.J. Endod. 11, 203-211 (1985).
76. Chaniotis A.& Ordinola-Zapata, R. Present status and future directions: management of curved and calcified root canals.Int. Endod. J. 55, 656-684 (2022).
77. Heboyan, A.et al.Tooth root resorption: a review.Sci. Prog. 105, 368504221109217(2022).
78. Umashetty G., Hoshing U., Patil S.& Ajgaonkar, N. Management of inflammatory internal root resorption with biodentine and thermoplasticised gutta-percha.Case Rep. Dent. 2015, 452609(2015).
79. Plascencia, H.et al.Intra- and interobserver agreement during the assessment of the different stages of root development using 4 radiographic classifications.J. Endod. 47, 906-913 (2021).
80. Ruddle, C. J. Non-surgical endodontic retreatment. In Pathways of the Pulp 8th edn (eds Cohen, S. & Burns, R. C.) 875 (Mosby, St. Louis, 2002).
81. de Chevigny, C.et al. Treatment outcome in endodontics: the Toronto study—phase 4: initial treatment.J. Endod. 34, 258-263 (2008).
82. Brignardello-Petersen, R. et al. Apical underfilling, but not overfilling, in root canal treatment probably increases the odds of unfavorable outcomes.J. Am. Dent. Assoc. 150, e160(2019).
83. Huang, C., Zhu, J.& Wang, Q. The infection control of post-and-core crown restoration.West China J. Stomatol. 41, 247-253 (2023).
84. Mulvay P. G.& Abbott, P. V. The effect of endodontic access cavity preparation and subsequent restorative procedures on molar crown retention.Aust. Dent. J. 41, 134-139 (1996).
85. Schwartz R. S.& Robbins, J. W. Post placement and restoration of endodontically treated teeth: a literature review.J. Endod. 30, 289-301 (2004).
86. Peciuliene V., Rimkuviene J., Maneliene R.& Pletkus, R. Factors influencing the removal of posts.Stomatologija 7, 21-23 (2005).
87. Gomes A. P., Kubo C. H., Santos R. A., Santos D. R.& Padilha, R. Q. The influence of ultrasound on the retention of cast posts cemented with different agents.Int. Endod. J. 34, 93-99 (2001).
88. Abbott P. V.Incidence of root fractures and methods used for post removal.Int. Endod. J. 35, 63-67 (2002).
89. Friedman, S., Stabholz, A.& Tamse, A. Endodontic retreatment—case selection and technique. 3. Retreatment techniques.J. Endod. 16, 543-549 (1990).
90. Sjogren U., Hagglund B., Sundqvist G.& Wing, K. Factors affecting the long-term results of endodontic treatment.J. Endod. 16, 498-504 (1990).
91. Haug S. R., Solfjeld A. F., Ranheim L. E.& Bårdsen, A. Impact of case difficulty on endodontic mishaps in an undergraduate student clinic.J. Endod. 44, 1088-1095 (2018).
92. Iqbal, M. K., Kohli, M. R.& Kim, J. S. A retrospective clinical study of incidence of root canal instrument separation in an endodontics graduate program: a PennEndo database study.J. Endod. 32, 1048-1052 (2006).
93. Wolcott, S.et al.Separation incidence of protaper rotary instruments: a large cohort clinical evaluation.J. Endod. 32, 1139-1141 (2006).
94. Lambrianidis T.Ledging and blockage of root canals during canal preparation: causes, recognition, prevention, management, and outcomes.Endodont. Top. 15, 56-74 (2006).
95. Bhuva B.& Ikram, O. Complications in endodontics.Prim. Dent. J. 9, 52-58 (2020).
96. Ingle, J. I.et al. Outcome of endodontic treatment and retreatment. In Endodontics 5th edn (eds Ingle, J. I. & Bakland, L. K.) 747 (BC Decker, Hamilton, 2002).
97. Seltzer, S., Sinai, I.& August, D. Periodontal effects of root perforations before and during endodontic procedures.J. Dent. Res. 49, 332-339 (1970).
98. Canadian Academy of Endodontics. Standards of Practice (Canadian Academy of Endodontics, Winnipeg, Edmonton, Canada, 1998).
99. Ungerechts, C., Bårdsen, A.& Fristad, I. Instrument fracture in root canals—where, why, when and what? A study from a student clinic.Int. Endod. J. 47, 183-190 (2014).
100. Dechouniotis, G., Petridis, X. M.& Georgopoulou, M. K. Influence of specialty training and experience on endodontic decision making.J. Endod. 36, 1130-1134 (2010).
101. McCaul, L. K., McHugh, S. & Saunders, W. P. The influence of specialty training and experience on decision making in endodontic diagnosis and treatment planning.Int. Endod. J. 34, 594-606 (2001).
102. De Moor, R., Hülsmann, M., Kirkevang, L. L., Tanalp, J. & Whitworth, J. Undergraduate curriculum guidelines for endodontology.Int. Endod. J. 46, 1105-1114 (2013).
103. Ng, Y. L., Mann, V.& Gulabivala, K. Outcome of secondary root canal treatment: a systematic review of the literature.Int. Endod. J. 41, 1026-1046 (2008).
104. General Dental Council. Standards for the Dental Team (General Dental Council London, 2013).
105. Bierenkrant, D. E., Parashos, P.& Messer, H. H. The technical quality of nonsurgical root canal treatment performed by a selected cohort of Australian endodontists.Int. Endod. J. 41, 561-570 (2008).
106. De Cleen, M. J., Schuurs, A. H., Wesselink, P. R. & Wu, M. K. Periapical status and prevalence of endodontic treatment in an adult Dutch population.Int. Endod. J. 26, 112-119 (1993).
107. Essam O., Boyle E. L., Whitworth J. M.& Jarad, F. D. The endodontic complexity assessment tool (E-CAT): a digital form for assessing root canal treatment case difficulty.Int. Endod. J. 54, 1189-1199 (2021).