Instrument separation during endodontic therapy is a frequent accident with rotary instruments being more likely to separate than manual ones. The treatment of cases with a separated instrument can be either conservative or surgical. A conservative approach involves the following treatment choices: a) bypass of the fragment, b) removal of the fragment, c) instrumentation and obturation coronally to the fragment. Concerning the removal of a separated instrument, a variety of techniques and systems have been developed. Ultrasonics, in combination with the operative microscope constitute the most effective and reliable tools for removing a separated endodontic instrument from a root canal. The likelihood of successful removal depends on: the level of separation (coronal, middle or apical third); location in relation to the root canal curvature; the type of separated instrument; its length; the degree of canal curvature and the tooth type. Several complications may occur during the management of a separated instrument: separation of the ultrasonic tip or file used for bypassing or removing the instrument; further separation of the fragment; perforation; ledge; extrusion of the file into periapical tissues; tooth weakening due to dentin removal, as well as excessive temperature rise in periodontal tissues. Prognosis for a tooth retaining a separated instrument depends on the presence of a periapical lesion, the microbial load of the root canal during the time of separation and the quality of the obturation.
1. Suter B, Lussi A, Sequeira P. Probability of removing fractured instruments from root canals. Int Endod J, 2005;38:112-123.
2. Iqbal MK, Kohli MR, Kim JS. A retrospective clinical study of incidence of root canal instrument separation in an endodontics graduate program: A PennEndo database study. J Endod, 2006;32:1048-1052.
3. Tzanetakis GN, Kontakiotis EG, Maurikou DV, Marzelou MP. Prevalence and management of instrument fracture in the postgraduate endodontic program at the Dental School of Athens: A five-year retrospective clinical study. J Endod, 2008;34:675-678.
4. Ramirez-Salomon M, Soler-Bientz R, de la Garza-González R, Palacios-Garza CM. Incidence of Lightspeed separation and the potential for bypassing. J Endod, 1997;23:586-587.
5. Baumann MA, Roth A. Effect of experience on quality of canal preparation with rotary nickel-titanium files. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 1999;88:714-718.
6. Al-Fouzan KS. Incidence of rotary ProFile instrument fracture and the potential for bypassing in vivo. Int Endod J, 2003;36:864-867.
7. Hülsmann M, Herbst U, Schäfers F. Comparative study of root-canal preparation using Lightspeed and Quantec SC rotary NiTi instruments. Int Endod J, 2003;36:748-756.
8. Ankrum MT, Hartwell GR, Truitt JE. K3 Endo, ProTaper, and ProFile systems: breakage and distortion in severely curved roots of molars. J Endod, 2004;30:234-237.
10. Spili P, Parashos P, Messer HH. The impact of instrument fracture on outcome of endodontic treatment. J Endod, 2005;31:845-850.
11. Knowles KI, Hammond NB, Biggs SG, Ibarrola JL. Incidence of instrument separation using lightspeed rotary instruments. J Endod, 2006;32:14-16.
12. Wolcott S, Wolcott J, Ishley D, Kennedy W, Johnson S, Minnich S, et al. Separation incidence of Protaper rotary instruments: A large cohort clinical evaluation. J Endod, 2006;32:1139-1141.
13. Wu J, Lei G, Yan M, Yu Y, Yu J, Zhang G. Instrument separation analysis of multi-used ProTaper universal rotary system during root canal therapy. J Endod, 2011;37:758-763.
14. Wang NN, Ge JY, Xie SJ, Chen GZM. Analysis of Mtwo rotary instrument separation during endodontic therapy: a retrospective clinical study. Cell Biochem Biophys, 2014;70:1091-1095.
15. Cunha RS, Junaid A, Ensinas P, Nudera W, Bueno CE. Assessment of the separation incidence of reciprocating WaveOne files: a prospective clinical study. J Endod, 2014;40:922-924.
16. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis: A clinical investigation. J Am Dent Assoc, 1970;80:1341-1347.
17. Hülsmann M, Schinkel I. Influence of several factors on the success or failure of removal of fractured instruments from the root canal. Endod Dent Traumatol, 1999;15:252-258.
18. Ungerechts C, Bårdsen A FI. Instrument fracture in root canals - where, why, when and what? A study from a student clinic. Int Endod J, 2014;47:183-190.
19. Di Fiore PM, Genov KA, Komaroff E, Li Y, Lin L. Nickel-titanium rotary instrument fracture: A clinical practice assessment. Int Endod J, 2006;39:700-708.
20. Cujé J, Bargholz C, Hülsmann M. The outcome of retained instrument removal in a specialist practice. Int Endod J, 2010;43:545-554.
21. Cohen SJ, Glassman GD, Mounce R. Rips, strips and broken tips: Handling the endodontic mishap. Oral Health, 2005:10-20.
22. Madarati AA, Watts DC, Qualtrough AJ. Opinions and attitudes of endodontists and general dental practitioners in the UK towards the intracanal fracture of endodontic instruments: part 1. Int Endod J, 2008;41:693-701.
23. Cohen S, Schwartz S. Endodontic complications and the law. J Endod, 1987;13:191-197.
24. Torabinejad M, Lemon RR. Procedural accidents. In: Walton R, Torabinejad M, editor. Priciples and Practice of Endodontics. Philadelphia: W.B. Saunders Company; 2002. p. 310-330.
26. Lambrianidis T. Risk Management in Root Canal Treatment. Thessaloniki: University Studio Press; 2001.
27. Shen Y, Peng B, Cheung GS. Factors associated with the removal of fractured NiTi instruments from root canal systems. Oral Surgery. Oral Med Oral Pathol Oral Radiol Endod, 2004;98:605-610.
28. Nevares G, Cunha RS, Zuolo ML, Bueno CE. Success rates for removing or bypassing fractured instruments: A prospective clinical study. J Endod, 2012;38:442-444.
29. Ward JR, Parashos P, Messer HH. Evaluation of an ultrasonic technique to remove fractured rotary nickel-titanium endodontic instruments from root canals: clinical cases. J Endod, 2003;29:764-767.
30. Plotino G, Pameijer CH, Maria Grande N, Somma F. Ultrasonics in endodontics: A review of the literature. J Endod, 2007;33:81-95.
31. Fors UGH, Berg JO. A method for the removal of separated endodontic instruments from root canals. J Endod, 1983;9:156-159.
32. Weisman MI. The removal of difficult silver cones. J Endod, 1983;9:210-211.
33. Roda RS, Gettleman BH. Nonsurgical Retreatment. In: Hargreaves KM, Cohen S, editor. Cohen’s Pathways of the pulp. St Louis Missouri: Mosby Elsevier; 2011, p. 890-952.
34. Suter B. A new method for retrieving silver points and separated instruments from root canals. J Endod, 1998;24:446-448.
35. Roig-Greene JL. The retrieval of foreign objects from root canals: a simple aid. J Endod, 1983;9:394-397.
36. Terauchi Y, O’Leary L, Suda H. Removal of separated files from root canals with a new file-removal system: Case reports. J Endod, 2006;32:789-797.
37. Gettleman BH, Spriggs KA, ElDeeb ME, Messer HH. Removal of canal obstructions with the Endo Extractor. J Endod, 1991;17:608-611.
38. Spriggs KA, Gettleman BH, Messer HH. Evaluation of a new method for silver point removal. J Endod, 1990;16:335-338.
39. Yoldas O, Oztunc H, Tinaz C, Alparslan N. Perforation risks associated with the use of Masserann endodontic kit drills in mandibular molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2004;97:513-517.
41. Souyave LC, Inglis AT, Alcalay M. Removal of fractured instruments using ultrasonics. Br Dent J, 1985;159:251-253.
42. Nagai O, Tani N, Kayaba Y, Kodama S, Osada T. Ultrasonic removal of broken instruments in root canals. Int Endod J, 1986;19:298-304.
43. Kerekes K, Tronstad. Long-term results of endodontic treatment performed with a standardized technique. J Endod, 1979;5:83-90.
44. Park E. Ultrasonics in endodontics. Endod Topics, 2013;29:125-159.
45. Sleiman WP. The use of a chelating agent and ultrasonic tips in the retrieval of broken rotary NiTi. Oral health. 2006;49-53.
46. Terauchi Y, O’Leary L, Yoshioka T, Suda H. Comparison of the time required to create secondary fracture of separated file fragments by using ultrasonic vibration under various canal conditions. J Endod, 2013;39:1300-1305.
48. Yu DG, Kimura Y, Tomita Y, Nakamura Y, Watanabe H, Matsumoto K. Study on removal effects of filling materials and broken files from root canals using pulsed Nd:YAG laser. J Clin Laser Med Surg, 2000;18:23-28.
49. Cvikl B, Klimscha J, Holly M, Zeitlinger M, Gruber R, Moritz A. Removal of fractured endodontic instruments using an Nd:YAG laser. Quintessence Int, 2014;45:569-575.
50. Ormiga F, da Cunha Ponciano Gomes JA, de Araújo MC. Dissolution of nickel-titanium endodontic files via an electrochemical process: a new concept for future retrieval of fractured files in root canals. J Endod, 2010;36:717-720.
51. Ormiga F, da Cunha Ponciano Gomes JA, de Araújo MC, Barbosa AO. An initial investigation of the electrochemical dissolution of fragments of nickel-titanium endodontic files. J Endod, 2011;37:526-530.
52. Aboud LR, Ormiga F, Gomes JA. Electrochemical induced dissolution of fragments of nickel-titanium endodontic files and their removal from simulated root canals. Int Endod J, 2014;47:155-162.
53. Kowalczuck A, Silva Neto UX, Fariniuk LF, Westphalen VPD, Laurindo CAH, Carneiro E. Electrochemical dissolution of fractured nickel-titanium instruments in human extracted teeth. Int Endod J, 2017;50:578-585.
54. Amaral CC, Ormiga F, Gomes JA. Electrochemical-induced dissolution of stainless steel files. Int Endod J, 2015;48:137-144.
56. Ward JR, Parashos P, Messer HH. Evaluation of an ultrasonic technique to remove fractured rotary nickel-titanium endodontic instruments from root canals: an experimental study. J Endod, 2003;29:756-763.
57. Souter NJ, Messer HH. Complications associated with fractured file removal using an ultrasonic technique. J Endod, 2005;31:450-452.
58. Terauchi Y, O’Leary L, Kikuchi I, Asanagi M, Yoshioka T, Kobayashi C, et al. Evaluation of the efficiency of a new file removal system in comparison with two conventional systems. J Endod, 2007;33:585-588.
59. Alomairy KH. Evaluating two techniques on removal of fractured rotary nickel-titanium endodontic instruments from root canals: an in vitro study. J Endod, 2009;35:559-562.
60. Gencoglu N, Helvacioglu D. Comparison of the different techniques to remove fractured endodontic instruments from root canal systems. Eur J Dent, 2009;3:90-95.
61. Shahabinejad H, Ghassemi A, Pishbin L, Shahravan A. Success of ultrasonic technique in removing fractured rotary nickel-titanium endodontic instruments from root canals and its effect on the required force for root fracture. J Endod, 2013;39:824-828.
62. Garg H, Grewal MS. Cone-beam computed tomography volumetric analysis and comparison of dentin structure loss after retrieval of separated instrument by using ultrasonic EMS and ProUltra tips. J Endod, 2016;42:1693-1698.
63. Gerek M, Başer ED, Kayahan MB, Sunay H, Kaptan RF, Bayırlı G. Comparison of the force required to fracture roots vertically after ultrasonic and Masserann removal of broken instruments. Int Endod J, 2012;45:429-434.
64. Madarati AA, Qualtrough AJ, Watts DC. Effect of retained fractured instruments on tooth resistance to vertical fracture with or without attempt at removal. Int Endod J, 2010;43:1047-1053.
65. Madarati AA, Qualtrough AJ, Watts DC. A microcomputed tomography scanning study of root canal space: changes after the ultrasonic removal of fractured files. J Endod, 2009;35:125-128.
66. Madarati AA, Qualtrough AJ, Watts DC. Vertical fracture resistance of roots after ultrasonic removal of fractured instruments. Int Endod J, 2010;43:424-429.
67. Fu M, Zhang Z, Hou B. Removal of broken files from root canals by using ultrasonic techniques combined with dental microscope: a retrospective analysis of treatment outcome. J Endod, 2011;37:619-622.
68. Madarati AA, Qualtrough AJ, Watts DC. Endodontists experience using ultrasonics for removal of intra-canal fractured instruments. Int Endod J, 2010;43:301-305.
69. Gao Y, Shen Y, Zhou X, Haapasalo M. Remaining root dentin thickness in mesiobuccal canals of maxillary first molars after attempted removal of broken instrument fragments. Aust Endod J, 2015;41:122-127.
70. Atrizadeh F, Kennedy J, Zander H. Ankylosis of teeth following thermal injury. J Periodontal Res, 1971; 6:159-167.
71. Eriksson AR, Albrektsson T. Temperature threshold levels for heat-induced bone tissue injury: a vital-microscopic study in the rabbit. J Prosthet Dent. 1983; 50:101-7.
72. Saunders EM, Saunders WP. The heat generated on the external root surface during post space preparation. Int Endod J, 1989;22:169-173.
73. Saunders EM: In vivo findings associated with heat generation during thermomechanical compaction of gutta-percha. 2. Histological response to temperature elevation on the external surface of the root. Int Endod J, 1990;23:268-274.
74. Line SE, Polson AM, Zander HA. Relationship between periodontal injury, selective cell repopulation and ankylosis. J Periodontol, 1974;45:725-730.
75. Dominici JT, Clark S, Scheetz J, Eleazer PD. Analysis of heat generation using ultrasonic vibration for post removal. J Endod, 2005;31:301-303.
76. Budd JC, Gekelman D, White JM. Temperature rise of the post and on the root surface during ultrasonic post removal. Int Endod J, 2005;38:705-711.
77. Gluskin AH, Ruddle CJ, Zinman EJ. Thermal injury through intraradicular heat transfer using ultrasonic devices: precautions and practical preventive strategies. J Am Dent Assoc, 2005;136:1286-1293.
78. Huttula AS, Tordik PA, Imamura G, Eichmiller FC, McClanahan SB. The effect of ultrasonic post instrumentation on root surface temperature. J Endod, 2006;32:1085-1087.
79. Hashem AA. Ultrasonic vibration: temperature rise on external root surface during broken instrument removal. J Endod, 2007;33:1070-1073.
80. Madarati AA, Qualtrough AJ, Watts DC. Factors affecting temperature rise on the external root surface during ultrasonic retrieval of intracanal separated files. J Endod, 2008;34:1089-1092.
81. Madarati AA, Qualtrough AJ, Watts DC. Efficiency of a newly designed ultrasonic unit and tips in reducing temperature rise on root surface during the removal of fractured files. J Endod, 2009;35:896-899.
82. Gaffney JL, Lehman JW, Miles MJ. Expanded use of the ultrasonic scaler. J Endod, 1981;7:228-229.
83. Hulsmann M. Methods for removing metal obstruction from the root canal. Endod Dent Traumatol, 1993;9:223-237.
84. Zuckerman O, Katz A, Pilo R, Tamse A, Fuss Z. Residual dentin thickness in mesial roots of mandibular molars prepared with Lightspeed rotary instruments and Gates-Glidden reamers. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2003;96:351-355.
85. Kuttler S, McLean A, Dorn S, Fischzang A. The impact of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars. J Am Dent Assoc, 2004;135:903-909.
86. Wu MK, van der Sluis LW, Wesselink PR. The risk of furcal perforation in mandibular molars using Gates-Glidden drills with anticurvature pressure. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 2005;99:378-382.
87. Tilk MA, Lommel TJ, Gerstein H. A study of mandibular and maxillary root widths to determine dowel size. J Endod, 1979;5:79-82.
88. Raiden G, Koss S, Costa L, Hernandez JL. Radiographic measurement of residual root thickness in premolars with post preparation. J Endod, 2001;27:296-298.
89. Yang Q, Cheung GS, Shen Y, Huang D, Zhou X, Gao Y. The remaining dentin thickness investigation of the attempt to remove broken instrument from mesiobuccal canals of maxillary first molars with virtual simulation technique. BMC Oral Health, 2015; DOI 10.1186/s12903-015-0075-x
90. Iqbal MK, Rafailov H, Kratchman SI, Karabucak B. A comparison of three methods for preparing centered platforms around separated instruments in curved canals. J Endod, 2006;32:48-51.
91. Hulsmann M. Removal of fractured instruments using a combined automated ultrasonic technique. J Endod, 1994;20:144-147.
92. Madarati AA, Qualtrough AJ, Watts DC. Endodontists experience using ultrasonics for removal of intra-canal fractured instruments. Int Endod J, 2010;43:301-305.
93. Strindberg LZ. The dependence of the results of pulp therapy on certain factors:an analysis study based on radiographic and clinical follow up examination. Acta Odontol Scand, 1956; 14:1-175.
94. Sigurdsson A. Evaluation of success and failure. In: Walton R, Torabinejad M, editor. Priciples and Practice of Endodontics. Philadelphia: W.B. Saunders Company; 2002. p. 331-344.
95. Simon S, Machtou P, Tomson P, Adams N, Lumley P. Influence of fractured instruments on the success rate of endodontic treatment. Dent Update. 2008; 35:172-9.
96. Panitvisai P, Parunnit P, Sathorn C, Messer HH. Impact of a retained instrument on treatment outcome: a systematic review and meta-analysis. J Endod, 2010; 36:775-780.