CLINICAL CASES
The Broken Instrument or Separated Instrument
Endodontic treatment occasionally results in fracture or separation of the instruments used within the root canal system. The cause is related to the instruments binding within the tortuous and tight canals. Once the elastic limit or the yield strength of the instrument is exceeded, rupture of the metal occurs.
Remnants of various stainless steel or NiTi endodontic instruments (burs, reamers, files, lentulos) are evident radiographically and examples of these abound. When such events occur in the dental office, the practitioners are usually quite distraught as separation of any instrument type causes endodontic complications. This can be considered a “dental nightmare” as the instrument may prevent the disinfection of the root canal system and thereby compromise the prognosis.
The objective of endodontic treatment with or without a fractured instrument remains the same, namely to disinfect the root canal system and prevent its recontamination.
Our biggest concern first and most important is that the prognosis for the treatment outcome for a tooth with a separated instrument is compromised. On the basis of the current best available evidence from case control studies the prognosis for endodontic treatment when a fractured instrument fragment is left within a root canal is not significantly reduced.
Case-control studies in the literature
Year Success rate Influence of fractured instruments on outcome of endodontic treatment
1970 91% No effect
2005 92% Lower success rate if pre-operative apical lesion
In the Canadian Academy of Endodontics “Standards of Practice” document the following is cited:
“It is recognized that root canal instruments will occasionally fail due to circumstances which may be beyond the control of the practitioner. Attempts should be made to retrieve or bypass the obstruction. If the instrument is not retrievable, the remainder of the canal should be obturated and the practitioner should use discretion to determine the need for further treatment. The patient should be informed of the obstruction and all information should be documented on the patient’s chart. Instrument separation does not imply substandard care.”
In many cases the instruments cannot be retrieved and the question remains as to whether or not this will compromise the treatment outcome. It is stated that the prognosis is lower if periapical pathosis is present at the time of treatment, but only to the extent that effective canal disinfection is compromised. Canal disinfection can be accomplished even if an instrument cannot be removed as exemplified by the case study in the attached radiographs.
To prevent instrument separation, here are a few tips:
In summary, although instrument fatigue can result in separation which compromises endodontic treatment, this unwanted consequence usually does no harm and does not result in a lower success rate in endodontics. The dentist must attempt to debride the root canal system as well as possible and inform the patient of the complication when the dentist is assured of the consequences. This latter statement does not mean “as soon as the instruments separates” but rather, as stated in the CAE document, when the dentist is sure of the facts.
References:
1. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis: a clinical investigation. J Am Dent Assoc 1970;80:1341–7.
2. Spili P, Parashos P, Messer HH. The impact of instrument fracture on outcome of endodontic treatment
Remnants of various stainless steel or NiTi endodontic instruments (burs, reamers, files, lentulos) are evident radiographically and examples of these abound. When such events occur in the dental office, the practitioners are usually quite distraught as separation of any instrument type causes endodontic complications. This can be considered a “dental nightmare” as the instrument may prevent the disinfection of the root canal system and thereby compromise the prognosis.
The objective of endodontic treatment with or without a fractured instrument remains the same, namely to disinfect the root canal system and prevent its recontamination.
Our biggest concern first and most important is that the prognosis for the treatment outcome for a tooth with a separated instrument is compromised. On the basis of the current best available evidence from case control studies the prognosis for endodontic treatment when a fractured instrument fragment is left within a root canal is not significantly reduced.
Case-control studies in the literature
Year Success rate Influence of fractured instruments on outcome of endodontic treatment
1970 91% No effect
2005 92% Lower success rate if pre-operative apical lesion
In the Canadian Academy of Endodontics “Standards of Practice” document the following is cited:
“It is recognized that root canal instruments will occasionally fail due to circumstances which may be beyond the control of the practitioner. Attempts should be made to retrieve or bypass the obstruction. If the instrument is not retrievable, the remainder of the canal should be obturated and the practitioner should use discretion to determine the need for further treatment. The patient should be informed of the obstruction and all information should be documented on the patient’s chart. Instrument separation does not imply substandard care.”
In many cases the instruments cannot be retrieved and the question remains as to whether or not this will compromise the treatment outcome. It is stated that the prognosis is lower if periapical pathosis is present at the time of treatment, but only to the extent that effective canal disinfection is compromised. Canal disinfection can be accomplished even if an instrument cannot be removed as exemplified by the case study in the attached radiographs.
To prevent instrument separation, here are a few tips:
- establish a glide path to the working length with a hand K-file of size 15 to 20;
- obtain straight-line access to the apical half of the canal;
- avoid using an engine-file of a large body taper (0.06 or above) for canals with a mid-root curvature;
- avoid the use of an engine-file in abruptly curved canals;
- visually check instruments after each use to determine if there is distortion.
In summary, although instrument fatigue can result in separation which compromises endodontic treatment, this unwanted consequence usually does no harm and does not result in a lower success rate in endodontics. The dentist must attempt to debride the root canal system as well as possible and inform the patient of the complication when the dentist is assured of the consequences. This latter statement does not mean “as soon as the instruments separates” but rather, as stated in the CAE document, when the dentist is sure of the facts.
References:
1. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis: a clinical investigation. J Am Dent Assoc 1970;80:1341–7.
2. Spili P, Parashos P, Messer HH. The impact of instrument fracture on outcome of endodontic treatment
