Keywords
separated instruments - outcome assessment - endodontics - systematic review - retained
instrument
Introduction
Successful root canal treatment is determined on proper root canal shaping, disinfection,
and three-dimensional obturation. Practically, at any stage of treatment, practitioners
in the field of endodontics may meet a range of procedural errors and roadblocks to
ordinarily routine therapy.[1] One of the procedural errors include intracanal instrument fracture. Endodontic
files, Gates Glidden burs, lateral or finger spreaders, and paste fillers are examples
of fractured root canal instruments. They can be constructed of nickel-titanium (NiTi),
stainless steel, or carbon steel. The canal curvature, anatomic differences, practitioner
expertise, patient participation, frequency of usage, torque, and rotation speed are
variables that contribute to rotary file breaking.[2]
NiTi alloys are shape memory alloys due to their excellent biocompatibility and corrosion
resistance they are used in varied aspects of dentistry.[3] Because of their super-elasticity, shape memory effect, and corrosion resistance,
the alloy has a wide range of dental, medicinal, and commercial uses.[4] Sometimes they fail due to cyclic flexural fatigue, torsional failure, or a combination
of both and have been categorized accordingly.[5] The fracture rate among discarded rotary NiTi files after clinical usage was found
to be between 0.4 and 3.7%. Although there is a perspective that rotary NiTi instruments
can fracture without warning, recent research suggests that fracture is caused by
several factors, the most important of which appears to be the clinician's conscious
decision to use the instruments for a certain number of times or until defects (unwinding,
torsional fracture, or flexural fracture) became apparent, whereas stainless steel
file fracture is preceded by instrument distortion, which serves as a warning of impending
fracturing.[6] However without magnification, the distortion of rotational NiTi devices is generally
undetectable.[7]
[8]
[9]
There have been various studies in the past that have assessed the outcome of root
canal-treated tooth with a separated instrument in the canal. The success rate varies
from 67% to a 100% according to Engstromet al in 1964 and Engstrom and Lundberg in
1965. The success rates were reduced if the tooth had necrotic pulp at the beginning
of the treatment as separated instrument hampers the ability to disinfect the canal.[10]
[11]
The purpose of this review is to assess the impact of a retained instrument on treatment
outcome over the past 10 years and the PICO question was framed as in adult patients
who have had nonsurgical root canal treatment. Does the retention of a separated instrument,
compared with no retained separated instrument, result in a poorer clinical outcome?
Materials and Methodology
Materials and Methodology
Online databases such as PubMed, Wiley Online Library, SAGE journals, Cochrane library
were used for boolean search with MeSH terms. Search Strategy was developed to identify
articles related to retained instrument fragments.
Search strategy
Broken instrument OR fractured instrument OR separated instrument AND (''Endodontics''
[MeSH] OR ''Root Canal Filling Materials'' [MeSH] OR ''Dental Pulp Test'' [MeSH] OR
''Dental Pulp Diseases'' [MeSH] OR ''Periapical Abscess'' [MeSH] OR endodontics [Text
Word] OR root canal filling materials [Text Word] OR dental pulp test [Text Word]
OR dental pulp diseases [Text Word] OR periapical abscess [Text Word] OR apicoectomy
[Text Word] OR pulpectomy [Text Word] OR pulpotomy [Text Word] OR root canal therapy
[Text Word] OR dental pulp devitalization [Text Word] OR root canal obturation [Text
Word] OR root canal preparation [Text Word] OR retrograde obturation [Text Word] NOT
((''Dental Implantation, Endosseous, Endodontic'' [MeSH] OR ''Dental Pulp Capping''
[MeSH] OR ''Tooth Replantation'' [MeSH]) NOT (''Apicoectomy'' [MeSH] OR ''Pulpectomy''
[MeSH] OR ''Pulpotomy'' [MeSH] OR ''Root Canal Therapy'' [MeSH]))) NOT (''animals''
[MeSH:noexp] NOT humans [MESH]).
A thorough search was conducted to find all clinical papers that documented postoperative
healing following endodontic instrument separation. The results obtained were transferred
to the citation manager and duplicates were removed.
INCLUSION CRITERIA: Non-contributory medical history, mature teeth with radiographic
evidence of separated instruments, follow-up of at least 1 year, outcome assessment
based on clearly defined criteria, case–control study, studies in the past 10 years.
EXCLUSION CRITERIA: No results in terms of healing, no specified observational period,
follow-up less than a year, no specific criteria for evaluating outcome, not a case–control
study, studies older than 10 years.
Results
The PRISMA guidelines were followed and the PRISMA flow chart is listed below. A total
of 330 articles were obtained from the initial search. After removal of duplicates,
302 articles were identified. Upon screening by reading the title, seven full-text
articles were retrieved. However, on evaluating the full-text articles for inclusion,
none of the article met the inclusion and exclusion criteria. The reasons for the
rejection of the seven full-text articles are listed in [Table 1] ([Fig. 1]).
Fig. 1 PRISMA flow chart for search strategy.
Table 1
Reason for exclusion of studies
|
Author
|
Reason for exclusion
|
|
Tordai et al[12]
|
Retrospective study analyzing the effect of ultrasonics on instrument removal: not
relevant
|
|
Farid et al[13]
|
Technique commonly associated with instrument separation: not relevant
|
|
Shahabinejad et al[14]
|
In vitro study
|
|
Madarati et al[15]
|
In vitro study
|
|
Mohammadi et al[16]
|
Not within the past 10 years
|
|
Cunha et al[17]
|
Prospective clinical study
|
|
Tygesen et al[18]
|
Not within the past 10 years
|
Discussion
Clinicians may be misled by the false notion that endodontic errors, such as broken
tools, perforations, and overfilling, are involved directly in endodontic failures.
Although not all endodontic errors result in a poor prognosis, every mistake that
affects microbial control raises the likelihood of failure. One of the most unpleasant
situations in endodontic therapy is separation of root canal tools, particularly if
the tooth is non-vital and the fragment cannot be extracted. Unless a concurrent infection
is present, the procedure error does not immediately impact the prognosis in the majority
of instances.[19] As a result, it is critical to evaluate the influence of a retained broken instrument
on prognosis to compare it to the danger of injury during removal. The therapeutic
importance of retained fractured tools has been a point of contention among researchers.
For the management of broken tools in root canals, the literature suggests four treatment
strategies:
-
Allowing the detached instrument to remain in the canal while treating the rest of
the canal.
-
The detached component is bypassed, and the canal is treated.
-
The detached portion must be retrieved and the canal must be treated.
-
Surgical procedure for retrieving the detached component, followed by appropriate
therapy.[6]
The present systematic review has taken into consideration only the past 10 years
as the last systematic review on this topic was conducted in 2010 by Panitvisaiet.
It was concluded that there was no effect of retainment of instrument on the canal
to the outcome of the root canal treatment. However, the systematic review and meta-analysis
took into consideration only two studies conducted by Crump and Natkin in 1970 and
Spili et al in 2006. They are 36 years apart and the endodontic treatment protocols
have evolved over those years. The separated instruments were predominantly stainless
steel in 1970, whereas it was both stainless steel and Ni Ti in 2006. Irrigation protocols
have changed over the years, which are the main aspects of disinfection of the canal.[20] Hence, it was decided to keep a time frame of 10 years to assess the effect of treatment
outcome in cases of retained separated instruments in the canal.
Evidence from the past 10 years did not have any case–control studies that can only
be the highest form of evidence in case of instrument separation. Case reports with
over 2 years of follow-ups have been published over the past decade. Clear conclusions
cannot be drawn from case reports or case serious as it is difficult to compare due
to lack of standardization.[21]
Various instrument retrieval systems have been introduced but they involve the sacrifice
of some amount of radicular dentin, which has shown to weaken the tooth structure.
At present, there is a lack of consensus on the treatment option of the separated
instrument in the canal.[20]
[22]
Conclusion
Despite the fact that endodontic treatments are rather an intensive and demanding
technique, especially in complicated anatomies, they have a very high success rate.
Lack of awareness of the anatomy and also iatrogenic mistakes particularly during
instrumentation, might lead to errors during or after a root canal procedure. While
some of these issues may be foreseen, many others are impossible to predict. Short-term
endodontic failures are most commonly caused by recurrent infection, and a fractured
tool can be a source of reinfection or chronic infection. Within the limitation of
this systematic review, it can be concluded that there are not enough evidence to
draw a conclusion on the effect of retained instrument in the root canal system. Future
research should be directed in answer if they have any effect on the outcome of a
root canal treatment.
