Review articles Annals and Essences of Dentistry
Vol. - II Issue 3 July – Sept. 2010 114
SUCCESS RATE OF ROOT CANAL TREATMENT
*Professor, Conservative Dentistry Endodontics. Hitkarini Dental College, Jabalpur, M.P.
Much effort has been invested in attempts to answer this question. The reported mean success rate range from 31% to
96% based on strict criteria or from 60% to 100% based on loose criteria, with substantial heterogeneity in the estimates of
pooled success rates. This variability of the reported data; demands for the analysis of the reasons responsible for such
variability. Major reasons are the design of the studies, the endodontic techniques applied in them, the qualifications of the
operators performing treatment and difficulty of cases, observation period and Criteria used to evaluate treatment results.
The serious limitations of longitudinal clinical studies restrict the correct interpretation of root canal treatment outcomes.
KEYWORDS -Root canal treatment, Success rate, Variability factors.
Studies have presented data indicating a success
rate of Endodontic therapy ranging from 53% to
95%1-3. The higher figure suggests that almost
every endodontic treatment succeeds, whereas
the lower indicates that almost every second case
fails. The reported mean success rates ranged
from 31% to 96% based on strict criteria or from
60% to 100% based on loose criteria, with
substantial heterogeneity in the estimates of
pooled success rates4. This variability of the
reported data demands for the analysis of the
reasons responsible for such variability.
Major reasons responsible for variability are
i. Design of the studies.
ii. The endodontic techniques applied in them.
iii. The qualifications of the operators
performing treatment and difficulty of cases.
iv. Observation period.
v. Criteria used to evaluate treatment results.
I) Design of the studies:
a) Different methods of evaluation of treatment
Most investigators used radiographic and
clinical findings for evaluating treatment results.
Several used only radiographic findings, whereas
others used histological examinations. However
there are problems associated with each one of
the evaluation methods as well as with correlation
Clinical evaluation often relies on subjective
findings such as report of pain or discomfort upon
percussion that is subject to individual variations.
Resorting to only radiographic evaluation may
allow a pathosis, which is expressed clinically
without radiographic manifestations, to be
overlooked. The use of histological examination as
a routine evaluation is impractical. Moreover its
value is limited because of the need for
interpretation of the findings. Unfortunately, there
is only limited correlation between various
evaluation methods with regard to endodontic
b) Recall Rate:
It was observed that the recall rate in most
studies varied from 11% to 74% whereas some
reports did not mention the recall rate at all. It was
suggested that the success / failure ratio in the
unexamined portion of the population could not be
assumed to be the same as that found in
examined portion. So in order to be considered
valid, studies of failure in any clinical discipline
must contain adequate number of recall and that
the very least inclusion of the original sample
should be mandatory.
Review articles Annals and Essences of Dentistry
Vol. - II Issue 3 July – Sept. 2010 115
c) The presence of periapical pathosis
It has been pointed out that in previous
studies teeth with periapical radiolucency (a
potentially ‘failing’ factor) constituted between 18%
and 64% of the material. Such a significant
difference may explain why the results of those
studies also differ significantly.
II) Treatment techniques
The effect of endodontic treatment
techniques on the success rate has been clearly
demonstrated in different studies. It was found in
one of the studies that when Ingle’s standardized
technique was introduced to a Norwegian dental
school, a 10% higher success rate was reached
than the previous long term studies at the same
school. Similar findings were also reported in the
The most important therapeutic factors are
the apical extension of the filling material and the
obturation quality. These factors were examined in
several studies producing unanimous agreement
that they do influence treatment result. Both the
factors are directly related to treatment technique.
II) Qualification of operators and difficulty of
Washington study indicated that there was
no statistically significant difference in success
rate between cases treated by students and by
dentist in practice. The explanation to this finding
was that most of the university cases failed
because of error in treatment whereas majority of
practice cases failed because of error in case
Also the easy cases, whenever possible,
find their way to undergraduate clinics, where as
experienced dentist treat more complex cases,
which also have a more doubtful prognosis. In
other words, the difficulty of treated cases may
also contribute to the wide variation in the reported
IV) Observation period:
Some of the studies categorized treatment
results not only as success or failure, but also as
doubtful or uncertain. As the number of
successful cases increased with time, there was
decrease in the number of doubtful cases. This
may be because of slow process of healing. The
period of postoperative observation advocated by
various investigators varies between 6 months
and 4 years.
The first international conference on
Endodontics (1953) dealt with this dilemma and
recommended a 1 to 2 year period of observation
5. In third international conference on Endodontics
(1963), it was suggested that healing may still
occur in cases regarded as failures even after 4
years if the observation period is prolonged6.
V) criteria for definition of treatment
a) The use of different criteria in studies:
There is no agreement on the definition of success
or failure of endodontic treatment in as much as
there is no agreement on criteria. So it is
concluded that as long as investigators use
different criteria for evaluating success and failure,
this fact alone will contribute significantly to the
wide variation in reported treatment results.
Seltzer9suggested the following criteria for
successful endodontic therapy, admitting that they
are not all inclusive or conclusive.
1. Absence of pain or swelling
2. Disappearance of fistula.
3. No loss of function
4. No evidence of tissue destruction
5. Radiographic evidence of an eliminated or
arrested area of rarefaction after 6 to 24
b) Fallibilities of Radiographic Interpretation:
Since radiographic evaluation plays a basic
role in the assessment of treatment results, any
fallibility associated with the interpretation of
radiographs will directly distort the reported rates
of success and failure.
The following factors influencing fallibility
should be considered.
1. Change in angulations
2. Quality of film
3. Lack of radiographic changes
4. Proximity to anatomical landmarks
5. Radiolucency of periapical scar tissue
6. Personal bias and disagreement between
Traditionally, periapical radiography has been
used to assess the outcome of root canal
treatment with the absence of a periapical
radiolucency being considered a confirmation of a
healthy periapex. However, a high percentage of
cases confirmed as healthy by radiographs
revealed apical periodontitis on cone beam
computed tomography (CBCT) and by histology.
In teeth, where reduced size of the existing
radiolucency was diagnosed by radiographs and
considered to represent periapical healing,
enlargement of the lesion was frequently
confirmed by CBCT.
In clinical studies, two additional factors
may have further contributed to the overestimation
of successful outcomes after root canal treatment:
Review articles Annals and Essences of Dentistry
Vol. - II Issue 3 July – Sept. 2010 116
(i) extractions and re-treatments were rarely
recorded as failures; and (ii) the recall rate was
often lower than 50%. The periapical index (PAI),
frequently used for determination of success, was
based on radiographic and histological findings in
the periapical region of maxillary incisors. The
validity of using PAI for all tooth positions might be
questionable, as the thickness of the cortical bone
and the position of the root tip in relation with the
cortex vary with tooth position. In conclusion, the
serious limitations of longitudinal clinical studies
restrict the correct interpretation of root canal
treatment outcomes 12.
1. 1. Jokinen, MA et al: Clinical and radiographic
study of pulpectomy and root canal therapy
Scand J. Dent Res. 86: 366, 1978.
2. Morse DR et al: A radiographic evaluation of the
periapical status of teeth treated by the gutta percha
eucapercha endodontic method: one year follow up
study of 458 root canals, oral surg. 55: 607, 1983.
3. Pekruhn RB: The incidence of failure following single
visit endodontic therapy. J.Endod.12: 68, 1986.
4. Ng YL, Mann V, Rahbaran, Lewsey, 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 Dec; 40(12):921-39.
5. Grossman LI, editor: Transactions, First international
conference on endodontics, Philadelphia, 1953,
University of Pennsylvania.
6. Frostell G: Clinical significance of the root canal
culture. In Grossman LI, editor: Transactions, Third
international conference on Endodontics,
Philadelphia; 1963, University of Pennsylvania.
7. Harty FJ, Parkins BJ and Wengraf AM: Success rate
in root canal therapy: A retrospective study of
conventional cases, B.D.J. 70: 65, 1970.
8. Kerekes K and Tronstand L: Long term results of
endodontic treatment performed with standardized
techniques J Endod 5: 83, 1979.
9. Bender, IB, Seltzer S and Soltanoff W: Endodontic
success: a reappraisal of criteria. I and II, Oral Surg.
22: 780, 1966.
10.Ingle, J.I: Endodontics, Ed 3, Philadelphia, 1985 Lea
11.Stephen Cohen & Richard Burns: Pathways of the
Pulp, 5th Ed. California, 1991.Mosby Year Book.
12.Wu MK, Shemesh H, Wesselink PR: Limitations of
previously published systematic reviews evaluating
the outcome of endodontic treatment. Int Endod J.
2009 Aug; 42(8):656-66.
Corresponding Author :
Dr Shiv P. Mantri
Savitri Bhavan, Khaparde bagicha,
Amravati, M.S. 444602
Phone No. 9422672932