Four canals in the mesial root of a mandibular first molar. A case report under the operating microscope.

Abstract

In this era of microscope-assisted endodontics, finding variations in root canal system anatomy is not uncommon. Operating microscopes combined with careful clinical examination and radiographic interpretation can aid the clinician to successfully treat cases with such internal anatomy. The understanding of this view enables the possible location of additional canals in any tooth requiring endodontic treatment. The present clinical article demonstrates a rare anatomical complexity in the mesial root of a mandibular first molar. Four independent root canal orifices were found in this root by clinical detection with the aid of a dental operating microscope. This case shows that additional canals can be located in any root undergoing endodontic treatment and clinicians should always be aware of aberrant internal anatomy.

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© 2007 The Authors
Journal compilation © 2007 Australian Society of Endodontology
Aust Endod J 2007; 33: 84–88
Blackwell Publishing IncMalden, USAAEJAustralian Endodontic Journal1329-1947© 2007 The Authors; Journal compilation © 2007 Australian Society of Endodontology? 20073328488Case Report Four Canals in
the Mesial Root of a Mandibular First MolarE. G. Kontakiotis and G. N. Tzanetakis
CASE REPORT
Four canals in the mesial root of a mandibular first molar. A case
report under the operating microscope
Evangelos G. Kontakiotis, DDS, PhD and Giorgos N. Tzanetakis, DDS
Department of Endodontics, Dental School, University of Athens, Athens, Greece
Abstract
In this era of microscope-assisted endodontics, finding variations in root canal
system anatomy is not uncommon. Operating microscopes combined with care-
ful clinical examination and radiographic interpretation can aid the clinician to
successfully treat cases with such internal anatomy. The understanding of this
view enables the possible location of additional canals in any tooth requiring
endodontic treatment. The present clinical article demonstrates a rare ana-
tomical complexity in the mesial root of a mandibular first molar. Four inde-
pendent root canal orifices were found in this root by clinical detection with the
aid of a dental operating microscope. This case shows that additional canals can
be located in any root undergoing endodontic treatment and clinicians should
always be aware of aberrant internal anatomy.
Keywords
aberrant anatomy, endodontic treatment,
mandibular first molar, operating microscope.
Introduction
A major cause of failure in endodontic treatment is the
incomplete debridement of the entire root canal system
(1,2). It has been previously shown that pulp tissue rem-
nants and their subsequent infection by the invasion of
microorganisms can affect and compromise the treatment
outcome (3–5). In some of these cases, organic tissue
remains in the pulp cavity because the clinician could not
detect any additional root canals.
The mandibular first molar, as the earliest permanent
posterior tooth to erupt, is considered to be the one
most frequently involved in endodontic procedures (6).
Because of the great number of endodontic treatments
involving this tooth the clinician may be confronted in
many cases of mandibular first molars, with aberrant
internal anatomy.
Numerous in vitro and in vivo studies about the morphol-
ogy of mandibular first molars have provided new data
relating to the presence of extra roots, additional root
canals, lateral canals or transverse canal anastomoses
between the two or three canals in the mesial root (1,7–
12). These studies point out the need for careful inspection
for the existence of possible additional canals. From the
above studies, only one (radiographic) study has reported
an incidence of 3.3% of four canals in the mesial root of
mandibular first molar but the sample size was too small
for safe conclusions to be made (12).
Up till now, quite a few clinical reports have been pre-
sented in the literature describing more than two canals
in the mesial root of mandibular first molars (13–19).
Among these reports, only Reeh has described a retreat-
ment case of four canals in the mesial root of a mandib-
ular first molar (18). It is of prime importance for the
clinician to distinguish clearly and to identify completely
the topographic location of any additional canals orifices.
This is probably best achieved with the aid of a dental
operating microscope.
The aim of this clinical report is to present and describe
the endodontic management, through an operating
microscope, of a mandibular first molar with four canals in
the mesial root.
Case report
A 30-year-old male patient with a non-contributory med-
ical history presented at our private office with discomfort
and pain in the left mandibular region. The patient
reported that for the last week he had experienced a
Correspondence
Assistant Professor Evangelos G. Kontakiotis,
Antheon 2, Patisia, 11143 Athens, Greece.
Email: ekontak@dent.uoa.gr
doi: 10.1111/j.1747-4477.2007.00068.x

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E. G. Kontakiotis and G. N. Tzanetakis
Four Canals in the Mesial Root of a Mandibular First Molar
© 2007 The Authors
Journal compilation © 2007 Australian Society of Endodontology
85
spontaneous and constant pain in this area but he could
not detect the tooth that was responsible.
Clinically, the left mandibular first molar was covered
by a metal-ceramic crown and the left mandibular second
molar had a large amalgam restoration. Clinical examina-
tion revealed that the patient was sensitive to percussion
only on tooth 36. There was no mobility and probing did
not reveal any periodontal pocketing. The surrounding
teeth did not demonstrate any clinical signs or symptoms.
Because of the inability (owing to the presence of the
crown) to perform reliable vitality tests (electric pulp test –
EPT), tooth 36 was isolated with rubber dam and a tooth
bath was carried out with slightly hot water. The patient
reported that the pain he felt became worse after the test.
It was decided, with the consent of the patient, to remove
the crown in order to do reliable cold and EPTs. Vitality
tests (cold, EPT) on tooth 36 after the removal of the
crown showed responses longer than normal indicating
irreversible pulpitis.
A preoperative radiograph was taken before the
removal of the crown (Fig. 1A). No radiographic evidence
of apical periodontitis was observed. The radiograph did
not reveal any unusual anatomy of the molar. Endodontic
treatment was initiated immediately in order to alleviate
the patient’s symptoms. After achieving anesthesia
(1.7 mL Ubistesin forte, articaine, 1:100 000 epineph-
rine), the tooth was isolated with a rubber dam and the
access cavity preparation was performed using Endo
access and Endo-z burs (Dentsply, Maillefer, Baillaigues,
Switzerland).
Investigation of the root canal system was initially per-
formed with the aid of an endodontic explorer and then
with size 10 K-files (Dentsply). Five root canals were ini-
tially detected (three in the mesial root, two in the distal
root) and an operative radiograph (Fig. 1B) was taken to
estimate the separation of the canals. Coronal flaring of
the root canal orifices was carried out with GT Accessories
files No 35 12% taper (Dentsply) in order to enhance
access and visualisation. Observation of the pulp chamber
with the aid of an operating microscope (Global, Protégé
plus) under magnification 12.8× revealed an additional
fourth canal in the mesial root.
An apex locator (Bingo 1020 Forum Technologies, Ris-
hon Lezion, Israel) was used to verify the working length
in all six root canals. An additional operative radiograph
was then taken to confirm the independent presence of
the fourth canal in the mesial root (Fig. 1C). Individual
canal instrumentation was performed with HERO 642
(Micro-Mega, Rue du Tunnel, France) rotary Ni-Ti files No
20, 25, 30, 6%, 4% and 2% taper and No 35 2% taper. All
four canals in the mesial root were instrumented by HERO
Ni-Ti rotary instruments using a crown-down pressureless
technique to a master apical size 35. The two canals in the
Figure 1 (a) Preoperative radiograph. (b) Initial working length radiograph
with five endodontic files in place (three in the mesial root). (c) Second
working length radiograph with seven endodontic files in place (four in the
mesial root).
(a)
(b)
(c)

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© 2007 The Authors
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Four Canals in the Mesial Root of a Mandibular First Molar
E. G. Kontakiotis and G. N. Tzanetakis
distal root were instrumented by hand. During mechani-
cal instrumentation the distal canals were joined, creating
a quite wide canal with master apical size 50. Copious
chemical irrigation was performed with 2.5% sodium
hypochlorite. After completion of the chemomechanical
preparation, root canals were dried with sterile paper
points. The pulp chamber was examined again under the
operating microscope for any additional canals and photo-
graphs were taken under magnification 12.8× and 19.1×
from different observation angles (Fig. 2).
Obturation was performed at the second appointment
using cold lateral condensation of gutta-percha and AH-26
as a root canal sealer (Dentsply, De Trey, GmbH, Ger-
many). Prior to obturation, EDTA (17%) was used to
remove the smear layer and a final irrigation with 2.5%
sodium hypochlorite followed. Each canal in the mesial
root was obturated separately but the master gutta-percha
cones were in place for all four canals. This was done
because it was previously established that all the canals
joined near the apex. Excess gutta-percha cones were cut
at the level of the root canal orifices and vertical conden-
sation was performed immediately with ISO size 40 finger
pluggers. A temporary filling (Cavit G, 3M ESPE) was
placed and two postoperative radiographs were taken
from different horizontal angles in order to assess the
quality of obturation in all canals (Fig. 3). The patient was
recalled 1 year postoperatively (Fig. 4). At the recall
appointment, the patient was symptom free and the
tooth had been recrowned.
Figure 2 Clinical view of the four separate canal orifices in the mesial root,
under magnifications (a) 12.8×, (b) 19.1×.
(a)
(b)
Figure 3 (a) Ortho-radial postoperative radiograph. (b) Postoperative
radiograph taken from distal aspect.
(a)
(b)

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E. G. Kontakiotis and G. N. Tzanetakis
Four Canals in the Mesial Root of a Mandibular First Molar
© 2007 The Authors
Journal compilation © 2007 Australian Society of Endodontology
87
Discussion
Morphological variations in root canal system anatomy
should always be considered at the beginning of treat-
ment. Each case, independently of the type of tooth,
should be examined cautiously, clinically and radiograph-
ically in order to detect possible anatomical aberrations.
Once endodontic treatment has been initiated, proper
access cavity preparation is a basic prerequisite for the
investigation and successful detection of all root canal ori-
fices (20). An operating microscope can help the clinician
to identify morphological deviations and to understand
thoroughly the topographic anatomy of the pulp chamber
floor and the exact location of canals orifices. It is evident
from many studies, as well as from clinical practice in
endodontics, that the use of magnification is considered
helpful for the successful completion of endodontic treat-
ment (21,22).
The mesial root of mandibular first molars has been
investigated for many years. Sometimes, it is very wide in
the buccolingual direction so that more than two canals
can be located. According to endodontic literature, the
middle mesial canal can be found in 1–7% of the cases
(1,7–11). In most of the cases, this canal is hidden by a
dentinal projection of the mesial aspect of pulp chamber
walls. In all cases of mandibular molars, this dentinal
growth is usually located between the two main canals
(mesiobuccal-mesiolingual) and should be removed care-
fully in order to detect the additional canal or canals.
Ultrasound technology is a very useful tool for the clini-
cian to clean such an area efficiently. In the present case,
the two middle mesial canals seem to originate as separate
orifices but joined other canals before exiting (7).
The fact that initially a third (middle mesial) canal and
later a fourth canal was located in the mesial root of this
mandibular first molar underscores the necessity for thor-
ough investigation of root canal system anatomy during
endodontic treatment. Endodontists should always have
in mind that additional canals may exist and ensure that
all root canal orifices have been located.
In the past, many studies have reached the conclusion
that failure to locate and clean extra canals in any root
decreases the long-term prognosis of endodontic treat-
ment (23,24). All these extra canals, if any, should be
found if possible.
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Four Canals in the Mesial Root of a Mandibular First Molar
E. G. Kontakiotis and G. N. Tzanetakis
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