Aberrations in the root canal anatomy are
clinically challenging for clinicians. Mandibular first molars usually
have 2 roots and 3 or 4 canals, but various combinations may exist. A
distal root with three canals is rare and its incidence in literature is
about 0.2 - 3%. As a diagnostic tool, cone-beam computed tomography
(CBCT) may be a better choice for diagnosis of extra roots or canals
comparing to conventional radiography.
Methods
An
endodontic management of a mandibular first molar with six canals was performed.
CBCT was used to confirm the diagnosis and to understand the morphology of the
canals.
Results
Evaluation of the axial and coronal slices of CBCT
images confirmed the presence of 2 roots and 6 canals. The distal root had four
distinct root canal orifices with two apical foramens, being described as type
XIV canal configuration.
Conclusions
Dentists should be aware of
unexpected canal morphology when performing endodontic treatment. The present
case demonstrated the use of CBCT in diagnosis and negotiation of extra canals
in a mandibular first molar.
The main objective of the root canal therapy
is thorough debridement of the root canal space followed by complete
obturation for creating the three-dimensional seal [1]. According to
Nair [2], one of the main reasons associated with unsuccessful treatment
is the survival of microorganisms within the root canal system. Vertucci
[3] reported a substantial number of failures related to aberrant
anatomy, such as missing canals. Therefore, a comprehensive knowledge of
the root canal anatomy and its morphological variations is crucial for
successful treatment [4].
Over the years, there have been numerous
studies describing the internal morphology of teeth, including
mandibular first molar [5-10]. The majority of mandibular first molars
are two-rooted with two mesial and one or two distal canals. The major
variant of the root canal system of mandibular first molar is the
presence of a middle mesial canal with 1 - 15% incidence [6]. However,
three canals have also been reported in the distal root [7,8] with an
incidence of 0.2 - 3% [9]. The management of a mandibular first molar
with four distal canals in two separate distal roots was reported by
Ghoddusi et al. [10].
Since the introduction of CBCT, this
three-dimensional technique has been established as important tool for
diagnosis and treatment planning in an increasing number of fields in
dentistry [11,12]. CBCT has the ability of overcoming the limitations of
conventional radiography such as three-dimensional evaluation of the
complex canal anatomy during endodontic treatment [13]. An important
benefit of CBCT is in diagnosis of extra roots or canals. Tu et al. [14]
showed a higher prevalence of extra roots in the mandibular first molars
assessed by CBCT in comparison to conventional radiography.
This case report presents the successful,
non-surgical endodontic treatment of a mandibular first molar with four
canals in a distal root diagnosed by cone-beam computed tomographic
evaluation.
CASE DESCRIPTION AND RESULTS
A 42-year-old male patient was referred to
the dental office with chief complaint of severe spontaneous pain in the
left mandibular first molar. The patient’s medical history was
non-contributory.
The clinical examination showed extensive
amalgam restoration of this tooth. Vitality tests (cold by ice stick,
heat by warm instrument, and electric test by a pulp tester) were
negative; however, the tooth was tender to percussion. Periapical
radiographic examination revealed a deep restoration near distal pulp
horn with no signs of periapical radiolucency and aberrant anatomy
(Figure 1A). The clinical diagnosis of necrotic pulp with acute apical
periodontitis was made, and root canal therapy was planned.
The patient was anesthetized with 2%
lidocaine with 1:80,000 epinephrine. After rubber dam isolation,
endodontic access cavity was made. The pulp chamber was repeatedly
flushed with 5% sodium hypochlorite to remove necrotic tissue and
microorganisms. Inspection of the pulp chamber revealed four canal
openings in the distal root and two in the mesial root. In the distal
root, the third and fourth canals were located between distobuccal and
distolingual canals. The working lengths were established with an
electronic apex locator (Root ZX, Morita, Tokyo, Japan) and a radiograph
was taken (Figure 1B). The presence of six canals was confirmed and
pulpectomy was performed.
A = Preoperative periapical
radiograph of a left mandibular first molar.
B = Periapical radiograph showing
the working length determination of six root canals.
C = Enlarged axial CBCT image
section at the mid-root level showing 4 canals in the distal
root and 2 canals in the mesial root.
D = Enlarged coronal section of the
distal root showing the configuration of the four canals.
E = Enlarged sagital section of the
distal root showing the overlapping of the four canals.
F = Postoperative periapical
radiograph showing all root canals.
G = Six months follow-up of the root
canal treatment.
To confirm this unusual canal anatomy and to
understand its configuration, CBCT imaging of the tooth was performed.
Calcium hydroxide was placed as temporary dressing and the access cavity
was sealed by zinc oxide-eugenol cement. After obtaining the informed
consent from the patient, CBCT of the mandible with the focus on the
left mandibular first molar was performed (Vatech, PaX-Reve 3D plus, 5.5
cm field of view, and voxel size of 0.08 mm). Axial, coronal, and
sagital CBCT slices revealed six canals (four in the distal root and two
in the mesial root) in the referred tooth (Figure 1C - E).
At the next visit, the patient was
asymptomatic. Root canal preparation was performed with ProTaper rotary
instruments (Dentsply Maillefer, Ballaigues, Switzerland) in crown-down
technique. Irrigation was performed with 2.5% sodium hypochlorite during
instrumentation, followed by 17% EDTA. After a final rinse with normal
saline, canals were dried with sterile paper points (Ariadent, Tehran,
Iran) and obturated with gutta-percha (Ariadent, Tehran, Iran) and AH
Plus sealer (Dentsply, Maillefer, Konstanz, Germany) using cold lateral
condensation technique (Figure 1F). Then, the patient was refereed for
crown restoration. Six months after the endodontic treatment, the
patient was asymptomatic (Figure 1G).
DISCUSSION
The diagnosis and treatment of extra roots
or canals in mandibular first molars is definitely an endodontic
challenge. A comprehensive understanding of the most common root canal
configuration and its variations is essential to achieve long-term
success of the endodontic treatment. Hoen and Pink [15] reported 42%
incidence of missed root or canals in the teeth that needed retreatment.
Thus, complete debridement and obturation of the root canal system is an
utmost important procedure in endodontics.
Diagnostic imaging is an important tool for
locating canal orifices including a careful examination of the pulp
chamber floor with a sharp explorer, staining with 1% methylene blue
dye, sodium hypochlorite testing (Champagne bubble test), and
visualizing canal bleeding points. Magnifier loupes and operating
microscope would also increase the location of hidden canals [16].
Anatomical variations in the anatomy of the
distal root of mandibular molars may be identified through careful
evaluation of multiple angled pretreatment radiographs. Periapical
radiographs produce only a two-dimensional image. Thus, they are
decreased in value in cases of aberrant anatomy [17]. However, it should
be noted that significant constraint in conventional periapical
radiography is that it produces a two-dimensional image of a
three-dimensional object. So, periapical radiographs are of limited
value in cases with complex anatomy [18]. Recently, CBCT has been used
in endodontics for the evaluation of the root canal anatomy. An
advantage of the computed tomography (CT) scanning over the conventional
radiograph is that it permits the operator to look at multiple sections
of the roots and their canals [19]. Nance et al. [20] reported that the
detection of canals increased significantly by CT scan compared with
conventional radiography.
In this case report, CBCT imaging was used
for a better understanding of the complex root canal anatomy. Evaluation
of the axial and coronal slices of CBCT images confirmed the presence of
2 roots and 6 canals. The distal root had four distinct root canal
orifices with two apical foramens, which could be described as type XIV
canal configuration, according to Sert and Bayirli [21].
Treatment of extra canals may be challenging
to each endodontist or general practitioner; however, the inability to
find and properly treat the canals may cause failure. With advance
diagnostic aids such as CBCT, these challenges may be overcome.
CONCLUSIONS
Dentists should be aware of unexpected canal
morphology when performing endodontic treatment. The present report
demonstrated the use of a cone-beam computed tomography examination as a
tool for the diagnosis and negotiation of extra canals in the distal
root of a mandibular first molar.
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS
The authors wish to thank the members of the
Department of Oral and Maxillofacial Radiology and Department of
Endodontics (Faculty of Dentistry, Zahedan University of Medical
Sciences) for their assistance. The authors report no conflicts of
interest related to this report.