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International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-12, Dec- 2020]
https://dx.doi.org/10.22161/ijaers.712.32 ISSN: 2349-6495(P) | 2456-1908(O)
www.ijaers.com Page | 210
Multiple Roots and Canals in Mandibular
Canines and Premolars in a Brazilian
Population: A Cross Sectional Study Using
CBCT and Panoramic Radiography
Erick Carvalho Mendez, Ana Grasiela da Silva Limoeiro, Tatiana Dantas
Piana
School of Dentistry, Centro de Ensino Superior de Ilheus, Bahia, Brazil.
Received: 19 Nov 2020; Received in revised form: 09 Dec 2020; Accepted: 17 Dec 2020; Available online: 25 Dec 2020
©2020 The Author(s). Published by AI Publications. This is an open access article under the CC BY license
(https://creativecommons.org/licenses/by/4.0/)
Abstract— This study aimed to estimate the prevalence of external and internal numerical root variations of
mandibular canines and premolars in southern Bahia. 384 Panoramic Radiography (PAN) and 384 Cone Beam
Computed Tomography (CBCT) of patients over 14 years old who had all mandibular canines and premolars
were evaluated for internal and external numerical variation. Gender predilection of morphological
configurations was assessed using the x2 test (p <0.05). For the PAN, 0.5% of the patients had a canine with two
roots, while 2.1% and 3% had first premolar and second premolar with two roots, respectively. Regarding
internal variation, 2.9% had a canine with two canals, while 15.9% and 6.5% had a first premolar and second
premolar with two canals, respectively. For the CBCT, 2.7% of the patients had a canine with two roots, while
16.4% and 2.1% had first premolar and second premolar with two roots, respectively. Three rooted first and
second premolar accounted for 0.3%. Regarding the internal variation, 3.4% had a canine with two canals,
while 24% and 6.5% had a first premolar and second premolar with two canals, respectively. Three or four
canals accounted for 0,7% for first premolars and 0.3% for second premolars. Despite many variants, the most
prevalent root configuration for these groups in Bahia´s southern region is one root with one canal. This finding
may serve as a guide in clinical endodontic therapy.
Keywords— Cone-Beam Computed Tomography, Dental Pulp Cavity, Mandibular Teeth, Panoramic
Radiography
I. INTRODUCTION
The roots of human teeth vary in number, size and
morphology, which are anatomical changes resulting from
the genetic variability of populations, as well as sexual
dimorphism and different environmental factors. Among
these, the variation in the number of roots and root canals
represents great interest in the dental clinic, especially for
endodontic treatment [1].
Of all groups of teeth, mandibular premolars comprise
the group with most significant root numerical variability.
There are records of the first premolar with one root and
two or three canals, two roots and two or three canals,
three roots and three canals and four roots and four canals
[2]. Likewise, there are records of the second premolar
with one root and three, four or five canals, two roots and
two, three or four canals and four roots and four canals [2].
Conversely, the anterior teeth have little to none
numerical variability of the roots, in most cases single-
rooted teeth. However, the mandibular canine is the major
exception to the rule, as shown by reports of bifurcation
from the middle or apical third, as well as only bifurcation
of the root canal also from the middle or apical third [3].
The bifurcation of the mandibular canines generally forms
a vestibular root and a lingual root/canal. Very rarely,
bifurcation is observed from the cervical third of the root
[4, 5].
International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-12, Dec- 2020]
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The characterization of external variations as the
number of roots can be done by Panoramic Radiography
(PAN). This technique allows visualization of the
viscerocranium, with details centred on the maxillofacial
complex, making it possible to clearly visualize the
number of roots [6]. Although internal structures such as
root canals are not always clearly distinguishable on a
PAN, it is possible to visualize the root canal system [7].
A more accurate imaging option is Cone Beam
Computed Tomography (CBCT), which consists on the
emission of a beam-shaped ionizing radiation through the
entire cranial region. This technique allow us to evaluate
the skull´s anatomical structures in three dimensions (3D)
and provide two dimensional takes with high quality of
any part of the irradiated structure. This is of particular
importance for the evaluation of internal structures such as
root canals [8-10]. In fact, CBCT can be useful to a variety
of analysis that demand accuracy for the visualization of
facial structures [11, 12].
Therefore, these two techniques are useful to assess
external and internal root anatomical variations. This
information is of great clinical importance, for endodontic
treatment in particular but not only, for it allows to
estimate the prevalence of such variations for a given
population. Thus, this study aimed to estimate the
prevalence of numerical root variations in mandibular
canines and premolars in southern Bahia, based on PAN
and CBCT images.
II. METHOD
1. Sample selection and analysis
This present work was a retrospective cross-
sectional observational study using 384 PAN and 384
CBCT from patients over 14 years old who had all canines
and lower premolars (6 teeth in total). Images of patients
whose evaluated teeth had endodontic treatment or were
associated with injuries were excluded from the analysis.
The analyzed image exams were all done during 2019 and
2020 at the Dental Radiology Clinic Interface, located in
Itabuna, Bahia. The sampling was a stratified random type
and consisted of 163 men and 221 women for PAN and
153 men and 231 women for CBCT. Four researchers
independently assessed the external and internal variations
observed on the radiographs and tomographies. The dental
units were classified into three groups, lower canine, first
lower premolar and second lower premolar, which were
subdivided according to the number of roots and canals.
These groups were used to calculate the frequency of these
variations, as well as whether these variations had a gender
predilection.
2. PAN and CBCT capture and treatment
PAN images were acquired using the Orthopos
XG 5 (Sirona Dental System, Germany) at 70kvp voltage
and 10mA current for 13 seconds of exposure time. CBCT
images were acquired from two devices with different
settings. The Orthopos – XG5 (Sirona Dental System,
Germany) was used to acquire CBCT images with an HD
resolution at 8x8 Field of Vision (FOV), 0.20mm of voxel
for 14.3 seconds. The i-CAT (Kavo, USA) was used to
acquire CBCT images with HiRes resolution at 8x16 FOV,
0.25mm of voxel for 40 seconds.
3. Statistical Analysis
The sample size was established to represent the
estimated population of the southern Bahia region,
approximately 661,396 people (2018 estimative), as 384
people is the required size to satisfy a sampling error of
5% (p<0.05). The mandibular canine, mandibular first
premolar and mandibular second premolar were divided in
groups according to the number of roots and canals. The
frequency of each group was calculated, as well as whether
these variations had a gender predilection. The predilection
of gender variations was estimated by the non-parametric
test of x2 with yates correction.
III. RESULTS
1. Panoramic Radiography
The PAN analysis revealed a low external root
variation, with a higher prevalence of monoradicular teeth
for all groups analyzed. The mandibular canines had the
highest prevalence of teeth with one root, with a single
occurrence with two roots (Fig.1), representing only 0.5%
of the patients. This low occurrence of two roots was also
observed for mandibular first and second premolars,
representing only 2.1% and 3% of the patients. No teeth
with more than two roots were observed (Table 1).
The internal root variation was more abundant for
all groups of teeth analyzed, especially the mandibular first
premolar. Around 15.9% of patients had at least one
mandibular first premolar with two canals. Only 6.5% of
patients had at least one mandibular second premolar two
canals (Table 1).
Table.1: Root and canal number variation in 384 patients
assessed by PAN
Groups
nº
Teeth
% Teeth
nº Patients
% Patients
Canine 1
root
766
99.7%
382
99.5%
Canine 2
2
0.3%
2
0.5%
International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-12, Dec- 2020]
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roots
Canine 1
canal
756
98.4%
373
97.1%
Canine 2
canals
12
1.6%
11
2.9%
First
Premolar 1
root
758
98.7%
376
97.9%
First
Premolar 2
roots
10
1.3%
8
2.1%
First
Premolar 1
canal
683
89%
323
84.1%
First
Premolar 2
canals
85
11%
61
15.9%
Second
Premolar 1
root
752
97.9%
373
97%
Second
Premolar 2
roots
16
2.1%
11
3%
Second
Premolar 1
canal
721
94%
359
93.5%
Second
Premolar 2
canals
47
6%
25
6.5%
Fig. 1: Canine (33) with two roots on a panoramic
radiography
For the mandibular canines, the presence of two
canals was also more common than the presence of two
roots, though with a much lower prevalence of 2.9% of
patients. No teeth with more than two canals were
observed (Table 1). Finally, there was no gender
predilection detected for both external and internal
variation.
2. Cone-Beam Computed Tomography
Similar results were obtained with CBCT scans, but
with a substantial increase in teeth with two roots and two
canals and teeth with one root and two canals. Also, the
CBCT was able to detect variants not observed in PAN
images. Here, the mandibular canines also had the highest
prevalence of teeth with one root, with only 2.7% of
patients having two roots (Fig.2a). For first premolars,
16.7% of the patients had two roots (Fig.2b), while for
second premolars only 2.1% of patients had two roots
(Fig.2c). There was only one first and second premolar
with three roots (Table 2), both present in the same patient.
The internal root variation observed on CBCT scans was
greater than the external variation. The mandibular canines
with two canals (Fig.2d) were present in 3.4% of patients.
Again, premolars showed a more significant variability.
For the mandibular first premolar, the two canals variant
was present in 24% of the patients (Fig.2e). The
mandibular second premolar was less variable with 6.5%
of the patients presenting two canals (Fig.2f). CBCT was
also able to detect mandibular first premolars with three
canals (Fig.3), which accounted 0.7% of the patients. For
the mandibular second premolar the variability of this
variant was lower, with 6.5% of the patients with two
canals and 0,3% with three or four canals (Fig.3). Again,
there was no gender predilection for any numerical
variations.
Table. 2: Root and canal number variation in 384 patients
assessed by CBCT
Group
nº
Teeth
% Teeth
nº Patients
% Patients
Canine 1 root
757
98.5%
374
97.3%
Canine 2
roots
11
1.5%
9
2.7%
Canine 1
canal
748
97.3%
371
96.6%
Canine 2
canals
20
2.7%
13
3.4%
First
Premolar 1
root
674
87.7%
320
83.3%
First
Premolar 2
roots
93
12.2%
63
16.4%
First
Premolar 3
roots
1
0.1%
1
0.3%
First
Premolar 1
canal
628
81.7%
289
75.3%
International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-12, Dec- 2020]
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First
Premolar 2
canals
85
18%
92
24%
First
Premolar 3
canals
3
0.3%
3
0.7%
Second
Premolar 1
root
757
98.5%
375
97.6%
Second
Premolar 2
roots
10
1.4%
8
2.1%
Second
Premolar 3
roots
1
0.1%
1
0.3%
Second
Premolar 1
canal
734
95.5%
358
93.2%
Second
Premolar 2
canals
32
4.2%
25
6.5%
Second
Premolar 3
and 4 canals
2
0.3%
1
0.3%
Fig. 2: Transversal sections of Cone Beam CTs: (A)
Canine with two roots; (B) First premolar with two roots;
(C) Second premolar with two roots; (D) Canine with two
canals; (E) First premolar with two canals; (F) Second
premolar with two canals. Arrows indicate Bifurcation of
Canal and Root (BCR) and Mental Foramen (FM)
Fig. 3: Cone Beam CT axial section of patient with a first
premolar with three roots and three canals (44), a second
premolar with one root and three canals (35) and a second
premolar with three roots and four (45). Arrows indicate
canals.
IV. DISCUSSION
In general, the data obtained with CBCT had a higher
proportion of variants than to those obtained with PAN.
This observation was already expected due to inherent
characteristics of each technique. CBCT provides 3D
reconstructions of every section form the skull allows a
better visualization of external and internal structures,
some of which are not always distinguishable in PAN due
to overlaps and flattening to form a single take [8]. This
makes CBCT an ideal choice for the sort of analysis here
proposed, though it does not exclude the possibility of
using PAN. A study that compared the CBCT and PAN
techniques for visualizing the root anatomy, concluded that
in twelve patients with two canals viewed by CBCT, in
only two it was possible to suggest the existence of two
canals with the PAN [13].
A Brazilian study carried out with 830 canines
extracted in São Paulo reported that the prevalence of
mandibular canines with two canals was 6.1%, while the
presence of two roots was more rarely observed, with a
prevalence of 1.7% [14]. Compared to our data, this
prevalence of mandibular canines with two canals (6.1%)
is higher than that found in both PAN (1.6%) and CBCT
(2.7%). The prevalence of mandibular canines with two
roots (1.7%) is also higher than that we found in PAN
(0.3%), but similar to that we found in CBCT (1.5%). City
of Sao Paulo, which makes it mislead to compare.
International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-12, Dec- 2020]
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Studies carried out in other populations report a
highly variable prevalence of mandibular canines with two
canals or two roots. An Iranian study with 149 canines
extracted reported that 20.48% of canines had two canals
and 4.7% had two roots, values well above those observed
in Brazil [15]. Another Iranian study, now using CBCT of
400 patients, also reported a proportion of variants much
higher than that of Brazil, with 28.2% of the canines
having two canals and 12.08% with two roots [16]. In
contrast, a Malaysian study with CBCT scans of 208
patients found no canine with two roots or two canals [17].
Thus, the prevalence of root configurations of
lower canines in the southern Bahia region observed here
by PAN and CBCT was similar to that observed in São
Paulo, another Brazilian subpopulation. However, this
study´s sample number was not representative for the City
of Sao Paulo, which makes it misleading to establish a
trustful comparison with our data [14]. In fact, the same
can be stated for much of the studies regarding teeth
anatomical variations. Nonetheless, much of the
discrepancy in data is believed to be caused by natural
genetic variation, whose pool frequency varies
considerably across different geographic regions [18].
For the mandibular premolars, PAN images could
not detect teeth with more than two roots and two canals,
though these are rarely reported and were here detected by
CBCT. There are reports of first premolars from two to
four roots, and up to four canals [19-21]. The same
happens for the second premolar, for which there are
reports from two to four roots, and up to five canals [22-
24]. However, much of these reports were in vitro studies
with extracted teeth, allowing better visualization of root
morphology through clearing, sectioning, radiography and
Micro-CT scanning.
Regardless of such rich variability, the majority
accounts for teeth with one root and one canal. A
compilation of 8 studies, with 4462 extracted teeth, found
that 97.9% of the first lower premolars had a single root,
1.8% had two roots, 0.2% had three roots and 0.1 % had
four roots. Concerning the number of canals, a compilation
of 16 studies with 4733 extracted teeth showed that 75.8%
of the teeth had one canal, while 24.2% had two or more
canals [25]. These data are similar to the data we obtained
with PAN images, in which 98.7% of the evaluated first
premolar had a single root and only 1.3% had two roots,
but inferior to those observed with CBCT, in which we
had 87.7% with one root and 12.3% with two roots. As for
the internal variation, a more conservative trend was
observed with PAN images, as 89% of the first premolars
had only one canal, and 11% had two canals, while with
CBCT the percentage of teeth with two or more canals was
closer to that observed in this compilation, with 18.3%. In
all cases, the configuration of one root and two canals was
more frequent than the configuration of two roots and two
canals, in agreement with the same study.
Similarly, a compilation of 8 studies with a total
of 4019 extracted teeth and another one of 11 studies with
3063 extracted teeth revealed the prevalence of mandibular
second premolar variations in the number of roots and
canals, respectively. This study found that 99.6% of
second premolars had only one root, while two or three
roots were rarely observed, with a prevalence of 0.3% and
0.1%, respectively, while only 9% of the teeth had two or
more canals [26]. As with the analysis for mandibular first
premolars, we found similar data with PAN images, in
which 97.9% of the lower second premolars had a single
root and 2.1% have two roots. This number is also similar
to that found with CBCT, in which 98.5% had 1 root and
1.5% had two roots. As for the number of root canals, our
data point to a more subtle variation of 6% with PAN and
5.5% in the CBCT images. In general, there is a
correlation between the findings, with a general prevalence
of mandibular premolars for the configuration of one root
and one canal, but a lower frequency of variations when
compared to the mandibular first premolar. Interestingly,
the mandibular second premolar was the only group in
which our data obtained by CBCT showed less variability
than that obtained by PAN.
Much of this root variability in premolars is
believed to be due to different worldwide genetic
backgrounds, particularly the genes involved in
rhizogenesis. There seems to be a correlation between the
size of posterior teeth and the number of roots and canals.
It is observed that the larger the premolar crown, the
greater the number of roots and, as a consequence, of root
canals. The hypothesis that the number of roots and canals
is directly related to the crown´s dimensions would not be
anything unusual, since rhizogenesis is initiated after the
formation of the bell in morphogenesis [27].
Based on this theory, there are several
correlations suggested for root variation, among those is
the involvement of sexual dimorphism in the number of
roots, since male individuals tend to have larger teeth [27].
However, in our study, there was no gender predilection
observed in any group, agreeing to many studies with
mandibular premolars, but one exception for mandibular
first premolars and two exceptions for mandibular second
premolar [28, 29]. There was also no gender predilection
for the mandibular canine bifurcation.
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V. CONCLUSION
Our data allow us to conclude that mandibular canines
with more than one canal are rare, and even more rare is
the presence of two roots for this group of teeth in the
southern region of Bahia. On the other hand, such
variations are more common in mandibular premolars,
although with a general prevalence for the configuration of
one root and one canal. In general, the most prevalent
configuration was the same as found in other studies
around the globe for each group of teeth, though the
variants’ frequencies differ in variable degrees to other
populations. Finally, as expected, CBCT images produced
more reliable data than PAN images.
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