Keywords
Qatari population - maxillary molars - morphology
Introduction
Successful root canal therapy depends on thorough debridement and complete obturation
of the root canal system.[1] For this to be achieved, it is necessary to locate all root canals. The inability
to locate and consequently treat all these canals will lead to posttreatment disease.[2]
[3] A clinician should be aware of the internal morphology of the teeth and the wide
range of anatomical variations possibly encountered during the root canal therapy.
The root canal system of the maxillary first and second molars is usually complex
and variable.[2]
[4]
[5] The mesiobuccal root was reported to be showing the most variations especially regarding
the prevalence of a second mesiobuccal canal and the types of canal configurations.[2]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11] Certain factors contribute to the wide variations reported in the incidence of second
mesiobuccal canal in maxillary molars and these include race, age, and gender of the
population studied.[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
The introduction of cone-beam computed tomography (CBCT) has significantly improved
the understanding of root canal morphology.[19] The advantages of CBCT scans are nondestructive way to study root canal morphology
at lower radiation doses and higher resolution compared with other methods that studied
the root canal anatomy of human teeth which make it more favorable for clinical application
as well as a reliable method of research.[20]
[21]
[22]
The aim of this study was to identify the root canal morphology of the maxillary first
and second molars in Qatari population using CBCT imaging in vivo.
Materials and Methods
This retrospective descriptive study was performed with the approval of the Medical
Research Center and the Institutional Review Board at Hamad Medical Corporation in
Doha, Qatar. The study population is a sample of the Qatari population, who were referred
for dental treatment. A total of 544 CBCT records of Qatari patients who attended
Hamad Dental services were included in this study. The CBCT images were requested
for different treatment purposes including examination, diagnosis, or treatment planning,
and they were performed by expert radiologists. I-CT CBCT scanner (Imaging Sciences
International, Hatfield, Pennsylvania, United States) was used operated with 120 kVp
(eff) tube voltage, 20 mA tube current, 14.7 second, Voxel size 0.4 to 0.2 mm, with
field of view of 160 × 40 mm.
The CBCT images were reviewed by two endodontists with more than 10 years of clinical
experience independently. The images were scrutinized through the sagittal, coronal,
and axial views, and three-dimensional reconstruction of the jaws was applied when
needed using Infinite software version 11.4 and Xelis dental three-dimensional viewer
software version 1.0 (Infinitt, Seoul, South Korea) to extract the wanted information.
In the beginning, 20% of the sample was viewed by each viewer alone twice and with
3 weeks apart, and the data collected were used to measure interexaminer and intraexaminer
agreement.
For the data collection, patient’s identification was not revealed where each patient
was given a specific code. The data collection was as follows: age and gender of the
patient, inclusion or exclusions and the reason of exclusion, each tooth type and
location, the number of roots, canal configuration type according to Vertucci classification[1]; in addition to incidental findings such as the presence of anatomical variations,
congenital anomalies, or pathologic changes.
The teeth included in this study were selected according to the following criteria:
(1) permanent teeth with fully formed root; (2) no intracanal or extraradicular restorations;
(3) no apical pathosis; (4) no calcification of the canals or resorption, and (5)
clear CBCT images with no artifact. When one of these criteria was not applicable,
the teeth were excluded mentioning the reason.
The statistical analysis was performed using Statistical Product and Service Solutions
(SPSS), version 20 (SPSS Inc, Chicago, Illinois, United States). A descriptive analysis
was implemented in this study to describe a detailed characteristic of the root anatomy
and root canal configuration of the permanent teeth including frequency, percentages,
and mean. Chi-squared test was used to compare right teeth to the left. Kappa agreement
analysis was performed to assess the interexaminer and intraexaminer agreement.
Results
A total of 544 CBCT records were evaluated that included 1,088 examined teeth. The
interexaminer agreement result was 95.13% (range: 74-100%) and the intraexaminer agreement
was 91.7% (range: 87.4-98.1%).
Out of 1,088 examined teeth, 277 maxillary first molars teeth were included (25%)
in this study.
One-hundred sixty-one (58.2%) teeth belong to females, while 116 (41.9%) teeth belong
to males. The average age was 32.2 years (range: 10-70). The number of roots most
commonly observed were three roots in 270 teeth (97.5%). Only seven teeth (2.5%) had
two roots, and in three teeth, the roots were located in buccal and palatal position,
while in 4 teeth, the roots were located in mesial and distal position ([Table 1]).
Table 1
Summary of gender, age, and root number of maxillary first and second molars
|
Tooth type
|
No. of patients included (%)
|
No. of patient excluded (%)
|
Female (%)
|
Male (%)
|
Age mean
|
4 roots (%)
|
3 roots (%)
|
2 roots (%)
|
1 root (%)
|
|
Maxillary first molar
|
277 out of 1,088 (25.5)
|
811 (74.5)
|
161 (58.2)
|
116 (41.9)
|
32.2 (10-70)
|
0
|
270 (97.5)
|
7(2.5)
|
0
|
|
Maxillary second molar
|
330 out of 1,088 (30.3)
|
758 (69.7)
|
207 (62.7)
|
123 (37.3)
|
32.5 (12-69)
|
4 (1.2)
|
291 (88.2)
|
24 (7.3)
|
11 (3.3)
|
The root canal configuration of maxillary first molar, Vertucci type I classification
was always observed in the palatal root (100%) and most of the distobuccal root (97%)
except for eight teeth, five (1.9%) had Vertucci type III and three (1.1%) had type
V classification. Different Vertucci classifications were observed in the mesiobuccal
root, in which Vertucci type IV was the predominant configuration (35.9%) followed
by type II (21.1%), type III (17%), type I (12.9%), type V (9.3%), and type VI (2.6%).
Three (1.2%) mesiobuccal roots had complex anatomy. Two rooted maxillary first molars
with buccal and palatal roots and one of which had mesial and distal root had Vertucci
type I classification in all the roots. Two mesial roots had type III and one root
had type IV. Three distal roots had type IV ([Table 2]).
Table 2
Number and percentage of root canal system in maxillary first molar
|
Maxillary first molar
|
Root
|
Type I (1), n (%)
|
Type II (2-1), n (%)
|
Type III (1-2-1), n (%)
|
Type IV (2-2), n (%)
|
Type V (1-2), n (%)
|
Type VI (2-1-2),
n (%)
|
Complex anatomy
|
|
|
Abbreviations: B, buccal; D, distal; DB, distobuccal; M, mesial; MB, mesiobuccal;
P, palatal.
aComplex anatomy of mesiobuccal root.
|
|
3 roots
|
MB
|
35 (12.9)
|
57 (21.1)
|
46 (17)
|
97 (35.9)
|
25 (9.3)
|
7 (2.6)
|
3 (1.1)
|
2-1-2-1a
|
|
DB
|
262 (97)
|
0 (0)
|
5 (1.9)
|
0
|
3 (1.1)
|
0 (0)
|
2-1-2-1-2a
|
|
P
|
100
|
0
|
0
|
0
|
0
|
0
|
2-3-1a
|
|
2 roots
|
B
|
3
|
0
|
0
|
0
|
0
|
0
|
|
|
|
P
|
3
|
0
|
0
|
0
|
0
|
0
|
|
M
|
1
|
0
|
2
|
1
|
0
|
0
|
|
D
|
1
|
0
|
0
|
3
|
0
|
0
|
The comparison between the upper right and left maxillary first molars in the same
individuals found to be symmetrical in 96.9% and dissimilar in 3.1%, while the root
canal configuration was found to be symmetrical in 46.9% and asymmetrical in 53.1%
([Table 3]).
Table 3
Symmetry of maxillary first and second molars
|
Maxillary first molar
|
Symmetry
|
Asymmetry
|
Maxillary second molar
|
Symmetry
|
Asymmetry
|
|
Abbreviations: Lt, left; Rt, right.
|
|
Root number
|
96.9% Rt and Lt the same
|
3.1% Rt and Lt different
|
Root number
|
89.4% Rt and Lt the same
|
10.6% Rt and Lt different
|
|
Root canal configuration
|
46.9% Rt and Lt the same
|
53.1% Rt and Lt different
|
Root canal configuration
|
39.8% Rt and Lt the same
|
60.2% Rt and Lt different
|
For maxillary second molar, 330 teeth (30.3%) were included, in which 62.7% of teeth
belong to females and 37.3% of teeth belong to males. The age ranged from 12 to 69
years with an average of 32.5 years. The number of the roots most commonly observed
were three (88.2%), two (7.3%), one (3.3%), and four roots (1.2%) ([Table 1]). The two rooted maxillary second molars were found to be either in mesial and distal
or buccal and palatal position.
In the three rooted maxillary second molars, the root canal configuration was mainly
Vertucci type I classification in the palatal root (99.7%) except for one palatal
root that had type V. Distobuccal roots were type I (99.3%) except for two distobuccal
roots that had Vertucci type III. Mesiobuccal root showed almost all different types
of Vertucci classification and the most predominant types were type IV (27%), type
III (21.3%), type I (19.6%), type II (18.9%), followed by type V (9.3%), type VI (3.1%),
and type VII (0.7%). The two rooted maxillary second molars with buccal and palatal
roots showed Vertucci type I classification in all palatal and nine buccal roots,
three buccal roots showed type III and three buccal roots showed type V, two buccal
roots showed type II, and one buccal root showed complex canal configuration. In the
four rooted maxillary second molars, Vertucci type I classification was predominant
in all the canals except in one mesiobuccal root that was type II. Four teeth with
single root second molar were type II, three teeth type I, two type VIII, and one
showed complex anatomy ([Table 4]).
Table 4
Number and percentage of root canal system in maxillary second molar
|
Maxillary second molar
|
Root
|
Type I
(1), n (%)
|
Type II (2-1), n (%)
|
Type III (1-2-1), n (%)
|
Type IV (2-2), n (%)
|
Type V (1-2), n (%)
|
Type VI (2-1-2), n (%)
|
Type VII
(1-2-1-2), n (%)
|
Type VIII (3), n (%)
|
Complex anatomy
|
|
|
Abbreviations: B, buccal; D, distal; DB, distobuccal; M, mesial; MB, mesiobuccal;
MP, mesiopalatal; P, palatal.
aComplex anatomy of Buccal root.
bComplex anatomy of single root maxillary second molar.
|
|
3 roots
|
MB
|
57 (19.6)
|
55 (18.9)
|
62 (21.3)
|
79 (27)
|
27 (9.3)
|
9 (3.1)
|
2 (0.7)
|
0 (0)
|
|
|
|
DB
|
289 (99.3)
|
0 (0)
|
2 (0.7)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
P
|
290 (99.7)
|
0 (0)
|
0 (0)
|
0 (0)
|
1 (0.3)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
2 roots
|
M
|
0 (0)
|
0 (0)
|
1 (4)
|
4 (16.6)
|
0 (0)
|
0 (0)
|
0 (0)
|
1 (4)
|
1
|
B2-1-3-2a
|
|
D
|
5 (20.8)
|
0 (0)
|
0 (0)
|
1 (4)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
B
|
9 (37)
|
2 (8)
|
3 (12)
|
0 (0)
|
3 (12)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
P
|
18 (75)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
4 roots
|
MB
|
3
|
1
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
|
|
DB MP DP
|
4
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
|
One root
|
|
3
|
4
|
1
|
0 (0)
|
0 (0)
|
0 (0)
|
0 (0)
|
2
|
1
|
2-3b
|
The number of roots in maxillary second molars in the right and left were symmetrical
in 89.4% and dissimilar in 10.6%, while the root canal configuration was symmetrical
in 39.8% and asymmetrical in 60.2% ([Table 3]).
Discussion
The aim of this study was to provide detailed root canal morphology of the maxillary
first and second molars in Qatari population based on a retrospective analysis of
CBCT images. The study revealed that the predominant number of roots in the maxillary
first molars was three (97.5%) while (2.5%) of the first molars with two roots. The
results are consistent with previous findings of different populations.[4]
[6]
[7]
[9]
[12] The maxillary second molar showed more variations in root number with the majority
of three roots in 88.2%. However, three other variants were observed in the maxillary
second molars; two roots (7.3%), one root (3%), and four roots (1.2%) were less frequently
observed. This is common finding in many studies of root canal anatomy.[5]
[7]
[16]
Understanding the correct number of roots and canal morphology is essential in root
canal therapy. Accurate knowledge of possible variations in root canal system before
root canal therapy is crucial for endodontists with high rates of variation in maxillary
molars. In line with other studies,[5]
[7]
[10]
[18]
[23]
[24] mesiobuccal roots of maxillary first and second molar teeth had more variation in
their root canal configuration compared with distobuccal and palatal roots that had
been mostly one canal in this study. The incidence of two separated canals, Vertucci
type IV, was 35.9% of the maxillary first molar and 21.1% started with two canals
even if it will rejoin somewhere in the root trunk, Vertucci type II. It was demonstrated
that root canal treatment of maxillary molars has the highest rates of clinical failure
probably because complexity in root canal anatomy and not easily detected during root
canal treatment.[24]
[25]
[26]
[27]
[28] Wolcott et al examined 3,578 root canals treated first molars during a 5-year period
and found that the overall prevalence of second mesiobuccal canal was 60% suggesting
that failure to find and treat existing second canal will decrease the long-term prognosis.
As a result, these anatomic variations should be considered during root canal treatment
of maxillary molars.[28] The important factors that help in treating second mesiobuccal canal in routine
practice is the clinician’s knowledge of its presence and always allocating sufficient
time and use of sophisticated tools to locate these canals. It has been observed that
mesiobuccal root of the maxillary second molar represents technical challenge for
the clinician with substantial variations in root canal anatomy. In the present study,
almost all Vertucci type classifications were detected particularly in this root ([Table 4]).
There are few studies that have compared the right and left teeth of the same individual.[29]
[30]
[31]
[32] In the present study, it was interesting to find out that more than half of root
canal configuration of maxillary first and second molars were not alike in both sides
of the same patient (53.1 and 60.2%). These data are important from a clinical perspective
as these variations in symmetry should be considered when treating two opposite molars
in the same patient.
Conclusion
In vivo CBCT study showed that Qatari population has a higher prevalence of three
roots in first and second molars. The root canal configuration of the maxillary first
and second molars was variable. The incidence of two canals in the mesiobuccal root
was higher in the maxillary first molar than in maxillary second molar. High bilateral
asymmetry was found in configuration of canals in the same individuals. These variations
should be taken into consideration during root canal treatment.
