Anatomic comparison and prevalence of additional canals in contralateral maxillary first and second molars using cone beam computed tomography - An ex vivo study.

Background: Numerous cone beam computed tomography (CBCT) studies have been done to analyze the canal anatomy of maxillary molars. However, research on comparison of symmetry in contralateral molars in the Indian population is limited. Aim: The aim of this study is to identify and assess the variations in the internal anatomy based on Vertucci's classification and to compare the prevalence of additional canals in contralateral maxillary first molar (Mx 1 M) and maxillary second molar (Mx 2 M) using CBCT. Settings and Design: A total of 120 small and medium field of view CBCT images with Mx1M and Mx2M were collected and retrospectively evaluated. Materials and
Methods: Coronal, sagittal, and axial views of CBCT scans were analyzed by scrolling the scans, adjusting the contrast and brightness, and magnifying the canal configuration, along with additional canals and symmetry were identified and recorded. Statistical Analysis: Data were analyzed using McNemar's test and Chi-square test.
Results: Both Mx1M and Mx2M showed bilateral symmetry in the mesiobuccal root with Type I canal anatomy in 86.1% and 97.8%, respectively. The MB2 canal was evident in 34.1% of Mx1M and 8.4% of Mx2M.
Conclusion: Variations such a single-rooted and two-rooted teeth in Mx2M with Type I Vertucci's canal anatomy were seen. The MB2 canal was the only additional canal found. Copyright:

INTRODUCTION

Knowledge of the internal anatomic variations is essential for successful therapy. Anatomic variability is a challenge to the dental clinician during endodontic treatment. It's believed that failure in most cases of endodontic treatment is due to the inability to treat all the canals effectively.[1]

There are extensive reports on the canal anatomies of the maxillary first molar and maxillary second molar (Mx1M and Mx2M) because of their complex root canal morphologies.[23456] There are studies that have investigated the morphologic symmetry of contralateral teeth and found about 70%–82% bilateral asymmetry,[45678] which is of clinical significance while treating contralateral teeth in the same patient. Reports of ethnic differences in the canal anatomies are a challenge to clinicians during treatment. In the Korean population, a rare morphological variations were reported like one root with one canal and three buccal roots in Mx1M.[7] In the Saudi Arabian population, there are reports of C-shaped canals and fused roots in Mx1M and Mx2M.[9] Single rooted, two rooted with varied canal configurations were reported in the Indian population.[10] In the Egyptian population, Type III and V canal configurations were rare.[11]

Various methods in identifying canal morphologies such as sectioning, staining and tooth clearing techniques,[12] conventional radiograph techniques,[13] computed tomography (CT) scanning, and contrast medium-enhanced radiography[14] are studied and compared.

Although clearing method was considered the “gold standard” for assessing canal morphology in laboratory studies. However, all these techniques have some limitations. For instance, the staining and clearing technique is an in vitro technique and cannot be performed on patients.

Conventional radiography being 2-dimensional has its own drawbacks which include superimposition of structures and images,[15] which can lead to misunderstanding of the canal anatomy.[16] Cone-beam computed tomography (CBCT) imaging allows three-dimensional (3D) assessment of teeth; however, conventional tomographic imaging has higher radiation doses, which makes it unsuitable for clinical application.[12] The use of dental loupes with headlights, surgical operating microscopes, and ultrasonic methods has greatly improved the clinical detection of canals.

In cases where CBCT has been used preoperatively on teeth indicated for nonsurgical root canal treatment, the working length of each canal can be measured accurately in the sagittal section. Reports have shown the accuracy of CBCT to detect the root canal system similar to staining and clearing techniques and more precise than intraoral periapical radiography.[12] Therefore, CBCT scans are considered a reliable tool in studying internal anatomies because of their nondestructive in vivo usage.

The purpose of the study was to identify and assess the variations in the internal anatomy based on Vertucci's classification (VC) and to compare the prevalence of additional canals in contralateral Mx1M and Mx2M using CBCT.

MATERIALS AND METHODS

The Institutional Ethics Committee approval was obtained and a certificate no. 17107 was issued. The sample size was calculated using the formula with 95% confidence level and 80% power with respect to P = 50,[5] the sample size comes to be 96 with 20% nonresponse the total size comes to be 120.

One hundred and twenty CBCT scans of patients belonging to the South Indian Dravidian population were taken using Planmeca ProMax 3D Mid unit (PLANMECA OY, ASENTAJANKATU 6 FI-00880 HELSINKI, FINLAND). Operating parameters which were set at 5.6 mA, 90 kV, and exposure time for 27 s for small field of view (FOV), 8 mA, 90 kV, and exposure time of 12 s for medium FOV. Scan of patients who underwent scan for the purpose of dental examination, diagnosis, and treatment planning in the Department of Oral Radiology was retrospectively collected. Sequential sampling was done and all scans which had Mx1M and Mx2M were taken during January 2018 to April 2019 and studied. CBCT scans either small or medium FOV scans were chosen on the basis of the inclusion criteria (1) the presence of Mx1M and Mx2M bilaterally, (2) completely developed and erupted molars, (3) clear and complete view of all the roots and canals, and (4) patients in the age group ranging from 14–80 years. Exclusion criteria were: (1) maxillary molars with root canal fillings, (2) post and cores, and 3) full crown prosthesis.

Radiographic evaluation

Images were analyzed using the Romexis Viewer® Software in a 21-inch LCD Dell monitor with a resolution of 1024 × 768 pixels (DELL COMPUTER CORPORATION, USA). All the scans were visualized at 0.1 mm voxel size. The brightness and saturation of the scans were adjusted to ensure optimum visualization. CBCT images were acquired and each serial coronal, sagittal, and axial views were scrolled from the buccal to palatal, mesial to distal, and cementoenamel junction to the apex, respectively with each scan was analyzed by both examiners simultaneously in the case of disagreement an oral radiologist was consulted and an agreed consensus was reached. The information analyzed and recorded were the position of the tooth, canal anatomy, and number of roots (according to Vertucci's criteria) [Figure 1]. The collected data were tabulated (Microsoft Excel 2016).

Figure 1

Cone-beam computed tomographic images showing Vertucci's Type IV canal configuration in maxillary first molar – (a) Axial section showing two orifices in the mesiobuccal root, (b) Saggittal section showing two separate canals from the cementoenamel junction to apex, (c) Coronal section showing the mesiobuccal root

Statistical analysis

Statistical Product and service solution, version 20.0 (SPSS Inc., Chicago, IL, USA) was used. The Chi-square test was applied to test the statistical significance of the number and frequency of additional canals in the mesiobuccal (MB) root based on tooth position and gender, and McNemar test was applied to test the significance of bilateral symmetry in the left and right MB roots of Mx1M and Mx2M. The P was kept <0.05.

RESULTS

Around 476 maxillary molar teeth were analyzed. Among the Mx1M, all the teeth studied presented with three roots. The MB root showed a varied configuration that is Type I (66.25%) then Type II (25.41%), Type III (5%), and Type IV (3.33%) similarly in the distobuccal (DB) root Type I (99.5%) and Type III (0.5%) configuration were observed, whereas in Palatal (P) root only Type I (100%) configuration was observed. In Mx2M, three variations were observed. Among which the three-rooted molar was the most commonly noted, with the MB root showing a varied canal configuration of Type I (90.5%), Type II (4.7%), Type III (2.3%), and Type IV (2.3%) whereas, in the DB and P roots only Type I (100%) configuration was observed. Other variations found were a single root Mx2M with a Type I (100%) configuration and a two-rooted Mx2M with a buccal and palatal canal which showed a similar Type I (100%) configuration in both the canals [Table 1].

Table 1

Root canal configuration of maxillary molars based on Vertucci’s classification

Root Morphology	Roots	Type I (1)	Type II (2-1)	Type III (1-2-1)	Type IV (2)	Type V (1-2)	Type VI (2-1-2)	Type VII (1-2-1-2)	Type VIII (3)
Maxillary First Molar
One Root (n=0)		-	-	-	-	-	-	-	-
Two root (n=0)		-	-	-	-	-	-	-	-
Three roots (n=240)	MB	159 (66.25%)	61 (25.41%)	12 (5%)	8 (3.33%)	-	-	-	-
	DB	239 (99.5%)	-	1 (0.5%)	-	-	-	-	-
	P	240 (100%)	-	-	-
Maxillary Second Molar
One Root (n=2)		2 (100%)	-	-	-	-	-	-	-
Two root (n=22)	B	22 (100%)	-	-	-	-	-	-	-
	P	22 (100%)
Three roots (n=212)	MB	192 (90.5%)	10 (4.7)	5 (2.3)	5 (2.3)	-	-	-	-
	DB	212 (100%)	-	-	-	-	-	-	-
	P	212 (100%)	-	-	-	-	-	-	-

The bilateral symmetry of the MB canal of the first molar showed no significant difference in the canal configuration on the contralateral side (P = 0.446). Similarly in the MB canal of the second molar showed no significant difference in canal configuration on contralateral side (P = 0.392) [Table 2]. Whereas the DB and P roots of Mx1M and Mx2M recorded 100% bilateral symmetry.

Table 2

Bilateral symmetry based on Vertucci’s classification and incidence of additional canals based on gender and tooth position in maxillary molar

	Maxillary First Molar	Maxillary second molar
Bilateral Symmetry
Canal Configuration
Type I	68 (86.1%)	91 (97.8%)
Type II	19 (63.3%)	3 (50.0%)
Type III	1 (14.3%)	2 (66.7%)
Type IV	2 (50.0%)	2 (100%)
Additional Canals
MB2 Present	82/240	20/236
Based on Gender
Male	31 (37.8%)	16 (80%)
Female	51 (62.2%)	4 (20%)
Based on Tooth Position
Right	41 (50%)	9 (45%)
Left	41 (50%)	11 (55%)

The presence of second MB (MB2) canal in Mx1M was not statistically affected by gender (P = 0.19) or position (P = 1.0). Whereas, in Mx difference based on gender (P = 0.003) was statistically significant, but not significant in position (P = 0.640) [Table 2].

DISCUSSION

The current study aimed to give an in-depth description of the anatomy, symmetry, and gender variability of Mx1M and Mx2M using CBCT imaging because of high variations seen in maxillary molars.[171819]

Several problems were faced in earlier studies conducted on root canal morphology. Roentgenographic studies can reveal only a single plane of the tooth, which is not always the actual picture of the condition present in the tooth.[20]

Unlike the traditional periapical radiographs, CBCT images provide a 3D view of the root canals in coronal, axial, and sagittal sections, thereby avoiding image distortion and superimposition of structures at a low dose when exposed at appropriate parameters and within a FOV.

Domark et al.[21] evaluated the CBCT and micro-CT images of the canal anatomy of maxillary molars and found no significant difference between the images. Micro-CT is restricted to ex vivo laboratory studies and can be used as reference for comparative evaluation with other techniques.

Matherne et al.[22] compared charge-coupled device, photostimulable phosphor plate, and CBCT images and inferred that images obtained from CBCT were better in the identification of morphology than others.

Maxillary molars have shown variations in the anatomy, with the highest disparities in previous studies were in the MB root when compared to DB and P roots.[101123] In the current study, the MB root of Mx1M showed a greater incidence of VC Type I, canal anatomy followed by Type II, Type III, and Type IV which was observed in our study which is in accordance with earlier studies by Neelakantan et al.[10] done on the Indian population with an incidence of 51.8% Type I canal, 38.6% Type IV, and 5.5% Type II, and by Singh and Pawar[23] reported the incidence of Type I canal anatomy in 69%, followed by 24% Type II, 4% Type IV, and 2% Type V.

The outcomes of the present study when compared to other ethnical different populations studied have reported varying results.[82425]

In the present study, among the evaluated DB and P roots 99.5% and 100% Type I canal anatomy was observed, respectively. The frequency of occurrence of Type I canal configuration of the DB root in the Indian population by Neelakantan et al.[10] was 90.4% and in another report Singh and Pawar[23] showed a prevalence of 100%.

The findings of the P root in our study were similar to other studies which reported 100% VC Type I canal anatomy.[71023] In studies done on ethnically diverse populations, an incidence of 100% Type I palatal canal anatomy was reported.[1125]

In the current study, the Mx2M showed a greater incidence of VC Type I canal anatomy in the MB root is followed by Type II, Type III, and Type IV. The outcome of the current study is similar to previous researches, where a greater incidence of Type I canal anatomy was found in the MB root. Neelakatan et al.[10] reported 62% of VC Type I canal anatomy, Singh and Pawar[23] reported a frequency of 80.6% Type I canal anatomy, whereas, in other ethnically diverse populations, the reports were varying.[7102425]

In the current study, we found the DB and P roots showed Type I canal anatomy in 100% of the scans analyzed. This is contrasting from earlier studies done on the Indian population by Neelakantan et al.[10] reported an incidence of Type I canal anatomy in 84.9% of the DB root and 87.8% in the P root canal. Singh and Pawar[23] reported a similar incidence of type I canal anatomy of 100% in the DB canal and 97.2% in the P canal.

In the current study, MB2 was evident in 34.16% of Mx1M with a slightly greater incidence in female which was not significant and 8.47% of Mx2M with a greater incidence in males which was significant. This result was in variation with a previous study by Neelakantan et al.[10] which showed MB2 canals presenting an incidence of 44.1% in Mx1M and 30.7% in Mx2M. Singh and Pawar[23] reported an incidence of 30% MB2 canals in Mx1M and 19.4% in Mx2M. The incidence of MB2 in the current study was not affected by gender or tooth position except for Mx2M which showed a significant difference between males and females.

Both Mx1M and Mx2M showed bilateral symmetry of 75% and 81.6%, respectively which indicates a greater chance of finding a similar anatomic variation on the contralateral side. Studies conducted by Felsypremila et al.[4] and Tian et al.[2] reported similar findings.

In the current study, some variations in Mx2M were observed a two-rooted (9.16%) and single-rooted (0.83%) variants were found. Which was reported in previous studies by Neelakantan et al.[10] where a single root variant was seen in 0.9% and two root variants were seen in 4.9%.

CONCLUSION

The majority of the Mx1M and Mx2M was three rooted with single canal in the MB, DB, and P. Variations of two rooted and single rooted were noted in Mx2M. Most of the molars were bilaterally symmetrical with no association statistically. CBCT analysis which facilitates 3D imaging is a noninvasive and clinically efficient tool for examining complex and intricate root canal morphology which conventional radiographic imaging fails to capture. This can result in a better quality of treatment outcomes. However, the benefits to the patient must outweigh the potential hazards which can be justified with proper history and clinical examination.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.