|Year : 2022 | Volume
| Issue : 2 | Page : 171-179
A cone-beam computed tomographic study of root and root canal morphology of primary maxillary and mandibular second molars in Indian Children: An in vitro study
Farhin Katge, Uma B Dixit
Department of Pedodontics and Preventive Dentistry, School of Dentistry, D.Y. Patil University, Navi Mumbai, Maharashtra, India
|Date of Submission||30-Mar-2022|
|Date of Decision||14-Apr-2022|
|Date of Acceptance||03-May-2022|
|Date of Web Publication||15-Jul-2022|
Dr. Farhin Katge
Department of Pedodontics and Preventive Dentistry, School of Dentistry, D.Y. Patil University, Nerul, Navi Mumbai - 400 706, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: The root canal system in primary molars is considered to be complex. The aim of the present study was to assess the morphology of roots and root canals of primary maxillary and mandibular second molars using the cone-beam computed tomography (CBCT). Materials and Methods: From a total of 104 collected primary maxillary and mandibular molars (51 maxillary second molars and 53 mandibular second molars), 60 teeth (30 each of maxillary and mandibular second molars) were selected randomly and accordingly assigned into two groups: MAX2M (primary maxillary second molars) and MAN2M (primary mandibular second molars). CBCT was used to assess the number of roots and root canals, length of root, mesiodistal and buccolingual width of the canal, shape of the canal, and intercanal communications. Descriptive statistical analysis was performed using the SPSS software version 17.0. Results: The mandibular second molars showed the presence of two roots in 27 sample molars while the presence of three roots was observed in three MAN2M group. In these molars, all three roots exhibited Type I root canal configuration. The maxillary second molars exhibited three roots. A total of nine intercanal communications were seen in MAX2M group, whereas two communications were seen in MAN2M group. The palatal root in MAX2M group was more angulated (mean value: 127.21 ± 9.10) as compared to mesial (mean value: 95.39 ± 8.64) and distal roots (114 ± 11.24). Conclusion: The comprehensive knowledge of root and canal morphology of primary molars and anatomic variations is essential for successful endodontic therapy.
Keywords: Cone-beam computed tomography, morphology, primary molars, root, root canal, second molars
|How to cite this article:|
Katge F, Dixit UB. A cone-beam computed tomographic study of root and root canal morphology of primary maxillary and mandibular second molars in Indian Children: An in vitro study. J Indian Soc Pedod Prev Dent 2022;40:171-9
|How to cite this URL:|
Katge F, Dixit UB. A cone-beam computed tomographic study of root and root canal morphology of primary maxillary and mandibular second molars in Indian Children: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2022 [cited 2022 Aug 12];40:171-9. Available from: http://www.jisppd.com/text.asp?2022/40/2/171/351040
| Introduction|| |
Primary teeth are vital in child's orofacial growth and development. In addition to esthetics, phonetics, and mastication, primary teeth play a very important role in maintaining the space for permanent teeth, jaw growth, and development of oral musculature. In providing an optimum dental treatment, all of these functions should be taken into consideration. Primary molars have the thinner layers of enamel and dentin as compared to their permanent successors. Similarly, they also show a lower level of mineralization than permanent molars. Hence, the progression of dental caries is faster and aggressive in primary molars., Hence, the preservation of primary molars till exfoliation is always preferred in day-to-day clinical practice.
The endodontic procedure of primary molars is commonly carried out in routine dental practice. In primary molars, factors such as poor knowledge of root canal anatomy, unable to locate root canal orifice or identify the course of ribbon-shaped root canals may lead to failure of endodontic procedure. The detailed knowledge of the roots and root canal anatomy is considered to be an essential requisite for endodontic treatment. Several problems observed during or after endodontic procedure of primary molars occur majorly due to inadequate knowledge of the root canal anatomy. In previous literature, several studies on the internal and external morphology of teeth have shown that anatomic variations can occur in all traits of teeth which can be complex in nature.,,, Root canal morphology can be studied by various methods such as conventional radiography, clearing technique (using methyl salicylate as clearing agent), observation of cross-sections under stereomicroscope, and three-dimensional (3D) reconstructions models using computed tomography (CT) and micro CT.
Dental intraoral periapical radiograph, which is usually used for diagnostic and endodontic purpose reveals the only two-dimensional view of the tooth. As a result, some findings such as an extracanal, extra root, or intercanal communication often go unnoticed. Furthermore, overlapping of bony, dental structures, and distortion are other disadvantages of conventional periapical radiograph. Cone-beam CT (CBCT) is a highly accurate, noninvasive method that overcomes these shortcomings and provides three-dimensional information of teeth including roots and root canal system.
The root canal system in primary molars is considered to be complex, as canals demonstrate several small anastomoses running throughout the root dentin. The detailed knowledge regarding the same is very important while performing endodontic procedure in primary molars. The anatomical study of primary molars comprises anatomy of the pulpal cavity, roots, and root canals. It also comprises specific measurements of the length and diameter of each root canals and their variations, which may influence the success of endodontic procedures. A thorough knowledge of the complexities of the root and root canal system plays an important role in the success of endodontic procedure of primary teeth. These complexities can be diverse course of root canals, discrete intercanal or intracanal communications, nonidentical pulpal cavity anatomy, and bizarre anatomical variations of roots. The detailed and quantitative data on the morphological characteristics of primary teeth in different dental groups, however, are scarce.,,, Furthermore, the literature on the root and root canal morphology of primary molars using CBCT is very less.
Thus, the aim of the present study was to assess the anatomy of roots and root canals of primary maxillary and mandibular second molars using CBCT in Indian children.
| Materials and Methods|| |
Ethical approval for this cross-sectional in vitro study was obtained from the Institutional Research and Ethical Board (IREB/2021/PHD/PEDO/01).
Extracted human primary maxillary and mandibular second molars were used for the present study. Primary maxillary and mandibular second molars that were extracted by dentists from more than 20 dental colleges and hospitals from the various regions in India were obtained. The reasons for the extraction were not known to the authors and were not related to the present study.
The sample size was calculated based on the root length data of primary maxillary (mean ± standard deviation [SD]: Mesial root – 8.50 ± 0.83, distal root – 7.81 ± 0.71, and palatal root – 8.85 ± 0.98) and mandibular second molars (mean ± SD: mesial root – 10.67 ± 0.73 and distal root – 9.83 ± 0.58) from an earlier study by Dutta et al. By using 5% error and 95% confidence interval, the sample size was estimated to be 30. The characteristics of both maxillary and mandibular second molars were studied separately and we estimated a total sample size of 60 teeth, 30 each of primary maxillary and mandibular second molars.
Extracted primary maxillary and mandibular second molars with no evidence of root resorption were selected for the present study. Primary molars with root fracture in any of the roots, internal root resorption, external root resorption, canal obliteration, restored teeth, and dental anomaly of shape, size, and structure were excluded from the present study.
From the total of 104 collected primary maxillary and mandibular molars (51 maxillary second molars and 53 mandibular second molars), 60 teeth (30 each of maxillary and mandibular second molars) were selected randomly and accordingly assigned to two groups: MAX2M (deciduous maxillary second molars) and MAN2M (deciduous mandibular second molars).
All the selected molars were ultrasonically cleaned. The teeth were then stored in a glass container-containing saline solution at the room temperature. All the selected molars were then mounted on modeling wax in an arch form after identifying the various aspects of the tooth: Buccal, lingual, mesial, and distal. This was done to maintain uniformity in the mounted samples.
The 60 sample teeth were then scanned using a CBCT machine (NewTom, Giano/VG3, Imola, Italy). The specifications maintained for the scanning of sample teeth were 90 KVp and 10.80 mA with the field of view 11 cm × 5 cm and voxel size of 0.3 mm. All the CBCT scans were made according to the manufacturer's recommended guidelines.
3D image reconstruction was done using NNT viewer software (NewTom, version 10.0 Imola, Italy). All the CBCT images were assessed in three planes: Sagittal, axial, and coronal by two independent expert pediatric dentists. Both the examiners with a clinical and academic experience of more than 20 years were trained in using CBCT software. Dell Inspiron 3891 desktop and Dell E-series 24 inch HD screen with 1920 × 1080 resolution (Dell, Round Rock, USA) was used for viewing and analyzing the images. The following eight parameters were considered, analyzed, and recorded for each selected molar:
- The number of roots per tooth was counted manually on 3D reconstructed images [Figure 1]a
- The number of root canals in each root were counted after assessing the coronal and sagittal section of CBCT images [Figure 1]b
- The morphology of the root canal system was classified according to Vertucci's classification. Root canal morphologies which were not listed in Vertucci's classification were analyzed according to their forms
- Presence, location, and number of accessory canals and intercanal communications were recorded using axial, coronal, or sagittal sections of CBCT images [Figure 1]c
- The length of each root was measured using the measurement tool in NNT viewer software by taking the maximum length from the apex of the tooth to the greatest area of constriction at cementoenamel junction (CEJ) on the coronal or sagittal section of CBCT image [Figure 1]d
- Angulation of each root was calculated using the angulation tool in NNT viewer software on the sagittal section of CBCT images. The first line was drawn at the greatest area of constriction on CEJ, whereas the second line was drawn along the length of the root. The angle formed at the intersection of two lines was calculated [Figure 1]e
- Width of the root canal of each root was measured at 2 mm apical from CEJ on the axial section of CBCT image. The line was drawn from the mesial aspect to the distal aspect of the inner root canal wall, and this was calculated as mesiodistal (MD) width of the root canal. Similarly, buccolingual (BL) width of the canal was calculated from the buccal aspect to the lingual aspect of the inner root canal wall [Figure 1]f
- The shape of each canal in each root was categorized as S-shaped, curved, or straight on the sagittal section of CBCT image [Figure 2]a, [Figure 2]b, [Figure 2]c. For the categorization of straight and curved canals, Weine's method was used [Figure 2]d. In Weine's method, the straight line is drawn from the orifice through the coronal portion of the curve and a second line is drawn from the apex through the apical portion of the curve. The intersection of these two lines forms the canal angulation. Weine categorized canal curvatures as straight (5° or less), moderately curved (10°–20°), or severely curved (>20°). The categorization was modified in the present study. The angle ≤5° was considered straight canals, whereas angle more than 5° was considered curved canals.
|Figure 1: (a) Number of roots per tooth; (b) Number of root canals in each root; (c) Intercanal communications (Yellow arrows indicates the intercanal communication in axial and sagittal section); (d) Length of each root; (e) Angulation of each root; (f) BL and MD width of root canal. BL = Bucco-lingual, MD = Mesio-distal|
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|Figure 2: Shape of each root canal: (a) S-Shaped, (b) curved, (c) straight and (d) Weine's method for determining root canal curvature|
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The data obtained were tabulated and analyzed statistically using the SPSS software version 17.0 (SPSS, Inc., Chicago, IL, USA). Descriptive statistics were performed to calculate the frequency of categorical variables and mean, standard deviation, and range for continuous variables. Inter-examiner and intra-examiner reliability was calculated using the interclass correlation coefficient (ICC). The ICC value <0.5 is indicative of poor reliability, value between 0.5 and 0.75 indicates moderate reliability, value between 0.75 and 0.9 indicates good reliability whereas value >0.9 indicates excellent reliability.
| Results|| |
Sixty primary maxillary (n = 30) and mandibular molars (n = 30) were examined for root and root canal morphology using CBCT for the present study. [Table 1] depicts inter-examiner and intra-examiner reliability of length of the root and angulation of the root, whereas, [Table 2] depicts inter-examiner and intra-examiner reliability of MD and BL widths of the root canals. In both the groups (MAX2M and MAN2M), the ICC value for inter-examiner reliability showed good concordance with respect to the length of root, angulation of root, BL width, and MD width of each root canal [Table 1] and [Table 2]. Whereas, intra-examiner reliability was excellent with all the above-mentioned parameters in both the groups [Table 1] and [Table 2].
|Table 1: Inter-examiner and intra-examiner reliability of length of the root and angulation of the root|
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|Table 2: Inter-examiner and intra-examiner reliability of mesio-distal and bucco-lingual widths of root canals|
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The frequency and percentage of the number of root canals in primary maxillary and mandibular second molars are shown in [Table 3]. In MAX2M group, all sample molars exhibited three roots; mesial, distal, and palatal roots. All distal and palatal roots showed a single canal with Type I configuration of Vertucci's classification. In mesial roots, 28 samples showed a single canal with Type I configuration, whereas two samples showed two canals (MB1 and MB2 root canals) with Type IV root canal configuration. In MAN2M group, 27 sample molars showed two roots (mesial and distal roots). In the mesial root, 70% (n = 19) of MAN2M group exhibited Type IV root canal configuration of Vertucci's classification, whereas 4% (n = 1) and 26% (n = 7) of samples showed Type I and Type V root canal configuration. Type I root canal configuration was predominantly found in 48% (n = 13) of the distal root, whereas 26% (n = 7) of the distal root showed Type V root canal configuration and remaining 26% (n = 7) showed Type IV root canal configuration [Figure 3]. Three-rooted molars were observed in three primary mandibular second molars. In these molars, all three roots (mesial, distobuccal [DB], and distolingual [DL] root) exhibited Type I root canal configuration [Figure 4].
|Table 3: Frequency of number of root canals in primary mandibular second molars|
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|Figure 3: Root canal configuration according to Vertucci's Classification in mesial and distal root of primary mandibular second molars (Type I and Type IV root canal configuration is highlighted in axial and sagittal sections in yellow circle and oval shape) |
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|Figure 4: Type I and Type IV root canal configuration in primary maxillary and mandibular second molars|
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A total of nine intercanal communications were seen in MAX2M group [Figure 5]. Most of the communications were observed between the mesial and palatal canal and were located in the middle third location. Two intercanal communications were observed in MAN2M group [Figure 5]. The incidence was equally seen in the distal root (n = 1) and mesial roots (n = 1). Both the communications were seen in the middle 3rd of mesial and distal roots.
|Figure 5: Location of intercanal communications in MAX2M and MAN2M groups|
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[Table 4] shows the mean values of length of root, angulation of root, BL, and MD width of root canals for both MAX2M and MAN2M groups. The palatal root in MAX2M group was more angulated (mean value: 127.21 ± 9.10) as compared to the mesial (mean value: 95.39 ± 8.64) and distal roots (114 ± 11.24). Root canals were wider in BL dimension as compared to MD dimension in the mesial and distal roots of MAX2M group suggestive of oval-shaped canals in the axial section. Whereas, palatal roots were comparatively rounder with similar BL and MD dimensions [Table 4]. The BL and MD dimensions of MB2 canals (n = 2) were smaller as compared to other canals. Similarly, in MAN2M group, BL width of the canal was more than MD width of the canal. This was seen in all canals (mesial, distal, DB, and DL) suggestive of oval-shaped canal in the axial sections.
|Table 4: Mean value and standard deviation of length of root, angulation of root, bucco-lingual width, and mesio-distal width of the root canal|
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In MAX2M group, curved root canals and S-shaped root canals were predominantly found in the mesial root as compared to the straight root canal, whereas, the prevalence of straight and curved root canals was higher in the distal root. Palatal root predominantly exhibited straight root canals followed by S-shaped canals and curved canals [Figure 6]. In MAN2M group, curved-shaped canals were found more in mesiobuccal (MB) and mesiolingual (ML) canal. S-shaped canal was not observed in both MB and ML canals. In DB canal, straight-shaped canal was more in the number followed by S-shaped canal and curved canal. DL canals exhibited more straight-shaped canals as compared to curved and S-shaped canals [Figure 6].
|Figure 6: Shape of each root canal in each root in MAX2M and MAN2M groups. MB = Mesiobuccal, ML = Mesiolingual, DL = Distolingual, DB = Distobuccal|
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| Discussion|| |
There are many studies in the literature describing root canal morphology of primary molars, but most of these studies lack in defining root morphology, detailed morphology of root canals, and intercanal communications.,,, Hence, the present study provides a detailed descriptive analysis of root and root canal morphology of primary maxillary and mandibular second molar using CBCT. The present study used all the parameters which were considered to be important for assessing the root and root canal morphology of primary molars. CBCT is the noninvasive method of radiographic visualization that allows reconstruction of radiographic images in three dimensions. This helps in visualizing the internal and external morphology of primary teeth.
Primary maxillary second molar
In the present study, all the primary maxillary second molars exhibited three roots. This was contrasting to the results by Datta et al. and Wang et al., In a study by Wang et al., out of 10 maxillary second molars, one molar had only two roots and others were three-rooted. Similarly, Datta et al. reported two molars with two roots. This was because authors considered fused roots as single root. Most likely fusion was observed with DB and palatal roots. In the present study, no fusion was observed with any of the roots of primary maxillary second molar. The result of the present study was supported by Zoremchhingi et al. and Bagherian et al. which showed three-rooted primary maxillary second molars., Zoremchhingi et al. used CBCT to study root canal morphology, whereas Bagherian et al. studied using the clearing technique.
In maxillary second molars, all three roots (mesial, distal, and palatal) exhibited single canal with Type I root canal configuration. This was also reported by Bagherian et al. and Mohd Ariffin et al. Bagherian et al. reported Type I configuration in all three roots in 100% of their sample molars. Whereas, Mohd Ariffin et al. reported three-rooted primary maxillary second molar in 77.19% of sample teeth. In the present study, only two molars of the sample teeth exhibited two canals with Type IV configuration in the mesial root. Type IV configuration was confirmed after observation of MB1 and MB2 canals in the mesial root. In the literature, many authors reported MB1 and MB2 canal in the mesial root of primary maxillary second molar.,, In a study by Abdelkhalik et al., Type IV configuration was more common in MB and DB root of 47.1% of the sample molars. They also reported Type I and Type IV configuration in the palatal root.
Nine intercanal communications were seen in primary maxillary second molars. These communications were seen at the middle 3rd location between the mesial and palatal roots. Wang et al. reported intercanal communication between MB and DB canal. The frequency and location of intercanal communication were not mentioned in the study by Wang et al.
The mean length calculated for mesial, distal, and palatal roots of primary maxillary second molars was 9.71 ± 1.48, 9.22 ± 1.20, and 9.76 ± 1.64, respectively. The mean root length calculated by Gaurav et al., Datta et al., and Zoremchhingi et al. was much smaller than the results of the present study. The mean root length calculated by Gaurav et al. for mesial, distal, and palatal roots was 7.75, 7.61, and 8.03 mm, respectively. Similarly, Zoremchhingi reported 8.2, 8.06, and 8.27 mm root lengths for mesial, distal, and palatal root. Angulation of mesial, distal, and palatal roots was 95.39 ± 8.64, 114.49 ± 11.24, and 127.21 ± 9.10, respectively. The angulations reported for mesial, distal, and palatal root in a study by Gaurav et al. were 81.02°, 83.80°, and 78.47°. As seen the angulation reported in the present study were higher as compared to Gaurav et al. In the present study, the inner angle of the root was measured. This might be the reason for the variation seen in the angulations measured by Gaurav et al. where the angle (inner or outer) measured was not specifically mentioned. Furthermore, the type trait of the sample molars involved in their study was also not mentioned. The sample molars might be first molars or second molars.
In consideration of the widths of root canals in the axial section, oval-shaped canals were observed in the mesial and distal root canals, whereas circular widths were observed in the palatal canals of primary maxillary second molar. This results were in contrast to the study by Wang et al. where they reported ovoid- and ribbon-shaped canals in cross-sections of mesial, distal, and palatal roots. Fumes et al. also reported oval-shaped canals in maxillary molars. In literature, Gaurav et al. and Zoremchhingi et al. studied the diameter of root canals for morphology of the root canal., As the canals in primary molars are oval, ribbon, or C-shaped, the width of canals rather than diameter was considered in the present study. The shape of canals observed in maxillary second molars was straight, curved, and S-shaped. This parameter is of great importance as it will help in determining the proper course of the root canal from orifice to apex, influencing the success of endodontic therapy. However, the MB2 canals observed in the present study were straighter in course, but the results cannot be definite as they were found in fewer molars.
Primary mandibular second molar
Most of the mandibular molars (90%) were two rooted and only three molars (10%) exhibited three roots. In the present study, one mesial and two distal roots were seen in three-rooted molars. These results were in accordance to the study by Wang et al., Dutta et al., Yang et al., Bagherian et al., Sarkar and Rao. In their study, they observed two- and three-rooted deciduous mandibular second molar. Whereas, Zoremchhingi et al., Katge and Wakpanjar reported two-rooted primary mandibular second molar. Katge and Wakpanjar also studied the root canal morphology of primary molars using the clearing technique. The variations seen among the number of roots of primary mandibular second molar might be due to the ethnic variations of sample teeth collected. As it is observed that most of the studies from South Asian continent exhibited three rooted molars. However, a definitive conclusion cannot be drawn because of the smaller sample size.
In the present study, 86.67% (n = 26) of the mesial root of two-rooted mandibular second molar showed two canals (MB and ML), whereas four molars showed a single canal in the mesial root. In the distal root of two-rooted molars (n = 27), 77.78% (n = 21) showed canals and remaining 22.22% (n = 6) showed single canal. This was reported by the Zoremchhingi et al., Wang et al., and Sarkar and Rao.,, They reported two canals in 44.4%, 53.3%, and 21.4%, respectively, in the distal root of two-rooted mandibular second molars. This result was in concordance with a study by Wang et al. and Fumes et al., Root canal configuration observed in primary mandibular second molar is Type I, Type IV, and Type V. Type IV predominantly showed higher incidence in the mesial root as compared to Type I and Type V. In the distal root, Type I was more commonly seen as compared to Type IV and Type V. This results were supported by studies of Bagherian et al., Katge and Wakpanjar, and Demiriz et al.,, Abdelkhalik et al. contrastingly reported type II and type IV in the mesial root and type IV in the distal root. One of the least found root canal configurations in our study was Type V. Contrasting to our results, Type V configuration was not reported by Bagherian et al., Katge, and Wakpanjar., A study by Demiriz et al. is the only study in the literature who reported Type V canal configuration in 10.53% of sample molars.
Intercanal communication was observed at the middle 3rd location in both mesial and distal roots of primary mandibular second molar. In the literature, no studies reported intercanal communication in primary mandibular second molar. The mean length of mesial (n = 30) and distal (n = 27) roots for mandibular second molar observed in the present study was 9.76 ± 1.29 and 9.86 ± 1.16. The root length for DB and DL root in three-rooted mandibular molars (n = 3) was 9.16 ± 0.05 and 8.55 ± 0.63. This was almost comparable to the root length measured by Zoremchhingi et al., Ozcan et al., Bagherian et al. and Fumes et al,,, The length measured in their studies ranges from 8.2 mm to 9.4 mm. The angulation measured for mesial, distal, DB, and DL roots was 98.92 ± 6.02, 98.72 ± 8.60, 102.76 ± 9.56, and 101.73 ± 6.66. Here it can be observed that the three-rooted molars were more angulated as compared to two-rooted molars. However, a significant difference cannot be drawn from this finding, as these molars were very few in number. The angulation calculated by Gaurav et al. was 84.90° for the mesial root and 85.71° for the distal root which were smaller than the angulation measured in present study. Oval-shaped canals were observed in the axial section in all the canals of primary mandibular second molars. This finding was in accordance with the study by Fumes et al. In MB and ML canals, curved-shaped canals were more prominent, whereas in DB and DL, straight canals were more prominently observed.
| Conclusion|| |
This article provides an insight on the incidence of morphological variation in the root and canal morphology of primary maxillary and mandibular second molars. Many such findings are usually missed on routine two-dimensional radiographic images. CBCT was used in this study which provides accurate details regarding the internal and external anatomy of teeth. Knowledge regarding the presence of unusual variations such as MB2 canal in primary maxillary second molars, three-rooted mandibular second molars, presence of intercanal communications, and incidence of curved and S-shaped canals is important as it can help a clinician increase the success rate of endodontic treatment.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4]