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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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Year : 2012  |  Volume : 30  |  Issue : 2  |  Page : 94-102

Radix entomolaris and paramolaris in children: A review of the literature

1 Department of Pediatric and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India
2 Department of Oral and Maxillofacial Surgery, Bapuji Dental College and Hospital, Davangere, Karnataka, India

Date of Web Publication23-Aug-2012

Correspondence Address:
N B Nagaveni
Department of Pediatric and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-4388.99978

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Pediatric dentistry in the current scenario is not just about teeth and gums that are easily visible in children's mouth anymore. It is all about those structures that are hidden, difficult to identify, and often remain undiagnosed. Dentist can come across various anomalies pertaining to the crown structure during the clinical practice. Although supernumerary tooth is the most commonly seen anomaly, the presence of extra roots in molars is an interesting example of anatomic root variation. It is well known that both primary and permanent mandibular first molars usually have roots, one mesial, and the other distal root. Very rarely an additional third root (supernumerary root) is seen and when it is located distolingually to the main distal root is called "radix entomolaris (RE)" and when it is placed mesiobuccaly to the mesial root is called "radix paramolaris (RP)." The purpose of this article is to discuss the prevalence, morphology, classification, clinical diagnosis, and significance of supernumerary roots in contemporary clinical pediatric dentistry.

Keywords: Distolingual root, endodontic treatment, extra third root, periapical radiographs, radix entomolaris, radix paramolaris

How to cite this article:
Nagaveni N B, Umashankara K V. Radix entomolaris and paramolaris in children: A review of the literature. J Indian Soc Pedod Prev Dent 2012;30:94-102

How to cite this URL:
Nagaveni N B, Umashankara K V. Radix entomolaris and paramolaris in children: A review of the literature. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2023 Jan 29];30:94-102. Available from: http://www.jisppd.com/text.asp?2012/30/2/94/99978

   Introduction Top

Molars are frequently affected by caries at an early age and may require successful endodontic treatment for their long-term retention in the oral cavity. The objective of pediatric endodontic therapy is thorough removal of the pulp tissue from all the roots and canals followed by chemo-mechanical cleaning and filling with a suitable material. Failure to diagnose and treat the extra roots in molars may lead to the endodontic treatment failure and even tooth loss at an early age resulting patient to suffer functionally, esthetically, and psychologically. Therefore, pediatric dentist must be aware of these unusual root structures to provide the overall benefit to a child patient because when they are present are highly challenging to diagnosis as well as to endodontic treatment. The purpose of this article is to discuss the prevalence, morphology, classification, clinical diagnosis, and significance of supernumerary roots in contemporary clinical pediatric dentistry.

   Review of the Literature Top

"Radix entomolaris" (RE) an additional third root was first mentioned in the literature by Carabelli [1] in 1844 and is described by various terms, such as "extra third root" or "distolingual root" or "extra distolingual root." [2] Radix paramolaris (RP) is known as the "mesiobuccal root" [3] was first described by Bolk [4] in 1915.

Prevalence of RE and RP

Various prevalence studies have been done using periapical radiographs, [5],[6],[7],[8],[9] extracted teeth [10],[11],[12],[13],[14] recently by microcomputed tomography (micro-CT), [15],[16],[17] and cone-beam computed tomographic images (CBCT) [Table 1]. [18],[19],[20],[21] Therefore, interstudy variations can be seen among different surveys. In periapical radiographic method it is not easy to identify the extra root, as superimposition of two roots occur resulting inaccurate diagnosis. In the case of extracted teeth, teeth might fracture during the extraction procedure as they are more slender and curved. From studies based on extracted teeth, [10],[11],[12],[13],[14] it was impossible to compare precisely the prevalence related to gender and bilateral occurrence of three-rooted permanent first molars. It has been speculated that recent studies using advanced techniques showed higher prevalence compared to previous 2D image studies; [15],[16],[17],[18],[19],[20] the reason could be attributed to the use of 3D image analysis, which provides more accurate determination.
Table 1: Survey of available studies showing prevalence of 3-rooted mandibular first molar

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Ethnic differences in permanent molars

The existence of RE/RP in permanent mandibular first molar is associated with certain ethnic and racial groups. The dentist therefore must be aware of racial anatomic variations when diagnosing and managing endodontic patients because he/she may see patients of diverse ethnicities daily. Tu et al. [5] found a prevalence of 21.1% using periapical radiographs and 33.33% using the cone-beam computed tomography in Taiwanese subjects. [18] Compared with the prevalence of the permanent three-rooted mandibular molars in Taiwanese individuals, 33.33% data of the prevalence in the Tu et al.[18] study are higher than those 2D image study by Tu et al. [5] By using extracted teeth, Walker and Quackenbush [22] found a prevalence of 14.6% in Hong Kong Chinese and Loh [10] found a prevalence of 7.9% in Singapore Chinese subjects. A maximum frequency of 3% is documented in the African population [23] while in Eurosian and Indian populations the frequency is less than 5%. [14] In Mangoloid traits such as Eskimo, Chinese, and American Indians, it has been reported that RE seen with a frequency ranging from 5-30%. [14],[22],[23],[24],[25],[26],[27] Because of its high prevalence in these populations, the RE is considered to be a normal morphological variant (Eumorphic root morphology). In Caucasians low frequency of 3.4-4.2% has been found and considered to be unusual or dysmorphic root morphology [9],[28] [Table 1].

Prevalence of three roots in primary molars

Most previous surveys into the occurrence of an extra root investigated extracted teeth, and hence considered mainly permanent molars and virtually no primary molars. [10],[11],[12],[13],[14] Analyzing the root configuration in primary molars can be difficult because of the presence of physiologic or pathologic root resorption, and extracting primary molars with sound roots is difficult because of root divergence. Therefore, fewer studies have investigated the incidence of third roots in the primary molars.

The prevalence of root variations is lower in the primary dentition than in the permanent dentition. There are several case reports [29],[30] on the existence of three-rooted primary mandibular molars but studies of the prevalence of extra roots are few in number. Tratman [14] reported that three-rooted mandibular first molars are rare with a frequency of <1% in the primary dentition and common in the permanent dentition. Curzon and Curzon [31] suggested that the incidence of primary anomalies is higher in Native American than white populations. 21.1% of Taiwanese (Chinese) have permanent three-rooted mandibular molars, but there is little information on primary three-rooted mandibular molars in those of Mongolian descent. [5] Jorgensen [32] reported seven cases (0.67%) of an additional root in 1041 second primary molars extracted from Danish subjects. Tratman [14] found no extra root in samples collected from Europe and India, but found an additional root in 3 of 42 second primary molars (7.1%) from Japanese subjects. A Japanese radiographic study revealed that 5.6% of 1408 samples of mandibular primary first molars had an additional distolingual root. [33] In a study by Tu et al.[34] the prevalence of supernumerary root in primary first molars of Taiwanese children was 5%. Recently Song et al.[35] found a maximum prevalence of 27.8% and 9.7% of second primary and first primary molars respectively in Korean children and Liu et al. [36] reported 18 (9%) cases of three-rooted primary second molars in Chinese subjects [Table 1].

Although extra root can be found in both first and second molars of the primary dentition, there is no definitive proven study showing whether the presence of RE in primary molars, indicates extra root in permanent molars, although the commonly hypothesized field of development influence suggests that this is the case. A long-term prospective study involving the primary and permanent molars certainly would add to the present knowledge. However, recently Song et al.[35] assessed the incidence and relationship of an additional root in the mandibular first permanent molar and primary molars in 4050 children examined. They found additional roots in 33.1%, 27.8%, and 9.7% of the first permanent, second primary, and first primary molars, respectively, and concluded that when an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3%.

Gender differences

Gender predilection for an additional root in the first permanent molar has been reported by several investigators. Some claimed it to be a sex-linked, dominant character and others reported that it has no sex predilection. Most studies have found male predominance. [36],[37],[38],[39] However, others reported that the prevalence of extra root was similar in both sexes [10],[34],[36] or rather more in females. [5] Tratman [14] mentioned that it is more common on the right for the male and bilateral for the female. Loh [10] did not show statistically significant difference in predilection of RE for either sex. Based on these reports, it is not common for RE to occur symmetrically.

Topological predilection

The incidence of supernumerary roots in the first permanent molar on the left and right side are variable as seen from the reported studies. [14] Many studies have found right-side predominance not only for the permanent molar, but also for the primary molars. [5],[14],[39] In contrast, some investigators reported a predilection for the left side. [10]

Unilateral or bilateral occurrence of an additional root is also a controversial issue. Some studies reported bilateral occurrence of the RE ranging from 50-67%. [5],[10],[36],[39] According to Quackenbusch [40] and other reports, this extra root occurred unilaterally in approximately 40% of all cases and predominantly on the right side. This is noticed in other reports also.­ [5],[14],[39] This finding highly emphasized the fact that in treating most right mandibular molars clinician always look for additional distal root to prevent root canal treatment failure.

   Prevalence of RE/RP in other Teeth Top

RE has been reported occurring in the first (7.4%), second (0%), and third mandibular permanent molars (3.7%) occurring with a least frequency or none on the second molar. [41]

The existence of RP root variant is very rare and occurs less frequently than the RE. It seems to be rare in Europian and Mongolian populations. [41] Visser [41] found 0% (0/1954) for the mandibular first molar, 0.5% (11/2086) for the second and 2% (28/1405) for the third molar.

   Etiology Top

The exact etiology behind the development of RE/RP is still unknown. The literature suggests that, in dysmorphic, extra roots, its formation could be related to external factors during odontogenesis, or to penetrance of an atavistic gene or polygenetic system whereas in eumorphic roots, racial genetic factors cause more profound expression of a particular gene that results in the more pronounced phenotypic manifestation. [27] The high degree of RE in Mongoloid populations has provoked more specific analyses of the heritable basis of this supernumerary radicular structure by various authors. [14],[36],[37] More specifically, only Curzon [42] suggested that certain traits such as the "three-rooted molar" had a high degree of genetic penetrance as its dominance was reflected in the fact that pure Eskimo and Eskimo/Caucasian mixes had similar prevalence of the trait.

   Morphology of RE and RP Top

The identification and external morphology of RE and RP root complexes are described by Carlsen and Alexandersen. [3],[43] RE is found distolingually with its coronal third completely or partially fixed to the distal root. It usually appears smaller and more curved than the distobuccal or mesial root and is located in the same transverse plane as the two other roots.[Figure 1] This suggests that dentists must pay special attention when considering root canal treatment and/or extraction for a molar with RE. The dimension of RE can vary from a short conical extension to a mature root with normal length and root canal [Figure 2]. [2],[43] It is cross-sectionally more circular than the distal root, projected lingually about 45° to the long axis of the tooth, and has the type I canal system. [2],[43] In most cases, the pulpal extension is radiographically visible. In the apical two thirds of the RE, a moderate to severe mesially or distally oriented inclination can be seen in addition to this inclination the root can be found straight or curved to the lingual. Tratman [14] stated that RE is not simply a division of the distal root but rather is a true extra root with a separate orifice and apex.

RP is seen buccally to the mesial root and may be found separate or fused with the mesial root.[Figure 3] The dimensions of the RP can vary from a "mature" root with a root canal, to a short conical extension. [3] This additional root exists in two forms as separate and nonseparate. [3]
Figure 1: Morphology of RE from different aspects (arrows)

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Figure 2: Radix entomolaris in permanent right first molar (arrow)

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Figure 3: Radix paramolaris in permanent right first molar (arrow)

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Classification of RE and RP

RE a distolingual root exhibit diverse morphologic features varying from severe curvature [2] to an underdeveloped conical form. [21] De Moore et al.[2] classified RE based on the curvature of the root or root canal in bucco-lingual orientation (separate RE) evaluated from 18 extracted human teeth into three types [Table 2]. In 1991, Carlson and Alexandersen [43] classified four types of RE (A, B, C, and AC), based on the location of the cervical portion of the root and this helps in identification of separate and non separate RE [Table 3]. Recently in 2010 Song et al.[21] have suggested a new classification based on morphologic characteristics assessed from cross-sectional computed tomography technique [Table 4].
Table 2: Classification of RE, based on its curvature[2]

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Table 3: Classification of RE, based on the location of its cervical portion[43]

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Table 4: New classification of RE[21]

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Carlsen and Alexandersen [3] classified RP into two types by examining 203 permanent mandibular molars with root complexes containing RP [Table 5].
Table 5: Classification of RP[3]

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   RE in Association with Other Ano-malies Top

Some reports [23],[44] showed that RE in the first molars occurred in association with additional cusp usually on the buccal side (protostylid). Therefore, it has been suggested that extra root is nearly always associated with an increased number of cusps and with an increased number of root canals. [44] However, an increased number of cusps are not necessarily related to increased number of roots. George et al.[45] reported simultaneous occurrence of shovel-shaped incisors, three-rooted primary and permanent molars, talon cusp and supernumerary tooth in a 7-year-old Hispanic male patient. Whereas, Winkler and Ahmad [46] reported multiroot anomalies including bifurcated maxillary primary canine, primary three-rooted first molar and bilateral primary three-rooted first and second primary molars in Native Americans.

   Examination of RE/RP Top

Clinical diagnosis

The crown and the two normal roots of a molar with a distolingual/mesiobuccal root are very similar to those found in a normal molar. [44] Hence, identification of RE/RP is not really possible from only a clinical examination of the crown. The literature has reported that clinical observation and analysis of the cervical morphology of the roots by means of periodontal probing facilitate identification of RE. It has also been reported that the presence of an extra cusp (tuberculum paramolare) or more prominent occlusal distal or distolingual lobe, in combination with a cervical prominence or convexity, can indicate the presence of an additional root. [44] If an RE or RP is diagnosed before endodontic treatment, one knows what to expect or where to look once the pulp chamber has been opened.

There are various methods to locate the orifice of the extra roots. They can be listed as knowledge of law of symmetry and law of orifice location, tactile sensation with hand instruments, using various instruments like endodontic explorer, path finder, DG 16 probe and microopener, use of fiber-optic illumination dental endoscopy, intraoral camera, using surgical loupes, using operating microscope, microcomputed tomography, and magnetic resonance microscopy. [44]

Radiographic diagnosis

Anatomical variations of roots in the mandibular first molar may be identified by reading radiographs carefully. An accurate diagnosis of RE/RP is very important to avoid complications or missing of canal during RCT. As the RE/RP is mostly located in the same bucco-lingual plane as the other two roots, a superimposition of both roots can appear on the preoperative radiograph and remain undiagnosed. [2],[3],[44] A thorough examination of the preoperative radiograph and interpretation of particular marks or characteristics, such as an unclear view or outline of the distal/mesial root contour or the root canal, can suggests the presence of a "hidden" RE/RP. [44] Ingle et al.[47] has recommended a thorough radiographic study of the involved tooth, using exposure from the standard buccal-to-lingual projection, one taken 20° from the mesial, and the third taken 20° from the distal to obtain basic information regarding the anatomy of the tooth. [Figure 4] Loh [10] has claimed that the RE/RP does not normally appear in periapical radiographs that are taken in the traditional manner. Adjusting the exposure time and dose of the x-ray and angulating the main beam (to avoid superimposing the larger distobuccal/mesial root) can to help make RE/RP more evident although accurate interpretation of radiographs depends on the trained eye. [10] A 1985 study by Walker and Quackenbush [22] claimed that panoramic radiographs resulted in an accuracy rate of approximately 90%.
Figure 4: Evidence of RE (c) and RP (d) in radiographs taken with angulation. They are not evident on conventional radiographs (a and b)

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Significance of RE/RP in clinical pediatric dentistry

Apart from its role as a genetic marker, RE/RP has significance in clinical pediatric dentistry. Many studies have discussed the endodontic, exodontic, and periodontal implications of extra roots in permanent mandibular first molars. [44],[45],[46],[48],[49] The same caution should be followed in the treatment of primary mandibular molars with accessory roots as permanent mandibular molars.

Endodontic implications

Root canal treatment should result in the thorough mechanical and chemical debridement of the entire pulp cavity, followed by complete obturation with a hermetic seal. As a result, RE/RP pose a great endodontic challenge, as incomplete pulp extirpation due to missed canal can result in treatment failure. Dentists should be familiar with multiple root anatomy to avoid missing canals.

With RE, the conventional triangular access cavity opening must be modified to take the form of a trapezoid or rectangular form to better locate and access the distolingual orifice of the additional root. [2],[44] A severe root inclination or canal curvature, particularly in the apical third of the root (in type III RE), can cause shaping aberrations such as straightening of the root canal or a ledge that displays a loss of working length in the ledge canal. Calberson et al.[44] recommend using flexible nickel-titanium rotary files to increase the chance of centering the canal third and orifice relocation. Nevertheless, unexpected complications (such as instrument separation) occur and are more likely to happen in the RE due to the severe curvature or narrow root canals. Therefore, after relocation and enlargement of the orifice of the RE, Calberson et al.[44] suggested initial root canal exploration with small files (size 10 or less), determining the working length of the curved root, and creating a glide path before preparation to avoid procedural errors.

It also has been reported that regardless of the type of root canal, the orifice of the RE can be located distolingually from the root canals in the main distal root. In 2009, Tu et al.[18] did a prevalence study in Taiwanese subjects using cone-beam computed tomography and estimated the interorifice distance of all canals in mandibulat first molar with RE. The mean interorifice distances from the distolingual canal to the distobuccal (DB), mesiobuccal (MB), and mesiolingual (ML) canals of the permanent three-rooted molars were 2.7, 4.4, and 3.5 mm, respectively. These values might help dentists to locate orifices and to achieve successful endodontic treatments of permanent molars with distolingual root.

In the case of RP, the access cavity must be extended in mesiobuccal direction that involves modification in access cavity from triangular to rectangular or trapezoidal form in order to better locate and access the canal of this root. [3],[44] The same precautions and procedure should be followed as in RE during endodontic procedure.

Exodontic procedure

During extraction of primary molars with three roots, the clinician should make sure that the crown of the premolar is not trapped in the inter-radicular area of the primary molar as this could cause accidental removal of the developing permanent tooth bud. [46] After the extraction, dentist should examine the extracted anomalous primary molar to confirm that all roots have been retrieved.

Extraction of permanent first molar with RE is difficult compared to the molar without RE. If rotational movements are used, root fractures could occur. It is expected that an extra distolingual root would fracture during extraction due to its divergent and curved form. [2] The low incidence of distolingual roots documented previously is probably because the root's curvature was in the line of extraction movements and withdrawal. [10]

A 2004 study [50] suggested that molars are extracted more frequently than anteriors and premolars among some races because those groups have a higher prevalence of three-rooted mandibular first molars, combined with the possibility of misinterpretation of extra distolingual root aberrations during root canal treatment.

Orthodontic implications

Other clinical difficulties resulting from distolingual root would relate to orthodontic procedures, where the extra root would render movement difficult. [10],[49] It is also hypothesized that the presence of extra root (RE) adds to the stability of molars by providing an increased surface area of attachment to the alveolus. [10],[49]

Since it is not known whether abnormal root configurations like three-rooted molar affect, the normal exfoliation of the primary teeth, it is unclear whether these anomalous teeth present orthodontic problems.

RE as a contributing factor to localized periodontitis

According to Huang et al. [48] RE may be a contributory factor in localized periodontal destruction. In their study, patients with a distolingual root demonstrated significantly greater probing depth and attachment loss at distolingual sites than at distobuccal sites. Molars with RE demonstrated greater loss around the distolingual root compared with molars that had only one distal root.

Forensic odontology

The presence of a third root, whether primary or permanent may have forensic value for identifying people of the Mongoloid origin. [5],[49]

   Discussion Top

The present article reports 15 extra roots in mandibular molars of Indian children that were diagnosed using both periapical radiographs (12 cases) and extracted teeth (three cases). There have been several reports of the occurrence of supernumerary roots in both permanent and primary mandibular molars of different populations. But studies of the prevalence of extra root variants in Indian population are few in number. [14] Garg et al.[51] have found 5% prevalence of three-rooted permanent mandibular first molars in Indian adult patients.

In the present report, the number of three-rooted mandibular molars including both primary and permanent did not show difference with gender, which is consistent with findings of other reports of permanent first molars done in Hong Kong Chinese, [22] Taiwanese, [5] and Singapore Chinese [10] and Japanese patients. [9],[52] However, some studies found male predominance. [36],[37],[38],[39] Only four cases of three-rooted primary molars were diagnosed with remaining 11 cases of extra roots in permanent first molars. This finding is in accordance with the results suggesting that three-rooted mandibular first molars are rarer in primary than permanent dentition. [14],[35]

Most of the three-rooted mandibular fist molars in Asians show a bilateral occurrence. [5],[10],[36],[39] Only one patient of our report showed bilateral occurrence of extra root in primary mandibular first molar. ]The incidences of bilateral occurrence were 67.8%, 64.0%, and 39.3% for the first permanent, second primary, and first primary molars, respectively as shown in one study. [35] Sabala et al.[53] reported that aberrant root morphology in a given tooth is observed with varying frequency in the corresponding contra lateral tooth, but it is not found in mandibular primary first molars with three roots. Tu et al.[34] found bilateral occurrence of primary first molars (17.67%) less than the report by Song et al. [35] Both Taiwanese and Korean populations appeared much more unilateral occurrence of three-rooted primary mandibular first molars than permanent mandibular first molars do. [34],[35]

The first morphologic classification of distolingual root (RE) was established by De Moore et al.[2] who examined extracted first molar and divided morphologic features of third root into three types according to the pattern of their curvature. They found two cases of type I, five cases of type II, and 11 cases of type III. In contrast to this, our study found 12 cases of type I, 1 case of type II, and 2 cases of type III. In case of mesiobuccal root (RP), Carlsen and Alexandersen [3] found five cases of type A and none of type B in the total 203 permanent molars examined. Our study found only two cases of type A mesiobuccal root.

Association of extra roots with adjacent molars was not seen in none of the reported cases. One study done by Song et al.[35] showed the relationship of extra roots with adjacent molars and have suggested that when an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3% that help to predict the presence of an extra root in molars posterior to it.

For successful root canal treatment it is necessary to locate all roots and canals as unfilled canals remain a nidus for infection and can compromise treatment outcome. [31] This was evident in three of our cases due to undiagnosed and untreated third root [Figure 1]. Therefore, to make RE/RP evident and for accurate diagnosis, a second radiograph should be taken from a more mesial or distal angle and clinician should be aware of the existence of additional roots in molars of both dentition.

The limitation of the present report is that it provides information about only 15 cases of extra roots in mandibular molars. From this it is difficult to state precisely the prevalence of extra roots in mandibular molars of Indian children. Therefore, further studies involving large samples are highly essential to assess the prevalence of additional roots in group of children from Indian origin which will add more knowledge to the existing literature.

   Conclusion Top

Dentists should take into account the prevalence of extra root variants in both primary and permanent mandibular first molars among children during their routine endodontic and exodontic procedures. Before initiating root canal treatment or extraction, clinician should utilize two periapical radiographs (taken at different angles) to confirm the presence of an extra root in order to achieve the successful treatment.[64]

   References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

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