Root Canal Morphology and Anatomy

*Esra Pamukcu Guven*

#### **Abstract**

Success in root canal treatment depends on the proper application of all procedures of root canal treatment. This wholistic approach includes leakproof crown restoration, following ideal instrumentation, irrigation and hermetic obturation. Therefore, the first step of root canal treatment begins with understanding the tooth morphology in detail. The teeth vary according to their localization at the jaws and the gender and race of people. Detection of the extra canals, canal curvatures, isthmuses and lateral and accessory canals plays an important role in the success of root canal treatment. With all this, the academic knowledge and proficiency of the dentist and/or endodontist enable tooth morphology to be more clearly understandable.

**Keywords:** tooth morphology, root canal morphology, dental anatomy, technologic devices, illumination and magnification systems

#### **1. Introduction**

Understanding the anatomy of the root canal system is essential for a successful root canal treatment. Complexity of root canals depends on reasons such as ethnicity, gender, age, the existence of lateral/accessory canals, isthmuses, the location of the teeth at the jaws and anomalies of the teeth (dens invaginatus, dens evaginatus, fusion, gemination, dens in dente). Besides all of these, some physiological alterations occur in enamel and dentin with age. Mineralization of dentin results in calcification of dentinal tubules; thus, dentin becomes sclerotic. Several difficulties occur during root canal treatment in such cases. The utilization of novel technologic equipments for magnification and lightning of the root canal system like dental microscope, loupe, radiographic visualization systems and cone beam computed tomography (CBCT) in dentistry enlightens endodontic treatment [1].

#### **2. Maxillary incisor teeth**

Maxillary central teeth have one root and one main canal [2]. Rarely, at 6% rate one canal of maxillary central teeth is divided into two parts at the apical foramina which can be classified as Vertucci type V (**Figure 1**). Apical root canal anatomy should be regarded because of its main effect on the success of root canal treatment (**Figure 2**). In the study of Adorno et al. [3], accessory canals in the apical 3 mm at Japanese population were found in 46% of the specimens.

**Figure 1.** *Endodontic treatment of a maxillary left first incisor tooth with lateral canal.*

**Figure 2.** *Accessory canals in the apical 3 mm of the root.*

According to Vertucci's classification, maxillary lateral incisor teeth have one main canal (100%) [2]. Generally, maxillary lateral incisor teeth are single-rooted with a single canal [4]. The apex of the maxillary lateral teeth is positioned at the palatal side. In the study of Adorno et al. [3], among Japanese population, accessory canals in the apical 3 mm were found in 29% of the specimens.

**149**

*Root Canal Morphology and Anatomy*

**3. Maxillary canine teeth**

**4. Maxillary premolar teeth**

one canal by merging.

1/3 of the apex.

foramen.

*DOI: http://dx.doi.org/10.5772/intechopen.86096*

palatal side of the tooth in oval shape in these teeth.

*Type I:* One canal extending to the apex.

canals with separate apical foramina.

side, and one is at the palatal side [7].

**5. Maxillary molar teeth**

According to Vertucci's classification, maxillary canine teeth have one main canal (100%) [2]. In the study of Adorno et al. [3], among Japanese population, accessory canals in the apical 3 mm related with the maxillary canine teeth were found in 38% of the specimens. The endodontic cavity should be prepared at the

In the study of Tian et al. [5], it was found that in Chinese population, 66% of the premolar teeth had one root, 33% had two roots and 1% had three roots. According to Vertucci's classification, root canal morphology is classified into eight types:

*Type II:* One canal beginning from the pulp chamber, dividing into two parts at

*Type III:* One canal leaving the pulp chamber, dividing into two and ending as

*Type IV:* Two canals leaving the pulp chamber and ending as two separate canals. *Type V:* One canal leaving the pulp chamber and dividing into two distinct

*Type VI:* Two separate canals leaving the pulp chamber, merging in the 1/3 of the

*Type VIII:* Three separate, distinct canals extend from the pulp chamber to the apex. According to Weine (1976), the classifications are divided into four groups as:

*Type II:* Two separate canals leaving from the pulp chamber and merging at the

*Type III:* Two canals leaving the pulp chamber and extending as two canals to the

*Type IV:* One canal leaving from the pulp chamber, dividing into two parts at the

In the study of Pan et al. [6], the prevalence of maxillary first premolar teeth with one main root canal was 67.8%, with two roots was 31.9% and with two canals was 88.2%. In Malaysian population, according to Vertucci's classification, second premolars were detected to be single-rooted with type I in the 58.2% incidence [2]. Based on the detection of premolars in molar shape, the endodontic cavity of the maxillary premolar teeth should begin to be prepared as "T-shaped" on the occlusal surface instead of oval shape. In these teeth, two root canal orifices are at the buccal

The upper first molar teeth have three roots and three or four canals (palatal, mesiobuccal 1 (MB1), mesiobuccal 2 (MB2) and disto-buccal (DB)). In the study of Kumar et al. [8], the upper molar teeth were shown to have seven canals. At Burmese population, the prevalence of two canals in mesiobuccal roots of the upper first molar teeth decreases towards the upper third molar teeth. Around 85.2% of

*Type VII:* One canal leaving the pulp chamber, merging in the 1/3 of the root

the 1/3 middle of the root and then ending in one part at the apex.

root canal and then separating to exist as two distinct canals.

canal and then separating to exist as two distinct canals.

*Type I:* One canal extending as one canal to the apex.

1/3 middle of the root and extending as two canals to the apex.

## **3. Maxillary canine teeth**

*Human Teeth - Key Skills and Clinical Illustrations*

**148**

**Figure 2.**

*Accessory canals in the apical 3 mm of the root.*

**Figure 1.**

According to Vertucci's classification, maxillary lateral incisor teeth have one main canal (100%) [2]. Generally, maxillary lateral incisor teeth are single-rooted with a single canal [4]. The apex of the maxillary lateral teeth is positioned at the palatal side. In the study of Adorno et al. [3], among Japanese population, accessory

canals in the apical 3 mm were found in 29% of the specimens.

*Endodontic treatment of a maxillary left first incisor tooth with lateral canal.*

According to Vertucci's classification, maxillary canine teeth have one main canal (100%) [2]. In the study of Adorno et al. [3], among Japanese population, accessory canals in the apical 3 mm related with the maxillary canine teeth were found in 38% of the specimens. The endodontic cavity should be prepared at the palatal side of the tooth in oval shape in these teeth.

## **4. Maxillary premolar teeth**

In the study of Tian et al. [5], it was found that in Chinese population, 66% of the premolar teeth had one root, 33% had two roots and 1% had three roots. According to Vertucci's classification, root canal morphology is classified into eight types:

*Type I:* One canal extending to the apex.

*Type II:* One canal beginning from the pulp chamber, dividing into two parts at the 1/3 middle of the root and then ending in one part at the apex.

*Type III:* One canal leaving the pulp chamber, dividing into two and ending as one canal by merging.

*Type IV:* Two canals leaving the pulp chamber and ending as two separate canals. *Type V:* One canal leaving the pulp chamber and dividing into two distinct canals with separate apical foramina.

*Type VI:* Two separate canals leaving the pulp chamber, merging in the 1/3 of the root canal and then separating to exist as two distinct canals.

*Type VII:* One canal leaving the pulp chamber, merging in the 1/3 of the root canal and then separating to exist as two distinct canals.

*Type VIII:* Three separate, distinct canals extend from the pulp chamber to the apex. According to Weine (1976), the classifications are divided into four groups as: *Type I:* One canal extending as one canal to the apex.

*Type II:* Two separate canals leaving from the pulp chamber and merging at the 1/3 of the apex.

*Type III:* Two canals leaving the pulp chamber and extending as two canals to the foramen.

*Type IV:* One canal leaving from the pulp chamber, dividing into two parts at the 1/3 middle of the root and extending as two canals to the apex.

In the study of Pan et al. [6], the prevalence of maxillary first premolar teeth with one main root canal was 67.8%, with two roots was 31.9% and with two canals was 88.2%. In Malaysian population, according to Vertucci's classification, second premolars were detected to be single-rooted with type I in the 58.2% incidence [2]. Based on the detection of premolars in molar shape, the endodontic cavity of the maxillary premolar teeth should begin to be prepared as "T-shaped" on the occlusal surface instead of oval shape. In these teeth, two root canal orifices are at the buccal side, and one is at the palatal side [7].

#### **5. Maxillary molar teeth**

The upper first molar teeth have three roots and three or four canals (palatal, mesiobuccal 1 (MB1), mesiobuccal 2 (MB2) and disto-buccal (DB)). In the study of Kumar et al. [8], the upper molar teeth were shown to have seven canals. At Burmese population, the prevalence of two canals in mesiobuccal roots of the upper first molar teeth decreases towards the upper third molar teeth. Around 85.2% of

270 roots of the upper molar teeth have one canal in one root at the apex, 14% have two canals at the apex and 0.8% have three canals at the apex [9]. According to Pan et al. [6], a second palatal canal was detected in 0.9% in the maxillary first molar teeth in Malaysian population. Ninety-one percent of mesiobuccal roots of maxillary first molars was detected to have accessory canals [10, 11]. Accessory canals with 85% of incidence were found to be located in the apical third of the roots [10]. According to micro-computed tomography analysis of the mesiobuccal root canal anatomy referring to second mesiobuccal canals of maxillary first molar tooth, the results were in 60% in accordance with Weine et al.'s (1969) classification and in 70% with Vertucci's (1984) classification [10].

Mikrogeorgis et al. [12] determined two root canals in conjunction with the apexIn addition, as the morphological differences determined related with the mesiobuccal root of upper molar teeth, distal root has also been detected to have two seperate canals; distobuccal 1(DB1) & distobuccal 2 (DB2) as shown in **Figure 3**.

#### **Figure 3.** *The radiograph of a maxillary second molar tooth with two distal canals.*

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roots.

*Root Canal Morphology and Anatomy*

**6. Mandibular incisors**

**7. Mandibular canine teeth**

**8. Mandibular premolar teeth**

premolars have one main root canal [17].

**9. Mandibular Molar teeth**

is seen in **Figure 5**.

*DOI: http://dx.doi.org/10.5772/intechopen.86096*

In the study of Sert et al. [17], in Turkish population, it was pointed out that 68% of mandibular central incisors have two canals and 6.5% have lateral canals. In addition, in the same study, it was pointed out that 63% of mandibular lateral incisors had two canals and the prevalence of lateral canals was 13% in Turkish population. Mandibular first incisor tooth with a lateral canal is seen in **Figure 4**.

According to a morphological study of Soleymani et al. [18], in the Iranian population, 89.7% of the mandibular canine teeth were found to have type I, 5.7%

The endodontic cavity has to be prepared in oval shape on the occlusal surface of the premolar teeth regarding the localization of root canal orifices. In Turkish population, 62% of the mandibular premolar teeth have one main root canal [17]. Vertucci found out a second canal in 26% of the mandibular first premolars and 3% at the second premolars [2]. In Turkish population, 71% of the mandibular second

According to Vertucci's classification, 44% of the mesial roots of the mandibular first molar teeth were found to be type I, whilst 54% were type II. Al-Qudah et al. [16] reported that in Jordanian population, the mandibular first molar teeth had three canals (48%) and four canals (46%). The frequency of the mesial root canals' combination in the first (56, 34%) and second (67, 41%) mandibular molars is more common in three-rooted teeth than four-rooted teeth [19]. Huang et al. [20] pointed out that the incidence of mandibular first molars with two, three and four roots was 55.5, 26.5 and 18.0%, respectively. They also added that double-rooted distal root was associated with two mesial canals. In a CBCT assessment study of mandibular molars, the distance from the apex to the canal orifice is found to be 13.15 mm [21]. The existence of isthmus is a type of morphological difference seen in mandibular molar teeth. Endodontic treatment of a mandibular right first molar tooth with an isthmus located between the mesiobuccal and the mesiolingual canals

The results of a study evaluating the root canals of the mandibular second molar teeth showed that 76% of the two-rooted mandibular second molars had a single distal canal and 87.5% had two mesial canals that combined apically with the prevalence of 53% [17]. In South Asian Pakistani population, the mesial roots of the mandibular molar teeth were found to have two canals (97%), whereas the distal roots had single canals (50%) [22]. In the study of Al-Qudah et al. [16], the incidence of three canals in Jordanian mandibular second molars was reported as 58%, two canals as 19% and four canals as 17%. Gulabivala et al. [23] reported that 68% of Thai mandibular molars had two distinct roots and 20% had fused

had type III, 3.7% had type II and 1% had type V morphology.

**Figure 4.** *Endodontic treatment of a mandibular right first incisor tooth with a lateral canal.*

### **6. Mandibular incisors**

*Human Teeth - Key Skills and Clinical Illustrations*

70% with Vertucci's (1984) classification [10].

*The radiograph of a maxillary second molar tooth with two distal canals.*

**Figure 3**.

**Figure 3.**

270 roots of the upper molar teeth have one canal in one root at the apex, 14% have two canals at the apex and 0.8% have three canals at the apex [9]. According to Pan et al. [6], a second palatal canal was detected in 0.9% in the maxillary first molar teeth in Malaysian population. Ninety-one percent of mesiobuccal roots of maxillary first molars was detected to have accessory canals [10, 11]. Accessory canals with 85% of incidence were found to be located in the apical third of the roots [10]. According to micro-computed tomography analysis of the mesiobuccal root canal anatomy referring to second mesiobuccal canals of maxillary first molar tooth, the results were in 60% in accordance with Weine et al.'s (1969) classification and in

Mikrogeorgis et al. [12] determined two root canals in conjunction with the apexIn addition, as the morphological differences determined related with the mesiobuccal root of upper molar teeth, distal root has also been detected to have two seperate canals; distobuccal 1(DB1) & distobuccal 2 (DB2) as shown in

**150**

**Figure 4.**

*Endodontic treatment of a mandibular right first incisor tooth with a lateral canal.*

In the study of Sert et al. [17], in Turkish population, it was pointed out that 68% of mandibular central incisors have two canals and 6.5% have lateral canals. In addition, in the same study, it was pointed out that 63% of mandibular lateral incisors had two canals and the prevalence of lateral canals was 13% in Turkish population. Mandibular first incisor tooth with a lateral canal is seen in **Figure 4**.

## **7. Mandibular canine teeth**

According to a morphological study of Soleymani et al. [18], in the Iranian population, 89.7% of the mandibular canine teeth were found to have type I, 5.7% had type III, 3.7% had type II and 1% had type V morphology.

#### **8. Mandibular premolar teeth**

The endodontic cavity has to be prepared in oval shape on the occlusal surface of the premolar teeth regarding the localization of root canal orifices. In Turkish population, 62% of the mandibular premolar teeth have one main root canal [17]. Vertucci found out a second canal in 26% of the mandibular first premolars and 3% at the second premolars [2]. In Turkish population, 71% of the mandibular second premolars have one main root canal [17].

#### **9. Mandibular Molar teeth**

According to Vertucci's classification, 44% of the mesial roots of the mandibular first molar teeth were found to be type I, whilst 54% were type II. Al-Qudah et al. [16] reported that in Jordanian population, the mandibular first molar teeth had three canals (48%) and four canals (46%). The frequency of the mesial root canals' combination in the first (56, 34%) and second (67, 41%) mandibular molars is more common in three-rooted teeth than four-rooted teeth [19]. Huang et al. [20] pointed out that the incidence of mandibular first molars with two, three and four roots was 55.5, 26.5 and 18.0%, respectively. They also added that double-rooted distal root was associated with two mesial canals. In a CBCT assessment study of mandibular molars, the distance from the apex to the canal orifice is found to be 13.15 mm [21]. The existence of isthmus is a type of morphological difference seen in mandibular molar teeth. Endodontic treatment of a mandibular right first molar tooth with an isthmus located between the mesiobuccal and the mesiolingual canals is seen in **Figure 5**.

The results of a study evaluating the root canals of the mandibular second molar teeth showed that 76% of the two-rooted mandibular second molars had a single distal canal and 87.5% had two mesial canals that combined apically with the prevalence of 53% [17]. In South Asian Pakistani population, the mesial roots of the mandibular molar teeth were found to have two canals (97%), whereas the distal roots had single canals (50%) [22]. In the study of Al-Qudah et al. [16], the incidence of three canals in Jordanian mandibular second molars was reported as 58%, two canals as 19% and four canals as 17%. Gulabivala et al. [23] reported that 68% of Thai mandibular molars had two distinct roots and 20% had fused roots.

#### **Figure 5.**

*Endodontic treatment of a mandibular right first molar tooth with an isthmus located between the mesiobuccal and the mesiolingual canals.*

#### **10. C-shaped root Canals**

C-shaped root canals' anatomy is defined as the connection of two distal roots internally and C-shaped appearance panoramically. C-shaped root canals can be observed in the upper and lower first and second molar teeth. They are seen at high rates in the mandibular second molar teeth in Asian population. The treatment of C-shaped root canals needs more care because of their wide, oval and complex anatomy and the bleeding potential of wide pulpal tissue. In the study of Kim et al. [13], the problems with the treatment of C-shaped root canals were found as unsuccessful sealing ability of the canal (45.2%), overlooked canal (9.5%), overfilling (7.1%) and iatrogenic problems (7.1%).

Irrigation protocols have significant importance for removing pulpal remnants and hard tissue debris, especially for the unreachable points in the root canals [4]. The morphology of C-shaped root canals may result in elbows during root canal shaping in curved canals. The percentages of elbow formation were reported as 42.1% in C form canals, 40.0% in J form canals and 19.3% in straight form canals. Zip formation was observed in 83.5% of C form canals [14]. Eighty percent of C-shaped root canals were found to have 1–3 apical foramina [15]. In Malaysian population, the C-shaped root canals were found to have 48.7% of incidence [6]. In Jordanian population the mandibular second molar teeth had C-shaped roots in 10% of incidence [16].

#### **11. Dental anomalies**

Dental morphological anomalies accompany some growth and developmental abnormalities. Dens invaginatus, dens evaginatus, dens in dente, fusion and gemination are among the often seen dental anomalies. Dental anomalies could also be associated with syndromes, such as Down syndrome.

Dens invaginatus is determined as an infolding of dentin and enamel extending into the pulp chamber. In a case report of Kottoor et al. [24], a maxillary lateral incisor was found to have four main canals called distal, labial, mesial and lingual in a dens invaginatus case. Dens invaginatus is more often characterized with an immature tooth with a periapical lesion. The decision on treatment type depends on the tooth's morphological situation. This pathology is treated by regenerative procedures in which root dentin thickness and newly developed apical foramina are expected.

**153**

**Author details**

Istanbul, Turkey

Esra Pamukcu Guven

provided the original work is properly cited.

*Root Canal Morphology and Anatomy*

root proportions.

**12. Conclusion**

literature for dentistry [26].

*DOI: http://dx.doi.org/10.5772/intechopen.86096*

In a morphology study conducted among individuals with Down syndrome,

Focusing on the tooth morphology considering root canal complexity allows dentists to perform successful root canal treatment. Besides the dentists' knowledge and interest in root canal morphology and anatomy, proficiency on root canal treatment and the tendency to use novel technological devices enable prosperous endodontic treatment. The novel tooth morphology classification presented by Ahmed and Dummer, based on the simplicity and clarity respecting tooth number, number of roots and root canal configuration types, is the prominent leading

it was reported that all teeth, except mandibular first premolars, showed significantly shorter crown and root lengths [25]. This information is valuable during making a decision of the crown restoration type regarding the crown-

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Faculty of Dentistry, Department of Endodontics, Istanbul Okan University,

\*Address all correspondence to: esra.pamukcu@okan.edu.tr

#### *Root Canal Morphology and Anatomy DOI: http://dx.doi.org/10.5772/intechopen.86096*

In a morphology study conducted among individuals with Down syndrome, it was reported that all teeth, except mandibular first premolars, showed significantly shorter crown and root lengths [25]. This information is valuable during making a decision of the crown restoration type regarding the crownroot proportions.

#### **12. Conclusion**

*Human Teeth - Key Skills and Clinical Illustrations*

**10. C-shaped root Canals**

*and the mesiolingual canals.*

**Figure 5.**

(7.1%) and iatrogenic problems (7.1%).

**11. Dental anomalies**

C-shaped root canals' anatomy is defined as the connection of two distal roots internally and C-shaped appearance panoramically. C-shaped root canals can be observed in the upper and lower first and second molar teeth. They are seen at high rates in the mandibular second molar teeth in Asian population. The treatment of C-shaped root canals needs more care because of their wide, oval and complex anatomy and the bleeding potential of wide pulpal tissue. In the study of Kim et al. [13], the problems with the treatment of C-shaped root canals were found as unsuccessful sealing ability of the canal (45.2%), overlooked canal (9.5%), overfilling

*Endodontic treatment of a mandibular right first molar tooth with an isthmus located between the mesiobuccal* 

Irrigation protocols have significant importance for removing pulpal remnants and hard tissue debris, especially for the unreachable points in the root canals [4]. The morphology of C-shaped root canals may result in elbows during root canal shaping in curved canals. The percentages of elbow formation were reported as 42.1% in C form canals, 40.0% in J form canals and 19.3% in straight form canals. Zip formation was observed in 83.5% of C form canals [14]. Eighty percent of C-shaped root canals were found to have 1–3 apical foramina [15]. In Malaysian population, the C-shaped root canals were found to have 48.7% of incidence [6]. In Jordanian population the mandibular second molar teeth had C-shaped roots in 10% of incidence [16].

Dental morphological anomalies accompany some growth and developmental

gemination are among the often seen dental anomalies. Dental anomalies could also

Dens invaginatus is determined as an infolding of dentin and enamel extending into the pulp chamber. In a case report of Kottoor et al. [24], a maxillary lateral incisor was found to have four main canals called distal, labial, mesial and lingual in a dens invaginatus case. Dens invaginatus is more often characterized with an immature tooth with a periapical lesion. The decision on treatment type depends on the tooth's morphological situation. This pathology is treated by regenerative procedures in which root dentin thickness and newly developed apical foramina are expected.

abnormalities. Dens invaginatus, dens evaginatus, dens in dente, fusion and

be associated with syndromes, such as Down syndrome.

**152**

Focusing on the tooth morphology considering root canal complexity allows dentists to perform successful root canal treatment. Besides the dentists' knowledge and interest in root canal morphology and anatomy, proficiency on root canal treatment and the tendency to use novel technological devices enable prosperous endodontic treatment. The novel tooth morphology classification presented by Ahmed and Dummer, based on the simplicity and clarity respecting tooth number, number of roots and root canal configuration types, is the prominent leading literature for dentistry [26].

#### **Author details**

Esra Pamukcu Guven Faculty of Dentistry, Department of Endodontics, Istanbul Okan University, Istanbul, Turkey

\*Address all correspondence to: esra.pamukcu@okan.edu.tr

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Peters OA, Laib A, GÖhring TN, Barbakow F. Changes in root canal geometry after preparation assessed by high resolution computed tomography. Journal of Endodontia. 2001;**27**:1-6

[2] Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surgery, Oral Medicine, and Oral Pathology. 1984;**58**:589-599

[3] Adorno CG, Yoshioka T, Suda H. Incidence of accessory canals in Japanese anterior maxillary teeth following root canal filling *ex vivo*. International Endodontic Journal. 2010;**43**:370-376

[4] Konstantinidi E, Psimma Z, Chavez de Paz LE, Boutsioukis C. Apical negative pressure irrigation versus syringe irrigation: A systematic review of cleaning and disinfection of the root canal system. International Endodontic Journal. 2017;**50**:1034-1054

[5] Tian Y-Y, Guo B, Zhang R, Yu X, Wang H, Hu T, et al. Root and canal morphology of maxillary first premolars in a Chinese subpopulation evaluated using cone-beam computed tomography. International Endodontic Journal. 2012;**45**:996-1003

[6] Pan JYY, Parolia A, Chuah SR, Bhatia S, Mutalik S, Pau A. Root canal morphology of permanent teeth in a Malaysian subpopulation using cone beam computed tomography. BMC Oral Health. 2019;**14**:1-15

[7] Sieraski SM, Taylor GT, Kohn RA. Identification and endodontic management of three-canalled maxillary premolars. Journal of Endodontia. 1989;**15**:29-32

[8] Kumar R. Report of a rare case: A maxillary first molar with seven canals confirmed with cone-beam computed tomography. Iranian Endodontic Journal. 2014;**9**(2):153-157

[9] Ng Y-L, Aung TH, Alavi A, Gulabivala K. Root and canal morphology of Burmese maxillary molars. International Endodontic Journal. 2001;**34**:620-630

[10] Verma P, Love RM. A micro CT study of the mesiobuccal root canal morphology of the maxillary first molar tooth. International Endodontic Journal. 2011;**44**:210-217

[11] Gu Y, Lee JK, Spangberg LS, Lee Y, Park CM, Seo DG, et al. Minimumintensity projection for in depth morphology study of mesiobuccal root. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics. 2011;**112**:671-677

[12] Mikrogeorgis G, Lyroudia KL, Nikopoulos N, Pitas I, Molyvdas I, Lambrianidis TH. 3D computeraided reconstruction of six teeth with morphological abnormalities. International Endodontic Journal. 1999;**32**:88-93

[13] Kim Y, Lee D, Kim DV, Kim SY. Analysis of cause of endodontic failure of C-shaped root canals. Scanning. 2018:1-7. DOI: 10.1155/2018/2516832

[14] Nagy CD, Bartha K, Berna M, Verdes E, Szabo J. The effect of root canal morphology on canal shape following instrumentation using different techniques. International Endodontic Journal. 1997;**30**:133-140

[15] Cheung GSP, Yang J, Fan B. Morphometric study of the apical anatomy of C-shaped root canal systems in mandibular second molars. International Endodontic Journal. 2007;**40**:239-246

[16] Al-Qudah AA, Awawdeh LA. Root and canal morphology of mandibular first and second molar teeth in a Jordanian population. International Endodontic Journal. 2009;**42**:775-784

**155**

*Root Canal Morphology and Anatomy*

[17] Sert S, Aslanalp V, Tanalp J. Investigation of the root canal configurations of mandibular permanent teeth in the Turkish population. International Endodontic

Journal. 2004;**37**:494-499

*DOI: http://dx.doi.org/10.5772/intechopen.86096*

[25] Kelsen AE, Love RM, Kieser JA, Herbison P. Root canal anatomy of anterior and premolar teeth in Down's syndrome. International Endodontic

[26] Ahmed HMA, Dummer PMH. A new system for classifying tooth, root and canal anomalies. International Endodontic Journal. 2018;**51**:389-404

Journal. 1999;**32**:211-216

[18] Soleymani A, Namaryan N, Moudi E, Gholinia A. Root canal morphology of mandibular canine in an Iranian population: A CBCT assessment. Iranian Endodontic Journal. 2017;**12**(1):78-82

[20] Huang R-Y, Cheng W-C, Chen C-J, Lin C-D, Lai T-M, Shen E-C, et al. Three-dimensional analysis of the root morphology of mandibular first molars with Disto-lingual roots. International Endodontic Journal. 2010;**43**:478-484

[21] Gambarini G, Ropini P, Piasecki L, Costantini R, Carneiro E, Testarelli L, et al. A preliminary assessment of a new dedicated endodontic software for use with CBCT images to evaluate the canal complexity of mandibular molars. International Endodontic Journal.

[22] Wasti F, Shearer AC, Wilson NHF. Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis. International Endodontic Journal.

[23] Gulabivala K, Opasanon A, Ng Y-L, Alavi A. Root and canal morphology of Thai mandibular molars. International Endodontic Journal. 2002;**35**:56-62

[24] Kottoor J, Murugesan R, Albuquerque DV. A maxillary lateral incisor with four root canals. International Endodontic Journal.

2018;**51**:259-268

2001;**34**:263-266

2012;**45**:393-397

[19] Furri M. Differences in the confluence of mesial canals in mandibular molar teeth with three or four root canals. International Endodontic Journal. 2008;**41**:777-780 *Root Canal Morphology and Anatomy DOI: http://dx.doi.org/10.5772/intechopen.86096*

[17] Sert S, Aslanalp V, Tanalp J. Investigation of the root canal configurations of mandibular permanent teeth in the Turkish population. International Endodontic Journal. 2004;**37**:494-499

[18] Soleymani A, Namaryan N, Moudi E, Gholinia A. Root canal morphology of mandibular canine in an Iranian population: A CBCT assessment. Iranian Endodontic Journal. 2017;**12**(1):78-82

[19] Furri M. Differences in the confluence of mesial canals in mandibular molar teeth with three or four root canals. International Endodontic Journal. 2008;**41**:777-780

[20] Huang R-Y, Cheng W-C, Chen C-J, Lin C-D, Lai T-M, Shen E-C, et al. Three-dimensional analysis of the root morphology of mandibular first molars with Disto-lingual roots. International Endodontic Journal. 2010;**43**:478-484

[21] Gambarini G, Ropini P, Piasecki L, Costantini R, Carneiro E, Testarelli L, et al. A preliminary assessment of a new dedicated endodontic software for use with CBCT images to evaluate the canal complexity of mandibular molars. International Endodontic Journal. 2018;**51**:259-268

[22] Wasti F, Shearer AC, Wilson NHF. Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis. International Endodontic Journal. 2001;**34**:263-266

[23] Gulabivala K, Opasanon A, Ng Y-L, Alavi A. Root and canal morphology of Thai mandibular molars. International Endodontic Journal. 2002;**35**:56-62

[24] Kottoor J, Murugesan R, Albuquerque DV. A maxillary lateral incisor with four root canals. International Endodontic Journal. 2012;**45**:393-397

[25] Kelsen AE, Love RM, Kieser JA, Herbison P. Root canal anatomy of anterior and premolar teeth in Down's syndrome. International Endodontic Journal. 1999;**32**:211-216

[26] Ahmed HMA, Dummer PMH. A new system for classifying tooth, root and canal anomalies. International Endodontic Journal. 2018;**51**:389-404

**154**

*Human Teeth - Key Skills and Clinical Illustrations*

[9] Ng Y-L, Aung TH, Alavi A, Gulabivala K. Root and canal morphology of Burmese maxillary molars. International Endodontic

[10] Verma P, Love RM. A micro CT study of the mesiobuccal root canal morphology of the maxillary first molar tooth. International Endodontic Journal.

[11] Gu Y, Lee JK, Spangberg LS, Lee Y, Park CM, Seo DG, et al. Minimumintensity projection for in depth morphology study of mesiobuccal root. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics. 2011;**112**:671-677

[12] Mikrogeorgis G, Lyroudia KL, Nikopoulos N, Pitas I, Molyvdas I, Lambrianidis TH. 3D computeraided reconstruction of six teeth with morphological abnormalities. International Endodontic Journal.

[13] Kim Y, Lee D, Kim DV, Kim SY. Analysis of cause of endodontic failure of C-shaped root canals. Scanning. 2018:1-7. DOI: 10.1155/2018/2516832

Journal. 1997;**30**:133-140

2007;**40**:239-246

[15] Cheung GSP, Yang J, Fan B. Morphometric study of the apical anatomy of C-shaped root canal systems in mandibular second molars. International Endodontic Journal.

[16] Al-Qudah AA, Awawdeh LA. Root and canal morphology of mandibular first and second molar teeth in a Jordanian population. International Endodontic Journal. 2009;**42**:775-784

[14] Nagy CD, Bartha K, Berna M, Verdes E, Szabo J. The effect of root canal morphology on canal shape following instrumentation using different techniques. International Endodontic

Journal. 2001;**34**:620-630

2011;**44**:210-217

1999;**32**:88-93

[1] Peters OA, Laib A, GÖhring TN, Barbakow F. Changes in root canal geometry after preparation assessed by high resolution computed tomography. Journal of Endodontia. 2001;**27**:1-6

[2] Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surgery, Oral Medicine, and Oral Pathology. 1984;**58**:589-599

[3] Adorno CG, Yoshioka T, Suda H. Incidence of accessory canals in Japanese anterior maxillary teeth following root canal filling *ex vivo*. International Endodontic Journal.

[4] Konstantinidi E, Psimma Z, Chavez de Paz LE, Boutsioukis C. Apical negative pressure irrigation versus syringe irrigation: A systematic review of cleaning and disinfection of the root canal system. International Endodontic

Journal. 2017;**50**:1034-1054

Journal. 2012;**45**:996-1003

Health. 2019;**14**:1-15

[6] Pan JYY, Parolia A, Chuah SR, Bhatia S, Mutalik S, Pau A. Root canal morphology of permanent teeth in a Malaysian subpopulation using cone beam computed tomography. BMC Oral

[7] Sieraski SM, Taylor GT, Kohn RA. Identification and endodontic management of three-canalled maxillary premolars. Journal of Endodontia. 1989;**15**:29-32

[8] Kumar R. Report of a rare case: A maxillary first molar with seven canals confirmed with cone-beam computed tomography. Iranian Endodontic Journal. 2014;**9**(2):153-157

[5] Tian Y-Y, Guo B, Zhang R, Yu X, Wang H, Hu T, et al. Root and canal morphology of maxillary first

premolars in a Chinese subpopulation evaluated using cone-beam computed tomography. International Endodontic

2010;**43**:370-376

**References**

**157**

**Figure 1.**

*mandibular second molar.*

**Chapter 10**

**Abstract**

The C-Shaped Root Canal

A thorough understanding of root canal anatomy is of paramount importance in the field of dentistry. The C-shaped root canal is an anatomical variation occurring mostly in mandibular second molars. In a transverse section, the shape of this canal is observed as the letter C. The presence of a fin or web connecting the individual root canals is another anatomic feature. Due to its complex anatomy, different classifications have been proposed through the years for a better comprehension. In endodontic literature, the C-shaped root canal has been of high interest and its prevalence is reported in different regions of the world. Additionally, its endodontic

The C-shaped root canal is considered an anatomical variation in human teeth [1] and was firstly documented in endodontic literature by Cooke and Cox in 1979 [2]. This anatomical variation has been widely studied. Additionally, several case reports

The main cause of a C-shaped root is due to the failure of the Hertwig's epithelial

root seath to fuse on the lingual or buccal root surface [1]. The roots of human molars with C-shaped canals may be conical and fused. For these characteristics, studies suggested that C-shaped root canals could be identified based on preoperative radiographs [6, 7]. However, not all conical roots have a C-shaped canal and various reports stated that a C-shaped root canal is not easily seen using only radiographs [6]. On the other hand, additional reports have demonstrated that a

*(A) Unilateral C-shaped root canal in mandibular second molar; (B) bilateral C-shaped root canal in* 

*Jesús Alejandro Quiñones Pedraza*

management has been widely described and analyzed.

have described its endodontic management [3–5].

canal configuration, human teeth

**1. Introduction**

**Keywords:** C-shaped root canal, anatomy, anatomical variation,

## **Chapter 10** The C-Shaped Root Canal

*Jesús Alejandro Quiñones Pedraza*

## **Abstract**

A thorough understanding of root canal anatomy is of paramount importance in the field of dentistry. The C-shaped root canal is an anatomical variation occurring mostly in mandibular second molars. In a transverse section, the shape of this canal is observed as the letter C. The presence of a fin or web connecting the individual root canals is another anatomic feature. Due to its complex anatomy, different classifications have been proposed through the years for a better comprehension. In endodontic literature, the C-shaped root canal has been of high interest and its prevalence is reported in different regions of the world. Additionally, its endodontic management has been widely described and analyzed.

**Keywords:** C-shaped root canal, anatomy, anatomical variation, canal configuration, human teeth

#### **1. Introduction**

The C-shaped root canal is considered an anatomical variation in human teeth [1] and was firstly documented in endodontic literature by Cooke and Cox in 1979 [2]. This anatomical variation has been widely studied. Additionally, several case reports have described its endodontic management [3–5].

The main cause of a C-shaped root is due to the failure of the Hertwig's epithelial root seath to fuse on the lingual or buccal root surface [1]. The roots of human molars with C-shaped canals may be conical and fused. For these characteristics, studies suggested that C-shaped root canals could be identified based on preoperative radiographs [6, 7]. However, not all conical roots have a C-shaped canal and various reports stated that a C-shaped root canal is not easily seen using only radiographs [6]. On the other hand, additional reports have demonstrated that a

#### **Figure 1.**

*(A) Unilateral C-shaped root canal in mandibular second molar; (B) bilateral C-shaped root canal in mandibular second molar.*

C-shaped canal may be bilateral [8] (i.e., when it is present on one side, it can also be present in the contralateral tooth) (**Figure 1**).

The C-shaped root canal has been found in mandibular and maxillary molars [9, 10], mandibular premolars [11], and even in some incisors [12]. However, it is most commonly present in mandibular second molars [3]. As other anatomical variations, its prevalence has been associated with ethnicity. Interestingly, the prevalence of this canal in Asian populations has been higher than other populations [13].

## **2. Classification**

Different techniques have been used to analyze the morphology of C-shaped root canals [14, 15]. In a transverse section of a tooth with this morphology, the shape of the canal is observed as the letter C (**Figure 2**) and different patterns may be present along the canal. The presence of fins connecting the individual root canals is other anatomical feature [1]. Likewise, the shape of the letter C may be interrupted and observed as separate canals [16]; for this reason, different anatomical classifications have been proposed through the years for a better understanding [17, 18].

Although there are different classifications, the following [18] has been commonly cited and well accepted by clinicians (**Figure 3**):


**159**

*The C-Shaped Root Canal*

*DOI: http://dx.doi.org/10.5772/intechopen.89121*

**3. Endodontic management**

*II; (C) and (D) category III; (E) category IV and (F) category V.*

these cases may require specific skills.

teeth with aberrant anatomies [26].

tive disinfection process [27].

**4. Conclusions**

management [22].

**Figure 3.**

In the field of dentistry, the C-shaped root canal has been of high interest, especially in endodontics. Lack of knowledge regarding root canal anatomy may lead to deficient endodontic treatments [19]. Irregular areas in a C-shaped canal can keep remnants of soft tissue, debris, and infected tissue or may be a source of bleeding during a root canal treatment [20, 21]. Therefore, root canal treatments in

*This representative illustration explains the classification of C-shaped root canal. (A) Category I; (B) category* 

In 1979, the first case reports of C-shaped root canals were documented [2]. Clinical images were presented where the C shape was evident in mandibular and maxillary molars. Since then, numerous case reports have described their clinical

The chemomechanical preparation and obturation of C-shaped canals have been challenging in some cases [23]. Sodium hypochlorite has been the most used endodontic irrigant because of its antimicrobial properties and tissue-dissolving capabilities [24]. Obturation techniques with warm condensation have been indicated in some cases of C-shaped root canals [25]. Likewise, the use of manual, rotary, and reciprocating files has resulted effective in mechanical preparation of

The disinfection process is affected for isthmuses and other irregularities. Careful exploration with a small, precurved file may be helpful to locate additional canals. Although it is not possible to carry out an appropriate negotiation in all the canals, the penetration of sodium hypochlorite with ultrasonics may allow an effec-

A thorough understanding of root canal anatomy is of paramount importance in the field of dentistry. Variations in the number of roots and root canal system

**Figure 2.** *C-shaped root canal, the shape of the canal is observed as the letter "C."*

#### **Figure 3.**

*Human Teeth - Key Skills and Clinical Illustrations*

populations [13].

**2. Classification**

understanding [17, 18].

division.

than 60°.

beta, were less than 60°.

near the apex only).

be present in the contralateral tooth) (**Figure 1**).

monly cited and well accepted by clinicians (**Figure 3**):

*C-shaped root canal, the shape of the canal is observed as the letter "C."*

C-shaped canal may be bilateral [8] (i.e., when it is present on one side, it can also

The C-shaped root canal has been found in mandibular and maxillary molars [9, 10], mandibular premolars [11], and even in some incisors [12]. However, it is most commonly present in mandibular second molars [3]. As other anatomical variations, its prevalence has been associated with ethnicity. Interestingly, the prevalence of this canal in Asian populations has been higher than other

Different techniques have been used to analyze the morphology of C-shaped root canals [14, 15]. In a transverse section of a tooth with this morphology, the shape of the canal is observed as the letter C (**Figure 2**) and different patterns may be present along the canal. The presence of fins connecting the individual root canals is other anatomical feature [1]. Likewise, the shape of the letter C may be interrupted and observed as separate canals [16]; for this reason, different anatomical classifications have been proposed through the years for a better

Although there are different classifications, the following [18] has been com-

• Category I (C1): the shape was an uninterrupted "C" with no separation or

• Category II (C2): the canal shape resembled a semicolumn resulting from a discontinuation of the "C" outline, but either angle alpha or beta was no less

• Category III (C3): two or three separated canals and both angles, alpha and

• Category V (C5): no canal lumen could be observed (which was usually seen

• Category IV (C4): only one round or oval canal in that cross-section.

**158**

**Figure 2.**

*This representative illustration explains the classification of C-shaped root canal. (A) Category I; (B) category II; (C) and (D) category III; (E) category IV and (F) category V.*

#### **3. Endodontic management**

In the field of dentistry, the C-shaped root canal has been of high interest, especially in endodontics. Lack of knowledge regarding root canal anatomy may lead to deficient endodontic treatments [19]. Irregular areas in a C-shaped canal can keep remnants of soft tissue, debris, and infected tissue or may be a source of bleeding during a root canal treatment [20, 21]. Therefore, root canal treatments in these cases may require specific skills.

In 1979, the first case reports of C-shaped root canals were documented [2]. Clinical images were presented where the C shape was evident in mandibular and maxillary molars. Since then, numerous case reports have described their clinical management [22].

The chemomechanical preparation and obturation of C-shaped canals have been challenging in some cases [23]. Sodium hypochlorite has been the most used endodontic irrigant because of its antimicrobial properties and tissue-dissolving capabilities [24]. Obturation techniques with warm condensation have been indicated in some cases of C-shaped root canals [25]. Likewise, the use of manual, rotary, and reciprocating files has resulted effective in mechanical preparation of teeth with aberrant anatomies [26].

The disinfection process is affected for isthmuses and other irregularities. Careful exploration with a small, precurved file may be helpful to locate additional canals. Although it is not possible to carry out an appropriate negotiation in all the canals, the penetration of sodium hypochlorite with ultrasonics may allow an effective disinfection process [27].

#### **4. Conclusions**

A thorough understanding of root canal anatomy is of paramount importance in the field of dentistry. Variations in the number of roots and root canal system

anatomy are not uncommon in human teeth. The C-shaped root canal represents an important and challenging anatomical variation. Likewise, knowledge of the different morphologies of C-shaped root canals can help avoid complications during endodontic treatments.

#### **Acknowledgements**

The author denies any conflict of interest related to this study.

#### **Author details**

Jesús Alejandro Quiñones Pedraza Department of Endodontics, Intracanal, Monterrey, Nuevo León, México

\*Address all correspondence to: aqp.endo@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**161**

*The C-Shaped Root Canal*

**References**

*DOI: http://dx.doi.org/10.5772/intechopen.89121*

[1] Jafarzadeh H, Wu YN. The C-shaped root canal configuration: A review. Journal of Endodontics. 2007;**33**:517-523 C-shaped molar. Journal of Endodontics. 2016;**42**:383-389

[10] Weine FS. The C-shaped

[11] Martins JNR, Francisco H, Ordinola-Zapata R. Prevalence of C-shaped configurations in the

2017;**43**:890-895

1999;**30**:707-711

2017;**43**:1442-1447

mandibular second molar: Incidence and other considerations. Journal of Endodontics. 1998;**24**:372-375

mandibular first and second premolars: A cone-beam computed tomographic in vivo study. Journal of Endodontics.

[12] Boveda C, Fajardo M, Millan B. Root canal treatment of an invaginated maxillary lateral incisor with a C-shaped canal. Quintessence International.

[13] von Zuben M, Martins JNR, Berti L, Cassim I, Flynn D, Gonzalez JA, et al. Worldwide prevalence of mandibular second molar C-shaped morphologies evaluated by cone-beam computed tomography. Journal of Endodontics.

[14] Helvacioglu-Yigit D, Sinanoglu A.

tomography to evaluate C-shaped root canal systems in mandibular second molars in a Turkish subpopulation: A retrospective study. International Endodontic Journal. 2013;**46**:1032-1038

[15] Seo MS, Park DS. C-shaped root canals of mandibular second molars in Korean population: Clinical observation and in vitro analysis. International Endodontic Journal. 2004;**37**:139-144

[16] Amoroso-Silva PA, Ordinola-Zapata R, Duarte MA, Gutman JL, del Carpio-Perochena A, Bramante CM, et al. Micro-computed tomographic analysis of mandibular second molars with C-shaped root canals. Journal of Endodontics.

2015;**41**:890-895

Use of cone-beam computed

[2] Cooke HG 3rd, Cox FL. C-shaped canal configurations in mandibular molars. Journal of the American Dental

Association. 1979;**99**:836-839

[3] Kato A, Ziegler A, Higuchi K, Nakamura H, Ohno N. Aetiology, incidence and morphology of the

[4] Martins JN, Quaresma S,

2011;**44**:857-862

C-shaped root canal system and its impact on clinical endodontics. International Endodontic Journal. 2014;**47**:1012-1033

Quaresma MC, Frisbie Teel J. C-shaped maxillary permanent first molar: A case report and literature review. Journal of Endodontics. 2013;**39**:1649-1653

[5] Zheng Q, Zhang L, Zhou X, Wang Q, Wang Y, Tang L, et al. C-shaped root canal system in mandibular second molars in a chinese population evaluated by cone-beam computed tomography. International Endodontic Journal.

[6] Sinanoglu A, Helvacioglu-Yigit D. Analysis of C-shaped canals by

[7] Fan B, Cheung GS, Fan M, Gutman JL, Fan W. C-shaped canal system in mandibular second molars: Part II-radiographic features. Journal of

Endodontics. 2004;**30**:904-908

configuration in maxillary first molars. Journal of Endodontics. 1990;**16**:601-603

[9] Martins JN, Mata A, Marques D, Anderson C, Caramês J. Prevalence and characteristics of the maxillary

[8] Dankner E, Friedman S, Stabholz A. Bilateral C shape

panoramic radiography and cone-beam computed tomography: Root type specificity by longitudinal distribution. Journal of Endodontics. 2014;**40**:917-921

#### **References**

*Human Teeth - Key Skills and Clinical Illustrations*

endodontic treatments.

**Acknowledgements**

anatomy are not uncommon in human teeth. The C-shaped root canal represents an important and challenging anatomical variation. Likewise, knowledge of the different morphologies of C-shaped root canals can help avoid complications during

The author denies any conflict of interest related to this study.

**160**

**Author details**

Jesús Alejandro Quiñones Pedraza

provided the original work is properly cited.

Department of Endodontics, Intracanal, Monterrey, Nuevo León, México

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: aqp.endo@gmail.com

[1] Jafarzadeh H, Wu YN. The C-shaped root canal configuration: A review. Journal of Endodontics. 2007;**33**:517-523

[2] Cooke HG 3rd, Cox FL. C-shaped canal configurations in mandibular molars. Journal of the American Dental Association. 1979;**99**:836-839

[3] Kato A, Ziegler A, Higuchi K, Nakamura H, Ohno N. Aetiology, incidence and morphology of the C-shaped root canal system and its impact on clinical endodontics. International Endodontic Journal. 2014;**47**:1012-1033

[4] Martins JN, Quaresma S, Quaresma MC, Frisbie Teel J. C-shaped maxillary permanent first molar: A case report and literature review. Journal of Endodontics. 2013;**39**:1649-1653

[5] Zheng Q, Zhang L, Zhou X, Wang Q, Wang Y, Tang L, et al. C-shaped root canal system in mandibular second molars in a chinese population evaluated by cone-beam computed tomography. International Endodontic Journal. 2011;**44**:857-862

[6] Sinanoglu A, Helvacioglu-Yigit D. Analysis of C-shaped canals by panoramic radiography and cone-beam computed tomography: Root type specificity by longitudinal distribution. Journal of Endodontics. 2014;**40**:917-921

[7] Fan B, Cheung GS, Fan M, Gutman JL, Fan W. C-shaped canal system in mandibular second molars: Part II-radiographic features. Journal of Endodontics. 2004;**30**:904-908

[8] Dankner E, Friedman S, Stabholz A. Bilateral C shape configuration in maxillary first molars. Journal of Endodontics. 1990;**16**:601-603

[9] Martins JN, Mata A, Marques D, Anderson C, Caramês J. Prevalence and characteristics of the maxillary

C-shaped molar. Journal of Endodontics. 2016;**42**:383-389

[10] Weine FS. The C-shaped mandibular second molar: Incidence and other considerations. Journal of Endodontics. 1998;**24**:372-375

[11] Martins JNR, Francisco H, Ordinola-Zapata R. Prevalence of C-shaped configurations in the mandibular first and second premolars: A cone-beam computed tomographic in vivo study. Journal of Endodontics. 2017;**43**:890-895

[12] Boveda C, Fajardo M, Millan B. Root canal treatment of an invaginated maxillary lateral incisor with a C-shaped canal. Quintessence International. 1999;**30**:707-711

[13] von Zuben M, Martins JNR, Berti L, Cassim I, Flynn D, Gonzalez JA, et al. Worldwide prevalence of mandibular second molar C-shaped morphologies evaluated by cone-beam computed tomography. Journal of Endodontics. 2017;**43**:1442-1447

[14] Helvacioglu-Yigit D, Sinanoglu A. Use of cone-beam computed tomography to evaluate C-shaped root canal systems in mandibular second molars in a Turkish subpopulation: A retrospective study. International Endodontic Journal. 2013;**46**:1032-1038

[15] Seo MS, Park DS. C-shaped root canals of mandibular second molars in Korean population: Clinical observation and in vitro analysis. International Endodontic Journal. 2004;**37**:139-144

[16] Amoroso-Silva PA, Ordinola-Zapata R, Duarte MA, Gutman JL, del Carpio-Perochena A, Bramante CM, et al. Micro-computed tomographic analysis of mandibular second molars with C-shaped root canals. Journal of Endodontics. 2015;**41**:890-895

[17] Melton DC, Krell KV, Fuller MW. Anatomical and histological features of C-shaped canals in mandibular second molars. Journal of Endodontics. 1991;**17**:384-388

[18] Fan B, Cheung GS, Fan M, Gutmann JL, Bian Z. C-shaped canal system in mandibular second molars: Part I-anatomical features. Journal of Endodontics. 2004;**30**:899-903

[19] Nair PN. On the causes of persistent apical periodontitis: A review. International Endodontic Journal. 2006;**39**:249-281

[20] Ordinola-Zapata R, Bramante CM, de Moraes IG. Analysis of the gutta-percha filled area in C-shaped mandibular molars obturated with modified mocroseal technique. International Endodontic Journal. 2009;**42**:186-197

[21] Gok T, Capar ID, Akcay I, Keles A. Evaluation of different techniques for filling simulated C-shaped canals of 3-dimensional printed resin teeth. Journal of Endodontics. 2017;**43**:1559-1564

[22] Ring J, Ring KC. Rare root canal configuration of mandibular second premolar using cone-beam computed tomographic scanning. Journal of Endodontics. 2017;**43**:1897-1900

[23] Walid N. The use of two pluggers for the obturation of an uncommon C-shaped canal. Journal of Endodontics. 2000;**26**:422-424

[24] Zhender M. Root canal irrigants. Journal of Endodontics. 2006;**32**:389-398

[25] Liewehr FR, Kulild JC, Primack PD. Obturation of a C-shaped canal using an improved method of a warm lateral condensation. Journal of Endodontics. 1993;**19**:474-477

[26] Solomonov M, Paqué F, Fan B, Eliat Y, Berman LH. The challenge of C-shaped canal systems: A comparative study of the self-adjusting file and protaper. Journal of Endodontics. 2012;**38**:209-214

[27] Fan B, Min Y, Lu G, Yang J, Cheung GSP, Gutman JL. Negotiation of C-shaped canal systems in mandibular second molars. Journal of Endodontics. 2009;**35**:1003-1008

**163**

Section 3

Pathology and Clinical

Considerations

## Section 3
