C- SHAPED CANALS pptx by DR. AMAL DEVADAS

C SHAPED CANALS

1. C- SHAPED CANALS DR. AMAL DEVADAS POST GRADUATE DEPT. OF CONSERVATIVE AND ENDODONTICS 1

2. CONTENTS INTRODUCTION HISTORY ETIOLOGY INCIDENCE ANATOMIC FEATURES roots, pulp chamber, root canal system CLASSIFICATION 2

3. DIAGNOSIS preoperative R/F analysis, preoperative clinical diagnosis, clinical diagnosis following access cavity preparations, clinical & R/F diagnosis during working length determination MANAGEMENT location & negotiation of canals, cleaning & shaping, obturation , post endo restoration, endodontic surgery CONCLUSION 3

4. INTRODUCTION The traditional ‘one canal per root’ concept is being challenged with observations from newer diagnostic tools and current scientific literature. It is therefore important to be familiar with variations in tooth anatomy to help in identification, negotiation and management of aberrant canals . 4

5. A thorough knowledge of the root canal anatomy and its variations are required for achieving success in root canal therapy, along with diagnosis, treatment planning and clinical expertise. One such variation of the root canal system is the C-shaped canal configuration . It is termed so because of the C-shaped cross-sectional anatomical configuration of the root and root canal . 5

6. In contrast to normal anatomy, the orifice of a C-shaped canal is ribbon-shaped and transcribes an arc of 180 degree. The feature usually starts at mesiolingual line angle of the chamber, curves buccally and ends at the distal aspect. 6

7. Below the orifice level, the root structure can be basically divided into two groups . 1. With three or more distinct canals below the orifice. 2. With single, ribbon-like, C-shaped canal from orifice to apex. 7

8. C-shaped canals often present a challenge in debridement and obturation . Roots of this type of teeth may be fused in buccal or lingual aspect and may have a conical or square configuration. Fins or webs may be seen connecting individual root canals. This seminar is an attempt to address the etiology, classification, prevalence, diagnosis and management of C-shaped canals. 8

9. HISTORY Historically, Keith & Knowles in 1911 were the first authors to depict a C-shaped root canal . The C-shaped root was first analysed in detail by Nakayama in 1941 , who gave it the name ‘ gutter-shaped root’. In addition, Nakayama & Toda in 1941 reported on the ‘ gutter- shaped root canal’, focusing on its morphology and aspects of treatment. 9

10. Tratman in 1950 stated that the C-shaped root morphology can frequently be observed in mandibular second molars from Asian individuals. This condition was described for the first time in literature by Cooke and Cox in 1979 . Manning in his description of root canal anatomy of mandibular second molars, stated that C-shaped roots and root canals were first documented in 1908 and 1911 , 10

11. ETIOLOGY The most accepted theory for the formation of C-shaped canal configuration is the failure of Hertwig’s epithelial root sheath (HERS) to fuse on the buccal or lingual root surface. This results in a conical or prism shaped root with a thin interradicular ribbon-shaped isthmus connecting them. 11

12. INCIDENCE The C-shaped canal configuration shows an ethnic predilection . Studies in Chinese and mexican populations have shown a preponderance of this condition in mandibular second molars. The C-shaped anatomy has been found to be more common in Asians than in whites. 12

13. 13 JOE — Volume 43, Number 9, September 2017

14. C-shaped configuration prevalence among women was 16.5 %, which was significantly higher than the 10.4% prevalence recorded in male patients . Despite its high occurrence in mandibular second molars, this variation has also been reported in mandibular and maxillary first molars (0.12%), maxillary (4.7%) and mandibular third molars (3.5%-4%), mandibular first and second premolars (1%) and even in maxillary lateral incisors . 14

15. Bilateral incidence of C-shaped canals has been reported in 70%-81% of cases Singla & Aggarwal reported this configuration in the palatal canal of a maxillary second molar. 15

16. ANATOMIC FEATURES The following are the pertinent features in relation to the external root anatomy and configuration of the pulp chamber and the root canal system usually found in C-shaped mandibular molars, though similar features may be found in C-shaped maxillary molars and mandibular premolars. 16

17. ROOTS A conical or square configuration is characteristic of roots having a C-shaped canal. The root configuration of molars having this canal shape may be represented by fusion of either the facial or lingual aspect of the mesial and distal roots The roots display an occluso -apical groove on the buccal or lingual surface, which represent the line of fusion between mesial and distal roots. 17

18. The surface opposite this radicular groove is convex referred to the C-shaped roots of mandibular second molars as being ‘ gutter-shaped ’. 18

19. PULP CHAMBER The pulp chambers of teeth with C-shaped canals mostly have greater apico-occlusal width with a low bifurcation . This results in a deep pulp chamber floor, which has uncommon anatomical configuration. The connecting slit that gives the tooth its name of “C-shaped” may have closure to the buccal or lingual. 19

20. If the buccal portion of the mesial and distal roots are fused , the slit goes through the area of fusion, and so the “C” is closed to the lingual. If the lingual portion of the roots are fused, then the “C” is closed to the buccal . 20

21. ROOT CANAL SYSTEM The root canal system of C-shaped canals shows broad, fan-shaped communications from the coronal to the apical third of the canal. The canals change shape from the coronal aspect of the root . For example: A continuous C-shaped canal would change to a semicolon configuration in the midroot and then becomes continuous C-shape in the apical third of the root or vice versa. 21

22. Accessory and lateral canals, inter-canal communications and apical delta can be found in a prevalence of 11-41%, in the apical region of C-shaped canals. Cross-sectional C-shaped canal morphology reveals thinner lingual walls than buccal with the lowest value measured being 0.26 mm. The varied intricacies in the C-shaped canal anatomy are outlined in the section on classification 22

23. MANDIBULAR PREMOLARS All C-shaped premolars have shallow or deep radicular grooves located on the external mesiolingual surface of the root. These grooves usually start 3 mm below the cemento -enamel junction (CEJ) and may or not extend to the apex. The mean depth of the grooves at some areas on the root can be around 1.5 mm. This must be taken into consideration during cleaning and shaping . 23

24. The morphology of C-shaped canals in mandibular first premolars may present one of the following four features: Continuous C-shaped canal only, Semilunar buccal canal only, Combination of continuous C-shape and semi-lunar buccal canal C-shaped canal interrupted by non-C-shaped canal 24

25. CLASSIFICATION A comprehensive classification of C-shaped canal system is essential for its diagnosis and management. The earliest classification were proposed by Manning and Melton et al. However, there was no clear distinction between the categories in Melton’s classification. 25

26. Besides, Melton’s and Manning’s classifications describe only the appearances of the canal orifices, but fail to describe how the C-shaped configuration may vary along the root length Various other classifications were then proposed by Al- Fouzan , Fan et al , Gao et al and Min et al. 26

27. Melton’s Classification Melton et al. in 1991 proposed the following classification of C-shaped canals based on their cross-sectional shape. Category I : continuous C -shaped canal running from the pulp chamber to the apex defines a C-shaped outline without any separation (C1). Category II : the semicolon-shaped ( ; ) orifice in which dentine separates a main C-shaped canal from one mesial distinct canal (C2). 27

28. 28

29. Category III : refers to those with two or more discrete and separate canals: Subdivision I : C-shaped orifice in the coronal third that divides into two or more discrete and separate canals that join apically. Subdivision II : C-shaped orifice in the coronal third that divides into two or more discrete and separate canals in the mid root to the apex. Subdivision III : C-shaped orifice that divides into two or more discrete and separate canals in the coronal third to the apex (C3). 29

30. Fan’s Classification Fan et al in 2004 modified Melton’s classification into Anatomic and Radiographic classification Anatomic classification Category I (C1): uninterrupted “C” with no separation or division 30

31. Category II (C2): the canal shape resembled a semicolon resulting from a discontinuation of the “C” outline , but either angle α or β should be no less than 60°. 31

32. Category III (C3): 2 or 3 separate canals (Fig.1C and D) and both angles, α and β, were less than 60°. 32

33. Category IV (C4): only one round or oval canal in that cross section. Category V (C5): no canal lumen could be observed (which is usually seen near the apex only) 33

34. 34

35. Fan’s classification (Radiographic ) Fan et al classified C-shaped roots according to their radiographic appearance into three types . Type I : conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. Mesial and distal canals merged into one before exiting at the apical foramen. 35

36. Type II : conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. Mesial and distal canals continue on their own pathway to the apex . 36

37. Type III : conical or square root with a vague, radiolucent longitudinal line separating the root into distal and mesial parts. Of the mesial and distal canals, one canal curved to and superimposed on this radiolucent line when running toward the apex, and the other canal continued on its own pathway to the apex. 37

38. Classification of pulp chamber floor, by fan Type I : a peninsula-like floor with a continuous C-shaped orifice. 38

39. Type II : a buccal , strip-like dentin connection exists between the peninsula-like floor and the buccal wall of the pulp chamber that separates the C-shaped groove into mesial (M) and distal (D) orifices. 39

40. Type III : only one mesial , strip-like dentin connection exists between the peninsula-like floor and the M wall, which separates the C-shaped groove into a small ML orifice and a large MB-D orifice . The MB-D orifice was formed by the merging of the MB orifice and the D orifice. 40

41. Type IV : Non-C-shaped floor. One distal canal orifice and one oval or two round mesial canal orifices are present. 41

42. Coronal view of C-types: (A)C1-type mandibular molar, (B)C2-type mandibular molar, (C)C1-type 3D printed resin replica, (D)C2-type 3D printed resin replica. 42

43. DIAGNOSIS Preoperative Radiographic Analysis A preoperative radiograph usually provides various clues in the identification of any variation in root canal morphology. However, there are differences in opinions on the value of a preoperative radiograph in diagnosing a C-shaped case. Cooke & Cox were of the opinion that it is not possible to diagnose C-shaped canals on preoperative radiographs . 43

44. Conversely, some investigators described four radiographic characteristics that can allow prediction of the existence of this anatomical condition: radicular fusion , radicular proximity , a large distal canal or a blurred image of a third canal in between. When the communication or fin connecting the two roots is very thin, it is not visible on the radiograph and may thus give the appearance of two distinct roots. 44

45. The radiograph may also reveal a large and deep pulp chamber, usually found in C-shaped molars. Wang et al. reported a higher incidence in the recognition of C-shaped canals using a combination of radiography and clinical examination under the microscope (41.27%) than using the radiography (34.64%) or clinical examination (39.18%) alone. 45

46. Preoperative clinical diagnosis The crown morphology of teeth with C-shaped anatomy does not present with any special features that can aid in the diagnosis. A longitudinal groove on lingual or buccal surface of the root with a C-shaped anatomy may be present. Such narrow grooves may predispose the tooth to localized periodontal disease, which may be the first diagnostic indication. 46

47. Clinical diagnosis following access cavity preparations Some investigators asserted that since radiographic diagnosis is difficult, clinical diagnosis of C-shaped canals can be established only following access to the pulp chamber. The pulpal floor in C-shaped teeth can vary from peninsula like with a continuous C-shaped orifice to non C-shaped floor. 47

48. However, when a C-shaped canal orifice is observed, say, under the operating microscope, one cannot assume that such a shape continues throughout its length. Clinical recognition of C-shaped canals is based on the anatomy of the floor of the pulp chamber and the persistence of hemorrhage . 48

49. Fan et al. stated that, for a mandibular second molar to qualify for a C-shaped canal system, it has to exhibit all the following three features : a. Fused roots b. A longitudinal groove on lingual or buccal surface of the root. c. At least one cross-section of the canal should belong to the C1, C2, or C3 configuration , as per Fan’s anatomic classification. 49

50. Clinical and radiographic diagnoses during working length determination Working length radiographs are more helpful than preoperative and final radiographs in diagnosing C-shaped canals. In a true C-shaped canal, (single canal running from the orifice to the apex) it is possible to pass an instrument from the mesial to the distal aspect without obstruction. 50

51. In the semicolon type, (one distinct canal and a buccal or lingual C-shaped canal) whenever an instrument was inserted into any side of the C-shaped canal, it always ends in the distal foramen of the tooth and a file introduced in this canal could probe the whole extension of the C. When negotiating the C-shaped canal, instruments may be clinically centered. 51

52. Radiographically , the instruments may either converge at the apex or may appear to be exiting the furcation , thus adding to the confusion and troublesome task of determining whether a perforation has occurred. 52

53. Interpretation of more than one radiograph or use of an apex locator gives a differential diagnosis of C-shaped molars from furcation perforation. Film combinations - “preoperative and working length radiographs” or “preoperative and final radiographs” or “all three radiographs” make radiographic interpretation more effective than single radiographs in diagnosing the C-shape. 53

54. Working length radiographs are more helpful while preoperative radiographs are least effective. Newer imaging modalities like spiral CT and micro CT aid in the diagnosis of C-shaped canals. Both are time consuming and have limited application in in-vivo studies. 54

55. Limited - volume CBCT with low radiation dose and high resolution , on the other hand, is a precise and nondestructive technique which allows for both qualitative and quantitative evaluation of root canal morphology in three dimensions Further, it gives greater diagnostic data with reduction of subjectivity in interpretation, as the problem of overlap, common in two dimensional views is eliminated. 55

56. Micro-computed tomography (micro-CT) is a non-destructive, three-dimensional analytical method that permits the accurate evaluation of root canal systems prior and subsequent to enlarging and shaping by superimposing pre- and post-instrumentation scanning data. 56

57. Recently, micro-CT has been used for evaluating the amount and distribution of hard-tissue debris in canal isthmi ( Paqué et al. 2009) and the reduction of hard-tissue debris after different final irrigation regimens ( Paqué et al. 2012, Freire et al. 2015, Keles et al. 2016) 57

58. MANAGEMENT The high percentage of canal irregularities, such as accessory to lateral canals, and apical delta in a C-shaped canal makes it difficult to clean and seal the entire canal system adequately. The wide fins and small surface area of these canals preclude complete debridement using traditional hand instrumentation techniques, which can lead to failure of root canal therapy. 58

59. Therefore, careful location and negotiation of the canals and the meticulous mechanical and chemical debridement of the pulp tissue should be carried out in order to successfully treat a C-shaped canal. 59

60. Location and negotiation of canals After achievement of endodontic access and removal of tissue from the pulp chamber, modifications in the access design facilitates location and negotiation of the complete canal system. 60

61. When the orifice is continuous C-shape or arc like Mesiobuccal - Distal (MB-D), the number of canals can vary from one to three; when the orifice is oval or flat , the number of canals may be one or two; and when the orifice is round , there is usually only one canal below the orifice. 61

62. Hence, for continuous C-shape orifice, 3 initial files are inserted, one at either end and one in the middle. When the orifice is oval, two files are inserted, that is, one file at each end of the orifice and when the orifice is round, one initial file is inserted. Calcifications present in the pulp chamber may disguise the C-shape of the canal system. In such cases, several orifices may be probed that link up on further instrumentation. 62

63. There are also chances of missing out on canals because of bifurcation, dentin fusion, and curvatures. Exploration should be carried out with small size endodontic files, such as a no. 8, 10, 15 K-file with a small, abrupt apically placed curve, to ensure that these irregularities are not missed. 63

64. Cleaning and Shaping In most situations, the mesiobuccal and distal canal spaces can be prepared utilizing a conventional approach . Instrumentation of the isthmus above # 25 size files should be avoided to minimize the potential for strip perforation. The orifice portion of the slit can be widened with Gates Glidden drills to access all the irregularities. 64

65. For narrow, interconnecting isthmus areas as in C1 (continuous C type) and C2 (semicolon type) configurations, Gates Glidden drills should not be used and cleaning should be carried out using #25 or smaller instruments, with copious irrigation using 5.25% sodium hypochlorite . 65

66. Abou-Rass et al. recommended anti-curvature filing technique to avoid danger zones. Perforation of the thinner lingual walls can be minimized by instrumentation directed buccally . 66

67. Apical instrumentation should be limited to #30(0.06 taper) Following rotary instrumentation, filing using K-files or H-files may be specifically directed towards the isthmus areas to obtain better debridement 67

68. Self-adjusting file (SAF) system is more efficacious than the protaper system for shaping C-shaped canals. Intracanal instruments are unable to access and debride the entire portion of the large canal space, making the role of irrigation more relevant. Canal irrigation techniques incorporating ultrasonics is more effective in achieving adequate debridement. 68

69. Deeper penetration with small instruments and increased volume of irrigant allows more cleansability in fan-shaped areas of the C-shaped canal. However, injudicious ultrasonic instrumentation carries the risk of perforation . In C-shaped molars with a single apex, the mesiolingual canal is separate and shorter than the other canals. 69

70. The mesiobuccal canal swings back and merges with the distal canal and exits through a single foramen. This feature can result in over instrumentation of the mesiolingual canal. Some authors have advocated the use of calcium hydroxide as an intracanal medicament for a period of 7-10 days. 70

71. With regard to the management of C-shaped canal configuration in mandibular premolars, many complicating factors make them difficult to treat. Anatomically the diameter and width of mandibular first premolar is much smaller than mandibular second molars. The small size of mandibular first premolar limits the coronal access to the complex root canal system, which unlike the mandibular second molar, is found apically. 71

72. Advanced file systems to be used in a C shaped canal Reciproc Blue (RB; VDW, Munich, Germany) is a new-generation single-file system that prepares root canals using reciprocal motion. The proprietary heat treatment procedure results in a blue titanium oxide layer on the surface of the instrument. 72

73. When compared with Reciproc (VDW) instruments made of M-Wire, Reciproc Blue is more flexible and fatigue resistant due to the alteration of the alloy molecular structure (De-Deus et al. 2017). The R25 file in the RB system created a larger taper in the apical 3 mm (.08 taper) and smaller diameter (0.25 mm), 73

74. XP- endo Shaper (XP-S; FKG Dentaire , La Chaux-deFonds , Switzerland) is a NiTi instrument made of MaxWire alloy ( Martensite -Austenite Electropolishing -Flex, FKG Dentaire ) that enhances efficiency during canal shaping. 74

75. At ambient temperature , XP-S is in the martensitic phase and has a size 30, .01 taper. At body temperature , the file transforms into the austenitic phase along with the changes of shape, which can make the final canal preparation reach size 30.04 taper ( Lacerda et al. 2017). 75

76. The XP-S system is a single-file system and makes serpentine movement inside the canals. According to the manufacturer, the XP-S has a small, free-floating adaptive core that adapts to the root canal anatomy, enables ideal shaping in difficult canal systems, and decreases debris compaction in the irregular regions of those canals 76

77. Best irrigation methods for C-shaped Canals The use of SNI alone has been reported to be ineffective in removing tissue remnants and cleaning the apical region of a root canal system (Thomas et al. 2014). The main reason is that fluid flow dynamics beyond the needle tip is limited (Nielsen & Baumgartner 2007). 77

78. In addition, entrapment of gas bubbles in the apical region may also prevent irrigants from reaching the entire working length, a phenomenon that has been referred to as the ‘ vapor lock effect’. Previous studies reported that ultrasonic activation of irrigants significantly reduces debris within the canal space (Lee et al. 2010a, 2010b). The good performance of PUI may be attributed to the production of acoustic microwaves, cavitation and heat generation ( Macedo et al. 2014, Arslan et al. 2015). 78

79. When XP-F is used in the austenite phase shape and in rotation mode, its functional rotational diameter may be expanded to a maximum of 6 mm , which is a 100-fold greater than an equivalent-sized file ( Leoni et al. 2017). 79

80. During rotating in the root canal, XP-F is claimed by the manufacturer to be capable of removing debris by mechanically contacting canal areas that are not previously attainable by other file systems, while agitating the irrigant within the canal space by continuous irrigation. 80

81. 81

82. For RB and XP-S, 33.04% and 30.45% , respectively, of the canal wall remained untouched . For both groups, the apical third had larger AUCW% than the coronal third. Instrumentation with RB left more debris ( 2.8% ) than XP-S ( 1.1% ) . The PUI and XP-F subgroups had higher mean red% of AHTD than the SNI subgroup; the difference was significant for RB but not for XP-S 82

83. Conclusion of the study Both RB and XP-S systems were associated with similar AUCW after instrumenting C-shaped canals. RB left significantly higher levels of AHTD compared with XP-S. PUI and XP-F irrigation removed more debris than SNI when using the RB system. 83

84. OBTURATION Obtaining a three dimensional fill of a C-shaped canal may prove to be a problem due to the various intricacies present within the root canal system. If a cold condensation technique is adopted for obturation , deeper penetration of condensation instruments in several sites will be necessary. 84

85. To ensure proper placement of the master cones in C-shaped canals, Barnett recommended placing a large diameter file in the most distal portion of the canal, before seating the master cone in the mesial canal. The file is then withdrawn and the master cone of the distal canal is seated, followed by placement of accessory cones in the middle portion of the C-shaped canal 85

86. Sealing the buccal isthmus is difficult using lateral condensation alone, as the isthmus cannot be prepared with a flare to permit deeper placement of the spreader. This makes application of gutta-percha, thermoplasticized with electric spreaders or spreaders heated in an open flame or delivered by injectable systems more appropriate. 86

87. Studies have shown that following the cleaning and shaping, the remaining dentin thickness around the canals is usually 0.2 to 0.3 mm. The resultant forces of compaction during obturation can exceed the dentin canal resistance, which may result in root fracture and perforation of the root. In this regard, the thermoplasticized gutta-percha technique may prove to be more beneficial 87

88. The aim of this technique is to move the gutta-percha and sealer into the root canal system under a hydraulic force . But in C-shaped canals the hydraulic forces can dramatically decrease and can seriously compromise the obturation quality due to the following reasons: (a) there are divergent areas that are frequently unshaped, which may offer resistance to obturating material flow 88

89. (b) communications exist between the main canals of the C-shape through which the entrapped filling materials that should be captured between the apical tug back area and the level of condensation may pass from one canal to another. Regardless of the choice of obturation technique, proper placement of sealer with ultrasonic endodontic files is critical . 89

90. Walid’s technique aimed to overcome these problems by the simultaneous use of two pluggers to down pack the main canals in a C-shaped canal. Two fine-medium cones were seated in the mesiolingual and distal canals. No accessory cones should be placed in the fin between them and a medium point was fitted in the mesiobuccal canal. Three pluggers are used for obturation . 90

91. Using Touch’N Heat (Sybron Endo/Analytic, Irvine, CA) gutta-percha at the mesiolingual orifice level was seared off where the largest plugger was placed, while down packing the distal canal with the smallest plugger . While packing the mesiolingual canal, the smallest plugger used in the distal canal was held in place. 91

92. 92

93. The resistance toward the passage of obturating material from one canal to another was increased by placing two master points and blocking the canal entrance with a plugger This offers backpressure on entrapped filling materials and enhances the seal. 93

94. 94

95. Zapata et al. analyzed gutta-percha filled area of C-shaped canals filled with Maggiore’s modified MicroSeal technique with reference to the radiographic features. They found that the apical third was less accurately filled and concluded that C2 canals with a 60° angle could be less difficult to fill than a 120° or 150° C2 canal. 95

96. Martin developed the EndoTec II ( Medidenta , Inc. Woodside, NY) that combined the qualities of both the ease and speed of lateral compaction as well as the superior density gained by vertical compaction of warm gutta-percha. Using the “ zap and tap ” maneuver, improved compaction could be achieved while obturating a C-shaped canal by using the device. 96

97. This involves heating the EndoTec plugger for 4 to 5 seconds (zap) followed by moving the hot instrument in and out in short continuous strokes (tap) 10 to 15 times. 97

98. In 1989 Stephen Buchanan conceived a way to radically simplify 3D obturation , the Continuous wave compaction technique by combining the function of schilders pluggers and masreilez’s electric heat carrier into a single electric heat plugger . This new method collapsed schilders vertical condensation down packing procedure from 3 to 5 heating and packing steps requiring 5 min per canal into a down pack that required just 2 procedural steps and less than 15 sec per canal to complete 98

99. 99

100. Conclusion of the study Continuous wave obturation was more effective than lateral condensation in both C1- and C2-type , except for the apical 2 mm section of C1-type, suggesting the need for a modified CW technique. 100

101. POST ENDODONTIC RESTORATIONS The thin dentin cross section between the external surface of the root and the internal canal system can compromise the structural integrity of these teeth. The available undercuts of the deep pulp chamber provide ample retention. Bonded amalgam or composite is the preferred core buildup material for such teeth For resistance to root fracture, at least 1 mm of sound tooth structure should be present around a post. 101

102. Prefabricated or cast posts have a risk of creating a strip perforation. No prefabricated post (circular or conical) would fit the C-shaped canals Post placement is preferred in the tubular distal canal to facilitate adaptation and stress distribution. Placement of posts or anti-rotational pins in the mesiolingual and mesiobuccal areas of C-shaped root can cause perforation. 102

103. ENDODONTIC SURGERY Hemisection or root amputation is contraindicated pertaining to the absence of furca . The intercanal communications or fins make retro-preparation and retro-filling after apicoectomy extremely difficult. If surgical intervention is indicated for a molar with C-shaped root canal anatomy, extraction followed by extra oral retro filling and intentional replantation should be considered 103

104. Prognosis A suspicion of furcal breakdown should be kept in mind and evaluated in the follow-up radiographs since it is the most difficult area to obturate and is associated with the greatest risk of perforation. Furcal failures have a poor prognosis 104

105. CONCLUSION The intricacies present in the C-shaped anatomy pose a challenge during negotiation, debridement and obturation . However, with advances in the tools for diagnosis and treatment, the condition should no longer be an enigma for the clinician. 105

106. The advent of rotary and hand instrumentation assisted with ultrasonics as well as modified obturation techniques have improved the prognosis of this anatomical variant. It is appropriate to observe cautious optimism in the success of the root canal treatment of a C-shaped canal. 106

107. References Barnett F (1986) Mandibular molar with C-shaped canal. Endodontics & Dental Traumatology 2, 79–81 . Melton DC, Krell KV, Fuller MW. Anatomical and histological features of C-shaped canals in mandibular second molars. J Endod . 1991;17(8):384-88. Fan B, Cheung GS, Fan M, Gutmann JL, Bian Z. C-shaped canal system in mandibular second molars: Part I–Anatomical features. J Endod . 2004;30:899- 903. 107

108. Walid N. The use of two pluggers for the obturation of an uncommon C-shaped canal. J Endod . 2000;26:422-24 . Buchanan LS (1994) The continuous wave of condensation technique : a convergence of conceptual and procedural advances in obturation . Dentistry Today 13, 80–5. 108

109. Kato A, Ziegler A, Higuchi N, et al. Aetiology , incidence and morphology of the Cshaped root canal system and its impact on clinical endodontics . Int Endod J2014;47:1012–33 . Singla M, Aggarwal V (2010) C-shaped palatal canal in maxillary second molar mimicking two palatal canals diagnosed with the aid of spiral computerized tomography. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology,and Endodontology 109, e92–5. 109

110. C-shaped canal configuration : a review, merina fernandez et al Journal of Conservative Dentistry,Jul -Aug 2014 , Vol 17, Issue 4. Worldwide Prevalence of Mandibular Second Molar C-Shaped Morphologies Evaluated by Cone-Beam Computed Tomography, J.kottoor et al JOE — Volume 43, Number 9, September 2017 110

111. Evaluation of several instrumentation techniques and irrigation methods on the percentage of untouched canal wall and accumulated dentine debris in C-shaped canal, Y zhao et al, IEJ 52,1354-1365, 2019. Cohens , Pathways of pulp 10 TH ED. 111