Root canal anatomy

Endodontic treatment
dentistry
Al- Azhar University
Gaza
Palestine
Lama El Banna

1. Root Canal Anatomy Al- Azhar University –Gaza Faculty of Dentistry Department of Endodontics

2. Contents

3. Components of Root Canal System The entire space in the dentin where the pulp is housed is called the root canal system The root canal system is divided into two portions: the pulp chamber , located in the anatomic crown of the tooth, and the pulp or root canal(s), found in the anatomic root

4. APICAL DELTA

5. Accessory root canal

6. Accessory Canals Accessory canals are minute canals that extend in a horizontal , vertical, or lateral direction from the pulp space to the periodontium . In 74% of cases they are found in the apical third of the root, in 11% in the middle third, and in 15% in the cervical third. Accessory canals contain connective tissue and vessels but do not supply the pulp with sufficient circulation to form a collateral source of blood flow. They are formed by the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during calcification.

7. They may play a significant role in the communication of disease processes, serving as avenues for the passage of irritants, primarily from the pulp to the periodontium , although communication of inflammatory processes may occur from either tissue.

8. Root Canal Anatomy Consequently, complex anatomy must be considered the norm.

9. Classification of Root Canal System Type I: A single canal extends from the pulp chamber to the apex (1). Type II: Two separate canals leave the pulp chamber and join short of the apex to form one canal (2-1). Type III: One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal (1-2-1). Type IV: Two separate, distinct canals extend from the pulp chamber to the apex (2). Type V: One canal leaves the pulp chamber and divides short of the apex into two separate, distinct canals with separate apical foramina (1-2 ).

10. Type VI: Two separate canals leave the pulp chamber, merge in the body of the root, and separate short of the apex to exit as two distinct canals (2-1-2). Type VII: One canal leaves the pulp chamber, divides and then rejoins in the body of the root, and finally separates into two distinct canals short of the apex (1-2-1-2). Type VIII: Three separate, distinct canals extend from the pulp chamber to the apex (3).

11. Clinical Determination of the Root Canal Configuration Coronal Considerations

12. It is important to note that if only one canal is present, it usually is located in the center of the access preparation . The relationship of the two orifices to each other is also significant ,The closer they are, the greater the chance the two canals join at some point in the body of the root . The direction a file takes when introduced into an orifice is also important. If the first file inserted into the distal canal of a mandibular molar points either in a buccal or lingual direction , a second canal is present

13. Mid Root Considerations

14. As the canal leaves the coronal portion of the root and blends into the midroot portion, many changes can occur, including fins , webs, culs -de-sac, and isthmuses (also called anastomoses ). These structures are narrow, ribbon-shaped communications between two root canals that contain pulp or pulpally derived tissue, or they may represent a communication between two canals that split in the midroot portion of the canal. These structures contain variable amounts of tissue, and when the pulp is infected, they often contain bacteria and their byproducts.

15. Whenever a root contains two canals that join to form one , the lingual/palatal canal generally is the one with direct access to the apex, although this may require radiographic verification. When one canal separates into two, the division is buccal and palatal/lingual, and the lingual canal generally splits from the main canal at a sharp angle, sometimes nearly a right angle

16. Apical Considerations

17. The classic concept of apical root anatomy is based on three anatomic and histologic landmarks in the apical region of a root : the apical constriction (AC), the cementodentinal junction (CDJ), and the apical foramen (AF)

18. The AC generally is considered the part of the root canal with the smallest diameter ; it also is the reference point clinicians use most often as the apical termination for enlarging, shaping, cleaning, disinfecting , and filling.

19. The CDJ is the point in the canal where cementum meets dentin ; it is also the point where pulp tissue ends and periodontal tissues begin . The location of the CDJ in the root canal varies considerably . It generally is not in the same area as the AC, and estimates place it approximately 1 mm from the AF.

20. The AF is the “circumference or rounded edge, like a funnel or crater, that differentiates the termination of the cemental canal from the exterior surface of the root.

21. OBJECTIVES AND GUIDELINES FOR ACCESS CAVITY PREPARATION Objectives

22. (1) remove all caries when present. (2) conserve sound tooth structure, ( 3) unroof the pulp chamber completely. (4 ) remove all coronal pulp tissue (vital or necrotic ). ( 5) locate all root canal orifices, (6) achieve straight- or direct- line ccess to the apical foramen or to the initial curvature of the canal .

23. Visualization of the Likely Internal Anatomy

24. This visualization requires evaluation of angled periapical radiographs and examination of the tooth anatomy at the coronal, cervical, and root levels . Although only two-dimensional, diagnostic radiographs help the clinician estimate the position of the pulp chamber , the degree of chamber calcification, the number of roots and canals , and the approximate canal length.

25. Evaluation of the Cementoenamel Junction and Occlusal Tooth Anatomy

26. Centrality: The floor of the pulp chamber is always located in the center of the tooth at the level of the CEJ. Concentricity : The walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ; that is, the external root surface anatomy reflects the internal pulp chamber anatomy

27. Location of the CEJ: The distance from the external surface of the clinical crown to the wall of the pulp chamber is the same throughout the circumference of the tooth at the level of the CEJ, making the CEJ the most consistent repeatable landmark for locating the position of the pulp chamber .

28. Symmetry: Except for the maxillary molars, canal orifices are equidistant from a line drawn in a mesiodistal direction through the center of the pulp chamber floor. Except for the maxillary molars, canal orifices lie on a line perpendicular to a line drawn in a mesiodistal direction across the center of the pulp chamber floor. Color change: The pulp chamber floor is always darker in color than the walls .

29. Orifice location: The orifices of the root canals are always located at the junction of the walls and the floor; the orifices of the root canals are always located at the angles in the floor-wall junction; and the orifices of the root canals are always located at the terminus of the roots’ developmental fusion lines.

30. Preparation of the Access Cavity Through the Lingual and Occlusal Surfaces

31. `

32. Removal of All Defective Restorations and Caries before Entry Into the Pulp Chamber

33. Removal of Unsupported Tooth Structure

34. Removal of Unsupported Tooth Structure

35. Preparation of Access Cavity Walls that Do Not Restrict Straight- or Direct-Line Passage of Instruments to the Apical Foramen or Initial Canal Curvature

36. Inspection of the Pulp Chamber Walls and Floor

37. Tapering of Cavity Walls and Evaluation of Space Adequacy for a Coronal Seal

38. BURS

39. Endodontic Explorer

40. Access Cavity Preparation

41. Anterior Teeth Maxillary Central Incisor

42. Clinical Considerations A pulp horn can be exposed following a relatively small fracture of an incisal corner in the young patient. Placing the access cavity too far palatally makes straight line access difficult. In order to clean a ribbon shaped canal effectively, the operator relies on the effectiveness of irrigant solutions.

43. Maxillary Lateral Incisor

44. Clinical Considerations Cervical constriction may need to be removed during coronal preparation to produce a smooth progression from pulp chamber to root canal. Since palatal curvature of apical region is rarely seen radiographically , during cleaning and shaping ledge formation may occur at this curve. This may result in root canal filling short of apex and other problems. Apical curvature can also complicate surgical procedures like root end cavity preparation and root resection.

45. Maxillary Canine

46. Clinical Considerations Cervical constriction needs to be shaped during coronal flaring to produce uniformly tapered preparation. When long, sclerosed canal is being present, care must be taken to avoid blockage of the root canal. Surgical access sometimes becomes difficult because of their long length.

47. Posterior teeth Maxillary first premolar

48. Clinical Considerations To locate both the canals properly, a good quality of radiograph should be taken from an angle so as to avoid superimposition of canals. Avoid over flaring of the coronal part of the buccal root to avoid perforation of palatal groove present on it. Surgical procedures on first premolar should be given more consideration since palatal root may be difficult to reach. In maxillary first premolar, failure to observe the distal—axial inclination of the tooth may lead to perforation.

49. Maxillary second premolar

50. Clinical Considerations Narrow ribbon like canal is often difficult to clean and obturate effectively Care should be taken to explore, clean and obturate the second canal of maxillary second premolar (40% of the cases ).

51. Maxillary First Molar

52. Clinical Considerations Buccal curvature of palatal canal may not be visible on radiographs , leading to procedural errors MB2 should be approached from distopalatal angle since the initial canal curvature is mesial Sometimes isthmus is present between mesiobuccal canals , it should be cleaned properly for success of the treatment

53. Mesiobuccal canals show curvature sometimes which is not visible radiographically . So, care should be taken while doing endodontic therapy Since pulp chamber lies mesial to oblique ridge, pulp cavity is cut usually mesial to oblique ridge

54. Caries, previous restorative procedures, attrition, etc. can lead to formation of secondary dentin causing alteration in pulp cavity. So careful study of preoperative radiographs is mandatory to avoid any procedural errors Perforation of a palatal root is commonly caused by assuming canal to be straight.

55. Maxillary Second Molar

56. Clinical Considerations Similar to maxillary first molar.

57. Mandibular Teeth Central Incisor

58. Clinical Considerations If root canals are over prepared , because of presence of groove along the length of root and narrow canals , weakening of the tooth structure or chances of strip perforations are increased It is common to miss presence of two canals on preoperative radiograph if they are superimposed Since apex of mandibular central incisor is inclined lingually , the surgical access may become difficult to achieve.

59. Mandibular Lateral Incisor

60. Clinical Consideration They are similar to central incisor .

61. Mandibular Canine

62. Clinical Consideration In older patients, where there is deposition of secondary dentine , it is necessary to incorporate the incisal edge into the access cavity for straight line access.

63. Mandibular First Premolar

64. Clinical Considerations The access cavity in these teeth should have extended on to the cusp tip, in order to gain straight line access Surgical access to the apex of the mandibular first premolar is often complicated by the proximity of the mental nerve

65. The lingual canal when present, is difficult to instrument. Access can usually be gained by running a fine instrument down the lingual wall of the main buccal canal until the orifice is located Perforation at the distogingival is caused by failure to recognize the distal tilt of premolar

66. Apical perforation should be avoided by taking care of buccal curvature of the canal at the apex.

67. Mandibular Second Premolar

68. Clinical Consideration They are similar to mandibular first premolar.

69. Mandibular First Molar

70. Clinical Considerations Over-enlargement of mesial canals should be avoided to prevent procedural errors To avoid superimposition of the mesial canals, radiograph should be taken at an angle.

71. Mandibular Second Molar

72. Clinical Considerations C-shaped canals make the endodontic procedures difficult so care should be taken while treating them There may be only one mesial canal. The mesial and distal canals may lie in midline of the tooth Perforation can occur at mesial cervical region if one fails to recognize the mesially tipped molar.

73. Melton’s classification of C-shaped Canals

74. Thank You