Root canal anatomy for anterior teeth

seminar on root canal anatomy for anterior teeth

1. Tooth and Canal Anatomy, Access Cavity for Anterior Teeth Ibrahim Bayram

2. Root canal anatomy The knowledge of common root canal morphology and its frequent variations is a basic requirement for success during root canal procedures. Tapering canal and a single foramen is the exception not the rule. The outline of this system generally corresponds to the external contour of the tooth, however factors such as physiologic aging, pathosis, trauma and occlusion all can modify its dimensions through the production of dentin or reparative dentin. The root canal system is divided into two portions: Pulp chamber. Root canal(s).

3. Terminology: Root canal system: It is the space within the tooth that contains pulp tissue, the root canal system is divided into two portions: -The pulp chamber, which is located in the anatomic crown of the tooth. -The root canal(s): encased in the root(s). Root canal orifice: It is the opening of the canal system at the base of the chamber where the root canal begins. Generally, it is located at or just apical to the cervical line. Root canal configuration: It is the course of the root canal system that begins at the orifice and ends at the canal terminus (minor apical diameter). Major apical foramen: It is the exit of the root canal onto the external root surface  through which the nerve and blood vessels that supply the dental pulp pass, which is normally located within 3 mm of the root apex.

4. Terminology: Minor apical foramen/apical constriction: It is the apical part of the root canal with the narrowest diameter which is generally 0.5–1.5 mm from the major apical foramen (Vertucci 2005). It is the reference point often used as the apical termination of canal instrumentation and filling procedures. Accessory canal: Any branch of the main pulp canal or chamber that communicates with the external surface of the root (e.g. Lateral canal, Furcation canal). Apical delta: A pulp canal morphology in which the main canal divides into multiple accessory canals at or near the apex. Pulp horn: Extension of pulp tissue into occlusal or incisal projections following the cusp tips or developmental lobes.

5. General Root Canal Morphology The root canal begins as a funnel-shaped canal orifice, generally at or just apical to the cervical line, and ends at the apical foramen, which opens onto the root surface at or within 3 mm of the center of the root apex. Nearly all root canals are curved, particularly in a facio-lingual direction. In most cases, the number of root canals corresponds to the number of roots; however, an oval root may have more than one 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. They are formed by the entrapment of periodontal vessels in Hertwig’s epithelial root sheath during calcification. 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 (Vertucci, 1984). 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. Accessory canals that are present in the bifurcation or trifurcation of multi-rooted teeth are referred to as furcation canals.

7. Accessory Canals Of the 1,140 teeth studied, 313 teeth (27.4%) demonstrated lateral, secondary, and accessory canals. These root canal ramifications were located most frequently in the apical area (17.0%), less frequently in the body of the root (8.8%), and least frequently in the base of the root (1.6%) (De Deus, 1975). The premolars and molars showed the greatest variety of ramifications (De Deus, 1975).

8. Determining Pulp Space Several methods have been described, Multiple pretreatment radiographs. CBCT. Examination of pulp chamber floor with a sharp explorer. Visual assessment of color changes in the dentin. Troughing of anatomical grooves with ultrasonic tips. Staining the pulp chamber floor with 1% methylene blue dye. Performing a sodium hypochlorite “champagne bubble” test. Root canal bleeding points. Visualizing the pulp chamber anatomy from established documents

9. Performing a sodium hypochlorite “champagne bubble” test. Allowing sodium hypochlorite (NaOCl) to remain in the pulp chamber may help locate a calcified root canal orifice. Tiny bubbles may appear in the solution, indicating the position of the orifice. This is best observed through magnification.

10. Tips to consider for better visualization Clean and dry pulp chamber with 17% EDTA + 95% Ethanol. Sequential application of 17% aqueous (EDTA) and 95% ethanol has been recommended for effective cleaning and drying of the pulp chamber floor before visual inspection. Use dental operating microscope. Provide superior magnification, increased lighting and enhanced visibility.

11. Classification of root canal systems Methods used to define and describe the root canal space: Using sectioning and radiographic methods. Staining the pulp cavities with dyes. Using micro-CT technology (3D).

12. Weine’s classification In 1969, Weine provided the first clinical classification of more than one canal system in a single root and used the “MB” root of the maxillary first molar as the type specimen. Weine categorized the root canal systems in any root into three basic types (I,II and III) using sectioning and radiographic methods , in 1982 he added another type (IV).

13. Vertucci’s classification Vertucci further developed a system for canal anatomy classification, by staining the pulp cavities eight pulp space configurations were identified: 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). 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).

14. Vertucci’s classification

15. Further classifications Additional canal types not included in Vertucci’s original classification system have been reported by Gulabivala et al on a Burmese population.

16. Further classifications In 2016, a new system for classifying root and root canal morphology was developed by (H. M. A. Ahmed, M. A. Versiani, G. De-Deus & P. M. H. Dummer) to provide a simple, accurate and practical system that allows students, dental practitioners and researchers to classify roots and root canals configurations. -It provides detailed information on: Tooth number Number of roots Root canal configurations

17. Examples

18. Ethnic and racial variation of the pulp anatomy Both sex and ethnicity plays a important role in the morphological determination of the canal system. From the consistency of certain anatomical features in tooth type as well as different races, it is apparent that such features are genetically determined (Tratman 1938, 1950, Sperber 1967, Somogyi-Csizmazia & Simons 1971, Sperber 1990). Higher incidence of single-rooted and C-shaped mandibular second molars in Native American and Asians populations. (Fan B, Cheung GSP, Fan M, et al). In those with Mongoloid traits, such as Chinese, Eskimo and American Indian populations, three-rooted mandibular molars occurs with a frequency of 5% to more than 40%. (Gulabivala 2001)

19. Clinical Determination of the Root Canal Configuration Coronal Considerations: If one canal is present it usually in the center, however, if it is shifted another canal probably exists. If only one orifice is found and it is not in the center of the root, another orifice probably exists, and the clinician should search for it on the opposite side. As the distance between orifices in a root increases, the greater is the chance the canals will remain separate. Less degree of canal curvature, if there are more separation between orifices. If two canals are present, they will be smaller than one single canal.

20. Clinical Determination of the Root Canal Configuration Mid-root Considerations: Many changes can occur in this region especially (isthmus). The labiolingual diameter in all maxillary anterior teeth is approximately 50 μm more than the MD diameter. The splitting of a single root canal into two or more canals along with a wide variation in canal morphology. Isthmus (anastomosis): A thin communication between two or more canals in the same root or between vascular elements in tissues, it may contain pulp or pulpally derived tissue.

21. Isthmus classifications described by Kim and colleagues: Type I: Faint communication between two canals (Incomplete isthmus). Type II: Two canals with a definite connection between them (complete isthmus). Type III: Very short, complete isthmus between two canals. Type IV: Complete or incomplete isthmus between three or more canals. Type V: Two or three canal openings without visible connections. Isthmuses are found in 15% of anterior teeth

22. Clinical Determination of the Root Canal Configuration Apical Considerations: From apical constriction (minor apical diameter), the canal widens as it approaches the apical foramen (major apical diameter) and the mean distance between them is between 0.5 and 0.67 mm. (Kuttler 1955) Apical constriction: generally is considered the part of the root canal with the smallest diameter. It’s the reference point clinicians use most often as the apical termination for enlarging, shaping cleaning, disinfecting and filling.

23. Dummer at al. 1984, examined 270 extracted human teeth .

24. Topography of the apical constriction by Dummer et al. 1984 Type A: Traditional single constriction. Type B: Tapering constriction with the narrowest portion of the canal very near the actual apex. Type C: Number of constrictions were Present. Type D: The constriction was followed by a narrow, parallel portion of canal. A fifth type was also seen where the canal had been completely blocked with secondary dentine or cementum.

25. Clinical Determination of the Root Canal Configuration Apical Considerations: In maxillary anterior teeth, the root apex and main AF coincided in 17% of examined central incisors and canines and in 7% of lateral incisors. (Mizutani et al. 1992) Both the root apex and the AF of the central incisors and canines were displaced distolabially, whereas those of the lateral incisors were displaced distolingually. The apical foramen does not normally exit at the anatomic apex, but rather is offset 0.5 to 3 mm.

26. OBJECTIVES AND GUIDELINES FOR ACCESS CAVITY PREPARATION Remove all caries when present. Conserve sound tooth structure. Deroof the pulp chamber completely. Remove all coronal pulp tissue (vital or necrotic). Locate all root canal orifices. Achieve straight line access to the apical foramen or to the initial curvature of the canal. If done properly, a thorough assessment of the restorative needs of every tooth can be made

27. KEY STEPS TO CONSIDER IN ACCESS PREPARATION Understanding The Internal Anatomy: By evaluating an angled periapical radiographs and examining the tooth anatomy at the coronal, cervical, and root levels this might be aided by palpation along the attached gingiva. Evaluating CEJ and Occlusal Anatomy Centrality: The floor of the pulp chamber is always located in the center of the tooth at the level of CEJ. Concentricity: The walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ. 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 it the most consistent repeatable landmark for locating the position of the pulp chamber. Symmetry Color change: The pulp chamber is darker in color than the walls. Orifice location: The orifices of the root canals are always located at the junction of the walls and the floor, angles in the floor-wall junction and at the terminus of the roots developmental fusion lines. Krasner and Rankow

28. KEY STEPS TO CONSIDER IN ACCESS PREPARATION C. Access Cavity through the Lingual or Occlusal Surfaces Access cavities on anterior teeth usually are prepared through the lingual tooth surface, and those on posterior teeth are prepared through the occlusal surface. These approaches are the best for achieving straight-line access while reducing esthetic and restorative concerns. For inclined, rotated or crowned teeth the access should be determined by visualization and could be performed before the dental dam is placed.

29. KEY STEPS TO CONSIDER IN ACCESS PREPARATION Some authors have recommended that the traditional anterior access for mandibular incisors be moved from the lingual surface to the incisal surface in selected cases; this allows better access to the lingual canal and improves canal debridement.

30. KEY STEPS TO CONSIDER IN ACCESS PREPARATION D. Removal of All Defective Restorations and Caries To detect caries or fractures. Determine the restorability of the tooth. Preventing restorative debris to be pushed into the canal system. E. Removal of Unsupported Tooth Structure Unsupported tooth structure should be removed to prevent tooth fracture during or between procedures. F. Preparation of Straight Line Access Cavity

31. KEY STEPS TO CONSIDER IN ACCESS PREPARATION G. Inspection of the Pulp Chamber Walls and Floor Using magnification and illumination tools H. Tapering of Cavity Walls and Evaluation of Space Adequacy for a Coronal Seal

32. Access Cavity Preparation for Anterior Teeth In anterior teeth the starting location for the access cavity is the center of the anatomic crown on the lingual surface (X) X Preliminary outline form for anterior teeth. The shape should mimic the expected final outline form, and the size should be half to three fourths the size of the final outline form. External Outline Form

33. Access Cavity Preparation for Anterior Teeth The angle of penetration for the preliminary outline form is perpendicular to the lingual surface. The angle of penetration for initial entry into the pulp chamber is nearly parallel to the long axis of the root. Penetration of the Pulp Chamber Roof

34. Access Cavity Preparation for Anterior Teeth Completion of removal of the pulp chamber roof; a round carbide bur is used to engage the pulp horn, cutting on a lingual withdrawal stroke. Removal of the Chamber Roof

35. Access Cavity Preparation for Anterior Teeth Once the orifice or orifices have been identified and confirmed, the lingual shoulder or ledge is removed. Shelf of dentin that extends from the cingulum to a point approximately 2 mm apical to the orifice. Improve straight-line access Allows for more intimate contact of files with the canal’s walls for effective shaping and cleaning Expose an extra canal (Mandibular Anterior teeth) Removal of the Lingual Shoulder

36. Access Cavity Preparation for Anterior Teeth Enhance straight-line access Could be achieved by: NiTi orifice openers Safety-tip diamond or carbide bur Gates-Glidden Coronal Flaring of the Orifice

37. Access Cavity Preparation for Anterior Teeth Small intra-canal file can reach the apical foramen or the first point of canal curvature with no deflections. Without straight-line access, procedural errors may occur. If the lingual shoulder has been removed properly and a file still binds on the incisal edge, the access cavity should be extended further incisally until the file is not deflected. The final position of the incisal wall of the access cavity is determined by two factors: Complete removal of the pulp horns Straight-line access Straight-Line Access Determination

38. Access Cavity Preparation for Anterior Teeth Rough or irregular margins can contribute to coronal leakage through a permanent or temporary restoration. Proper restorative margins are important because anterior teeth may not require a crown as the final restoration. For maxillary anterior teeth, final composite resin restoration will be placed on a functional tooth surface. The incisal edges of the mandibular anterior teeth slide over these maxillary lingual surfaces during excursive jaw movements. Therefore, the restorative margins of an access cavity in maxillary anterior teeth should be created to allow a bulk of restorative material at the margin. Butt joint margins are indicated, rather than beveled margins, which produce thin composite edges that can fracture under functional loads and ultimately result in coronal leakage, this will be less critical if a crown is planned as the final restoration. Visual Inspection of the Access Cavity Refinement and Smoothing of Restorative Margins

39. Maxillary Central Incisor The root canal system outline of the maxillary central incisor reflects the external surface outline. Access: Rounded triangle with its base toward the incisal aspect. Variation: The outline form of the access cavity changes to a more oval shape as the tooth matures and the pulp horns recede because the mesial and distal pulp horns are less prominent . Majority of anatomical studies found that the maxillary central incisor is a single-rooted tooth . Has two or no pulp horns . Wider MD than LL . Lingual shoulder usually is present and should be removed to gain access to the lingual wall of the root canal. 100% one canal (Vertucci 1984 - United States)(Pineda and Kuttler 1972 – Mexico) etc. Possibility of a second canal have been documented by some case reports but it is rare . Four canals (Case report: Mangani and Ruddle 1994– United States). Average length of 22.5 mm.

40. Maxillary Central Incisor

41. Maxillary Lateral Incisor Outline similar to central incisor however it is smaller. Access: Rounded triangle or an oval depending on the prominence of the mesial and distal pulp horns. Majority of anatomical studies found that the maxillary central incisor is a single-rooted tooth , however there are a few reported cases of two roots associated with normal crown dimensions (no fusion, germination etc.) Two or no pulp horns . Wider MD than LL . Lingual shoulder is present. 100% one canal (Vertucci 1984 – United States)(Pineda and Kuttler 1972 – Mexico) etc. Possibility of a second canal have been documented by some case reports but it is rare , though it was reported to be as 4.9% in a study by (Calişkan et al. 1995 – Turkey). Three canals (Case report: Walvekar and Behbehani 1997 – Kuwait). Average length of 22.0 mm .

42. Maxillary Canine The root canal system of the maxillary canine is similar in many ways to that of the maxillary incisors. Access: oval or slot . Wider LL than MD . No pulp horns . The pulp chamber outline at the CEJ is oval . Lingual shoulder is present. Majority of anatomical studies found that the maxillary canine is a single-rooted tooth , however there are a few reported cases of two roots. 100% one canal (Vertucci 1984 – United States)(Pineda and Kuttler 1972 – Mexico) etc. Second canal has been reported by some studies 2.2% (Calişkan et al. 1995 – Turkey). Average length of 26.5 mm( longest root in the dentition).

43. Variations and Anomalies Developmental groove: The maxillary lateral incisor often has anomalies, one such variation in form is the presence of a palatal radicular or developmental groove. Although this groove may be present on the roots of all anterior teeth, it is more common in the maxillary lateral incisor. There is generally direct communication between the groove and the pulp cavity, and this occurs primarily through dentinal tubules. The incidence of radicular grooves was found to be 0.9% in the maxillary central incisors and 3.0% in the maxillary lateral incisors. This feature is common in Asian populations and rare in Caucasian populations Pecora and Cruz Filho 1992

44. Variations and Anomalies Dens invaginatus: More common in maxillary lateral incisor. Three types based on severity: Type 1: Invagination that is confined to the crown. Type 2: Invagination that extends past the CEJ but does not involve the periradicular tissues. Type 3: Invagination that extends beyond the CEJ and can have a second apical foramen. Root canal procedures (surgical or non-surgical) are necessary to properly manage this condition Oehlers 1957

45. Mandibular Central and Lateral Incisors Access: Rounded triangle or an oval depending on the prominence of the mesial and distal pulp horns. At the CEJ the pulp outline is oval and wider LL than MD . Removal of the lingual shoulder is critical to expose the possible second canal. Majority of anatomical studies found that the mandibular incisors are single-rooted teeth . 97.9% one canal , 2.1% two canals (Vertucci 1984 – United States) It was found that 41.4% has two clinically separate canals. Only 1.3% has two separate canals with two separate apical foramina (Benjamin & Dowson, 1974) One study determined that a relationship existed between crown size and the incidence of bifid root canals in these teeth. Double root canals occur more often in teeth with a smaller index. (Warren EM et al. 1981) Average length of 20.7 mm. Single canal Two canals Single apical foramen Three or more canals Mandibular CI 73.6% 26% 96.4% 0.4% Mandibular LI 71.8% 28.1% 97.4% 0.1%

46. Mandibular Central and Lateral Incisors Canal divide in the middle third, but these canals usually reunite below the dentine partition in the apical third, this partitioning may be incomplete and cross channels may connect the two canals. Turner, Textbook of operative dentistry by various authors 1911

47. Mandibular Canine The root canal system of the mandibular canine is very similar to that of the maxillary canine, except that the dimensions are smaller, the root and root canal outlines are narrower in the MD dimension, and the mandibular canine occasionally has two roots and two root canals located labially and lingually. Access: Oval or slot shaped. Wider LL than MD . Removal of the lingual shoulder is critical to expose the possible second canal. Most common form of the mandibular canine is one with a single root 94.8 while two-rooted mandibular canine was reported as 5.2%.(Alexandersen V 1963)(Pecora JD et al. 1993) 94% one canal , 6% two canals (Vertucci 1984 – United States) Average length of 25.6 mm.

48. Mandibular Canine

49. Summary of Classification and Percentage of Root Canals in the Maxillary and Mandibular Anterior Teeth

50. Ultrasonic Unit and Tips Used to trough and deepen developmental grooves, remove tissue, and explore for canals. Provide outstanding visibility compared with traditional hand piece heads, which typically obstruct vision. Permit careful shaving away of dentin and calcifications during exploration for canal orifices. Help in removing posts. Very effective in removal of canal obstructions: the tip placed between file and canal wall and is vibrated in counterclockwise direction.

51. Ultrasonic Unit and Tips

52. Access Cavity Preparation Demo

53. Thanks for listening Ibrahim Bayram