Molars

access and internal anatomy of molars

1. POSTERIOR TEETH MORPHOLOGY OF AND ACCESS CAVITY PREPARATIONS

2. The major objectives of the access openings include : 1. locating all canals 2. unimpeded straight-line access of the instruments in the canals to the apical one third or first curve 3. removal of the chamber roof and all coronal pulp tissue 4. conservation of tooth structure. ACCESS OPENINGS 2

3. 1. Outline form: is the recommended shape for access of a normal tooth. The outline form is a projection of the internal tooth anatomy onto the external root structure. 2. Convenience form: allows modification of the ideal outline form to facilitate unstrained instrument placement and manipulation. General Principles 3

4. 3. Caries removal : essential for several reasons --> 1st : permits an aseptic environment before entering the pulp chamber and radicular space. 2nd : allows assessment of restorability. 3rd : provides sound tooth structure for adequate provisional restoration. 4. Toilet of the cavity : involves preventing materials and objects from entering the chamber and canal space. 4

5. Canal Morphologies Round Ribbon-shaped (hourglass) 5

6. Ovoid Bowling pin 6

7. Kidney bean–shaped C-shaped 7

8. In difficult cases the access can be prepared without the rubber dam in place. Care must be taken to prevent tooth structure or restorative materials from entering the radicular portion. Before beginning the access the preoperative radiographs should be assessed to determine the degree of case difficulty. General Considerations 8

9. Access openings are best accomplished using a fissure bur in high-speed hand piece. 9 No single bur type is superior. High-speed burs are not used in the canals.

10. 10 ( Left to right ) : No. 4 round carbide, No. 557 carbide, Great White, Beaver bur, Transmetal , Multipurpose bur, Endo Z bur, and Endo Access bur.

11. A sharp endodontic explorer can be used for detection of the canal orifice or to aggressively dislodge calcifications. When a canal is located, a small file (.06, .08, or .10 stainless steel file) is used in the presence of irrigant or lubricant. 11

12. Crowns and fixed partial dentures, may have changed the coronal landmarks used in canal location. Class V restorations may have induced coronal calcification. It’s best to remove restorative materials that interfere with visualization before initiating root canal treatment. 12

13. The initial outline and penetration through all-ceramic crowns are made with a round diamond bur in the high-speed hand piece with water coolant. After penetration into dentin, a fissure bur can be used. 13

14. In teeth with porcelain fused to metal restorations, a metal cutting bur is recommended. Access should remain in metal to reduce the potential for fracture in the porcelain. 14

15. The maxillary 1st and 2nd molars have similar access outline forms. 15 Maxillary Molars MB1 DB L MB2 B L M D

16. The initial movement of the MB2 canal from the chamber is often not toward the apex but laterally toward the mesial. 16

17. Maxillary 1 st Molar : Erupt: 6-7 Y, calcfic .: 9-10 Y Largest tooth volume & most complex pulp anatomy Chamber wide BL Chamber cervical outline  rhomboid P orifice  centered palatally Line connecting 3 main orifices  Molar Triangle 17

18. P root  longest, easiest access  1, 2 or 3 canals  curves B at apical 1/3  type I (100%) DB root  conical  1 or 2 canals  canal oval then rounded  type I (100%) MB root  1 (oval), 2 or 3 canals ( circular )  conconavity on D wall .. Thin wall  type I (45%), type II (37%), type IV (18%) 18

19. Maxillary 2 nd Molar : Erupt: 11-13 Y, calcfic .: 14-16 Y 3 roots are grouped closer & sometimes fused. shorter than roots of 1st molar and not as curved. usually has one canal in each root 4 canals are less likely to be present floor of pulp chamber is convex, which gives the canal orifices a slight funnel shape. When two roots are present, each root may have 1 canal, or B root may have 2 canals that join before reaching a single foramen.. 2 P roots & 2 P canals occur in 1.47% of these teeth. 19

20. MB canal orifice is located more to B & M than in 1st molar; ** type I (71%), type II (17%), type IV (12%) DB orifice approaches midpoint between MB & P orifices; ** type I (100%) P orifice usually is located at most palatal aspect of root. ** type I (100%) ** canal orifices in maxillary 2nd molar are closer mesially 20

21. Maxillary 3 rd Molar : Erupt: 17-22 Y, calcific .: 18-25 Y root anatomy varies greatly.. can have 1-4 roots & 1-6 canals, C-shaped canals also can occur. tooth may be tipped to D, B, or both, which creates greater access problem. Because it typically has 1-3 canals,, the access preparation can be anything from an oval that is widest in BL dimension to a rounded triangle. 21

22. 22 D M 3 canals : 40% 4 canals : 60% Mesial Midroot Distal Single foramen : 80% two foramina : 20% Mesiobuccal 2 canals : 60% Maxillary Right First Molar :

23. 23 3 Roots: 60% 2 mesiobuccal canals : 38% Mesial Midroot Distal Single foramen : 15% 2 foramina : 10% Maxillary Right Second Molar

24. 24 2 roots: 25% L B Maxillary Right Second Molar Facial Facial Mesial Midroot Midroot L B 1 root : 10%

25. Mandibular 1st molar configuration is 2 canals in the mesial root, although 3 have been reported, & 1 canal in the distal root. 25 Mandibular Molars The presence of 2 canals in the distal root is 30% - 35%. MB DB ML D The most common configuration for the mandibular 2nd molar is 2 canals in the mesial root & 1 canal in the distal root. The incidence of 4 canals is low.

26. Mandibular 1 st Molar : erupt: 6 Y, calcific .: 9-10 Y most often requires an endodontic procedure It often is extensively restored, & is subjected to heavy occlusal stress.. Pulp chamber frequently is calcified. 2-3 canals in M root ( MB & ML ) & 1, 2 or 3 canals in D root ( DB, DL, MD ). middle mesial (MM) canal sometimes is present in develpmental groove between other M canals, but it may only represent a wide anastomosis between 2 M canals. ( incidence: 1% - 15%) 26

27. Orifices to all canals are located in M 2/3 of the crown chamber floor is roughly trapezoid or rhomboid. M root, the wider.. canals usually are curved, with the greatest curvature in MB canal presence of 2 separate D roots is rare, but if, DL root is smaller than DB root & usually more curved. If 2 canals (DB & DL) are present in D root, they are more round than oval for their entire length. Multiple accessory foramina may be located in furcation of the mandibular molars. 27

28. access cavity typically is trapezoid or rhomboid 28

29. 2/3 of 1st mandibular molars found in a Chinese population had an extra DL root of a type 1 canal configuration.. occurred in 4% of a Kuwaiti population. M  type I (12%), type II (28%), type IV (43%), type V (8%), type VI (10%), type VIII (1%) D  type I (70%), type II (15%), type IV (5%), type V (8%), type VI (2%) 29

30. Mandibular 2 nd Molar : Erupt: 11-13 Y, calcific .: 14-15 Y identified by the proximity of its roots, the two roots often sweep distally in a gradual curve. pulp chamber and canal orifices not as large as 1st molar M  type I (27%), type II (38%), type IV (26%), type V (9%) D  type I (92%), type II ( 3%),type IV (4%), type V (1%) 30

31. In mandibular 2nd molars with single or fused roots, a file placed in the MB canal may appear to be in D canal. This happens because 2 canals sometimes are connected by a semicircular slit, a variation of the C-shaped canal. 31

32. When 3 canals are present, the access cavity is similar to mandibular 1st molar. The access cavity for a 2 canal 2nd molar is rectangular, wide MD and narrow BL. The access cavity for a single-canal mandibular 2nd molar is oval. 32

33. Mandibular 3 rd Molar : Erupt: 17-21 Y, calcific .: 18-25 Y Fused short, severely curved, or malformed roots may have 1-4 roots & 1-6 canals C-shaped canals also can occur When 3 or more canals are present, a rounded triangle or rhomboid shaped access is typical. When2 canals are present, a rectangular shape is used. For single-canal molars, an oval shape is customary 33

34. 34 Mandibular Right First Molar M D Mesial 60% B Midroot Distal 70% 40% 20% 10% B L

35. 35 Mandibular Right Second Molar M D Mesial 40% B L Distal 92% 5% 35% 25% 3%

36. 36 Mandibular Right Second Molar M D B L C- shaped canal B L Midroot variations

37. 1. Inadequate Preparation : Direct effects are  Decreased access and visibility preventing locating of canals. The ability to remove coronal pulp tissue & obturation materials is limited Straight-line access can’t be achieved. 37 ERRORS IN ACCESS Indirectly leads to errors during the cleaning & shaping.

38. 2. Excessive Removal of Tooth Structure : Has direct consequences and is irreversible and can’t be corrected. A minimum consequence is weakening the tooth and subsequent coronal fracture. Appropriate access and strategic removal of tooth structure that doesn’t involve the marginal ridges won’t weaken the remaining coronal structure. 38

39. 39 T hank you ^_^

40. 40 A ny Questions ?

41. Endodontics - Principles & Practice - Saunders; 4 th Ed. Cohen’s Pathways of the Pulp, 11 th Ed. 41 Reference :

42. Submit to : Dr. David Done By : Ola Qatu 42