access cavity is first objective procedure done on an endodontically compromised tooth

access cavity is first objective procedure done on an endodontically compromised tooth

1. GOOD MORNING

2. CONTENTS: Introduction Objectives and guidelines Rules for access preparation Principles for endodontic access preparation Armamentarium for access cavity preparation Access cavity preparation of various teeth and errors in access preparation Conclusion References

3. Introduction: “All the treatment that follows hinges on the accuracy and correctness of the entry” Franklin S. Weine Access cavity is first objective procedure done on an endodontically compromised tooth. Endodontic treatment may be considered as a stair, each step representing a basic phase. To reach the top i.e. to effectively salvage a compromised tooth to its form and function in the masticatory apparatus, meticulous care is required to be shown at each step.

4. Case selection X-ray examination Access opening Cleaning & shaping Obturation Proper restoration

5. The main objective of this preparation is to enable direct access to the apical foramen by an endodontic instrument, not just exposing canal orifice. From earlier studies to the recent sophisticated works it is clear that multiple foramina, extra root canals, lateral and accessory canals, deltas etc are present in most teeth. This notes the need for a proper access opening even more important, since without proper access, the root canal system cannot be properly negotiated and therefore treated.

6. Accessory canals: found in apical III of the root and are branches of main root canal. End in accessory foramen. More in young age as they later get obliterated by cementum. Lateral canals: which opens approximately at right angles to the main pulp cavity are termed lateral canals and generally found in furcation area.

7. Definition of access cavity preparation: Defined as coronal opening into pulp cavity required for effective cleaning, shaping and filling of pulp space during root canal therapy. Harty Rugston dental dictionary

8. Objectives and guidelines for access cavity preparation: The objectives of access cavity preparation are To remove all caries, To conserve sound tooth structure, To completely unroof the pulp chamber, To remove all coronal pulp tissue, To locate all root canal orifices To achieve straight- or direct-line access to the apical foramen or to the initial curvature of the canal, and To establish restorative margins to minimize marginal leakage of the restored tooth.

9. Guidelines Krasner and rankow proposed nine guidelines, or laws, of pulp chamber anatomy to help clinicians determine the number and location of orifices on the chamber floor. Law of centrality: The floor of the pulp chamber is always located in the center of the tooth at the level of the CEJ. Law of 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.

10. Law of the CEJ: The CEJ is the most consistent repeatable landmark for locating the position of the pulp chamber. First law of 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. Second law of symmetry: 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.

11. Law of color change: The pulp chamber floor is always darker in color than the walls. First law of orifice location: The orifices of the root canals are always located at the junction of the walls and the floor. Second law of orifice location: The orifices of the root canals are always located at the angles in the floor-wall junction. Third law of orifice location: The orifices of the root canals are always located at the terminus of the roots developmental fusion lines. More than 95% of the teeth these investigators examined conformed to these laws. Slightly fewer than 5% of mandibular second and third molars did not conform because of the occurrence of C-shaped anatomy.

12. Rules For Proper Access Preparation To ensure the most efficient access cavity preparation, the following rules should be observed: The objective of entry is to give direct access to the apical foramina, not merely to the canal orifices. Because it is the apical foramen of each canal that must be sealed, the access cavity must allow for removal of any tooth structure that might impede the preparation and filling of that area. Direct access to apical foramen

13. Access Cavity preparations are different from typical operative occlusal preparation. The typical occlusal cavity preparations used in operative dentistry are based on the topography of occlusal grooves, pits, and fissures, and on the avoidance of underlying pulp. The access cavity preparations for endodontic therapy are designed for efficiently uncovering the roof of the pulp, chambers and providing direct access to the apical foramina by way of the pulp canals.

14. Because the two types of preparations must satisfy different criteria, it is only natural that they have differing configuration. Different from typical occlusal cavity preparation

15. The likely interior anatomy of the tooth under treatment must be determined. Before starting the access, radiographs taken from at least two different angles must be studied. Operator should have proper knowledge regarding typical length, number and configuration of roots and canals. Thus information gained before initiation of preparation will greatly facilitate the entry as well as further treatment.

16. When canals are difficult to find, the rubber dam should not be placed until correct location has been confirmed. It is often difficult to prepare access in a malposesd tooth or one that is part of a bridge or splint. The occlusal anatomy, which ordinarily gives excellent clues to the position of the underlying canals, may be considerably altered. Teeth with and / or deep restoration causing heavy dentinal sclerosis also may cause problems. Therefore, in such teeth, it is best to make the initial poison of the access preparation before the placement of the rubber dam so that the shape and inclination or the adjacent teeth, the gingival tissues, and the hard structures covering the roots help in determining the position of the canals.

17. Once the roof of the chamber is penetrated and the correct access is verified, the rubber dam may be applied. Because the canals will be enlarged considerably with heavy irrigation, the effect of any microorganism contamination before dam placement is minimal. If for some reason it is mandatory to use the rubber dam for every phase of treatment, the access cavity for complex cases should be prepared with multiple tooth rather than single tooth isolation. This will allow for visualization of adjacent teeth while the dam is in place.

18. Endodontic entries are prepared through the occlusal or lingual surface never through the proximal or gingival surface. When existing proximal or gingival opening is done from existing restoration or carious lesion, the canal –enlarging instruments must be bent at severe angles to pass through the access and still perform their function. Inadequate canal preparation and/or broken instruments may result. When proximal or gingival tooth destruction occurs, affected areas should be excavated and restored, with either a temporary seal, or a permanent filling material . Then the normal access cavity is prepared through the occlusal or lingual surface.

19. As part of the access preparation, the unsupported cusps pf posterior teeth must be reduced. Endodontic therapy requires the removal of much of the central portion of the treated tooth, greatly reducing resistance to stress. Although this problem is solved by the placement of a proper restoration after treatment, the tooth is severely weakened until that time. Therefore, as part of access preparation all unsupported cusps must be reduced by trimming with a tapered fissure carbide or diamond stone until a definite clearance in occlusal and lateral movement is obtained. This decreases the chances for cuspal fracture beneath the gingival or bony attachments, which is so difficult to repair, or vertical fracture of the root which is hopeless.

20. Principles Of Endodontic Access Preparation: Endodontic preparation deal with both coronal and radicular – each prepared separately but ultimately flowing together into a single preparation. Coronal cavity preparation principles : I. Outline form: External Outline form is established by mechanically projecting the internal anatomy of the pulp onto the external surface. This may be accomplished only by drilling into the open space of the pulp chamber and then working with the bur from the inside of the tooth to the outside, cutting away the dentin of the pulpal root and walls overhanging the floor of the chamber.

21. 3 factors of internal anatomy must be considered: Size of the pulp chamber: young patients, these preparations - more extensive than in older patients. Shape of pulp chamber: outline form - reflect the shape of the pulp chamber. E.g. coronal pulp of maxillary premolar. Number, position and curvature of root canals: To prepare each canal efficiently without interference, the cavity walls often have to be extended to allow an unstrained instrument approach to the apical foramen.

22. II. Convenience form: makes more convenient preparation and filling of the root canal. 4 important benefits are: Unobstructed access to the canal orifice: Easy access to the instrument to place in the canal orfice Search for extra canals.

23. Loebke stated that the entire wall need not be extended in the event that instrument impingement occurs owing to an extra canal. Extending only that portion of the wall needed to free the instrument, a cloverleaf appearance may evolve as the outline form termed as SHAMROCK PREPARATION. Shamrock preparation.

24. Direct access to the apical foramen: Enough tooth structure must be removed to allow the endodontic instrument freedom within the coronal cavity. so they can extend down the canal in an unstrained position. Extension to accommodate filling techniques: To make certain filling techniques more convenient . E.g. rigid vertical pluggers are used in a vertical thrust. Complete authority over the enlarging instrument: If the instrument is impinged at the canal orifice by tooth structure, the dentist will lost control of the direction of the tip of the removed instrument, and the intervening tooth structure will dictate the control of the instrument.

25. on the other hands the tooth structure is removed around the orifice so that the instrument stands free in this area of the canal, the instrument will then be controlled by the clinician fingers on the handle of the instrument.

26. III. Removal of the remaining carious dentin and defective restorations: Caries and defective restorations remaining in an endodontic cavity preparation must be removed for these reasons. To eliminate mechanically as many bacteria as possible from the interior of the tooth. To eliminate the discolored tooth structure, that may ultimately lead to staining of the crown.

27. If carious perforation of the wall is allowing salivary leakage, the area must be repaired with cement, preferably from inside the cavity.

28. IV. Toilet of the cavity All the caries, debris and necrotic material must be removed from the chamber before the radicular preparation is begun. If the debris is left in the chamber and carried into canal, it can cause obstruction. Soft debris - increases bacterial count . Done with Round burs excavation by Long blade endodontic spoon Sodium hypochlorite irrigation Chamber may be finally wiped out with cotton, and a careful flush of air will eliminate the remaining debris.

29. Radicular cavity preparation: Objectives: 2 objectives Debridement of the root canal system and the specific shaping of the root canal preparation to receive a specific type of filling. Ultimate objective, is to create an environment which produce healing of the apical periodontal attachment apparatus. Cleaning and debridement of the root canal: Skillful instrumentation + irrigation will help to eliminate most bacterial contaminants of the canal as well as the necrotic debris and dentin. Intracanal medication -  sterilization during intra appointment period.

30. Principles – Outline form and convenience form: The margins of the cavity must clear of all interference Toilet of the cavity : Irrigation is important for total debridement of the root canal system .

31. Retention form: obtained by apical third where 2-3mm of the canal walls are parallel to ensure firm seating of the primary cone or one should get a ‘tug back’ or resistance when the primary cone is inserted.

32. Resistance form: Resistance to overfilling is the primary objective of resistance form. Maintaining the integrity of the natural constriction of the apical foramen is a key to successful therapy. over instrumentation leads to complication. Acute inflammation of periradicular tissue from the injury by instrument, bacteria or canal debris forced into tissue. Chronic inflammation of this tissue caused by presence of a foreign body - filling material forced during obturation.

33. C—retention form B—resistance form

34. Armanentarium for access preparations: Should contain following things: Front surface mirror - For maximum visibility Endodontic explorer – DG-16 , DE-17 Endodontic excavator. # 17 operative explorer Handpieces Ultrasonic unit and tips

35. Burs

36. Rubber dam materials should be available i.e. sheets, punch, frame, clamp holder and clamps No. 26 and 27 - wingless clamps for molars. No. 12A and 12B - winged clamps for molars No. 209 - for bicuspids and bulky anterior teeth No. 211 or 9 - For small anterior and broken down teeth .

37. Access cavity preparation for various teeth: Because internal anatomy dictates the access shape, the first step in preparing an access is visualization of the location of the pulp spaces. Buccolingual angulations and coronal anatomy are judged visually. Cervical anatomy can be determined tactically using an explorer under the sulcus to feel the cervical shape. Palpation along the attached gingiva will help determine root location and direction. Diagnostic radiograph in one straight and one in mesial or distal angulation will help to estimate pulp chamber position, degree of calcification of pulp chamber and approximate canal length.

38. In difficult situations it is sometimes recommended that the initial access be prepared without rubber dam in place. Any restorative material impinging on straight line access should be removed before the pulp chamber is accessed to prevent the lodging of debris in the canal. Occasionally necessary to place an interim restoration, creating an efficient seal and facilitating rubber dam placement. 1-2mm of occlusal adjustment of teeth may be done to establish a more accurate point for measuring canal length and to reduce postoperative pressure sensitivity.

39. Endodontic entry – Ingle – Initial entrance through the enamel surface – Round end 702U carbide bur / endodiamond stone. With this instrument enamel perforation is easily accomplished and surface extension may be rapidly completed. Used always with coolant to reduce heat. But PFM : Tungsten carbide bur chatter severely, vibration results in patient discomfort and tends to loosen the crown from luting cement so diamond points are preferred. After preparation of enamel / restorative penetration slow speed 3000 to 8000 contrangle handpeice is used.

40. Three round burs, 2, 4 and 6 - two lengths: regular 9mm, surgical 14mm are used along long access for drop and also for removal of roof of the pulp chamber. No. 2 – Mandibular anterior, maxillary premolars No. 4 – Maxillary anterior, mandibular premolars, adult molars. No. 6 – Molars with large pulp chambers.

41. Weine - access cavity preparation is by using tapered fissure bur – tungsten carbide 701 or 558. Once entered the pulp chamber then safe tip tissue bur is used to enlarge the access. Cohen (VII Edition) - Initial round bur for entry i.e. bur drop then tapered tissue bur for preparation of side walls.

42. a) endodontic preparation for maxillary anterior teeth. Entrance is always gained through the exact center in the lingual surface of anterior teeth. Initial entrance prepared with round point tapering tissue bur with accelerated speed contrangle handpiece operated at right angle to the long axis of the tooth. Only enamel is penetrated at this time. Convenience extension towards the incisal continues the initial penetrating cavity preparation. Maintain the point of the bur in the central cavity and rotate the handpeice towards the incisal so that bur parallels the long axis of the tooth. Enamel and dentin are beveled toward the incisal.

43. Preliminary cavity outline is funneled and fanned incisally with a fissure bur. Enamel has a short bevel towards the incisal, and a ‘nest’ is prepared in the dentin to receive the round bur to be used for penetration. Surgical length No.2 or 4 round bur in a slow speed contrangle handpeice is used to penetrate the pulp chamber – bur is operated nearly parallel to the long axis of the tooth. Then round bur is used inside the chamber to outside to remove the lingual and labial walls of the pulp chamber. The resulting cavity is smooth, continuous and flowing from cavity margin to canal orifice. Then lingual shoulder is removed with round or long, tapering diamond point.

44. Occasionally No. 1 or 2 round bur must be used laterally and incisally to eliminate pulp horn debris and bacteria – preventing future discoloration. Final preparation – relates to internal anatomy of the chamber. In young tooth with large pulp – large triangular internal anatomy (Same type access which allows through cleansing as well as passage of large instrument). In adult teeth – chamber ovoid in shape due to secondary dentin deposition.

45. Further the pulp has receded; the more difficult it is to reach to this depth with a round bur. Therefore, when the radiograph reveals advanced pulpal recession, convenience extension must be advanced further incisally to allow the bur shaft and instruments to operate in central axis. Final preparation with the reamer in place. The instrument shaft clears the incisal cavity margin and reduces lingual shoulder allowing an unrestrained approach to the apical third of the canal.

46. Endodontic preparation for maxillary anterior teeth

47. Maxillary Central incisor: Pulp anatomy and coronal preparation: Pulp chamber of the maxillary central incisor is located in the center of the crown equidistant from the dentinal walls; it is broad mesiodistally, with its broadest part incisally. 3 pulp horns that correspond to the developmental mamelons in young tooth. Chamber is ovoid mesiodistal .

48. Cross section at 3 levels – Root canal is broad labiopalatally, large and simple in outline, conical in shape and centrally located. Cervical -Ovoid Mesiodistally Midroot – ovoid Apical third – round Large triangular shaped coronal preparation. Adult incisor: Pulp recession. Narrow labio-lingual width of pulp.

49. Access cavity - maxillary central incisor

50. Maxillary Lateral incisor: Pulp chamber: Shape is similar to maxillary central incisor but smaller. Only 2 pulp horns corresponding to developmental mamelons.

51. Root and root canal: configuration of root canal is conical. Cross sections: Cervical - Ovoid labiopalataly. Mid root – ovoid Apical III – round Large triangular funnel shaped coronal preparation. Adult incisor – pulp recession. narrow labiolingual width of the pulp

52. Operator should recognize: Small orifice difficult to find Axial inclination of root – A “Cork Screw” curve to the distal and lingual complicates preparation of the apical III of the canal. Apical foramen is centrally located in the anatomic apex 22% of case and apical delta 3% of cases.

53. Access cavity -- maxillary lateral incisor

54. Maxillary cuspid: Pulp chamber is largest of any single rooted teeth labiopalatally. The chamber is triangular in shape, with the apex toward the single cusp and a broad base in the cervical III of the crown. Mesiodistally it is narrow, sometimes resembling a flame. Only one pulp horn. Chamber ovoid in cross section with greatest diameter labiopalatally

55. Root : larger than maxillary incisor. Wider labiopalatally than mesiodistally. Cervical – ovoid Midroot – ovoid Apical – round Preparation – Extensive ovoid, funnel shaped coronal preparation .

56. Adult-tooth and view – Pulp recession. Narrow labiolingual width. Operator recognize – Apical labial curvature Distolingual inclination of the root for careful orientation and alignment of the bur to prevent gouging

57. Cross sections at 3 levels: Cervical – slightly ovoid Middle – canal smaller but ovoid Apical – round Preparation – Ovoid funnel shaped preparation must be nearly as large as for a young tooth. The apical foramen is centrally located in the anatomic apex in 14% of cases and apical delta present in 3% of times.

58. Access cavity -- maxillary canine

59. Maxillary anterior teeth: Errors: Perforation at the labiocervical – caused by failure to complete convenience extension toward the incisal, prior to the entrance of the shaft of the bur. Pear shaped preparation of the apical canal caused by failure to complete convenience extension. The shaft of the instrument rides on the cavity Margin and lingual shoulder. Discoloration of the crown : Failure to remove pulp debris access with no incisal extension

60. Ledge formation at apical distal curve caused by using an uncurved instrument too large for the canal. Ledge, formation at the apical labial curve caused by failure to complete the convenience extension. The shaft of the instrument rides on the cavity margin and shoulder.

61. b) Endodontic preparation of mandibular anterior teeth: Lingual surface at center Similar to upper anterior and initial entrance is by 701U tapering fissure bur. Pulp chamber penetrated by No.2 round bur surgical length inside to outside and shift of bur should be parallel to long axis of the tooth Lingual shoulder is removed with fine tapered diamond point No.1 round bur to eliminate pulp horn debris.

62. Final preparation – Young tooth - triangular In adult tooth pulp receded, less triangular.

63. Access cavity preparation for mandibular anterior teeth

64. Mandibular central and lateral incisor: Pulp anatomy and coronal preparation: Central pulp chamber, small and flat mesiodistally, 3 distinct pulp horns present in a recently erupted tooth but disappear early in life because of constant masticatory stimulus.

65. Root canal : Central incisor- Root which is flat and narrow mesiodistally but wide labiolingual. Lateral incisor- Root configuration same but larger than CI. Cross sections : cervical - ovoid Midroot – ovoid Apically - round

66. Preparation - young, large triangular, funnel shaped. Adult- ovoid funnel shaped. Reduced size of lingual shoulder and unsuspected presence of bifurcation of pulp into the labial and lingual canals nearly 30% of the time.

67. Cross sections – Cervical III- ovoid Midroot – 2 canal, round Apical - round. Important that all mandibular anterior teeth be explored to both labial and lingual for possibility of two canals

68. Mandibular Central incisor has Lateral canals - 20% Apical delta - 5% Apical foramen situated centrally in root - 25%. Mandibular Lateral incisor has Lateral canal - 18%, Apical delta - 6% Apical foramen in center of radiographic apex - 20%.

69. Access cavity for mandibular incisors

70. Mandibular cuspid: Pulp chamber resembles maxillary cuspid but smaller in dimension. Chamber is narrow mesiodistally. When viewed buccolingually, the chamber tapers to a point in the incisal third of the crown, but it is wide in the cervical area. One pulp horn Cross section of chamber is ovoid

71. Root and root canals: generally single root but may have two Cross section Cervical – ovoid Middle – ovoid Apical – round Preparation – Extensive ovoid shaped canal preparation

72. Lateral canal - 30% Apical delta - 8% Apical foramen located centrally - 30%.

73. Access cavity for mandibular canine

74. Mandibular anterior teeth - Errors in cavity preparation: Gouging at the labiocervical caused by failure to complete convenience extension toward incisal prior to entrance of the shaft of the bur Failure to explore, debride or fill the second canal. Discoloration - failure to remove pulp debris Ledge formation caused by complete loss of control of the instrument.

75. c) Endodontic preparation of Maxillary premolar teeth: Entrance always through occlusal surface of all posterior teeth. Initial preparation is made parallel to the long axis of the tooth in the exact center of the central groove. 701U tapering fissure bur in an accelerated speed contra angle hand piece

76. Regular length No.2 or No 4 round burs - used to open into pulp chamber but will be felt to drop when the pulp chamber is reached. The orifice is widened buccolingually to twice the width of the bur to allow room for exploration of canal orifices.

77. Buccolingual extension and finish of the cavity walls completed with 701 U fissure bur at high speed. Final preparation should provide unobstructed access to canal orifices. Outline form of final preparation: Buccolingual ovoid, reflecting the anatomy of the pulp chamber and position of buccal and lingual canal orifice.

78. Access cavity preparation for maxillary premolar

79. Maxillary I premolar: Pulp anatomy and canal preparation: Pulp chamber – is narrow mesiodistally 2 pulp horns under each cusp. Wide buccopalatally and buccal pulp horn more prominent than the palatal in young teeth. Cross section of pulp chamber is wide and ovoid in a buccolingual direction.

80. Root and root canal: Have 2 roots in 54.6% of cases. In 21.9% of the double rooted cases the roots are separated, when s in 32.7% the roots are partially fused.

81. When 2 root canals are present: The cervical III are ovoid mid root almost round apical III round and small

82. Adult: - Pulp recession. - Buccolingual width revealing the pulp to be “ribbon shaped” rather than “thread like” Operator recognize: - Small orifices are found well to the buccal and lingual and are difficult to locate - Virtually always there will be 2 and occasionally 3 canals.

83. Access cavity preparation for maxillary I premolar

84. Maxillary II premolar: Pulp anatomy and canal preparation: Pulp chamber – narrow mesiodistally wider buccopalatally than maxillary I premolar with 2 pulp horns. Roof of the pulp chamber is similar to I premolar. In cross section pulp chamber is narrow, ovoid-shape.

85. Root and root canals – - Have only a single root 90.3% of patients. Only 2% have 2 well developed roots where as 77% have 2 roots that are partially fused.

86. Cross section- - Cervical - very wide in B-L direction. Canal orifice is directly in the centre of the tooth. - Midroot - ovoid - Apical - round. Preparation is ovoid. Adult view: - Pulp recession thread like appearance. - B-L width revealing canal pulp - ribbon shaped.

87. Apical foramen is centrally located in 12% of the cases and an apical delta is present only in 3.2% of cases.

88. Errors in cavity preparation: Perforation – mesiocervical indentation. Failure to observe distal axial inclination and mesial groove. Broken instrument twisted off in a cross over canal. This frequent occurrence may be obviated by extending the internal preparation to straighten the canals. Failure to explore, debride and obturate 2or 3 canals.

89. Access cavity preparation for maxillary II premolar

90. d) endodontic preparation of Mandibular premolar teeth: Initial preparation is made in the exact center of the central groove with bur directed parallel to the long axis of the tooth. 701U tapered fissure in an accelerated speed is used . Final ovoid preparation is a tapered funnel from the occlusal to the canal, providing unobstructed access to the canal. Buccolingual outline form reflects the anatomy of the pulp chamber and position of the centrally located canal. Outline form of the final preparation will be identical for both newly erupted and adult teeth.

91. Access cavity preparation for mandibular premolars

92. Mandibular I premolar: Pulp anatomy and coronal preparation: Pulp chamber: pulp chamber is narrow buccolingually; the pulp chamber is wide with a prominent buccal pulp horn that extends under a well developed buccal cusp. In young tooth small lingual pulp horn that may disappear with age and give the pulp chamber an appearance smaller to that of the mandibular cuspid Cross section- chamber is ovoid with greater diameter buccolingually.

93. Roots are generally shorter than the root of the adjacent cuspid . Cross section: Cervical - pulp enormous and wide in B-L dimension- ovoid. Midroot - ovoid Apical - round Preparation - ovoid

94. Operator recognize: small orifices are difficult to locate and presence of a bifurcated canal. Lateral canals are present 64.3% of cases. Apical deltas are found 5.7%. Apical foramen is centrally located in only 15% of the teeth.

95. Access cavity preparation for mandibular I premolar

96. Mandibular II premolar: Pulp chamber: Similar to I premolar except the lingual horn is more prominent under a well developed lingual cusp.

97. Cross section: Cervical: ovoid; mid - root ovoid; apical - round. Preparation- ovoid. Adult - pulp recession and buccolingual ribbon shaped pulp Lateral canals are present 48.3% of time, Apical delta 3.4%. Apical foramen is centrally located in only 16.1% of these teeth.

98. Errors in cavity preparation: Perforation at distogingival caused by failure to recognize that premolar has a tilt towards distal. Bifurcation of a canal completely missed. Caused by failure to adequately explore the canal with curved instrument. Perforation of apical curvature caused by failure to recognize by exploration of buccal curvature.

99. Access cavity preparation for mandibular II premolar

100. E) Endodontic preparation of maxillary molar teeth: Entrance through occlusal surface. Initial penetration is made in the exact center of the mesial pit. The 701U tapering fissure bur in high speed hand piece is used. No. 4 to open into pulp chamber. The bur should be directed toward the orifice of the palatal canal or orifice where the greatest space in the chamber exists. Drop will be felt if pulp chamber is reached.

101. Bur removes enough roof of the pulp chamber for the exploration. An endodontic explorer is used to locate orifices of the palatal, MB and DB canals. Special care should be taken to explore 2 canal in MB root. Final finishing with 701U fissure or tapered diamond points at increased speed.

102. Outline form reflects anatomy of pulp chamber with base towards buccal, apex to lingual and cavity is entirely with in mesial half of the tooth and need not invade the transverse ridge but is extensive enough buccal to lingual, to allow positioning of instrument and filling material.

103. Access cavity preparation for maxillary molars

104. Maxillary I molar: Pulp chamber: Largest in dental arch with 4 pulp horns MB, DB, MP and DP. The arrangement of 4 pulp horn gives the pulpal roof a rhomboidal shape in cross section. The four walls forming the roof converge toward the floor where the lingual wall almost disappears; the floor of the pulp chamber thus has a triangular form in cross section. The orifices of the root canals are located in the 3 angles of the floor. Anatomic dark lines in the floor of pulp chamber connect the orifices.

105. Palatal orifice is largest and is round / oval in shape. MB orifice is under MB cusp, long buccopalatally and may have depression at palatal end in which the orifice of a fourth canal may be present. DB orifice : Is located slightly distal and palatal to the MB orifice.

106. MB root: Broad in B-P direction canal narrowest of 3, flattened in a M-D direction in the orifice but round in the apical III. Lateral canal 1% of cases, Apical delta  8%. Apical foramen located centrally in only 14% of cases.

107. DB root: Small and more or less round in shape, canal is narrow tapering canal ending in a small round canal in apical III. Lateral canals - 36%, Apical delta 2%. Apical foramen centrally located 19%. Palatal root: Largest diameter and largest root Canal is ovoid mesiodistally and tapers towards apex when it becomes a small, round canal.

108. Lateral canals present in 40%, Deltas - 4%, Apical foramen centrally located in only 18%. Lateral canals in trifurcation - 18% Triangular outline form with base toward the buccal and apex toward the lingual with the orifice positioned at each angle of the triangle. The cavity is entirely within the mesial half of the tooth. The orifice to an extra middle mesial canal may be found in the groove near the MB canal.

109. Adult: Pulp recession and thread like pulp. chamber constricted from secondary dentin formation. To uncover 4th canal safe tipped bur is moved form MB orifice toward the palatal canal.

110. Maxillary II molar: Pulp chamber: similar to maxillary I molar except narrower mesiodistally. Because of narrow dimension, roof of the pulp chamber is more rhomboidal in cross section. Floor of Pulp chamber is obtuse in cross section. MB and DB canals are close together and may appear to have a common opening. Sometimes all 3 canal orifice may almost be in straight line. Root and root canal: 3 roots closely grouped. Because of this close grouping, the buccal roots may fuse and occasionally all 3 roots fuse to form a single conical root - 46%. 16% of roots are foramina centrally located. 3% apical delta.

111. Outline form : triangular form is flattened. DB orifice is nearer to the center of the cavity floor. The entire preparation sharply slopes to the buccal and is extensive enough to allow positioning of instruments. Adult: pulp recessed and thread like. Ovoid outline form Two rooted maxillary molar - 10% of cases.

112. Maxillary III molar: Resemble II molar Pulp chamber: Can be similar to that of maxillary II molar with 3 canal orifices, but it may also have an odd-shaped chamber with 4 or 5 root canal orifices or a conical chamber with only one root canal. Root and root canals: Variations 3 well developed roots Fused roots One conical root 4/5 independent root. Root canals vary from 4/5 in number

113. Access opening similar to II molar: Careful examination of root morphology is recommended before initiating treatment. Radicular anatomy is completely unpredictable and is advisable to explore the root canal morphology before promising success. Errors in cavity preparation: Under extended : Only pulp horns are Nicked Over extended : Badly gouged

114. Ledge: Large straight instrument in curved canals. Perforation: palatal root as buccal curve is present in apical III.

115. F) Endodontic preparation of mandibular molar teeth: Initial preparation is made in the exact center of the mesial pit. The 701U tapering fissure bur in an accelerated speed No. 4 / No. 6 round bur to open into pulp chamber. The bur is directed towards the orifice of MB or canal, when the greatest space in the chamber exists.

116. The bur removes enough roof of the pulp chamber for exploration Endodontic explorer – to explore orifice and special care must be taken to explore for an additional canal in the distal root. The distal canal should form a triangle with 2 mesial canals. If it is asymmetric, always look for fourth canal (29% of the time).

117. Square outline form. Cavity is primarily with in the mesial root of the tooth. Further exploration should determine if a fourth canal can be found in the distal. If so the outline is extended in that direction and an orifice will be positioned at each angle of the square.

118. Access cavity preparation for mandibular molars

119. Mandibular I molar: Pulp anatomy and coronal preparation: Pulp chamber: Roof – rectangular in shape. Mesial wall straight, distal wall round and buccal and lingual walls converge to meet the mesial and distal walls and to form a rhomboidal floor. 4 pulp horns

120. 3 distinct orifices: MB orifice under MB cusp, ML orifice is located in a depression formed by the mesial and lingual walls. Distal orifice – oval with widest diameter buccolingually. 2 canals should be suspected

121. Roots and root canals: Usual Roots – Mesial and distal both roots are wide and flat buccolingually with a depression in the middle of the root buccolingually Cross section: Cervical: ovoid .

122. Midroot: Canals are ovoid . Apical III: round. General outline is trapezoidal with rounded corners. The shortest side is to the distal aspect, and the mesial side is slightly longer. Buccal and lingual walls are approximately of same length and taper toward each other distally.

123. Mandibular II molar: Pulp chamber is smaller than mandibular I molar and root canal orifices are smaller and closer together. Roots and root canals: Teeth with 2 roots – 71% 1 root – 27% 3 root – 2% May have ‘C’ shaped canal – first described by Cooke and Cox, 1979 - 8% [predominantly in mandibular II molar].

124. There is a C shaped trough on the floor of pulp chamber. ‘C’ shaped configuration refers to a continuous slit between all the canals so that the horizontal section through the root yields a space in the shape of letter C. Closed area of ‘C’ may be towards buccal or lingual. - If buccal – Then canal is continuous from the MB to be ML around the lingual to the DL to the DB. - If lingual – ML to the MB along the buccal to the DB to the DL and is difficult to treatment.

125. Cross section: Ovoid, round, Adult: Pulp recession, thread like Access similar to mandibular I molar Lateral Canals in mesial root - 49%. AD - 6% Distal root – 34%. AD - 7% Lateral canals in furcation – 11% When a single apical foramen is present, it is centrally located in 19% of cases in mesial root, 21% of cases in distal root.

126. Mandibular III Molar: Pulp chamber: Anatomically resembles the pulp chamber of the mandibular first and second molars. It is large and possesses many anomalous configurations such as “C shaped” root canal orifices.

127. Root and root canals: Usually have two roots and 2 canals but occasionally one root and one canal or 3 root and 3 canals. The roots are generally large and short. Access opening: Similar to mandibular I and II molars, with the variations that anatomic structure dictates.

128. CONCLUSION Thus the hard tissue repository of the human dental pulp takes on many configurations that must be understood before the treatment can begin. Detailed knowledge of anatomy of the teeth, armamentarium and knowledge regarding access cavity preparation are critical for the success of root canal therapy.

129. REFERENCES Endodontics.Ingle,Bakland V edition. Endodontic theraphy.Weine VI edition Pathways of pulp.Cohen VIII edition. Endodntics. Stalk Walker & Gulabivala III edition. Advanced endodontics for clinicians.Jacob Daniel Endodontics problems solving in clinical practice Pittford.

130. THANK YOU