Access cavity prepration

acces cavity preprations in endodontics

1. ACCESS CAVITY PREPARATION PRESENTED BY: DR NADEEM AASHIQ 2 ND YEAR MDS

2. Of all the phases of anatomic study in the human system, one of the most complex is the pulp cavity morphology. - M.T.Barrett A proper access is the most important step in non surgical endodontic treatment Without adequate access, instruments and materials become difficult to handle 2

3. Access cavity preparation is defined as endodontic coronal preparation which enables unobstructed access to the canal orifices, a straight line access to the apical foramen, complete control over instrumentation and accommodate obturation technique . A PROPER CORONAL ACCESS FORMS THE FOUNDATION OF PYRAMID OF ENDODONTIC TREATMENT 3

4. GOALS OF ACCESS CAVITY PREPARATION ACC. TO VERTUCCI 4

5. Guidelines for access cavity preparation 1. VISUALIZATION OF THE LIKELY INTERNAL ANATOMY Approx. Length of the canal Location of pulp chambers Coronal anatomy Number of roots and canals Thickness of the roots Extent of root curvature Changes in furcation area 5

6. 2. EVALUATION OF THE CEMENTOENAMEL JUNCTION AND OCCLUSAL ANATOMIES According to a study conducted by Krasner and Rankow , cementoenamel junction was the most important anatomic landmark for determining the location of the pulp chambers and canal orifices. The authors suggested guidelines/laws to determine the number and location of orifice on the chamber floor 6

7. LAW OF CENTRALITY The floor of the pulp chamber is always located at the centre of the tooth at the level of CEJ LAW OF CONCENTRICITY The walls of pulp chamber are always concentric to the external surface of the tooth at the level of CEJ LAW OF 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 CEJ. The CEJ is the most consistent, repeatable landmark for locating the position of the pulp chamber 7

8. FIRST LAW OF SYMMETRY : Except for maxillary molars, canal orifices are equidistant from a line drawn in a mesiodital line drawn through the pulp chamber floor SECOND LAW OF SYMMETRY : Except for maxillary molars, canal orifices lie on the line perpendicular to a line drawn in a mesiodistal direction across the centre of the pulp chamber floor 8

9. LAW OF COLOUR CHANGE : The pulp chamber is always darker in colour than the walls. LAW OF ORIFICE LOCATION 1 : The orifices of the root canals are always located at the junction of the walls and the floor LAW OF ORIFICE LOCATION 2 : The orifices of the root canals are located at the vertices of the floor-wall junction . LAW OF ORIFICE LOCATION 3 : the orifices of the root canals are always located at the terminus of the roots developmental lines. 9

10. 3. Preparation of the access cavity through lingual and occlusal surfaces. 4. Removal of all defective old restorations and caries before entering the pulp chamber 5. Removal of unsupported tooth structure 10

11. IDENTIFICATION OF ORIFICE ANATOMIC FAMILIARITY Knowledge, understanding and appreciation of the root canal anatomy RADIOGRAPHS Angulated periapical images CBCT VISION Magnification glasses Illuminating devices Headlamps 11

12. SURGICAL LENGTH BURS Long length burs improve the line of sight along the shaft of the bur and promotes safety when searching for canal ACCESS CAVITIES Axial walls should be flared flattened and finished to provide straight line access to the orifice Dyes Methylene blue gets absorbed in the orifice and isthmus area 12

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14. TRANSILLUMINATION A fibre optic wand is placed cervically to the tooth so that the light is perpendicular to the long axis of the tooth 14

15. RED LINE TEST In a vital teeth, blood emanates from the orifice or an isthmus area. Like a dye, blood serves to map and visually aid in identification of the underlying anatomy below the pulp chamber WHITE LINE TEST In necrotic teeth, dentinal dust frequently moves into any anatomical spaces such as orifice, fin or isthmus when performing ultrasonic procedures without water This dust forms a white dot or line that provides a visible road map. Eg to locate MB2 canal. 15

16. PERIO PROBING Circumferentially probing around the tooth is another important strategy for locating canal Intersulcular probing can provide important information as to the emergence profile of the clinical crown and the oriental alignment of the underlying root COLOUR A dark narrow line on the pulpal floor of a multi rooted tooth provides a visual trail of colour that leads to the orifice Orifice will appear darker in colour than the surrounding dentin MICRO OPENERS Micro openers are flexible stainless steel hand files attached to an ergonomically designed off-set handle They provide unobstructed view for initially penetrating and enlarging an offshoot that divides deep within the canal 16

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18. STAGES OF ACCESS CAVITY PREPARATION 18

19. PRE TREATMENT ASSESSMENT Adequate access for treatment  determines the treatment planning Once accessibility is confirmed  mentally visualise the location of the pulp chamber. The angulation and any rotation of the tooth or coronal restoration in relation to the roots should be assessed as this will have a bearing on the design of the access cavity. The position of the cemento -enamel junction and furcation should also be noted as these landmarks help indicate the location of the level of the pulp floor and the probable position of the canal entrances. 19

20. SIGNIFICANCE OF A STRAIGHT LINE ACCESS : Freedom of endodontic instrumentation in the coronal cavity and direct access to the apical canal MOUSE HOLE EFFCT : If the lateral wall of the cavity has not been sufficiently extended and the pulp horn portion of the orifice still remains in the wall, the orifice will have the appearance of a “ mouse hole ” This feature occurs due to extension of canal orifice into axial wall It can be prevented by extending the lateral wall of the cavity, thus removing all the intervening dentin from the orifice. 20

21. ARMAMENTARIUM FOR ACCESS CAVITY PREPARATION ENDODONTIC SPOON EXCAVATOR ENDODONTIC EXPLORER DIAMOND BURS WITH ROUND CUTTING EDGE FISSURE CARBIDE BURS WITH NON-END CUTTING SAFETY TIPS MUELLER BUR LN BURS 21

22. ADDITIONAL AIDS MAGNIFICATION AND ILLUMINATION AIDS ENDODONTIC TIPS MICRO-OPENER MICRO-DEBRIDER Transmetal Bur: The transmetal bur is specifically designed for cutting any type of metal . This bur has a saw-tooth blade configuration, which provides efficiency while reducing unwanted vibration, especially important when entering pulpitic or so-called “hot teeth.” 22

23. Endodontic Coronal Cavity Preparation 23

24. Outline Form The outline form of the endodontic cavity must be correctly shaped and positioned to establish complete access for instrumentation, from cavosurface margin to apical foramen. 2. Convenience form As conceived by Black, is a modification of the cavity outline form to establish greater convenience in the placement of intracoronal restorations. In endodontic therapy, however, this form provides more convenient and accurate preparation and filling of the root canal. Four important benefits are gained through convenience form modifications: 1. Unobstructed access to the canal orifice, 2. Direct access to the apical foramen, 3. Cavity expansion to accommodate filling techniques, and 4. Complete authority over them enlarging instrument 24

25. 3. Removal of remaining carious dentin and defective restorations To eliminate mechanically as many bacteria as possible from the interior of the tooth To eliminate discoloured tooth structure that might lead to staining To eliminate bacteria laden saliva leakage into the prepared cavity . 4. Cleansing of cavity All caries, debris and necrotic pulp must be removed before beginning the radicular preparation Calcified and metallic debris  obstruct the canal Soft debris  increases bacteria population in the canal 25

26. Tooth Tooth length Crown length Root length Number of roots Types of canals Maxillary central incisor A = 23.00 10.5 12.5 One I L= 28.0 12.0 16.0 S= 18.0 8.0 8.0 Maxillary lateral incisor A=22.5 9.0 13.5 One I L=27.0 10.5 16.5 S=17.0 8.0 8.0 Maxillary cuspids A=27.0 9.5 16.5 One I L=32.0 12.0 20.5 S=20.0 8.0 11.0 Mandibular incisor A=21.0 9.0 12.0 One I most frequent L=25.0 10.5 14.5 II less frequent S=16.0 7.0 9.0 III least frequent Mandibular cuspids A=24.0 10.0 15.0 One; two, buccal and lingual, rare I most frequent L=30.5 12.0 20.5 II less frequent S= 20.0 8.5 11.5 III least frequent 26

27. Tooth Total length Crown length Root length Number of roots types of canals Maxillary first bicuspid A=21.0 8.5 12.5 TWO most frequent (60%)  buccal and palatal II most common L=24.0 10.0 14.5 I less frequent One (40%) Three  rare S=17.5 7.0 10.0 III least frequent Maxillary second bicuspid A=21.0 8.5 12.5 One  85 % I most common L=25.0 10.5 15.0 Two  15 %  buccal and palatal II less frequent S=17.0 7.0 9.5 Mandibular first bicuspid A=21.5 7.5 14.5 One Two  rare  buccal and lingual I most common L=25.0 9.0 17.0 II less frequent S=17.0 6.5 11.5 mandibular second bicuspid A=22.0 8.0 14.0 One Two  buccal and lingual  very rare Three  two buccal and one lingual  extremely rare I most common L=25.0 10.0 17.0 II less frequent S=17.0 6.0 11.5 III least frequent 27

28. ANTERIOR ACCESS CAVITY PREPARATIONS 28

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30. POSTERIOR ACCESS CAVITY PREPARATIONS 30

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35. Maxillary central incisors Outline form- The inverted-triangular shaped access cavity is cut with its base at the cingulum to give straight line access. Width of base depends on distance between mesial and distal pulp horns. Shape may change from triangular to slightly oval due to less prominent pulp horns in older individuals. 35

36. The cingulum is chosen as a starting point, because, in contrast to the gingival margin which can retract and the incisal margin which can abrade, this ridge remains constant throughout the patient’s life. 36

37. Maxillary lateral incisors Shape of access cavity similar to maxillary central incisors,except that Smaller in size When pulp horns are present,shape of access cavity is rounded triangle If pulp horns are missing, shape is oval 37

38. Maxillary canine Shape of access cavity No pulp horn Access cavity is oval in shape with greater diameter labiopalatally 38

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42. Maxillary first premolar Oval shaped acess cavity-The two horns are situated just within the peaks of their cusps. The orifices of the two canals are also slightly more within the horns. Thus, one can generally prepare a good access cavity without involving the cusps. 42

43. Maxillary second premolar 43

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49. Maxillary second molar Mb2 less likely to be present Three canals form a rounded triangle with base towards buccal side. Mesiobuccal orifice is located more towards mesial and buccal than first molar. 49

50. Maxillary third molar Alavi et al. found that 50.9% of third maxillary molars had three separate roots of which 45.5% had two or more canals in the mesiobuccal root. About 45.7% had fused roots 2% had C-shaped canals 2% had four separate roots Modifications must be made in accessing these teeth compared to first and second molars to accommodate these anatomical variations. 50

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54. Mandibular incisors Access cavity of mandibular central and lateral incisors is almost similar Shape is long oval with greater dimensions directed incisogingivally 54

55. Mandibular canine Shape of acces opening similar to maxillary canine-oval, but, Smaller in size Root canal outline narrower in mesiodistal dimension Two canals may be present 55

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59. Mandibular first premolar Oval acess cavity,wider mesiodistally Presence of 30 degree lingual inclination of crown to root,hence starting point of bur should be half way up the lingual incline of buccal cusp. 59

60. Mandibular second premolar Similar to mandibular first premolar Enamel penetration initiated in central groove due to small lingual tilt Ovoid acess opening is wider mesiodistally 60

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65. Mandibular first molar This tooth most frequently requires endodontic treatment. The access cavity, which should not be triangular, rather trapezoidal or quadrangular with rounded corners. The classical triangular shape would hamper the identification of the second distal canal . 65

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67. Mandibular second molar The access cavity of this tooth is started from the central fossa , and it is created according to the same rules used for the first molar. Because of the slight distal angulation of its roots, the access cavity can, however, be less extensive in this case. The shape of the access cavity depends on whether there is one, two, three, or four canals; it may be round to oval, triangular, or quadrangular 67

68. C shaped canal The incidence of C-shaped canals is reported to be highest in the mandibular second molar. THE MAIN ANATOMIC FEATURE OF C - SHAPED CANALS IS THE PRESENCE OF A FIN OR WEB- connecting the individual root canals. The ‘‘C-shaped canal’’ by Cooke and Cox in 1979.This canal shape results from the fusion of the mesial and distal roots on either the buccal or the lingual root surface. 68

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70. RADIX ENTOMOLARIS AND RADIX PARAMOLARIS Supernumery roots in mandibular molars Radix entomolaris:Presence of an additional disto lingual root in mandibular molars;extra root on the lingual side. Radix paramolaris:presence of additional disto buccalroot in mandibular molars;extra root on buccal side.First reported by De Moor et al in 2004 70

71. Mandibular third molar The lower third molar may require endodontic therapy for the same reasons as the upper third molar. When it is the last distal abutment, this tooth acquires great importance. The most varied and bizarre root morphology can correspond to an almost normal coronal appearance . Nonetheless, this tooth can also be treated successfully by endodontic means . The same rules that apply to the other lower molars also hold for its access cavity. 71

72. CHALLENGING ACCESS PREPARATION HEAVILY RESTORED TEETH TEETH WITH CALCIFIED CANAL CROWDED TEETH ROTATED TEETH 72

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76. Failure to identify and excavate all caries and to remove unsupported, weak tooth structure or faulty restorations. 2) Failure to establish proper access to the pulp chamber space and root canal system. 3) Failure to identify the angle of the crown to the root and the angle of the tooth in the dental arch. 4) Failure to recognize potential problems in access openings through crowned teeth or teeth with excessively large restorations. Errors in access cavity preparation 76

77. PERFORATION at the labio cervical is caused by failure to complete convenience extension toward the incisal , prior to the entrance of the shaft of the bur. 77

78. LEDGE formation at the apical-labial curve is caused by failure to complete the convenience extension. The shaft of the instrument rides on the cavity margin and “shoulder”. 78

79. BIFURCATION of a canal is completely missed, caused by failure to adequately explore the canal with a curved instrument. 79

80. APICAL PERFORATION of an invitingly straight conical canal. Failure to establish the exact length of the tooth leads to trephination of the foramen. APICAL PERFORATION of an invitingly straight conical canal. Failure to establish the exact length of the tooth leads to trephination of the foramen. 80

81. INCOMPLETE preparation and possible instrument breakage caused by total loss of instrument control. Use only occlusal access, never buccal or proximal access. 81

82. BROKEN INSTRUMENT twisted off in a “cross-over” canal. This frequent occurrence may be avoided by extending the internal preparation to straighten the canals (dotted line). 82

83. PERFORATION into furcation caused by using a longer bur and failing to realise that the narrow pulp chamber had been passed. Measure the bur against the radiograph and the depth to the pulpal floor marked on the shaft with Dycal 83

84. CONTRACTED ACCESS CAVITY Contracted endodontic cavities are considered to be an alternative to traditional endodontic cavities in maintaining the mechanical stability and subsequently the long-term survival and function of  endodontically treated teeth. Since no restorative material or technique can replace the mechanical characteristics of the lost dentin in stress-bearing areas of the tooth, treatment steps directed toward dentin conservation are essential as the primary measure to reinforce root-filled teeth Boveda & A Kishen . Endodontic topics 2015, 33, 169 – 186 84

85. Why do we need modifications The long-term functional survival of initial endodontically treated permanent teeth was reported as 97.1% after 8 years in a very large epidemiologic survey. Coronal tooth fractures continue to remain important reasons for post endodontic tooth repairs and extractions. J Endod2004;30:846 . EndodDent  Traumatol1990;6:49 85

86. Pericervical dentin (PCD) PCD is the dentin near the alveolar crest. While the apex of the root can be amputated, and the coronal third of the clinical crown removed and replaced prosthetically , the dentin near the alveolar crest is irreplaceable. This critical zone, roughly 4 mm above the Crestal bone and extending 4 mm apical to crestal bone, is sacred for 3 reasons: (1) ferrule, (2) fracturing, and (3) dentin tubule Orifice proximity from inside to out. long-term retention of the tooth and resistance to fracturing are directly related to the amount of residual tooth structure. This regional dentin is significant for the distribution of functional stresses in teeth J Endod . 2003;29:523-528 86

87. Contracted endodontic access prioritizes the removal of: -restorative material ahead of tooth structure, -enamel ahead of dentin, and -occlusal tooth structure ahead of cervical dentin It overlooks the traditional requirements of straight-line access and complete unroofing of the pulp chamber while emphasizing the importance of preserving the crucial Pericervical dentin 87

88. In the case of incisors, the conservation of cingulum dentin( pericingulum dentin) is suggested to improve the functional stress distribution in teeth. A contracted endodontic cavity preserves a portion of the roof around the entire coronal aspect of the pulp chamber. This dentin is known as dentin roof strut or soffit. 88

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92. The endodontic cavity should be as small as possible while still achieving the biological objectives of the root canal treatment and as wide as the anatomy permits in a particular case. • Generally, a contracted cavity is suggested to be slightly wider than the coronal extension of the root canal. This permits the maintenance of some of the roof (dentin soffit) around the entire coronal portion of the pulp chamber 92

93. CT GUIDED ENDODONTIC ACCESSOPENING In these cases, preparing an adequate access and identifying the canal orifice can be challenging and may create a massive loss of tooth structure that Is associated with a higher risk of fracture and a high failure rate   ( cveket Et al. 2006) Therefore, preoperative planning is highly recommended and 3D imaging may be a useful tool. Templates can be produced by 3D-printing devices, based on matched 3D surface scans with CBCT data ( Kuhlet al. 2015) 93

94. Technique for CT-GEA Preoperative cbct images are stored 3d surface scans are performed using intraoral 3d surface scanner 94

95. CBCT data is uploaded into a planning software (co DiagnosticX ). The software allows the creation of a virtual image of a commercially available bur. In addition, a virtual sleeve for guidance is created for planning purposes. The virtual bur is superimposed on each tooth with the aim of creating a direct access to the apical third of the root canal. the surface scans are uploaded to the implant planning software Scans were matched with CBCT data by aligning the crowns of the teeth. 95

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97. Finally, a virtual template is designed by applying a tool of the software. Information on sleeve‘s position is considered in the planning. Exported stl -files allowed a 3D printer to produce the templates Templates are attached to the models, and their correct and reproducible fitting is checked. Marks are set through the template sleeves to indicate the region of access cavity. Enamel should be removed in the area using a diamond bur until dentine is exposed. Then, the specific bur is used to gain access to the root canal. The final position was reached when the bur hit the mechanical stop of the sleeve 97

98. Disadvantages of CT-GEA High price More time required for access cavity preparation. More exposure to radiation because of use full mouth CBCT and optical surface scan. 98

99. NINJA ACCESS 99

100. TRUSS ACCESS 100

101. Modern molar endodontic access and directed dentin conservation. David J Clark , John A Khademi Published 2010 in Dental clinics of North America The authors believe that the current models of endodontic treatment do not lead to long-term success, and that the traditional approach to endodontic access is fundamentally flawed. This article introduces a set of criteria that will guide the clinician in treatment decisions to maintain optimal functionality of the tooth and help in deciding whether the treatment prognosis is poor and alternatives should be considered 101

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103. Preoperative view of tooth #19 in a 20-year-old woman. (A) The deroofing problem. The likely bur used by the referring general dentist is a 56 carbide; one of the most popular burs in dentistry,6 it is possibly the most iatrogenic instrument in modern medicine. Red arrow delineates the typical gouging. (B) Postoperative view provided by the endodontist . Blue arrow indicates the grossly excessive dentin removal of pericervical dentin (PCD). This serious gouging is typical of round bur access. Yellow arrow indicates the large canal flaring with unacceptable dentin removal (blind funneling ). (C) Green circle highlights worsening lesion on mesial root ends. 103

104. Eighteen-month follow-up. Despite generous access and aggressive canal enlargement, the lesion on the mesial root continues to enlarge. A more appropriate access shape is overlayed . Partial deroofing and maintenance of a robust amount of PCD is demonstrated. A soffit that includes pulp horns on mesial and distal is depicted. 104

105. Traditional parallel-sided access (left), compared with the Cala Lilly enamel preparation (right). (Left) Unfavorable C factor and poor enamel rod engagement are typically present when removing old amalgam or composite restorations or with traditional endodontic access of 90 to the occlusal table. (Right) The enamel is cut back at 45 with the Cala Lilly shape. This modified preparation will now allow engagement of nearly the entire occlusal surface. 105

106. Refernces : Grossman’s endodontic practice 13 th edition Endodontic therapy. Franklin S. Weine , 6 th edition Cohen’s Pathways of pulp Guidelines for Access Cavity Preparation in Endodontics A Peer-Reviewed Publication Written by Ricardo Caicedo ; Dr. Odon; Stephen Clark, DMD; Liliana Rozo , DDS and Joseph Fullmer , BA 5. Access Opening and Canal Location, Endodontics Colleagues for Excellence; Spring 2010 106

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