This document discusses the principles and procedures for access cavity preparation in endodontics, defining it as essential for unobstructed access to canal orifices and effective control during instrumentation. Key concepts include the anatomy of root canals, classification of canal systems, required instruments, and techniques for accessing various tooth types, while emphasizing the importance of avoiding iatrogenic errors. It also covers potential challenges, such as calcified canals and the management of teeth with minimal crowns, providing guidelines to optimize the endodontic treatment process.

1. ACCESS OPENING IN
PERMANENT TEETH
DR. ALVI FATIMA
MDS I
1

2. DEFINATION
 Access cavity preparation is defined as an endodontic coronal
preparation which enables unobstructed access to the canal
orifices, a straight line access to apical foramen, complete
control over instrumentation and accommodate obturation
technique.
2

3. Objectives
 Direct straight line access to the apical foramen
 Improve instrument control because of minimal instrument deflection
and ease of introducing instrument in the canal.
 Improved obturation.
 Decrease incidence of iatrogenic errors.
3

4.  Completing deroofing of pulp chamber
 Complete debridement of pulp chamber .
 Improving visibility.
 Locating canal orifices.
 Permitting straight line access.
 Preventing discoloration of the teeth because of remaining pulp tissue.
4

5.  Conserve sound tooth structure as much as possible so as to
avoid weakening of remaining tooth structure.
5

6.  A proper coronal access forms the
foundation of the pyramid of endodontic
treatment
6

7. Before going for access cavity preparation, a
study of preoperative periapical radiograph
is necessary.
Radiograph helps in
Morphology of the tooth
Anatomy of the root canal system
Number of canals
Length of the canals
7

8.  Curvature of the branching canal
 Position and the size of the pulp chamber and its distance from the occlusal
surface
 Position of apical foramen
 Calcification, resorption present if any
8

9. Root canal anatomy of tooth
9

10. 10

11. Classification of canal morphology
 Number of root canal correspond with number of root but a root
may have more then one canal
 Weine described the four categories of root canal system as:
11

12. Type 1
SINGLE CANAL FROM
PULP CHAMBER TO APEX
12

13. Type 2
TWO SEPARATE CANALS
LEAVING THE CHAMBER
BUT EXITING AS ONE
CANAL
13

14. Type 3
TWO SEPARATE CANALS
LEAVING PULP
CHAMBER AND EXITING
AS TWO SEPARATE
FORAMINA
14

15. Type 4
ONE CANAL LEAVING
THE CHAMBER BUT
DIVIDING INTO TWO
SEPARATE CANALS AND
EXITING IN TWO
SEPARATE FORAMINA
15

16. 16

17. Instrument for access cavity preparation
 Mouth mirror.
 Rubber dam.
 Burs
 Endodontic explorer (DG-16, DE-17)
17

18. Mouth mirror
•INDIRECT VISION
•REFLECTING LIGHT ONTO DESIRED
SURFACES.
•RETRACTION OF SOFT TISSUES.
18

19. Rubber dam
• ISOLATE THE TEETH (ONE OR MORE
TEETH) FROM THE REST OF THE
MOUTH THAT NEEDS TO BE TREATED
•IT PREVENTS INSTRUMENTS AND
MATERIALS FROM BEING INHALED,
SWALLOWED OR DAMAGING THE
MOUTH.
19

20. Burs
•ACCESS OPENING BUR
•ACCESS REFINING BURS
20

21. Access opening
bur
•THEY ARE ROUND BURS
21

22. Access refining burs
THESE ARE
•COARSE GRIT FLAME SHAPED
•TAPERED ROUND AND
•DIAMOND
FOR REFINING THE WALLS OF ACCESS
CAVITY PREPARATION
22

23. Muller burs
•THEY ARE LONG SHAFT, ROUND
CARBIDE TIPPED BURS
•THEY ARE USED FOR CALCIFIED
CANALS BECAUSE OF LONG SHAFT IS
USEFUL FOR WORKING DEEP IN
RADICULAR PORTION.
•BUT SINCE THEY ARE MADE UP OF
CARBIDE , THEY DO NOT TOLERATE
STERILIZATION CYCLE AND BECOME
DULL QUICKLY
23

24. Endodontic explorer
• USED TO LOCATE
ORIFICES
24

25. Law of access cavity preparation for locating
canal orifices
 Law of centrality
 Law of cementoenamel junction
 Law of concentricity
 Law of color change
 Law of symmetry
 Law of orifice location
25

26. Law of centrality
Floor of pulp chamber is always located in the center of tooth at the
level of cementoenamel junction
26

27. Law of cementoenamel junction
Distance from external surface of clinical crown to the wall of pulp
chamber is same throughout the tooth circumference at the level of
CEJ
27

28. Law of concentricity
Wall of pulp chamber are always concentric to external surfaced of
the tooth at level of cej. This indicates anatomy of external tooth
surface reflects the anatomy of pulp chamber
28

29. Law of color change
Color of pulp chamber floor is darker than the cavity walls
29

30. Law of symmetry
Usually canal orifices are equidistance from a line draw in mesial
and distal direction through the floor of pulp chamber
30

31. Law of orifice location
Canal orifices are located at the junction of floor and walls, and at
the terminus of root development fusion lines.
31

32. Access cavity of the anterior teeth
 Remove all the caries and any defective restoration so as to
achieve a straight line access into the canal.
 Access opening is initiated at the center of the lingual surface.
 Direct a round bur perpendicular to he lingual surface at its
center to penetrate the enamel.
 Once the enamel is penetrated, the bur is directed, parallel to
the long axis of the tooth, until a ‘drop’ effect is felt.
32

33. 33

34.  once the pulp chamber is penetrated, the remainder of camber
roof is removed by working round bur from inside to out.
 Remove the lingual an labial wall of the pulp chamber.
 The lingual shoulder is removed
34

35.  Now locate the canal orifices using endodontic explorer.
 After the straight line access of the canal it is confirmed by
passing a file into the canal.
35

36. 36

37. Maxillary central
incisor
•ROOT – 1
•CANAL – 1
•AVERAGE LENGTH –23MM
•THE ORIFICES LIE APICAL TO THE
INCISAL EDGE
•SHAPE – ROUNDED TRIANGULAR
WITH BASE FACING THE INCISAL
ASPECT
37

38. Maxillary lateral
incisor
•ROOT – 1
•CANAL –1
•AVERAGE LENGTH – 22.8MM
•THE ORIFICES LIE APICAL TO THE
INCISAL EDGE
•SHAPE IS SIMILAR TO THAT OF
MAXILLARY CENTRAL INCISOR ,
EXCEPT THAT ITS SMALLER IN SIZE
38

39. Maxillary canine
•ROOT – 1
•CANAL – 1
•AVERAGE LENGTH – 26MM
•SHAPE – OVAL IN SHAPE WITH
GREATER DIAMETER
LABIOPALATALLY
39

40. Mandibular incisors
•ROOT – 1
•CANAL – 1
-- 2 (40%)
•AVERAGE LENGTH –
• mandibular central incisor -- 21.5mm
•Mandibular lateral incisor – 22.5mm
•SHAPE – TRIANGULAR IN YOUNGER
AND OVOID IN ADULTS
40

41. Mandibular canine
•ROOTS – 1
•CANALS – 1
-- 2 (14%)
•AVERAGE LENGTH -- 25.2MM
•SHAPE -- SIMILAR TO MAXILLARY
CANINE
• ROOT CANAL OUTLINE IS NARROWER
IN MESIODISTAL DIMENSION
41

42. Access cavity preparation for premolars
 The site of access opening in the premolar, is in the center of the
occlusal surface between buccal and lingual cusp tips.
 The bur should be directed parallel to the long axis of the tooth
and perpendicular to the occlusion.
 After the ‘drop’ is felt, penetrate deep enough to remove the floor
of pulp chamber, without cutting the floor of pulp chamber.
42

43.  To remove the roof of pulp chamber place a bur along side of the
wall of pulp chamber and work from inside to outside.
 After removal of pulp chamber, locate the canals orifices with the
help of endodontic explorer.
 Remove any remaining cervical bulges or obstruction and obtain a
straight line access to the canal
43

44.  Walls of the access cavity is smoothened and sloped slightly
towards the occlusal surface.
 The divergence of the access cavity walls create a positive seat
for temporary restorations.
44

45. Maxillary first
premolar
•ROOTS – 2
•CANALS – 1 (35%)
• -- 2
•AVERAGE LENGTH – 20.6MM
•SHAPE – OVOID, IN WHICH
BOUNDARIES SHOULD NOT EXCEED
BEYOND HALF THE LINGUAL INCLINE
OF BUCCAL CUSP AND HALF THE
BUCCAL INCLINE OF LINGUAL CUSP
45

46. 46

47. Maxillary second
premolar
•ROOTS – 1
•CANALS – 1
• -- 2 (50%)
•AVERAGE LENGTH – 21MM
•SHAPE – OVOID
47

48. Mandibular first premolar
 Because of lingual tilt of the mandibular
premolar, the access cavity should extend
on the buccal cusp inclines, in order to gain
straight line access
48

49. •Roots – 1
•Canal -- 1
• -- 2 (2-5%)
•Average length -- 21 mm
•Shape – ovoid
49

50. Mandibular second
premolar
•Roots – 1
•Canal – 1
•Shape – ovoid
•Average length – 21mm
50

51. Access cavity preparation for maxillary
molars
 Remove caries or any restoration
 Determine the shape and size of the access opening by
measuring boundaries of pulp chamber mesially and distally.
 Initial preparation is done in the mesial pit
 The cavity is then extended in the mesial half of the tooth to
include all canals.
51

52. 52

53.  Penetrate the bur deep into dentin until the ‘drop’ is felt.
 Now remove the roof of pulp chamber using tapered fissure,
round bur working from inside to outside.
 Explore the canals orifices by endodontic explorer.
 Remove the cervical budge, ledges or obstruction if present
53

54.  Smoothen and finish the access cavity walls so as to make them
confluent within the walls of pulp chamber
54

55. Maxillary first molar
•ROOTS – 3
•CANAL – 3
• -- 4 (>60%)
•AVERAGE LENGTH
•MB 20MM
•DP 19.5MM
•P 20.5MM
•SHAPE – IT IS OF RHOMBOID
SHAPE
55

56.  PALATA CANAL ORIFIES IS LOCATED PALATALLY
 MESIOBUCCAL CANAL IS LOCATED UNDER THE MESIOBUCCAL
CUSP
 DISTOBUCCAL CANAL ORIFICE IS LOCATED SLIGHTLY DISTAL
AND PALTAL TO THE MESIOBUCCAL ORIFICE.
56

57.  ALMOST ALWAYS THERE IS A
SECOND MESIOBUCCAL CANAL,
WHICH IS LOCATED PALATAL AND
MESIAL TO MB1
57

58. MAXILLARY
SECOND MOLAR
ROOTS – 3
CANAL – 3 (55%)
-- 4
AVERANGE LENGTH – 21.5MM
SHAPE – RHOMBOID
58
ITS IS SIMILAR TO FIRST MOLAR
BUT DIFFERS IN:
•THREE ROOTS ARE FOUND
TO BE CLOSER WHICH MAY
EVEN FUSE TO FORM A
SINGLE ROOT
•MB2 IS LESS LIKELY TO BE
PRESENT
•THE THREE CANALS FORMS
A ROUNDED TRIANGULAR
WITH BASE ON THE BUCCAL
SIDE

59. MAXILLARY THIRD
MOLAR
ROOTS 1-3
CANALS 1- 3
59

60. ACCESS CAVITY PREPARATION FOR
MANDIBULAR MOLARS
 REMOVE CARIES OR RESTORATION
 PENETRATE WITH OUND BUR ON THE CENTRAL FOSSA MID WAY
BETWEEN THE MESIAL AND DISTAL BOUNDARIES
 THE MESIAL BOUNDARY IS THE LINE JOINING THE MESIAL CUSP
TIP AND THE DISTAL BOUNDARY IS THE LINE JOINING BUCCAL
AND THE LINGUAL GROOVES
60

61. 61

62.  BUR IS PENETRATED IN THE CENTRAL FOSSA DIRECTED
TOWARDS THE DIATAL ROOT
 ONCE THE ‘DROP’ IS FELT, REMOVE ROOF OF PULP CHAMBER
WORKING FROM INSIDE TO OUTSIDE WITH THE HELP OF ROUND
BUR
 EXPLORE THE CANAL ORIFICES WITH THE HELP OF
ENDODONTIC EXPLORER
62

63.  FINISH AND SMOOTHEN THE CAVITY WITH A SLIGHT
DIVERGENCE TOWARDS THE OCCLUSAL SURFACE .
63

64. MANDIBULAR FIRST
MOLAR
ROOTS –2 - 3
CANALS – 3 – 4
AVERAGE LENGTH – 21MM
SHAPE – TRAPEZOIDAL OR
RHOMBOID IRRESPECTIVE OF
NUMBER OF CANALS
PRESENT
64

65. Mandibular second
molar
ROOTS – 2
CANAL – 3
AVERAGE SIZE – 19.8 MM
SHAPE– WHEN THREE CANALS CAN
BE PRESENT, IT IS MORE
TRIANGULAR AND LESS RHOMBOID
65
Second molar with fused roots
usually have 2 canals, buccal and
lingal, but the number, shape, type
and size can vary,

66. Mandibular third
molar
ROOTS – 1- 3
CANALS 1-3
AVERAGE LENGTH – 18-19MM
66

67. Errors in cavity preparation
 Failure to identify and excavate all caries and to remove
unsupported, weak tooth structure or faulty restorations
 Failure to establish proper access to the pulp chamber space and
root canal system.
 Failure to identify the angle of the crown to the root and the angle
of the tooth in the dental arch.
67

68.  errors in access preparation include gouging, perforation, ledge
formation, instrument breakage and these errors occur due to
failure to adhere to the principles of access opening.
68

69. Perforation
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.
69

70. LEDGE
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”.
70

71. Bifurcation
BIFURCATION OF A CANAL IS
COMPLETELY MISSED, CAUSED
BY FAILURE TO ADEQUATELY
EXPLORE THE CANAL WITH A
CURVED INSTRUMENT.
71

72. APICAL
PERFORATION
APICAL PERFORATION OF AN
INVITINGLY STRAIGHT CONICAL
CANAL. FAILURE TO ESTABLISH
THE EXACT LENGTH OF THE
TOOTH LEADS TO TREPHINATION
OF THE FORAMEN.
72

73. INCOMPLETE
preparation
INCOMPLETE PREPARATION AND
POSSIBLE INSTRUMENT
BREAKAGE CAUSED BY TOTAL
LOSS OF INSTRUMENT CONTROL.
USE ONLY OCCLUSAL ACCESS,
NEVER BUCCAL OR PROXIMAL
ACCESS.
73

74. BROKEN
INSTRUMENT
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).
74

75. PERFORATION
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.
75

76. Management of cases with calcified canal
 Calcification of the canal is a common occurrence
 Teeth with calcification results in difficulty in locating and further
treatment
 Special tip for ultrasonic handpieces are used for précised
removal of dentin from the pulp floor while locating calcified
canals
76

77. 77

78.  If special tips are not available then a pointed ultrasonic tip can
be used for removal of calcification from the pulp space
 Over cutting of the dentin should be avoided in order to locate
canals, this will further result in loss of landmark and the tooth
weakening
 At first indication that the canal is found, introduce the smallest
with a gentle motion both rotation and apical to negotiate the
canal.
78

79. Management of teeth with no or minimal
crown
 Some precautions are required while dealing with such cases
 Evaluate the preoperative radiograph to access the root angulations
 Start the cavity preparation without applying rubber dam
 Apply rubber dam after location of the canal
 If precautions are not taken there are chances of iatrogenic errors
like perforation due to misdirection of the bur
79

80.  Some times it become imperative to build the tooth previous to
endodontic treatment.
 Return the tooth to normal form and function
 Prevent coronal leakage during treatment
 Allow use of rubber dam clamps
 Prevent fracture of walls which can complicate=e the endodontic
procedure
80