Endodontic Access Cavity Preparation

1. ENDODONTIC ACCESS
CAVITY PREPARATION
Aaron Sarwal
MDS 3rd Prof
Batch 2017

2. “...all the treatment that follows hinges on
the accuracy and correctness of the entry”
- FRANKLIN.S.WEINE

3. CONTENTS
 DEFINITION
 OBJECTIVES
 RULES FOR PROPER ACCESS PREPARATION
 PRINCIPLES OF ENDODONTIC ACCESS PREPARATION
 ARMAMENTARIUM
 GUIDELINES
 AIDS IN ACCESS PREPARATION
 ACCESS PREPARATION OF ANTERIOR AND POSTERIOR TEETH
 ERRORS IN ACCESS CAVITY PREPARATION
 CHALLENGES IN ACCESS PREAPARATIONS
 CONCLUSION

4. INTRODUCTION
 The hard tissue that encompasses the human dental
pulp takes on numerous configurations and shapes.
 A thorough understanding of the complexity of the
root canal system is essential for understanding the
principles and problems of shaping and cleaning, for
determining the apical limits and dimensions of
canal preparations, and for performing successful
microsurgical procedures.

5. DEFINITION
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.
According to Stephen Cohen, “it generally refers to
the part of the preparation from the occlusal table to
the root canal orifices.”

6. A PROPER CORONAL ACCESS FORMS THE
FOUNDATION OF PYRAMID OF ENDODONTIC
TREATMENT
OBJECTIVES
According to R.E Walton:-
Straight line access
Improved instrument
control
Improved obturation
Decreased procedural
errors

7. OBJECTIVES (ACC. TO RE WALTON)
Conservation of tooth structure
• Minimal weakening of tooth
• Prevention of perforation
Un-roofing the chamber and
exposure of pulp horns
• Maximum visibility
• Location of canals

8. RULES FOR PROPER ACCESS
PREPARATION
 The objective of entry is to give direct access to the apical
foramina, not merely to the canal orifice.
 Access cavity preparations are different from typical operative
occlusal preparations.
 The interior anatomy of the tooth under treatment must be
determined.
 Rubber dam – when canals difficult to find the rubber dam should
not be placed until correct location has been confirmed
 Endodontic entries are prepared through the occlusal or lingual
surface never through the proximal or gingival surface.
 As a part of access preparation, the unsupported cusps of posterior
teeth must be reduced.
(Franklin S. Weine)

9. A PREOPERATIVE PERIAPICAL RADIOGRAPH IS A
MUST, PRIOR TO ACCESS CAVITY PREPARATION
RADIOGRAPHS HELP US
GLEAN:
• Morphology of tooth
• Anatomy of root canal system
• Number and length of canals
• Branching of canal system
• Position and depth of pulp
chamber
• Position of apical foramen
• As well, calcifications, or
resorption present, if any AN INTRA-ORAL PERIAPICAL RADIOGRAPH

10. DIVISIONS OF ACCESS CAVITY
PREPARATION
 For sake of descriptive convenience Ingle has divided
endodontic cavity preparation into
CORONAL
PREPARATION
•0
RADICULAR
PREPARATION

11. PHASES FOR ACCESS CAVITY
PREPARATION
Regardless of the tooth, there are
three phases in the preparation
of the access cavity:
A. Penetration
B. Enlarging
C. Finishing

12. INSTRUMENTS FOR ACCESS CAVITY
PREPARATION
Access opening burs:
They are round burs
with 16mm bur shank
(3mm longer than
standard burs)

13. INSTRUMENTS FOR ACCESS CAVITY
PREPARATION
Access refining burs:
These are coarse grit
flame shaped, tapered
round and diamonds for
refining walls of access
cavity preparation

14. INSTRUMENTS FOR ACCESS CAVITY
PREPARATION
 Surgical length burs
A. Munce Discovery Burs
B. Muller Burs

15. INSTRUMENTS FOR ACCESS CAVITY PREPARATION:
Endo Access Kit by Dentsply Mallifer

16. INSTRUMENTS FOR ACCESS CAVITY PREPARATION:
Endo Access Kit by Dentsply Mallifer
Cavity
Access Kit
Cavity
Access Z Kit

17. INSTRUMENTS FOR ACCESS CAVITY PREPARATION:
Endo Access Kit by Dentsply Mallifer

18. PRINCIPLES OF ENDODONTIC
CAVITY PREPARATION
I. Outline Form
II. Convenience Form
III. Removal of the remaining carious dentin and
defective restorations.
IV. Toilet of the cavity

19. PRINCIPLE I – OUTLINE FORM
 Must be correctly shaped and positioned.
 Establish complete access for
instrumentation, from cavity margin to
apical foramen.
 External outline form evolves from the
internal anatomy of the tooth established
by the pulp.

20. PRINCIPLE I: OUTLINE FORM
 Three factors of internal anatomy must be
considered:
1.Size of the pulp chamber
2. Number of individual root canals, their
curvature, and their position.
3.Shape of the pulp chamber

21. PRINCIPLE II: CONVENIENCE FORM
 Unobstructed access to the canal orifice
 Direct access to the apical foramen
 Cavity expansion to accommodate filling
techniques
 Complete authority over the enlarging
instrument.

22. UNOBSTRUCTED ACCESS TO
CANAL ORIFICE
 Enough tooth structure must be removed to
allow instruments to be placed easily.
 One should be able to see each orifice &
easily reach it with instrument points.
 Entire wall need not be extended if
instrument impingement occurs owing to
severely curved root or an extra canal.

23. SHAMROCK PREPARATION: LEUBKE
 Leubke showed there is no need
of extenstion of entire wall ,he
recommended extension of
only that portion of the wall
were extra canal is present
,resulting in a clover leaf
appearance in outline form-
shamrock preparation

24. DIRECT ACCESS TO APICAL FORAMEN
 Enough tooth structure
must be removed to allow
endodontic instruments
freedom within coronal
cavity so that they can
extend down the canal in
unstrained position.

25. CAVITY EXPANSION TO ACCOMMODATE
FILLING TECHNIQUES
To make filling techniques more
convenient or practical, outline
form may have to be widely
extended to accommodate these
instruments

26. COMPLETE AUTHORITY OVER ENLARGING
INSTRUMENT
 If the instrument is impinged at the canal
orifice by tooth structure the intervening
tooth structure will dictate the control of the
instrument.
 If the tooth structure is removed from the
orifice so that the instrument stands free in
this area of the canal the instrument will
then be controlled by only two factors: the
clinician’s fingers on the handle of the
instrument and the walls of the canal at the
tip of the instrument.

27. PRINCIPLE III: REMOVAL OF THE
REMAINING CARIOUS DENTIN AND
DEFECTIVE RESTORATIONS
To eliminate
mechanically as
many bacteria as
possible from the
interior of tooth
To eliminate
discoloration of
tooth structure
To eliminate the
possibility of any
bacteria-laden saliva
leaking into the
prepared cavity.

28. PRINCIPLE IV: TOILET OF THE CAVITY
 All of the caries, debris, and necrotic
material must be removed (before the
radicular preparation is begun).
 Use of hand instruments may be
required along with copious irrigation.

29. LAWS OF ACCESS CAVITY PREPARATION
(KRASNER AND RANKOW)
LAW OF CENTRALITY
LAW OF CEMENTO ENAMEL JUNCTION
LAW OF CONCENTRICITY
LAW OF COLOR CHANGE
LAW OF SYMMETRY
LAW OF ORIFICE LOCATION

30. 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 .

31. LAW OF SYMMETRY : 1
 Except for maxillary molars, the orifices of the canals
are equidistant from a line drawn in a mesial distal
direction through the pulp chamber floor.

32. LAW OF SYMMETRY : 2
Except for the maxillary
molars, the orifices of the
canals lie on a line
perpendicular to a line drawn
in a mesial-distal direction
across the centre of the floor
of the pulp chamber.

33. LAW OF COLOR CHANGE
The color of the pulp
chamber floor is always
darker than the walls.

34. LAW OF ORIFICE LOCATION
 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 angles in the floor wall junction.
 Law of orifice location 3: the orifices of the root canals are located
at the terminus of the root development fusion lines.

35. MOUSE HOLE EFFECT

36. MOUSE HOLE EFFECT

37. ARMAMENTARIUM FOR ACCESS
PREPARATION
• Front surface mirror
• Endodontic explorer
• DG 16
• Endodontic
excavator
• Irrigating solutions
• Cotton pliers
• Broaches
• Glass slab
• Files & reamers
• Burs
• Rubber dam kit
Armamentarium

38. THE ROUND BUR
 Three sizes of round burs, Nos. 2, 4, and 6, are
routinely used.
 No. 2
 Mandibular anterior teeth
 Maxillary premolar (narrow chambers & canals)
 Incisal pulp horn area (Maxillary anterior teeth)
 No. 4
 Maxillary anterior teeth
 Maxillary and mandibular premolar teeth
 Maxillary and mandibular molars No. 2 & No. 4 Round bur

39. THE ROUND BUR
 No. 6
 Only in large pulp chamber of molars
 Taurodontism
 No. 1
 Used in the floor of pulp chamber to seek
additional canal orifice. Eg MB2
 Maillefer Endo-Z carbide fissure bur
 It is safe-ended and will not scar the pulpal floor.
 Moreover, it is longer bladed (9 mm) for sloping and
funnelling the access cavity.

40. AIDS IN LOCATING ROOT
CANAL ORIFICES
 Endodontic explorer
 Troughing of grooves with ultrasonic
tips,
 Staining the chamber floor with 1%
methylene blue dye,
 Performing the sodium hypochlorite
‘champagne bubble’ test and
visualizing canal bleeding points are
important aids in locating root canal
orifices.
 Magnification and illumination

41. ACCESS PREPARATION GUIDELINES
 STEP 1- Diagnostic radiograph.
 Visualization of the location of the pulp
space.
 Bucco-lingual angulations and coronal
anatomy are judged visually.

42. ACCESS PREPARATION GUIDELINES
 STEP 2: Restorative material impinging on the straight-
line access should be removed before pulp chamber is
accessed to prevent lodging of debris in the canals.
 Caries is removed to prevent irrigating solutions from
leaking past the rubber dam into the mouth and to
prevent bacterial contamination of the canal system
with saliva.
 Place an interim restoration.
 A 1 mm to 2 mm of occlusal adjustment of teeth may be
done.

43. ACCESS PREPARATION GUIDELINES
 STEP 3: The roof of the pulp chamber is best
perforated with a round bur.
 A no.2 bur ( anterior and premolar teeth)
 A no. 4 bur should be used in molar teeth.
 For teeth with porcelain crowns.
 The bur is best directed toward largest part of pulp chamber.
 In calcified, multi-rooted teeth, it is better to direct the
access toward the largest canal.

44. ACCESS PREPARATION GUIDELINES
 STEP 4-Once the pulp chamber is located (with light
upward pressure), the round bur is used to remove the
roof of the pulp chamber from underneath; the “belly” of
the bur should be used to cut on the outstroke.
 This should establish an initial outline form.
 The pulp chamber should be frequently flushed with
sodium hypochlorite solution to remove debris and
bacteria.

45. ACCESS PREPARATION GUIDELINES
 STEP 5- A sharp DG 16 double
ended explorer is used to locate
canal orifices.
 In heavily calcified teeth -
transillumination, and the careful
examination of internal dentin
color.
 Once the canals are located, a
no.10 or no. 15 K type of file is
introduced into the canal to
determine patency.
 Tooth length may be determined at
this point.

46. ACCESS PREPARATION GUIDELINES
 STEP 6- Final outline form is established
with a round tip, tapered, diamond bur
after the canals have been located and the
initial opening has been completed.
 This important outline form is dictated by
the internal anatomy and modified to
improve visibility, establish convenience
form and conserve critical tooth structure.

47. Removal of caries/defects/restorations
Direct round bur perpendicular to the lingual/occlusal
surface at its centre and then parallel to long axis ,until
a drop in effect - i.e. pulp chamber entry
De-roofing of the chamber completed by
working inside out
Locate the canal orifices using endodontic
explorer
Remove the lingual shoulder using GG
drills/Orifice enlargement

48. ACCESS CAVITY PREPARATION FOR :
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.

51. ACCESS CAVITY PREPARATION FOR:
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

53. ACCESS CAVITY PREPARATION FOR:
Maxillary Canine
Shape of access cavity
No pulp horn
Acess cavity is oval in shape with
greater diameter labiopalatally

55. ACCESS CAVITY PREPARATION FOR:
Mandibular Incisors
Access cavity of mandibular
central and lateral incisors is
almost similar
Shape is long oval with greater
dimensions directed
incisogingivally

57. ACCESS CAVITY PREPARATION FOR:
Mandibular Canine
 Shape of access opening
similar to maxillary canine-
oval, but,
 Smaller in size
 Root canal outline narrower in
mesiodistal dimension
 Two canals may be present

59. ERRORS IN ENDODONTIC ACCESS
OPENING
Errors occur when the
operator fails to:
to excavate and
identify all caries
and to remove
unsupported, weak
tooth structure or
faulty restoration.
to establish proper
access to the pulp
chamber space
and root canal
system
to identify the
angle of the crown
to the root and
angle of the tooth
in the dental arch
to recognize
potential problems
in access opening
through crowned
teeth.

60. Gouging at the labio
cervical
Gouging of labial
wall
Gouging of distal
wall
Ledge formationDiscoloration of
crown
-
Failure to explore,
debride or fill the
second canal

61. ACCESS CAVITY PREPARATION FOR:
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.

63. ACCESS CAVITY PREPARATION FOR:
Maxillary Second Premolar

64. ACCESS CAVITY PREPARATION FOR:
Mandibular First Pre-molar
• Oval access 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.

66. ACCESS CAVITY PREPARATION FOR:
Mandibular Second Pre-molar
• Similar to mandibular first premolar
• Enamel penetration initiated in
central groove dueto small lingual tilt
• Ovoid acess opening is wider
mesiodistally

68. ERRORS OF ACCESS
PREPARATION IN PRE-MOLARS

69. ACCESS CAVITY PREPARATION FOR:
Maxillary First Molar
 Shape of pulp chamber –rhomboid;
 Palatal canal orifice located palatally,
mesiobuccal canal orifice located under
mesiobuccal cusp, distobuccal canal
orifice located slightly distal and palatal
to mesiobuccal orifice.
 A line drawn to connect all three orifices
forms a triangle- molar triangle

71. THE SECOND MESIOBUCCAL CANAL
In vivo, Stropko reported finding two canals in 73.2% of first molars
before using the microscope and 93% after; 90% of the MB2s were
negotiable to the apex.
Gilles and Reader found that the mean distance of MB2 orifice from
MB1 was 2.31mm (range 0.7 to 3.75 mm).
Kulild and Peters found that the distance between MB1 and MB2 was
on average 1.82 mm and the orifice was to the lingual of MB1
MB2 orifice can sometimes be found close to or even in the palatal
canal orifice. While two mesiobuccal orifices are most common,
three can also be present.

72. ACCESS CAVITY PREPARATION FOR:
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.

74. ACCESS CAVITY PREPARATION FOR:
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

75. ERRORS OF ACCESS PREPARATION
IN UPPER MOLARS

76. ACCESS CAVITY PREPARATION FOR:
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.

78. ACCESS CAVITY PREPARATION FOR:
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

80. ACCESS CAVITY PREPARATION FOR:
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.

81. ERRORS OF ACCESS PREPARATION
IN LOWER MOLARS
 Overextended
 Perforation into furcation
 Failure to find a second distal canal
 Ledge formation caused by faulty
exploration and using too large of an
instrument.

82. RECENT ADVANCES IN CONCEPTS OF
ACCESS OPENING
Many times straight line access leads to severe loss of strategic tooth structure which
may be required for the strength of crown
Atleast 2mm of of dentin thickness should be present between external tooth surface
and the endodontic access at the finish line
The dentin near the alveolar crest is irreplaceable
An area of 4mm above and below crestal bone is important for ferrule, strength of tooth
in cervical area, so it should be always conserved maximally
GG drills are non end cutting and self centering ,so care must be taken to avoid strip
perforation or overcutting at furcation area
Pulp chamber should not be completely de-roofed; some of the roof is preserved all
around the periphery of the tooth which is also called soffit to avoid damage to the
lateral walls

86. But why?
 Are endodontically treated
teeth stiffer due to loss of
structure?

87. If not…
 Are endodontically
treated teeth stiffer
due to loss of
moisture?

88. Then…
 There definitely
must occur some
changes in the
dentin quality?

89. RADIX ENTOMOLARIS AND
RADIX PARAMOLARIS
 Supernumerary roots in mandibular molarsRadix 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

90. CHALLENGING ACCESS CAVITY
PREPARATION
 Teeth with minimal or no clinical crown:-depth of
penetration needed to reach the pulp canal is
measured on the preoperative radiograph.
 Clinician should study their root angulation on
preoperative radiograph.
 Heaviliy restored teeth:-here crown / root
angulation is altered. As these restorations block
the passage of light ,poor visibility. Most cases,
restorations are removed for better visibility.

91. CHALLENGING ACCESS ACVITY
PREPARATION
 Teeth with calcified canals:- here use of
magnification and transillumination, as
well as color changes and pulp chamber
shapes, dyes and champagne test should
be used.
 Calcified dentin must be slowly removed
using ultrasonic tips.
 Angled direction radiographs are used
 A small K file #6 or #8 coated with chelating
agent is used.

92. CHALLENGING ACCESS ACVITY
PREPARATION
 Crowded teeth:-conventional access preparation may
not be possible instead buccal access preparation may
be treatment of choice.
 Rotated teeth:- have altered crown to root
relationships, so it poses additional problems:-
1. Failure to locate extra canals
2. Excessive gouging of the coronal or radicular tooth
structure
3. Instrument separation in an attempt to locate the orifice
4. Failure to debride all pulp debris from the chamber.

93. CONCLUSION

94. REFERENCES:
 Pathways of pulp-stephen cohen(9th edition)
 British Dental Journal 197, 379 - 383 (2004)
 Sch. J. App. Med. Sci., 2014; 2(5B):1613-1617
 Access Cavity and Endodontic Anatomy,by Arnaldo
castellucci, m.d., d.d.s.
 Grossman endodontic practice-eleventh edition
 Dentsply Mallifer website