Access Cavity Prepration

ACCESS CAVITY
PREPARATION
Khin Swe Aye
B.D.S., Dip.D.Sc., M.D.Sc., Dr.D.Sc.,
F.I.C.C.D.E
Department of Conservative Dentistry
U D M (Ygn)

Contents:
I. Introduction
II. Objectives
III. Guiding Principles
IV. Influencing Factors in Access Cavity
Preparation
V. Morphology of root canals
VI. Access Cavity Preparation Technique
VII. Common Errors During Access Cavity
Preparation

I. INTRODUCTION
 Access preparation is the most
important phase of the technical
aspects of root canal treatment
 Access is the key that opens the
door to maximize cleaning, shaping
and obturation
Dept. of Conservative Dentistry
3

4
Pulp and periapical
tissues pathology
RCT

3 phases of RCT
Access cavity preparation
Cleansing and shaping
Obturation
6

Access preparation
7

Cleansing
and
shaping
8

9

10

11
Obturation

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13

II. Objectives of
Access Cavity Preparation
1. Remove all caries when present
2. Conserve sound tooth structure
3. Unroof the pulp chamber completely
4. Remove all coronal pulp tissue
(V/NV)
5. Locate all root canal orifices
6. Achieve straight-line access to apical
foramen
14

2. Conserve Sound Tooth
Structure
Removal of excess enamel and dentine
weakens the tooth and increases the
possibility of fracture or perforation
Key to get adequate SLA is to remove
dentin and enamel in strategic areas,
leaving other areas intact
15

• A properly designed access preparation
must allow;
- Minimal weakening of tooth
- Prevention of accidents
(Perforation, Fracture )

3. Unroof Pulp Chamber
Completely (Exposure of Pulp
Horns)
It permits adequate access to root
canals and facilitates locating them
It decreases the incidence of
discoloration in anterior teeth
17

18

• It permits maximum visibility especially
in posterior teeth
• It improves SLA to the canals
(Dentin shelves that overlie canal
orifices are likely to impede SLA,
Removed them)

6. Achieve Straight-Line Access
 It is the most critical aspect
 In the ideal procedure,
the instruments have to pass through the
chamber without touching the walls and
through the straight part of the canal un-
deflected
 The initial curve of the instrument would
occur at the first bend of the canal,
usually in the apical third of the root
21

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23

24

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26

Advantages of SLA
i. Improved Instrument Control
Minimizing instrument curvature and
deflection increases the operator's ability to
manipulate files in as many areas of the
canal as possible without grossly altering
the internal canal anatomy
29

 It is resulting in better cleaning and
shaping of the canal system with less
chance of undesirable internal alterations
such as transportation, ledging and zipping

• Ease of introducing instruments into
canals and controlled funneling of
canal orifices

32

ii. Improved Obturation
 SLA to apical portion makes the
obturation easier and more effective
(better spreader and plugger penetration)
iii. Decreased Procedural
Errors
 SLA decreases the procedural errors
such as ledge formation, apical
perforation and furcal (stripping)
33

34A
B C D
E

III. Guiding Principles of
Access Cavity Preparation
1. Shape the cavity so that instruments are
not deflected by access cavity wall as they
are permitted to apical portion of the root
canal
2. Be large enough to allow complete
debridement of pulp chamber
35

3. Not be excessively large because this may
seriously weaken the tooth
4. The floor of pulp chamber of posterior teeth
must not be disturbed because the orifices of
root canals are usually funnel shape and
removal of tissue in that area reduce the
diameter of canal opening which make
subsequent instrumentation more difficult

37

IV. Influencing Factors in
Optimal Access
Preparation
1. The size of Pulp Chamber
2. The shape of the Pulp Chamber
3. The number of individual root canals
and their curvature
38

1. Size of Pulp ChamberIn the young patients
preparations are more extensive than in
the older patients, in whom the pulp has
receded and the pulp chamber is smaller
in all three dimensions
39

2. Shape of Pulp Chamber
The finished outline form should
accurately reflect the shape of
chamber
40

• The floor of the pulp chamber in a molar
tooth is triangular in shape, owing to
the triangular position of the orifices of
the three canals
• This triangular shape is extended up the
walls of the cavity and out onto the
occlusal shape, hence the final occlusal
cavity outline form is triangular

The coronal pulp of the premolar is
flat mesio-distally, but is elongated
bucco-lingually
The outline form is an elongated oval
that extends bucco-lingually rather
than mesio-distally
42

3. Number and Curvature
of Root Canals
In order to instrument each canal
efficiently without interference, the
cavity walls often have to be extended
to allow an unstrained instrument
approach to the apical foramen
43

μCT scans of maxillary
central incisors
A.Common anatomic
presentation
B.Central incisor with a lateral
canal, which is common
C.Rare multiple-canal variation
All teeth are shown from both a
buccal and a proximal
perspective, along with the
cross-sectional anatomy at the
coronal, middle, and apical
levels

External Outline Form of Maxi Central
Incisor
• Rounded triangle with its base toward
the incisal aspect
• Width of the base is determined by the
distance between mesial and distal pulp
horns

54

lateral incisors
A. Common anatomic
presentation
B. Lateral incisor with a large
lateral canal, which is
common
C. Lateral incisor with an
apical delta
All teeth are shown from both
a buccal and a proximal
coronal, middle, and apical
levels

External Outline Form of Maxi Lateral
Incisor
• Similar to that of maxillary central
incisor,
however, it is smaller
• Rounded triangle or oval depending
on the prominence of mesial and distal
pulp horns

57

μCT scans for the
maxillary canine
A. Common anatomic
presentation
B. Canine with two roots
C. Canine with significant
deviations of the canal
system in the apical
third
cross-sectional anatomy at
the coronal, middle, and

External Outline Form of Maxillary
Canine
• Oval or slot shaped because no
mesial and distal pulp horns are
present

60

first premolars
A. Common anatomic
presentation of this
tooth showing two roots
B. Premolar with only one
canal
C. Premolar with three roots
cross-sectional anatomy at
the coronal, middle, and
apical levels

External Outline Form of
Maxillary First Premolar
• Oval or slot shaped
• It is wide buccolingually,
narrow mesiodistally, and
centered mesiodistally between
the cusp tips
• When 3 canals are present,
outline form becomes triangular,
with the base on the buccal aspect

63

64

65

Pulp chamber floor and canal
orifices of premolar
66

67
Maxillary First Premolar
• Trough the isthmus
• Modify the traditional access to a “T”-shaped access

Schematic representation of a three-canal access
preparation

Diagrammatic representation of supplemental
canal configurations based on the work of
Gulabivala and colleagues on a Burmese
population

External Outline Form of
Maxillary Second Premolar
• When 2 canals are present,
nearly identical to that of maxi first
premolar, Oval or slot shaped
• If only 1 canal is present, bucco-lingual
extension is less

71

μCT scans of maxillary first
molars
A. Common anatomic presentation
showing accessory/lateral
canals
B. First molar with four canals, with
mesiobuccal and
mesiopalatal
sharing an anastomosis in
the midroot
C. Maxillary molar with four pulp
horns, five canals, and
significant anastomoses between
the canals
buccal and a proximal perspective,

External Outline Form of Maxillary First
Molar
• The most complex
• Because the maxillary first molar almost
always has four canals, the access cavity
has a
rhomboid shape, with the corners
corresponding to the four orifices
• Mesially, not extend into the mesial marginal
ridge
• Distally, the preparation can invade the
mesial portion of the oblique ridge, but it
should not penetrate through the ridge

74

75

Pulp chamber floor and canal orifices of
maxillary molar
76

77

μCT scans of maxillary second
molars; (4) possible variations
A. Uncommon anatomic
presentation of
this tooth with one canal
B. Second molar with two canals
C. Second molar with three canals
D. Second molar with four distinct
canals
along with the crosssectional
anatomy at the coronal, middle, and

External Outline Form of Maxillary Second
Molar
• When 4 canals are present…..Rhomboid
shape
• When 3 canals are present…..Rounded
triangle
• When 2 canals are present…..Oval
(widest in bucco-
lingually)

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81

• Deutsch and Musikant (JOE 2004)
studied the morphology of the chamber and
found that the ceiling of the pulp chamber
was at the level of the C E J in 97 - 98 % of
the maxillary and mandibular molars
Evaluation of CEJ
• In a study involving 500 pulp chambers,
Krasner and Rankow (JOE 2004) found that
the CEJ was the most important anatomic
landmark for determining the location of pulp
chambers and root canal orifices

• 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
the CEJ (Location of CEJ)
• Making the CEJ the most consistent
repeatable landmark for locating the
position of pulp chamber

μCT scans of mandibular
central incisors
A. Common anatomic
presentation
B. Central incisor with two
canals
C. Central incisor with an apical
delta
buccal (vestibular) and a
proximal perspective, along
with the cross-sectional
anatomy at the coronal, middle,
and apical levels

External Outline Form of Mandibular
Central and lateral Incisors
• Triangular or oval depending on the
promonence of mesial and distal pulp
horns
• When 2 canals are present…..extended
well into cingulum gingivally

87

88

MANDIBULAR INCISORS
89

Mandibular Incisors
Limited access will
impede the instrument
from getting into the
lingual canal
90

92Access for Mandibular Incisor
• The final shape of the
access cavity should be ovoid
or elliptical.

Access for Mandibular Incisor
93
A file can only enter the buccal canal with a considerable
coronal interference in a limited access cavity
Endodontics: Arnaldo Castellucci MD, DDS

Access for Mandibular IncisorDept. of Conservative Dentistry
94
• Removal of coronal obstacles will create an adequate
access cavity
• A file can now enter the lingual canal easily
Endodontics: Arnaldo Castellucci MD, DDS

95

canines
A. Common anatomic
presentation
B. Canine with an extra apical
canal
C. Canine that splits into two
but returns to one canal
apically
a

External Outline Form of Mandibular Canine
• Very similar to maxillary canine
• Oval or slot shape

98

first premolars
B. First premolar with significant
canal deviations in the middle
to apical third before returning to
a single large canal apically and
a small deviating canal to the
proximal
C. First premolar with a branching
main
canal lingually and multiple
accessory canals
along with the cross-sectional

First Premolar
• Oval
(typically wider mesio-distally than its
maxillary counterpart)
• Mesio-distally the access preparation is
centered between the cusp tips

101

second premolars
B. Second premolar with significant
canal deviations in the middle to
apical third
C. Second premolar with fused root
that exhibits two distinct canals
anatomy at the coronal, middle, and
apical levels

Second Premolar
• Very similar to mandibular first premolar

104

first molars
B. First molar with three main
canals and a deviant fourth
canal/fourth root
C. First molar with wide
connections or anastomoses
between the mesial canals,
demonstrating multiple canal
exits
anatomy at the coronal, middle,
and apical levels

• The access cavity for the mandibular
first molar typically is tringle or
trapezoid or rhomboid, regardless of
the number of canals present
First Molar

I. 3 mesial canal orifices and 1 distal canal orifice
II. 2 mesial and 2 distal canal orifices
(B, Buccal; D, distal, distal orifice; DB, distobuccal orifice;
DL, distolingual orifice; L, labial; M, mesial; MB,
mesiobuccal orifice; ML, mesiolingual orifice; MM, middle
mesial orifice)
MB
MM
ML
D
DB
DL
B B
L L
MB
ML

108

109

Pulp chamber floor and canal orifices
of mandibular molar
110

Mandibular First Molar
Three canals in the
mesial and one or two
canals in the distal
111

Mesial Middle Canal
112
• Note a quadrangle access
• Pulpal floor map

MESIAL MIDDLE CANAL
113
• Three separate POE in the mesial canals

second molars
A. Two-canal second molar with
fused roots
B. Second molar with three initial
canals ending in one canal
apically in both roots
C. Second molar with four distinct
canals
perspective, along with the cross-
sectional anatomy at the coronal,
middle, and apical levels

• When 3 canals are present….. similar to
that for the mandibular first molar, although
perhaps a bit more triangular and less
rhomboid
• When 2 canals are present….. rectangular,
wide mesiodistally and narrow
buccolingually
• When single canal is present….. oval and is
lined up in the center of the occlusal surface
Second Molar

119

C-Shape Canals
120

121
C-Shape Canals

VI. Access Cavity
Preparation
Techniques
124

Access of Choice
 From the carious cavity
Instrument will be carved
Incomplete debridement of pulp chamber
Ledge formation in root canal
 Cingulum Access Cavity
Instrument will be carved
Incomplete debridement of pulp chamber
Ledge formation in root canal

126

127

 At center portion
• Direct straight line to apical area
• Complete debridement of pulp chamber
and root canal

Basic Steps
in Access Cavity Preparation
Step 1. Out line form through enamel
The out line form should be completed
through enamel into dentin
All caries, weak restoration and weak
structure should be removed
Step 2. Location and exposure of pulp chamber
The pulp chamber is being searched for
keeping the floor of the preparation concave

Step 3. Refinement of opening and complete
removal of pulp chamber roof
All cutting is done with the bur
moving out from the pulp chamber
Step 4. Removal of pulp chamber contents
Step 5. Location of root canal

131

132

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134

135

136

137

138

139

140

141

142

143

144

145

146

Coronal Access
 Initial penetration to
chamber
 “de-roof” to
complete the access
147

Coronal Access
 straight line entry
 all canals are visible
148

149
Penetrate occlusal to the cingulum at a roughly 90 degree to the
palatal surface
Access Cavity Preparation for
Maxillary Central Incisor
Endodontics-Arnaldo Castellucci

ACCESS CAVITY
150

151

152

153

154

Access Opening of
Maxillary Anterior Teeth
1. The shape of access outline form for all anterior
teeth should reflect the shape of internal
anatomic structure of coronal pulp chamber of
each tooth
The access cavity shape is slightly triangular,
with the base of triangular facing towards the
incisal edge

2. Entrance is always gained through the lingual
surface
The first entry point is made just above the
cingulum
3. The direction of bur should be at right angle to
the lingual surfac
Only enamel is penetrated with a high-speed
hand-piece
4. After penetration of enamel, bur is directed
parallel to the long axis of the tooth until the
pulp chamber is reached

157

5. When the sensation of dropping through the roof of the
pulp chamber has been felt, dentin shelves that
usually overlie and obscure the canal orifices are
removed including the pulp horns with low speed
bur moving out from the pulp chamber
6. Direct access can be verified by placing straight end of
endodontic explorer into the canal orifice
The explorer should follow the path of canal without
impedance from the walls of the surrounding
access preparation

159

160

VII. Common errors
1. Over extension
2. Inadequate access
3. Misdirection
4. Labial perforation
5. Perforation at furcation area of multi
rooted teeth
6. Accidental obturation of canal orifices
with debris
7. Weakening of tooth structure
8. Failure to reach the pulp chamber
161

Overzealous tooth removal
caused by improper bur
angulation and failure to recognize
the lingual inclination of the tooth
This results in weakening and
mutilation of the coronal tooth
structure, which often leads to
coronal fractures

164

165

Inadequate opening; the
access cavity is positioned too
far to the gingival, with no incisal
extension
This can lead to bur and file
breakage, coronal discoloration
because the pulp horns remain,
inadequate instrumentation and
obturation, root perforation,
canal ledging, and apical
transportation

Labial perforation
caused by failure to
extend the preparation to
the incisal before the bur
shaft entered the access
cavity

Buccal Perforation
168

Furcation perforation caused by failure
to measure the distance between the
occlusal surface and the furcation
The bur bypasses the pulp chamber and
creates an opening into the periodontal
tissues. Perforations weaken the tooth and
cause periodontal destruction
To ensure a satisfactory result, they must
be repaired as soon as they are made

Perforation of the mesial tooth
surface caused by failure to recognize
that the tooth was tipped and failure to
align the bur with the long axis of the
tooth
This is a common error in teeth with
full crowns
Even when these perforations are
repaired correctly, they usually cause
a permanent periodontal problem
because they occur in a difficult
maintenance area

The most embarrassing error,
with the greatest potential for
medical and legal damage, is
entering the wrong tooth
because of incorrect dental dam
placement
When the crowns of teeth
appear identical, the clinician
should mark the tooth with a
felt-tip marker before placing
the dental dam

Burs and files can be broken if
used with an improper motion,
excessive pressure, or before the
access cavity has been properly
prepared
A broken instrument may lock into
the canal walls, requiring
excessive removal of tooth
structure to retrieve it
On occasion, fragments may not
be retrievable

• Multiple pretreatment radiographs,
• CBCTs,
• Examination of the pulp chamber floor with a sharp
explorer,
• Visual assessment of color changes in the dentin,
• Troughing of anatomic grooves with ultrasonic tips,
• Staining the chamber floor with 1% methylene blue
dye,
• Performing a sodium hypochlorite “champagne
bubble” test
• Visualizing the pulp chamber anatomy from
established documents,
• Root canal bleeding points
AIDS

The dental operating microscope (DOM)
has vastly improved locating the position of
the coronal canal anatomy

Access Cavity Prepration

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