Anatomy of Pulp Cavity and Its Access Opening

Anatomy of Pulp Cavity and Its
Access Opening
Presented By -
Aditya Bhagat
PG IIIrd Year

Pulp Cavity -
the central cavity entirely enclosed by dentin except at the apical foramen
Divided into the following:
A coronal portion - pulp chamber
A radicular portion - root canal
Pulp chamber
In anterior teeth - pulp chamber gradually - merges into the root canal
In multirooted teeth, pulp - cavity consists of a single pulp chamber and usually three
root canals, can vary from 1 to 4 or more.
Anatomy of Pulp Cavity and Its Access Opening 2

Roof of the pulp chamber consists of dentin covering
the pulp chamber occlusally or incisally
 Pulp horn is an accentuation of the roof of the pulp
chamber directly under a cusp or developmental
lobe. The term refers more commonly to the
prolongation of the pulp itself directly under a
cusp.
 Floor of the pulp chamber runs parallel to the roof
and consists of dentin bounding the
pulp chamber near the cervical area of the tooth,
particularly dentin forming the furcation area
The canal orifices- openings in the
floor of the pulp chamber leading into
the root canals.
Anatomy of Pulp Cavity and Its Access Opening
3

Root Canals - The root canal is the portion of the pulp cavity
from the canal orifice to the apical foramen. for
convenience it may be divided into three sections, namely: coronal,
middle, and apical thirds.
Accessory canals, or lateral canals, are lateral branching of the
main root canal generally occurring in the apical third or furcation
area of a root
Lateral canal is an accessory canal that branches to the lateral
surface of the root and may be visible on a radiograph.
 Apical foramen is an aperture at or near the apex of a root
through which the blood vessels and nerves of the pulp enter or
leave the pulp cavity.
 Accessory foramina are the openings of the accessory and
lateral canals in the root surface

Goals of Access Cavity Preparation
According to Vertucci, the following are the objectives of access cavity preparation:
• Removal of all carious tooth structure
• Conservation of sound tooth structure
• Complete de-roofing of the pulp chamber
• Removal of coronal pulp tissue (vital and necrotic)
• Location of all root canal orifices
• Straight line access to the root canal

Clinical Guidelines for Access Cavity Preparation
I. Preoperative Considerations
A. Armamentarium for Access Cavity Preparation
Front surface mouth mirrors
Airotor and slow-speed rotary handpieces
Burs: These include the following:
–– Round carbide burs (No. 2, No. 4, and No. 6) for caries removal and defining the external outline shape
–– Diamond burs with round cutting ends for axial wall extensions
–– Fissure carbide burs and diamond burs with safety tips.

Round diamond burs for entry into teeth with porcelain or ceramometal
restorations and trans metal burs for teeth with metal restorations
–– For calcified teeth, extended long shank burs such as Mueller burs (Brasseler,
USA) and LN burs (Dentsply Maillefer, USA)
Endodontic spoon excavator
Endodontic explorers, e.g DG-16
Additional aids
–– Magnification and illumination aids
–– Ultrasonic tips
–– Microopeners and microdebriders
(a) Endodontic excavator. (b) DG–16 endodontic
explorer. (Courtesy: Hu-Friedy Mfg Co., USA.)
Start X ultrasonic tips 1, 2, 3, and 5 for access refinement.
(Courtesy: Dentsply Maillefer.)
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B. Assessment of Occlusal Tooth Anatomy
The following clinical observations are indicative of an unusual root canal anatomy:
Abnormality in the size and shape of the tooth
(a) prominent cingulum of a mandibular incisor - an extra canal may be found lingually.
(b) Prominent lingual cusp of a mandibular bicuspid - extra canal may be found lingually.
(c) Prominent buccal cusp and wide crown mesiodistally - a mesiobuccal canal or root may be found in the maxillary
first premolar.
(d) Prominent buccal cusp and wide crown buccolingually on the mesial half in the maxillary molar – a second
mesiobuccal canal may frequently be found.
(e) Where unusually small canals are seen, an extra canal may be found, as in the distal root of a mandibular molar.

Major principle of the endodontic cavity outline form:
The internal anatomy of the tooth (pulp) dictates the external outline form. - accomplished
by extending preparation from the inside cavity to the outside surface, that is, working from
inside to outside.
Size and shape of endodontic coronal preparations relates to the size and shape of the pulp and
chamber.
C. Complicating Factors
Access cavity preparation would be challenging and has to be prepared carefully in the following conditions:
• Rotated teeth/malpositioned teeth
• Tipping/mesial tilting of the tooth
• Grossly decayed teeth
• Teeth with full-coverage restorations
• Abutment teeth of fixed prostheses
• Teeth with extensive calcifications

D. Radiographic Assessment
Visualization of the internal anatomy of the tooth can be done using preoperative periapical radiographs. Box 12.1 presents
some of the features that can be visualized using periapical radiographs.
 Mesiodistal tilt of the tooth
 Size and shape of the pulp chamber
 Thickness of the roof of the pulp chamber
 Presence of pulp stones
 Variations in the number of canals and/or roots
 Extent of root and canal curvature
 Radiographic changes in the furcation and/or periradicular region
II. Clinical Considerations
A. Complete Removal of Carious Tooth Structure and Other Restorative Material
B. Complete De-Roofing and Removal of Dentinal Shoulders
The overhanging roof of the pulp chamber misdirects the instrument causing mishaps

Removal of the dentinal shoulders provides straight line access to the root canals.
The following dentinal shoulders are to be taken into consideration:
- Mandibular anteriors Lingual shoulder
- Maxillary anteriors Palatal shoulder
- Premolars Mesial and distal shoulders
- Maxillary molars Buccal and mesial shoulders
- Mandibular molars Mesial and distal shoulders

Krasner and Rankow’s Laws of Access Opening
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.
Law of the 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 the CEJ. The CEJ is the most consistent, repeatable landmark for
locating the position of the pulp chamber.

Law of symmetry 1: Except for maxillary molars, the orifices of the canals are equidistant from a line drawn in a
mesiodistal direction through the pulp chamber floor.
Law of symmetry 2: Except for maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn
in a mesiodistal direction across the center of the floor of the pulp chamber.
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Law of color change: The color of the pulp chamber floor is always darker than the walls.
Law of orifices location 1: The orifices of the root canals are always located at the junction of the walls and the
floor.
Law of orifices location 2: The orifices of the root canals are located at angles in the floor–wall junction.
Law of orifices location 3: The orifices of the root canals are located at the terminus of the root developmental
fusion lines.

Individual Tooth Anatomy
Maxillary Central Incisor
Single root with single canal.
Pulp Chamber
‰
. Located in the center of the crown and equidistant from the dentinal walls
‰
. Mesiodistally broad
‰
. In young patient, it shows three pulp horns correspond to enamel mamelons on the incisal edge
Root Canal
‰
. Usually one root with one straight root canal

Commonly Found Anomalies
‰
. Palatogingival groove
‰
. Talon’s cusp
‰
. Fusion
‰
. Gemination
Clinical Considerations
‰
. Pulp horn can be exposed following a relatively small fracture of an incisal corner in the young patient
‰
.I Placing the access cavity too far palatally makes straight line access difficult
‰
. . Labial perforation is most commonly seen during access cavity preparation

Access Opening:
Access Shape is slightly triangular, with the base of the triangle toward the
incisal edge (Fig. g and h).
The enamel is penetrated in the center of the palatal surface at an angle
perpendicular to it with a No. 4 round bur (Fig b).
After penetration of the enamel, the bur is directed along the long axis of the
tooth until A “drop” of the bur into the chamber may be felt if the chamber is
large enough. (Fig. c).
The roof of the pulp chamber are remove by working from the inside to the
outside following the internal anatomy (Fig.d).

This makes the access cavity walls confluent with the lateral and incisal walls of the pulp chamber and provides
the access cavity with a “straight line” penetration to the apical root canal.
A Gates-Glidden drill (usually No. 4) / orifice enlarger is used to remove the palatal shoulder by working from
inside to outside

Maxillary Lateral Incisor
Single root with a Single canal system
Pulp Chamber
Similar to central incisor except that
• Incisal outline is more rounded
• Two pulp horns are present
Root Canal
• Single root with smaller canal is seen when compared to central incisor
Maxillary Lateral Incisor

• Palatogingival groove
• Peg laterals
• Fusion
• Gemination
• Dens invaginatus

‰
. . Palatal curvature of apical third can cause ledge formation - complicate surgical procedures like root
end cavity preparation and root resection
‰
. Lateral canals are more common than maxillary central incisors
‰
. Labial perforation is common error during access cavity
Access Opening:
• Similar to that for the maxillary central incisor, but it is smaller and usually more ovoid.
• No. 2 round bur may be used instead of a No. 4.

Maxillary Canine
Single root with a single canal system - Type 1.
Pulp Chamber
Labiopalatally, pulp chamber is almost triangular in shape
Mesiodistallys it is narrow, resembling a flame
One pulp horn corresponding to one cusp is seen
Root Canal
A single root canal which is wider labiopalatally than mesiodistaly

•
• Dilacerations
• Two roots with two canals
Surgical access sometimes becomes difficult because of the long length of the tooth
32% canals may show distal apical curvature
Abscess of maxillary canine perforates the labial cortical plate below insertion of levator muscles of the upper lip and
drains into the buccal vestibule
If perforation occurs above the insertion of levator muscles of lip, drainage of abscess occurs into the canine space,
resulting in cellulitis

Access Opening:
The access opening for the maxillary canine is similar to maxillary central and lateral
incisors.
Shape of the access opening - circular to ovoid.

Maxillary First Premolar
It has two roots with two canals. Canal form is usually Type 1.
Pulp Chamber
It is wider buccopalatally with two pulp horns, corresponding to buccal and
palatal cusps
Palatal canal is usually larger than buccal canal
Roof of pulp chamber is coronal to the cervical line
Floor is convex with two canal orifices
Root Canal
Two roots with two canals are seen commonly.
Buccal canal is directly under the buccal cusp and palatal canal is directly under
the palatal cusp
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• Dens evaginatus
• Dilacerations
Radiograph with different angulations - to avoid superimposition of canals
Avoid overflaring of the coronal part of buccal root to avoid the perforation of mesial groove.
The buccal canal is directly under the buccal cusp - orifice can be located by following the buccal wall of the pulp
chamber.
The palatal canal is larger- directly under the palatal cusp - orifice can be penetrated by following the palatal wall
of the pulp chamber.

In teeth with single roots, straight roots - 38.4% and distal curve present in 36.8%.
Whether maxillary first premolars have one or two roots, they have two root canals at the
apex in 69% of cases.
Access Opening –
No. 2 round bur used to penetrate the enamel in the center of the occlusal surface
between the buccal and lingual cusps, along the long axis of the tooth.
The operator frequently feels the bur “drop” into the pulp chamber when the
chamber is large.
To remove the roof of the pulp chamber, one should place the bur alongside the
walls of the chamber and cut occlusally

A tapered cylinder, self-limiting diamond bur is used to remove the remaining roof of
the pulp chamber
Clinical Note
The border of the ovoid access cavity of a maxillary premolar should not extend
beyond half the lingual incline of the facial cusp and half the facial incline of the
palatal cusp

Maxillary Second Premolar
Single root with single canal system
Pulp Chamber
‰
. Pulp chamber - wider buccopalatally and narrower mesiodistally
‰
. Cross-section - narrow and ovoid shape
Root Canal
‰
. In more than 60% of cases, a single root with a single canal is found
‰
. If two canals - they may be separated along the entire length of the root
or merge to form a single canal apically

• Taurodontism
• Two roots with two or three canals
• Narrow ribbon-like canal is difficult to clean and obturate
• If one canal is present, orifice is indistinct, but if two canals are present, two orifices are
seen
The access opening for the maxillary second premolar is basically the same as that for the
maxillary first premolar. It is varied only as dictated by the anatomic structure of the pulp
chamber.

Maxillary First Molar
It has three roots with three to four canals.
Pulp Chamber
Largest pulp chamber
Bulk of pulp chamber lies mesial to the oblique ridge
Roof converges and lingual wall disappears, forming triangular form
Orifices of root canals are located in the three angles of the floor; palatal orifice
is the largest and easiest to locate and appears funnel-like in the floor of pulp
chamber
Distobuccal canal orifice is located more palatally than mesiobuccal canal
orifice
More than 80% of teeth show presence of two canals in mesiobuccal root.
MB2 is located 3 mm palatally and 2 mm mesially to the MB1 orifice

Access opening :
Bur is placed in central fossa and directed towards the palatal canal, where the pulp chamber of this tooth is
largest.
A “drop” of the bur into the pulp chamber may be felt if the chamber is large.
In partially calcified chambers, the drop of the bur is not felt, and the operator has to rely on the measurements
made from the radiograph to avoid Perforation.

The shape and size of the internal anatomy of the pulp chamber guide the cutting.
A tapered-cylinder, self-limiting diamond bur is used to deroof the pulp chamber.
The access opening is triangular, with round corners extending toward, but not including, the mesiobuccal cusp
tip, marginal ridge, and oblique ridge. This triangular preparation permits direct access to the root canal orifices.

Clinical Note
Š
Š
The triangular access preparation in a maxillary molar is modified into a rhomboidal shape whenever the MB-2 canal is suspected or
traced.
MB2 should be searched 2–3 mm palatal to the MB-1 canal, in the direction of an imaginary line connecting the MB-1
and palatal canal.
Modify the mesial wall of the access cavity and trough or countersink with the help of ultrasonic tips mesially and apically along the
mesiobuccal pulpal groove.
Š
Š
Two separate and distinct mesiobuccal canals occur in 84% of teeth in which two separate orifices are traced.
According to Nallapati, the following are the possible locations of the MB-2 canal in the maxillary first molar:
- Present on the developmental line that connects MB-1 and palatal canal
- Present mesial to the developmental line that connects MB-1 and palatal canal

- Appears as a groove on the palatal wall of the MB-1 canal
- Splits off the MB-1 canal in the middle third of the canal
- Splits off the MB-1 canal in apical third of the canal
- Š
Š
The clinician should always suspect the presence of the MB-2 canal and modify the access cavity accordingly.

Maxillary Second Molar
It has three roots with three to four canals almost similar to first molar.
Pulp Chamber
• Similar to first molar except that it is narrower mesiodistally
• ‰
Roof is more rhomboidal in cross-section and floor is an obtuse triangle
• Mesiobuccal and distobuccal canal orifices lie very close to each other.
• Sometimes all the three canal orifices lie in a straight line
Root Canal
• Similar to first molar except that roots tend to be less divergent and may be fused.
Anomalies present
• Two palatal canals and two palatal roots
• Fusion of roots
• Taurodontism
‰ Similar to maxillary first molar

• Maxillary second molar lies closer to the maxillary sinus than first molar
Access Opening:
Similar to maxillary first molar, with the variations in anatomic structure.
Anomalies:
The most frequent anomalies in the maxillary second molar are the presence of only one root and one canal.

Maxillary Third Molar
Pulp Chamber
It is similar to second molar but displays great variations in shape, size and form of pulp chamber with presence of
one, two, three or more canals at times.
Maxillary third molar is closely related to maxillary sinus and maxillary tuberosity.
Access Opening:
The access opening is similar to that for the maxillary second molar, with modifications for variations in anatomic
structure.

Mandibular Central Incisor
It is the smallest tooth in the arch.
Pulp Chamber
• It is wider labiolingually than mesiodistally
• Cross-section - ovoid
Root Canal
There can be
• Single canal with one foramen in 65% cases
• Two canals with one foramen in 28% cases
• Two canals with separate foramen in 7% cases
• ‰
Germination
• Fusion

‰
. Because of groove along the length of root and narrow canals, weakening of the tooth structure or
chances of strip perforations are increased
‰
. It is common to miss the presence of two canals on preoperative radiograph if they are
superimposed
‰
. Second canal is usually found lingual to the main canal
Access Opening:
Similar to maxillary anterior teeth, with the variations due to smaller size demands.
Shape - long and oval.
Proper access enables to explore the cervical third of the root to determine whether a second root
canal is present.

Mandibular Lateral Incisor
Pulp Chamber
Similar to central incisor except that it has larger dimensions.
Root Canal
‰
. Similar to central incisor
‰
. Root is straight or distally curved
These are similar to central incisor.
Access Opening: The access opening is made in the same manner as for the mandibular central incisor.

Mandibular Canine
It has single root with single canal system.
Pulp Chamber
‰
. Ovoid in cross-section - broader labiolingually and narrower
mesiodistally
Root Canal
‰
It has one root and one canal in 94% cases but two roots with
separate foramen are present in 6% cases

• Dilaceration
• Two canals in single root
Access Opening: Similar as for the maxillary canine, with the variations
dictated by a smaller anatomic dimension.

Mandibular First Premolar
It has single root with single canal but occasionally division of root is
present in apical third.
Pulp Chamber
• Buccolingually, wider and ovoid in cross-section
• Mesiodistally narrow
• Two pulp horns present, buccal horn being more prominent

• Dens evaginatus
• ‰
Single root splits into two, of which buccal is straight and lingual splits at right angle,
giving letter “h” appearance.
• Perforation at distogingival margin is caused by failure to recognize the distal tilt of
premolar

Access opening-
• The mandibular first premolar has 30° lingual tilt of the crown to the long axis
of the root.
• To compensate for the tilt and prevent perforations, the enamel is penetrated
at the upper third of the lingual incline of the facial cusp with a bur centered
mesiodistally and directed along the long axis of the root.
• The access cavity is ovoid, extending buccolingually.
• This ovoid access preparation permits exploration for bifurcations or
trifurcations in the middle and apical thirds.

Mandibular Second Premolar
Root Canal
Usually only one root and one canal is seen.
Clinical Consideration
They are similar to mandibular first premolar.
‰
Pulp Chamber
‰
. It is similar to first premolar except that lingual pulp horn is more prominent
‰
. Cross-section shows an oval shape with greater dimensions buccolingually

Access Opening:
Same as for the mandibular first premolar,
except that:
• the enamel penetration is initiated in the central fossa,
• the ovoid access opening is wider mesiodistally, as dictated by the wider pulp chamber.

Mandibular First Molar
Pulp Chamber
• It is quadrilateral in cross-section at the level of the pulp floor being wider
mesially than distally
• Roof is rectangular in shape with straight mesial and rounded distal wall.
• Four or five pulp horns are present
• Mesiobuccal orifice is present under the mesiobuccal cusp
• Mesiolingual orifice is located in a depression formed by the mesial and
lingual walls
• ‰
Distal orifice is the widest of all three canals. It is oval in shape with greater
diameter in buccolingual direction

Anomalies present
• Taurodontism
• Radix entomolaris—supernumerary roots
• C shaped canals
• Over enlargement of mesial canals should be avoided to prevent procedural errors
• To avoid superimposition of the mesial canals, radiograph should be taken at an angle
Access Opening: The access opening
for the mandibular first molar follows
the anatomic features of the pulp
chamber. The enamel and dentin are
penetrated in the central fossa with the
bur angled towards the distal root,
where the pulp chamber is largest.
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The access opening is usually trapezoidal with round corners or rectangular if a
second distal canal is present.
The access opening extends toward the mesiobuccal cusp to uncover the
mesiobuccal canal, lingually slightly beyond the central groove and distally slightly
beyond the buccal groove.
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Mandibular Second Molar
It has two roots with three canals.
Pulp Chamber
• It is similar to the first molar but smaller in size
• Root canal orifices are smaller and lie closer
Root Canal
• Two roots with two or three canals seen. If two canals are seen, both orifices are in mesiodistal midline
• If two orifices are not on mesiodistal midline, one should search for another canal on opposite side

Anomalies present
• C-shaped canals, that is, mesial and distal canals become fused into a fin
• Taurodontism
• Fused roots
• Single canal
• Radix entomolaris
• Perforation can occur at mesiocervical region if one fails to recognize the mesially tipped molar

Clinical Note
• apex of the root and the mandibular canal may be closer than that of the
mandibular first molar.
• There is a significant incidence of this tooth having two canals only: one mesial
and one distal
Access Opening:
Similar to mandibular first molar.
Because of the buccoaxial inclination, it is sometimes necessary to reduce a
large portion of the mesiobuccal cusp to clean and shape the mesiobuccal
canal.

Mandibular Third Molar
Pulp Chamber and Root Canals
Pulp cavity resembles the first and second molar but with enormous variations, that is, presence of one, two,
or three canals and “C-shaped” root canal orifices
• Root apex is closely related to the mandibular canal
• Alveolar socket may project onto the lingual plate of the Mandible
Access Opening: The access opening for the mandibular third molar is created as for the mandibular first and
second molars, with the variations that anatomic structure dictates.

A Paradigm Shift in Designs of Access Cavity Preparations
Newer advances in access designs
• Conservative Endodontic Access Cavity
• Ninja Endodontic Access Cavity
• Orifice-Directed Dentin Conservation Access Cavity
• Incisal Access
• Calla Lilly Enamel Preparation
• Image guided endodontic access preparations.

Conservative endodontic access cavity (cecs)
 Given by - David Clark and Khademi
 Developed Conservative or constricted access cavities
 Tooth penetrated centrally at the fossa and then as per need extended in order to find out canal orifices
 Care should be taken while instrumentation and using the right type of armamentarium during preparation.
 Fracture strengths in mandibular molar prepared according to the traditional endodontic as well as conservative
endodontic methods of preparing the cavities
A representation of traditional cavity
(green dots) and conservative cavity (brown line) in
mandibular molar
57

Ninja endodontic access cavity (necs)
The Ninja access cavity is also called as “PEAC” (point endodontic access cavity) as well as “UEC” (ultraconservative
endodontic cavity.
1-4 sketches showing, occlusal view (1-3)
and sagittal view (4) of designs of access
cavity of lower molars (first).
Traditional access cavity (1-4) (blue-dashed
line),
conservative access cavity (1,3 and 4)(green),
and the “ninja” ultraconservative cavity (2-
4)(pink).
Comparing the 3 kinds of access cavity
designs; in no.4 (sagittal view) and in no.3
(occlusal view) respectively.
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• It is seen to be in line same as enamel cut which is 90⁰ or greater, to occlusal area, leaving the root canal
orifices tracing from the various visual angulations a lot easier.
• Gianluca Plotino et al in a invitro study, compared fracture strength of the restored teeth and root with the
conservative cavity, the traditional cavity, or the ninja endodontic access cavity.
• The results showed reduction in the fracture probability of the teeth treated endodontically with Conservative
Endodontic Access Cavity and NEC
• Increased fracture strength were seen with CEC and NEC, which was greater than teeth with traditional
endodontic access cavity.
• Therefore, we can say that Ninja endodontic access cavity was found to have a better resistance of fracture
when compared to conventional access prepared cavity.
59

Dentin conservation and orifice-directed access cavity (truss access cavity)
• The main motive of the “truss” access cavity design is to leave some amount of dentin between two prepared
cavities for preserving the dentin.
• Different cavities are made in order to approach the canals.
• Here, we reach the pulp chamber through the crown discontinuities in either caries or a previously done
restoration.
• Hence, it is an approach which is decided by the lesion.
• It minimizes the restorative necessity of the teeth by taking benefit of the absent hard tissue structures for access.
• Two separate cavities made preserving the dentin in between the two cavities.
A representation of traditional cavity
(green dots) and truss cavity (orange dots) in
mandibular molar.
60

The limiting factors of this design of cavity :
 inclination of the tooth,
 complexity of the anatomy,
For example,
- in the mandibular molars, we make two different cavities to reach the mesial as well as the distal canals but
in the maxillary molars, the “mesio-buccal” and the “disto-buccal” canals are reached in a cavity only as well
as a complete different cavity for the palatal canal is made.
Experts conducted an invitro study of strength of teeth treated endodontically with NECs, TECs or CEC and found
that both CECs and NECs presented a higher fracture strength than TECs in maxillary as well as mandibular
molars and premolars
Traditional cavities leads to a good conservation of the canal’s original anatomy, present while shaping when
compared to Conservative Cavity, specifically at apical portion.
Rate of finding out MB2 of traditional (60%), conservative (53.3%) are higher than Ninja (31.6%) cavities
statistically.
61

• Fracture types are seen to be less serious in case of CEC preparation when compared to traditional cavity
• The conservation of dentin resulted in an increased fracture resistance in conservative category which is double
the resistance of fracture the traditional category.
It is clearly seen that in both traditional as well as conservative cavities there are both good and poor
results because focusing on too much of conservative cavities can result in improper cleaning and shaping as
well as the incapability to get more than the expected number of canals which leads to bad prognosis of the
ongoing treatment.
Hence, we should strike a balance between both the types of cavities and use a particular design which would
result in less failure.
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Calla lily enamel preparation
Enamel is cut at 45º in order to engage enamel rods and to provide a favorable C factor.
The shape of the preparation resembles a Calla Lily with almost complete involvement of the occlusal surface
that aid in resisting the compressive forces.
Traditional access cavity was compared with Calla Lily enamel preparation and it was seen that unfavourable C
factor as well as poor engagement of rods of enamel are present when the old amalgam or composite is removed
or in case of the traditional access, which makes 90 degree with the occlusal table.
At 45 degree, the enamel then is cut in shape of Calla Lily.
Traditional access cavity (parallel-sided) 90°
to the occlusal table (A), compared with the Calla Lily
access preparation where enamel is cut at 45° (B).
63

Calla Lily enamel preparation is based on the principle of
ICE:
“I”-Infinity edge
“C”-Compression based
“E”-Enamel driven (engage 70% enamel and 30% dentin)
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Image-guided endodontic access preparations
It utilizes those images easily accessible to clinicians.
Rather than “one common size fitting all”, it ascertains specific location as well as size of access cavity.
The purpose is to judiciously preserve dentin and prepare as small an access cavity possible [8].
To customize the kind of access depending on a particular tooth is the ideal action of this system.
Image guided endodontic access preparations are of two types mainly;
• CT Dynamic access
• CT/ CBCT guided static 3D templates
Dynamic access: known very commonly as X entry access.
• Popularized by Charles M Buchanan.
• The technique was traditionally used in implantology.
• The procedure utilizes CBCT volume plan to prepare access by 3D assessment of jaw position and bur
position with overhead cameras and software.
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Static 3D template:
This utilises CBCT images and 3D surface scanners to create virtual images of burs and
guide sleeves.
A virtual template is designed and printed using 3D printers. Templates are attached to models and
access is prepared with specially designed burs.
66

Yiseul Choi BSDH et al in 2021 conducted a study in which Access opening guide was
produced using a 3D printer (AOG-3DP).
The purpose of this study was to determine the effectiveness of using an AOG-3DP during access opening
for shortening the preparation time and preventing overpreparation of teeth during endodontic access.
Two groups were made. The AOG-3DP was produced and applied in the test group, while no aid was used in
the control group.
Production of the access opening guide
Images of each sample were obtained using 100-μm-resolution CBCT
Mimics software (Materialize, Leuven, Belgium) was used to convert the CBCT images into Stereo
Lithography (STL)
files of 3D reconstructions, which were used to design a three-unit AOG-3DP with the aid of Exocad
software.
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• On the occlusal side of the AOG-3DP, a hole with a diameter of at least 2 mm was drawn that connected
all of the orifices of the root canals.
• The height of the AOG-3DP was designed to be 10 mm,
• Finally, the occlusal surface was designed to be perpendicular to the pulp chamber.
• The final design was then 3D printed using a stereolithography type 3D from tough resin.
Designing the AOG-3DP. A simulated AOG-3DP (A) and a
produced AOG-3DP (B)
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Access opening
• Access preparations in both the control and test groups were performed
• The AOG-3DP was placed on the crowns of the samples in the test group, while no aid was used in the control
group.
• The preparation procedure for achieving each access opening was timed from the start of the access
preparation until all canals were identified.
• All prepared samples were imaged using CBCT for the 3D visualization and measurement of the preparation.
• This measurement was quantified as the volume difference between an ideal cavity and the prepared cavity.
• A 10-mm deep ideal cavity that had the same occlusal shape as that of the hole of the designed AOG-3DP was
simulated, and its volume was measured using Mimics software.
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The actual prepared cavity volume for both the group was measured with Mimics software by converting
the post preparation CBCT images into STL files (Figure 2).
3D visualization and measurement of overpreparation. Original prepared cavity (A), a 10-mm deep
ideal cavity (B), and comparison of the ideal and prepared cavities on the coronal side (yellow shading,
prepared cavity; red lines, ideal cavity) (C)
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The volume difference between the ideal and prepared cavities was calculated by subtracting the actual
volume from the ideal volume.
The mean times required for achieving access opening in the two groups are presented in the figure below.
Comparison of the control and AOG-3DP groups. (A) Comparison of access opening times. The times for
achieving access
opening in the control and AOG-3DP groups were 327.2 ± 135.5 and 97.4 ± 106.6 s (mean ± SD), respectively,
in the premolar group, and 547.43 ± 269.6 and 104.57 ± 55.5 s in the molar group. (B) Volume differences
between the ideal and prepared cavities, which were 38.1 ± 32.2 and 72.2 ± 60.6 mm3 for the premolars and
molars, respectively, in the control group, and −2.0 ± 14.4 and −8.7 ± 16.8 mm3 in the test group.
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• Using the AOG- 3DP significantly reduced the preparation time by 75.9% for premolars and by 81% for molars.
• Compared with the control group, samples in the test group generally demonstrated minimal preparation while still
achieving straight-line access into all canals.
• Periapical-view images of the test group showed straight line access into all canals, while the control groups displayed
errors such as over flaring from the orifice, a remaining pulp chamber roof, and excessive tooth removal that almost
resulted in perforation.
• The average volume differences between the ideal and prepared cavities were 38.1 and 72.2mm3 for the premolars and
molars, respectively, in the control group.
• In contrast, the prepared cavities were much closer to the ideal cavities when using theAOG-3DP, with a mean
difference of − 2.0mm3 for premolars and −8.7mm3 for molars.
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Difficulties encountered during the design and manufacture processes.
• Difficult to produce AOG-3DPs for use with the anterior teeth.
• When preparing anterior teeth with an AOG-3DP, the head of the handpiece was caught by the guide on
the incisal edge and so a special long bur was needed.
• When using a diamond bur, it will be necessary to consider the angle between the AOG-3DP and the head
of the handpiece in order to achieve a suitable angle for the preparation.
Second, accuracy errors could occur depending on the insertion direction of the bur used with the AOG-3DP.
If the bur is not positioned exactly perpendicular to the occlusal side of the guide, the produced area might be
distorted and overprepared
Several methods were investigated for reducing this error with the implant guide,
• drill guide sleeve,
• placing a metal tube in the hole, and
• designing a special bur for the hole.
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Third: Strength and stability of 3D printed guides.
Since 3D-printed guides wereprinted using light-curable resin, there was a possibility of destroying the AOG-
3DP as well as the teeth during access opening, making the end result different from the original design.
Biggest problem of the AOG-3DP based on CBCT is of exposing patients to radiation and the additional cost
According to the American Association of Endodontist and American Academy of Oral and Maxillofacial
Radiology, CBCT should be performed when the level of difficulty of RCT is high or when it is difficult to perform
the required evaluations using existing panoramic and periapical views.
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Anatomy of Pulp Cavity and Its Access Opening

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