Access Cavity Preparation
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Definition
What is an ideal access
Principles
Instruments used
Guidelines for access preparation
Laws of access cavity preparation
Procedure
Access cavity of maxilary and mandibular teeth
Management of difficult cases
Recent concept
conclusion
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.
A PROPER CORONAL ACCESS FORMS THE FOUNDATION OF PYRAMID OF
ENDODONTIC TREATMENT
A PREOPERATIVE PERIAPICAL RADIOGRAPH IS A MUST ,PRIOR ACCESS CAVITY
PREPARATION
RADIOGRAPHS HELP IN KNOWING:
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, calcification,resorption present,if any
What is an ideal access cavity?
• Improved instrument control
• Improved obturation
Straight line access
Complete
deroofing of pulp
chamber
• Ensure proper debridement
• Improve visibility
• Locate canal orifices
• Prevent teeth discoloration due to pulp remnants
• Avoid weakening of remaining tooth structure
Conservation of
tooth structure
Principles
• Regardless of the tooth, there are three
phases in the preparation of the access cavity:
Penetration
Enlarging
Finishing
Instruments for access cavity
preparation
ACCESS OPENING BURS
They are round burs with 16mm bur shank (3mm longer than standard burs)
• ACCESS REFINING
BURS
These are coarse grit flame shaped ,tapered round and diamonds for refining walls
of access cavity preparation
SURGICAL LENGTH BURS
MUNCE DISCOVERY BURS
MULLER BURS
Other burs used
Guidelines for access cavity preparation
Laws of access cavity preparation
LAW OF CENTRALITY
LAW OF CEMENTO ENAMEL JUNCTION
LAW OF CONCENTRICITY
LAW OF COLOR CHANGE
LAW OF SYMMETRY
LAW OF ORIFICE LOCATION
Laws of access cavity preparation
LAW OF CENTRALITY
Floor of pulp chamber is always located in the center of tooth att he level of
cementoenamel junction
LAW OF CONCENTRICITY
Walls of pup chamber are always concentric to external surface of tooth at the level of
CEJ. This indicates anatomy of external tooth surface reflects the anatomy of pulp
chamber
LAW OF COLOR CHANGE
Color of pulp chamber floor is darker than the cavity walls.
LAW OF SYMMETRY
Canal orifices are equidistant from a line drawn in mesial and distal direction through the
floor of pulp chamber.
LAW OF ORIFICE LOCATION
Canal orifices are located at the junction of floor and walls, and at the terminus of root
development fusion lines.
Access cavity
PROCEDURE
Removal of caries/defects/restorations
Direct round bur perpendicular to the lingual surface at
its center and then parallel to long axis ,until a drop in
effect-i.e pulp chamber entry
Deroofing of the chamber completed by working inside out
Locate the canal orifices using endodontic explorer
Remove the liungual shoulder using GG drills/Orifice enlargement
Straight line access/Refining access
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.
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
Maxillary canine
Shape of access cavity
No pulp horn
Acess cavity is oval in shape with greater
diameter labiopalatally
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.
Maxillary second premolar
Ovoid shape of
access cavity
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
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 formshamrock preparation.
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.
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.
Mandibular incisors
Access cavity of
mandibular central and
lateral incisors is
almost similar
Shape is long oval
with greater dimensions
directed incisogingivally
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
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.
Mandibular second premolar
•Similar to mandibular first
premolar
•Enamel penetration initiated
in central groove dueto small
lingual tilt
•Ovoid acess opening is wider
mesiodistally
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 .
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
C shaped canal
The incidence of C-shaped
canals is reported to be
highestin the mandibular
second molar. THE MAIN
ANATOMIC FEATURE OF C SHAPED CANALS IS THE
PRESENCE OF A FIN OR WEBconnecting 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.
3
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.
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
Clinical management of difficult cases
For treatment of teeth with abnormal pulpal anatomy following
are required:
GOOD QUALITY RADIOGRAPHS
MAGNIFICATION
KNOWLEDGE OF CLINICAL ANATOMY
COLOR OF PULPAL FLOOR
EXTENSION OF ACCESS CAVITY
Cases with extensive
restorations
If extensive
restorations are
marginally intact,then
access cavity can be cut
through them
•Porcelein
restorationsDiamond burs
•Metal crowns-Fine cross
cut metal carbide bur
If possible ,complete
removal of extensive
restoration allows most
favourable access
 In case of an
access cavity cut
through
restorations
following can
occur
• Coronal
leakage
• Poor visibility
and
accessibility
• Canal blockage
• Misdirection
of bur
penetration
Tilted and angulated crowns
• Preperative radiographs
should be thoroughly
assessed
• If not taken care followin
may occur
• Failure to locate canals
• Gouging of tooth
structure
• Procedural accidents
such as
 Instrumrent seperation
 Perforation
 Improper debridement
of pulp space
Calcified canals
• Calcifications in the pulp space are
very common
• Obliteration of pulp space may be
partial or complete by pulp stones
•Special ultrasonic tips used
•Avoid overcutting of dentin to prevent weakening of
tooth structure
•At first indication of canal,Introduce the smallest
instrument first gently (with passive motion rotational
and apical)
•Use of chelating agents is also helpful(overuse may
result in perforation)
SCLEROSED CANALS
•Dyes can be used to locate
sclerosed canals
•Precise dentin removal using
ultrasonic tips advised
•Long shank low speed no2
round burs also used
Teeth with no or minimal
crown
•Evaluate preoperative radiograph to assess root angulation and depth of
penetration
•Rebuild tooth structure prior endodontic procedures,if required
RECENT ADVANCES IN CONCEPT
OF ACCESS OPENING
Many times straight line access leads to severe loss of stategic 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 deroofed ;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
conclusion
An error in access cavity preparation would compromise all
subsequent work.
This preliminary step permits localization, cleaning, shaping,
disinfection, and three-dimensional obturation of the root canal
system.
Thus the success of the endodontic treatment depends entirely
on precise, proper execution of this step.
Reference sited
• Text book of endodontics-Nisha Garg.Amit Garg(3rd edition)
• 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
Thank you for your attention!!