ACCESS CAVITIES
Dr Saidah Tootla
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 Despite
advances there is always a
chance of error in endodontic
therapy, and diligence in the
involved procedures is necessary.
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 it
is important that the access
preparation be precise
 Entering
a tooth without an adequate
radiograph is a “fool’s errand.”
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 Preoperative
radiographs are
essential because they tell us where
pulp chambers are located in
relationship to coronal surfaces, and
at what angles canals enter pulp
chambers
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 Gaining
access to root canals,
wherein the root canal instruments
can be slipped easily into the canals
to reach the apical portion, is the
most important starting point of the
root canal treatment. Before you lift
that hand piece to start access cavity
preparation, stop and think about the
following three points:
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


Have you refreshed the knowledge of the
morphology and anatomy of the tooth you
are going to treat?
Have you taken a good look at the tooth
in the oral cavity? Its shape, size, tilt and
morphology need careful consideration.
Have you spent sufficient time studying
the radiograph?
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 When
the access preparation is cut
too small, it is often impossible to
find all the canals in the tooth.
 Even if all the canals are located, it
sets the stage for negotiation
difficulties, file breakage, and
unnecessary frustration during
obturation procedures (Figure 1).
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 Conversely,
access cavities that are
cut too big are a betrayal of the
clinician’s first admonishment to do
no harm, increasing the short-term
possibility of perforation and the
long-term probability of tooth and
root fracture.
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CHOOSE SAFE, EFFECTIVE
BURS
 choosing
the wrong bur can presage
a poor access result
 burs that are too large will inevitably
increase the size of the final cavity
preparation as well as significantly
increase the potential for tooth
perforation
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 #2
round is ideal for anterior and
premolar access
 a #4 is optimal for molar access
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 As
soon as the author drops into the
chamber, the round bur has
accomplished its purpose and is
replaced with a tapered diamond
bur.
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 In
anterior and premolar teeth, the
convenience form is afforded by
extending the preparation from
buccal to lingual; the conservation
form is accomplished by preserving
tooth structure in the mesial to distal
dimension
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Anterior - Triangular
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Canines - ovoid
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Premolar - Round
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 In
posterior teeth, the line-angle
extensions are cut to the working
cusps and stop 1 mm to 2 mm short
of the idling cusps.
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 In
maxillary premolars and molars,
the line angle extensions are taken
to the palatal cusps (working) and
are short of the buccal cusps (idling)
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Molar - Rhomboid
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 Conversely,
in mandibular premolars
and molars the line angle extensions
are taken to the buccal and are short
of the lingual cusps
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Straight-line access
 Success
in modern endodontic
treatment may be dependent upon a
well-designed access cavity to permit
straight-line access to all the main
root canals
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Flexural stress will be increased if the instrument must negotiate past
an overhang; arrow A indicates overhang preventing continuous
straight line access; arrow B indicates point of greatest curvature on
outside wall of canal
.
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Showing a canal opened to the apex to a No. 20 reamer or file; arrow
indicates the thickest, most engaged part of NiTi, most prone to fracture
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Questions???
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