Principles of intra coronal and radicular preparation
PRINCIPLES OF INTRA CORONAL
CAVITY PREPARATION AND
RADICULAR SPACE PREPARATION
Endodontic therapy involves treating vital or necrotic dental
pulps so that patients can retain their natural teeth in
function and aesthetics
Removal of infected / necrotic tissue
Disinfection of the root canal space
Widen the root canal space
Fill the root canal space with an inert material
Endodontic treatment can be divided into 3 main phases
1. Bio-mechanical preparation ( cleaning and shaping )
Objectives of cleaning and shaping
1. To remove and/or eliminate from the root canal, all of its
contents that may lead to the growth of micro-organisms or
breakdown of toxic products into the peri-radicular space.
2. To remove the irregularities of
canal walls as well as
obstructions such as calcifications, filling materials etc.
3. To prepare the root canal not only for its disinfection but also
to develop a shape that permits the simplest and most
effective 3D fitting.
Why not prepare the canals to a standard size and shape??????
1. A histological examination of root canal root canal
system tortuous turns,
apical foraminae and at times
2. This root canal system whose shape has been altered by
age, operative procedures, decay and trauma; is unique for
each tooth and is different from tooth to tooth.
3. A standard root canal is not existent.
CLINICAL OBJECTIVES (COHEN BURNS)
1. Pretreatment evaluation
Restorability of the tooth/teeth
Coexistant periodontal defect
Pulpal involvement?? Pulpectomy vs vital pulp therapy
2. Access for success
Access cavity is designed to deroof the pulp chamber
providing a straight line axis to orifices.
Shape determined by position of orifices.
Provide space for unhampered instrumentation and final
3. Shaping facilitates cleaning
Shaping facilitates cleaning by removing restrictive
dentin, allowing an effective volume of irrigant to work
deeper and more quickly into all aspects of root canal
It was demonstrated that a 5.25% solution of NaOCl is
able to penetrate, dissolve and flush out organic tissue
and related debris from inaccessible aspects of the root
canal system where files cannot reach.
Files shape and irrigants clean the root canal.
procedures is complete removal of pulp tissue
A continuously tapering preparation
Prepration must flow and progressively
narrow in an apical direction
Starting at orifice and moving apically,
every cross sectional diameter of
preparation should decrease
Original anatomy maintained
Position of the foramen maintained
Foramen as small as practical
Principles of Endodontic cavity preparation
Endodontic cavity preparation may be separated into two
(a) Coronal preparation
(a) Radicular preparation.
Black's principles of cavity preparation can be modified to
include the Root canal 'cavity' preparation
Black's principles are therefore divided into the following
Endodontic Coronal Cavity Preparation
I. Outline Form
II. Convenience Form
III. Removal of the remaining carious dentin
(and defective restorations)
IV. Toilet of the cavity
Endodontic Radicular Cavity Preparation
I and II. Outline Form and Convenience Form
IV. Toilet of the cavity (continued)
V. Retention Form
VI. Resistance Form
1. Outline form
The entire preparation, crown to apex, falls under outline
Governed solely by the anatomy of the root canal.
To achieve optimal preparation, three factors of
anatomy must be considered:
(1) the size of the pulp chamber,
(2) the shape of the pulp chamber, and
(3) the number of individual root canals, their
curvature, and their position
Size of Pulp Chamber:
•Outline form is affected by the size of the pulp chamber
•In young permanent teeth size of pulp camber is large
•In geriatric patients the pulp size decreases.
Shape of Pulp Chamber.
• The finished outline form should accurately reflect the
shape of the pulp chamber.
Number, Position, and Curvature of Root Canals:
To prepare each canal efficiently without interference, the
cavity walls often have to be extended to allow an unstrained
instrument approach to the apical foramen.
2. Convenience form
Removing excess of coronal dentin, so as to allow passage
of larger instruments, for better instrumentation, irrigation
Four important benefits are gained through convenience form
(1) unobstructed access to the canal orifice,
(2) direct access to the apical foramen,
(3) cavity expansion to accommodate filling techniques, and
(4) complete authority over the enlarging instrument.
•Modified outline form to accommodate the instrument
unrestrained in the severely curved mesial canal
•Extending only that portion of the wall needed to free the
instrument, a cloverleaf appearance may evolve as the outline
3. Removal of the Remaining Carious Dentin and Defective
Caries and defective restorations remaining in an endodontic
cavity preparation must be removed for three reasons:
1. To eliminate mechanically as many bacteria as possible from
the interior of the tooth,
2. To eliminate the discolored tooth structure, that may
ultimately lead to staining of the crown, and
3. To eliminate the possibility of any bacteria-laden saliva
leaking into the prepared cavity.
The Access cavity should preferably have 4 walls.
It serves several purposes
1.Correct positioning of the rubber dam so that the clamp is
2.Keeping the pulp chamber constantly flooded with as much
irrigation solution as possible
3.Defining easily recognizable and stable reference points for
the rubber stops on the endodontic files
4.Introducing a temporary cement so as to seal the pulp
When one or more walls are lacking→ reconstructed
Toilet of the Cavity
•All of the caries, debris, and necrotic material must be
removed from the chamber before the radicular preparation is
•If the calcified or metallic debris is left in the chamber and
carried into the canal, it may act as an obstruction during canal
• Soft debris carried from the chamber might increase the
bacterial population in the canal
Cleaning and Débridement of the Root Canal
1. The first objective is achieved by skillful instrumentation
coupled with liberal irrigation.
2. This double-pronged attack will eliminate most of the
bacterial contaminants of the canal as well as the necrotic
debris and dentin
Whenever drying the chamber or canals air
must never be aimed down the canals →
Emphysema of the oral tissues
4. Retention form
Near parallel walls in the apical 2-3 mm ensure a snugly
fitting G.P [ Apical TUG BACK ]
Most crucial for preventing apical leakage.
5. Resistance form
Resistance to overfilling is provided by maintaining the
integrity of the natural constriction of the apical
Prevents over instrumentation
Prevents forcing debris or obturating material
Provides a stop, against which G.P can be compacted.
Violating this integrity by over instrumentation leads to
(1)acute inflammation of the periradicular tissue from the
injury inflicted by the instruments or bacteria and/or canal
debris forced into the tissue,
(2) chronic inflammation of this tissue caused by the
presence of a foreign body—the filling material forced there
during obturation, and
(3)the inability to compact the root canal filling because of
the loss of the limiting apical termination of the cavity—the
important apical stop
A. Radiographic apex.
B. Resistance Form, development of the "apical stop" at
the Cementodentinal junction against which filling is
to be compacted and a stop to resist extrusion of
canal debris and filling material.
C. Retention Form to retain primary filling point.
D. Convenience Form subject to revision as
needed to accommodate larger, less flexible
instruments. External modifications change the
E. Outline Form, basic preparation throughout its length
dictated by canal anatomy.