Fundamentals in cavity preparation / endodontics courses

FUNDAMENTALSFUNDAMENTALS
ININ
CAVITY PREPARATIONCAVITY PREPARATION
INTRODUCTION
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Need for restorations:Need for restorations:
for a variety of reasonsfor a variety of reasons
a) Need to repair tooth after after destruction from a carious lesion
large carious lesion – large restoration small carious lesion conservation
b) replacement /repair of restoration with serious defects like improper prox
contact, ging excess caries risk margins and poor esthetics
c) restore the fractured teeth for proper form and function
d) when there is congenital deformation

ii) Objectives Of Cav preparation
a) remove all defects
b) give necessary protection to pulp
c) locate the margins of restoratins as
consrvative as possible
d) to form the cavity so that under force of
maslication the tooth or restoration or
both will not fracture and restoration
will not be displaced
e) allow for esthetic and functional
placement of restorative material

ii) Objectives Of Cav preparationii) Objectives Of Cav preparation
a) remove all defects
b) give necessary protection to pulp
c) locate the margins of restoratins as
consrvative as possible
d) to form the cavity so that under force of
maslication the tooth or restoration or
both will not fracture and restoration
will not be displaced
e) allow for esthetic and functional
placement of restorative material

iii) Cavity preparation:iii) Cavity preparation:
It is a mechanical alteration ofIt is a mechanical alteration of
a tooth to receive a restorativea tooth to receive a restorative
material which will return thematerial which will return the
tooth and area to prepare formtooth and area to prepare form
function and estheticsfunction and esthetics

Stages and steps in cavity preparationStages and steps in cavity preparation
For efficiency in cavity preparation the procedure is
divided into 2 stages
1) Initial cavity preparation stage:
Here the cavity margins are extended to sound tooth
structure (enamel supported by sound dentin) in all
directions while adhering to a specific restored
pulpal depth

The cavity walls are designed to both retain the restorative
material in the tooth and resist fracture of thr tooth or
restoration from masticatory forces
4 steps:
step 1 : Outline form and initial depth
2 : Primary resistances form
3 : Primary relention form
4 : Convenience form

II)First Cavity Preparation:II)First Cavity Preparation:
 is completion of cavity preparation
It includes excavating any
remaining infected carious
dentin ,protection of pulp,
incorporating additional cavity
Design features,finishing preparation
walls,debridement and final inspection of the prepared cavity

Step 5: removal of any remaining enamel pit / fissure, and /or infectedStep 5: removal of any remaining enamel pit / fissure, and /or infected
dentin ,and/or restorative materialdentin ,and/or restorative material
Step 6: pulp protection
Step 7: secondary resistance and
retention form
Step 8: procedures for finishing
external walls
Step 9: Final procedures;cleaning
inspecting ;varnishing ;conditioning

Rules: for pit and fissure cavities:Rules: for pit and fissure cavities:
1) All the Margins are extended in sound
tooth strucure no unsupported
/weakened enamal margin
2) Avoid terminating cavity margins on extreme
convinences like cusp heights or ridge crests to
of extension from thr groove includes half or
more of cusp unchins consider cusp capping if
extension is 2/3 cusp capping is done

3) Extend the cavity margins to3) Extend the cavity margins to
include all the fissures that cannot beinclude all the fissures that cannot be
eliminated by enamehaplasly E-iseliminated by enamehaplasly E-is
judicious reduction of the surface ofjudicious reduction of the surface of
enamels there by converting aenamels there by converting a
shallow fissure into smooth basedshallow fissure into smooth based
groove reshaping of enamel surfacegroove reshaping of enamel surface
AND secilable rolary unotr so that theAND secilable rolary unotr so that the
as secured and becomesas secured and becomes
cleanable,finishablecleanable,finishable

4) Restrict the depth of the preparation to a margin of o.24) Restrict the depth of the preparation to a margin of o.2
nn-0.5nn, into dentin or total depth of cavity from thenn-0.5nn, into dentin or total depth of cavity from the
cavosurface margin at cocentral fissure should be aroundcavosurface margin at cocentral fissure should be around
1.5nn1.5nn
5) When the distance between 2 pit and fissure cavity is5) When the distance between 2 pit and fissure cavity is
less than o.5nn they should be joined to eliminate weakless than o.5nn they should be joined to eliminate weak
enamel between themenamel between them
6) Outline .f varies from tooth to tooth depending on6) Outline .f varies from tooth to tooth depending on
anatomical form. The margins of cavity do not assume aanatomical form. The margins of cavity do not assume a
straight line rather they are in smooth curves whichstraight line rather they are in smooth curves which
preserve strong culp structurepreserve strong culp structure
7) Cavity preparation should as conservative as possible7) Cavity preparation should as conservative as possible
while cofirming to the above mentioned principleswhile cofirming to the above mentioned principles

Step1:Outline form and initial depths establishing outline
form means:
1) Placing the cavity margins in the positions they will
occupy in the final prepration except for finishing of
enamel walls and margin
2) Preparing the initial depth not more than 0.2 –0.8nn
below DEJ
PRINCIPLES:3
1) To eliminate all undermined enamel
2) To include all faults
3) To place the margin in a position that will afford
proper restorative margins
FACTORS Determining Outline form:
1) Extent of carious lesion,defect or faulty restortion obj
to extend to sound tooth structure except in a pulpal
depth

1) Esthetic Considerations: not only the
influences the choice of restoraton material
but also design of cavity to maximise the
estheticss
2) Occlusal relationships:
I) a cuspal form may be altered to get
between reln
ii) Avoid including the o.f in an area of heavy
occlusal contact
4) Adjacent tooth contact :
in order to secure appropriate proximal relationship and
provide optimal form and strength
5)Cavosurface Marginal configuration

Outline Form for Smooth Surface cavityOutline Form for Smooth Surface cavity
1) Restrict the axial wall depth of proximal
preparation to a maximum of 0.2-0.8mm into the
dentin
2) Extend ging margins apically of the contact to
provide a minimum of clearance of 0.5mm
between ging margin and adjacent tooth
3) Extend the facial lg margins into respective
entraseres to provide clearance so that the
margins are better visualized ,instrumented and
cleaned.

Step2 :Primary Resistance FormStep2 :Primary Resistance Form
Is defined as that shape andplacement of cavity walls that best
enables both the restoration and the tooth to withstand without
fracture masticatory forces decirered principally in the long axis
of the tooth
Principles:
1) To utilize the box shape AND a relatively flat floor which helps the
tooth to resist occlusal loading by virtue of being at RTLES
masticatory forces directed along the long axis of tooth
2) To restrict the extension of extension walls (minimally) to
maintain as much strength of remaining tooth structure as
possible AND sufficient dentin.
This resistance is against obliquely delivered force

3) Roundening of initial line angles to reduce stress
concentration in tooth structure
Internal line rounded reduce stress on tooth resistance to
fracture of tooth
External line rounded axiopulpal
a) reduces the stress on resorative materials resistance to
# of restorative material
4) In extensive cav preparation to cap weak cusps and
envelope or include weakened tooth structure to prevent
or resist fracture of tooth
5) To provide enough thicknes of restorative material to
prevent its fracture under load

Minimal Occlusal ThicknessMinimal Occlusal Thickness
 For amalgam 1.5 mm
 Cast metal 1-2 mm
 Porcelain 2 mm
Points to Remember
Flat pulpal/ging floor
Box shape
Inclusion of weak tooth structure
Preservation of cusps and marginig
Rounded internal circle
Adequate thicknessof restorative material
Seats on sound detin
Reduction of cusps for capping

Step 3: Primary Retention FormStep 3: Primary Retention Form
Is that snap or form of the prepared cavity that resists displacement
Or removal of the restoration from capping or lifting forces
PRINCIPLES: vary depending on the material used for amalgum cl I&
cl ii
1) External cav walls should converge occlusally
a) [facial,lg,prox walls should converge occlusally]
Not to be overdone because it leaves unsupported enamel rods
For cl iii and v) amalgam
b) The external walls diverge outwardly to provide strong margins
For cast metal restoration.
c) Retention is achieved by parellel walls and small circle diverge 2-50

d) For cl ii) preparation :
Occlusal dovetail is prepared to present tipping of the restoration
by occlussal forces
e) Retention in gold foil is the elastn compression developed in
dentin as a result of condensation of foil
Step 4: convience form:
is that shape or form of the cavity that provides for adequate
observation ,accessibility and case of operation in preparing
and restoring the cavity
This necessitates extension of mesial ,facial or lingual walls to
adequate access to deeper portion of cavity
for gold foil ,convergence from includes establishing convinience
points for starting of foil condensation

Final cavity preparation
step 5:
Removal of any remaining enamel pit/fissure and/or infected
dentin and /or old restorative material
this is the elimination of any infected carious tooth
structure or faulty restorative material left in the tooth of
the initial cav prepration
Affected Dentin: is an area of decalufication often discolored
and it does not contain microorgans
Infected denture –soft in consistency presence of m-0
always it is not acceptable to leave carious dentin at DEJ

Infected carious denture should be removed early in the
initial cavity preparation in large ccarifies exclusive
soft carier
It should be removed when a patient has numerous teeth
catevsive caries
in the first appt infected dentin is removed from all teeth
and temporary restrems are placed and later inr teeth
are treated accordingly this procedure stops the
progress of caries and is called caries control
technique
remaining old restmaterial should be removed when
1)the old material mau affect negatively the esthetic
result of new restoration
2) the old material may compromise that amount
anticipated
needed retention
3) there is radiographic curdence of caries under the red
material
4) pulp is symptomatic preoperatively
5) periphency of removing old restorative material is not
intact

Step 6: Pulp ProtectionStep 6: Pulp Protection
 when the thickness of remaining dentin is less than 2mm heat generated
by injudicious cutting can result in pulpal burn leison
abscess formation, pulp depth
So the reason for using liners or bases is to either protect the pulp or to aid
pulpal recovery
Other pulpal irritants are:
Same ingredients of various materials
thermal changes conducted through restorative material
forces transmitted through materials to dentin galvanic shock
ingress of noxious products and bal
Terms:
Liners are volatile or aqueous suspensions of Zno or ca(oH)2 that can be
applied to a cav surface in a relatively thin flor
bases are cements used in thicker dimensions beneath permanent restoration
to provide for mechanical,chemical and thermal protection of the pulp

step7:Secondary resistance and retention formstep7:Secondary resistance and retention form
 Additional resistance and retention feattures are necessary
for compound and complex cavity preparation. They are of
Two Types
1)Mechanical features
2)Cavity-wall conditioning features
Mechanical Features are:
a)Retention locks grooves and Coves:
locks and grooves are longitudinally oriented at axiolarial
axiolg line angels of cl ii cav preparation
i) Locks are for amalgam
ii) Grooves for cast metal restoration
Transversely oriented retention grooves are prepared in cl
iii & v cavity for amalgam.

Retention coves are approximately placed undercuts for
incisal retention of cl (iii) amalgam, occlusal portion of
some amalgam restoration and some cl (v) amalgam
b) Groove Extensions:carity preparation is extended on to
facial or lg surface to include a lingual groove. This is
usually done for cast restoration that results in additional
logitudinal (vertical) walls for retention
c) Skirts: are preparation features used in cast restorations
that extend the preparation around transitional longitudinal
line angels of the tooth that proreles retention and
increases resistance form by enveloping the tooth
d) beveled enamel margins
e) pins,slots steps, amalgapins
carity wall conditioning features:
Enamel wall conditioning Etching of enamel
Dentin wall conditioning DBA

Step 8:PStep 8:Proceduresrocedures For Finishing ExternalFor Finishing External
WallsWalls
sOBJECTIVESsOBJECTIVES
1. To create best marginal seal between restorative material and
tooth structure
2. To get a smooth marginal Junction.
3. To provide Maximum strength for both tooth and restorative
material and the margin
Theoretically the enamel rods radiates from DEJ and placed
perpendicular to ext-tooth Structure, that is; the rods converge
towards devp groove and diverge towards cusp height and ridges
ging 1/3rd
the rods are inclined slightly apically .
The finishing is done in such a way that all rods forming
the prepared wall have their inner ends resting on dentin or the
preparation wall should consider the direction of enamel rods
because of low heasile structure for amalgam and brittener of
enamel. Butl jt(90) produces maximum structure for amalgam
tooth structure
Enamel finishing can be done with hand cuthing instrument like
hatchet and GMT www.indiandentalacademy.com

Step 9: Cleaning,VarnishingStep 9: Cleaning,Varnishing
ANDAND
ConditioningConditioning
Cleaning,Varnishing and Conditioning is done to remove all
chips and loose delons with warm water from the syringe
and then remove moisture with few light surges of air do not
dehydrate during drying.
After cleaning cavity is inspected to conform the cav
preparation and then TWO coats of Varnish is applied to
reduce microleakage and post op pacin
Composite Rest and Bonded amalgam rests have to be
conditioned priory before restoring it. Conditioning
includes elating the enamel placing DBA or applying glass
ionomer lines

Fundamentals in cavity preparation / endodontics courses

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