FUNDAMENTALS OF TOOTH PREPARATION.pptx

FUNDAMENTALS OF CAVITY
PREPARATION
Presented By,
AISHWARYA KHARE
Guided By,
Dr.Anurag Jain
Dr.Sonal Bansal
Dr. SaurabhMankeliya

CONTENT
 INTRODUCTION
 CAVITY PREPARATION DEFINITION
 HISTORY
 OBJECTIVES OF CAVITY PREPARATION
 FACTORS AFFECTING CAVITY
PREPARATION
 CLASSIFICATION
 STAGES OF CAVITY PREPARATION

Introduction
 Dr. G.V. Black
Chicago, Illinois
1836-1915
 "The Grand Old Man of Dentistry"
 The basic principles governing the
design of cavity and steps in their
preparation was first suggested by
American Dentist and teacher
Dr.G.V.Black in the first decade of
last century.

The mechanical alteration of a
defective, injured, or diseased tooth
to receive a restorative material that
re-establishes a healthy state for the
tooth including esthetic corrections
where indicated, along with normal
form and function.
-by sturdevant

 Cavity preparation is the mechanical
removal of caries and shaping the
remaining tooth tissue in such a way so
that after restoration it can withstand
masticatory forces and will be able to
prevent subsequent caries.
- by DR. vimal k sikri

Types of cavity preparation
 CONVENTIONAL :- Tooth preparation that relates
to amalgam, gold and ceramic might be
considered conventional preparation that require
specific wall form, depth and marginal form.
 MODIFIED: Tooth preparation for bonded direct
restorations as composite or glass ionomer has
less need for specific depth , wall and marginal
form and is considered to be modified preparation.

OBECTIVES OF TOOTH
PREPARATION
• Remove all defects and provide
necessary protection to the pulp.
• Extend the restoration as
conservatively as possible .
• Tooth prep such that under
mastication both the tooth and
restoration will not fracture or displace.
• Allow the functional and esthetic
placement of a restorative material.

FACTORS AFFECTING
TOOTH PREPARATION
 GENERAL FACTORS
 Diagnosis
 Prevention
 Interception
 Preservation
 Restoration

 PATIENTS FACTORS
 Economic status
 Esthetic concern
 Age
 Choice of material

CLASSIFICATION
G.V. Black Classification
Modification of G.V.Black
Classification
Graham J Mount
V.K. Sikri

First Classification
Universally Accepted
Based on type of treatment and area
involved
Controlled by no. of factors
I.To gain access & visibility.
II.Removal of affected dentin from floor.
III.Room for restorative material.
IV.Extension for prevention.
V.Retentive designs.
VI.Cavosurface margins self cleaning areas.

G.J.MOUNT CLASSIFICATION
-DESIGN TO SIMPLIFY IDENTIFICATION OF
LESIONS
According to site lesion
1.Pits &fissure
2.Contact area
3.Cervical
According to size of lesion
1.Minimum
2.Moderate
3.Enlarged
4.Extensive
Sikri classification-classify same as G.V. Black and then gave
division in each class

TOOTH PREPARATION
TERMINOLOGY :
 Simple tooth preparation
-Only one tooth surface is
involved.
 Compound tooth
preparation – Only two
tooth surface is involved.
 Complex tooth
preparation – Involves
three or more surfaces.

Terminology in Cavity
Preparation
Definition –
Cavity-Cavity is defined as a
defect in enamel or dentin
resulting from pathologic process
of dental caries(breach in the
continuity of the surface integrity
of tooth).
The term cavity was used to
describe a carious lesion in a
tooth that has progressed to the
point that part of tooth structure
has been destroyed.

INTERNAL WALL-An internal wall
is prepared surface that does not
extend to external tooth surface.
AXIAL WALL – An axial wall is an
internal wall parallel with the long
axis of the tooth.
PULPAL WALL- A pulpal wall is
an internal wall that is
perpendicular to the long axis
tooth and occlusal of pulp.

External wall – An external wall is
prepared surface that extend to the
external tooth surface
Floor / seat-A floor is a prepared wall
that is reasonably flat and
perpendicular to the occlusal forces
that are directed occlusogingivally.
Enamel wall –Enamel wall is that
portion of a prepared external wall
consisting of enamel.
Dentinal wall- The dentinal wall is that
portion of a prepared external wall
consisting of dentin ,in which
mechanical features can be located.

CAVITY PREPARATION ANGLES
:
 Line angle : It is the junction of two planar surfaces of
different orientation along a line. internal line angle
and an external line angle.
 Internal line angle : Is a line angle whose apex points
into the tooth e.g. FP.
 External line angle : Is a line angle whose apex points
away from the tooth e.g. AP.
 Point angles : A point angle is junction of three planar
surfaces of different orientation.

Cavosurface angle :
The cavosurface angle is the angle of the tooth structure
formed by the junction of a prepared cavity wall and the
external surface of the tooth.
Line angles & point angles Cavo-surface angle

Classification of cavity

— G. V. Black

CLASS I CAVITY PREPARATION
All Pits & fissures preparation are termed as class I. these include
preparation on:
1) Occlusal surface of premolars & molars.
2) Occlusal 2/3rd of facial & lingual surface of molars.
3) Lingual surface of maxillary incisors.

DESIGNS OF CLASS I
CAVITY PEPARATION

 UPPER PREMOLAR: these preparation
are dumb bell shaped with their ends
somewhat triangular.
 LOWER PREMOLARS:- If they are
confined to pit only , the preparation are
circular, resembling snake eye.
 But if they involve entire occlusal surface
then the preparation will resemble design
of upper premolar, except that mesial end
of the dumb-bell in lower first premolar will
be more linear.

 LOWER 1ST MOLAR:- Elongated
mesio-distally with three lateral
extension, two buccal and one lingual,
corresponding the primary grooves
 LOWER 2ND AND 3RD MOLAR:-
Elongated shape with 2 lateral
projections, usually opposite one
another, corresponding the primary
groove.

 In tricuspid lower premolars, the
preparation will assume Y- shaped with
two of the arms of the Y ending in a
triangular cavity.

 UPPER 1ST MOLAR:- If the cavity involves
all of the occlusal surface , the preparation
will be elongated, mesio-distally , with
lateral projections not opposite one
another.
 if the oblique ridge is not crossed , the
mesial cavity preparation will assume a
“kidney” shaped and distal cavity
preparation will assume a “heart “ shape.
 UPPER 3RD MOLAR:- upper 3rd molar with
3 cusp , the cavity will assume T- and Y-
shape.

 These above mentioned shape are
generalizations and no cavity
preparation will assume these shapes
exactly . They can be modified
according to anatomical and cariogenic
consideration.
LOCATION OF THE MARGIN:
 Adjacent to ridges.
 Adjacent to cusps.

 INTERNAL ANATOMY:
Pulpal floor:-
1. The portion of preparation is usually
located in dentin 0.2-0.5mm from the
DEJ.
2. Should be flat planed and at a right
angle to the long axis of the tooth.

 Only exception is lower 1st premolar
where lingual cusp is small and buccal
cusp is very pronounced with a very
large pulp horn.
 Creating a flat pulpal floor will
jeopardize both the minute lingual cusp
and buccal pulp horn
 So in this case floor is prepared in a flat
plane, parallel to the imaginary line
joining the tip of buccal and lingual cusp.

 It is used for teeth with intact cusp i.e.,
cusp not undermined by backward decay.
 GENERAL SHAPE : Shapes of this
preparation is similar to design 1, except
there are more deviation from the
generalized shapes previously mentioned.
 LOCATION OF MARGIN: Similar as class
1 however in design to margins are closer
to cusp tip and crest of the ridge than
design 1 margins.

INTERNAL ANATOMY
 The pulpal floor will have probably different
levels in design 2.
 One is established by the penetration of the
caries cones and will have a concave shape .
 Another one , the main level, which should be
flat, is approximately 0.2-0.5mm from the
DEJ.
 Mesio- distal and buccolingual cross-section is
similar to that of design 1.

 Preparation will have same features as
mentioned in the above designs except
the wall of the preparation could be
more convergent and irregular according
to the anatomy of the invagination.

 INDICATION:-
1. Caries lesions at the facial or lingual pits
are connected to the occlusal surface or
lesion through the fissure , enamel decay
or backward decay.
2. Decay undermine the facial and lingual
marginal ridges, or thins them so they
cannot be self-resistant.
3. Caries cones, facially or lingually ,are
confined to the concavity of their
corresponding grooves.

 3.LOCATION OF MARGINS:-Margins of
occlusal part of cavity preparation will be
located at same site as described for
design 1
 Mesial and distal margins of facial and
lingual parts of the preparation will be
located on the corresponding surface.
 In these portion of preparation the must
be seperated from each other by atleast
1.5mm.

INDICATION
1. Portion of entire cusp are undermined by
backward decay, or badly thinned by
direct decay, necessitating partial or total
replacement of the cusp by a restorative
material.
2. The cariogenic situation leaves a cusp or
part of a cusp with a length to width ratio
of 3:1 or more in a functional cusp ,or 4:1
in a non functional cusp and there is no
interruption in continuity of surrounding
walls
.

3. The cariogenic situation leaves a cusp
or part of a cusp with a length to width
ratio of 2 or more on the functional cusp
and more on the non functional cusp and
the continuity of the surrounding walls is
interrupted at one part or another.
4. The marginal ridge adjacent to an
occlusal preparation is crossed by a
fissure to the facial or lingual embrasure.

5.A foundation for a future cast restoration
is needed.
6.A class 1 occlusal lesion is continuous
with a class VI lesion on the cusp tip or
their ridge crests.

INDICATIONS
 They are class 1 lesion with extensive
carious involvement.
 Due to substantial extent the resulting
deficiency of surrounding walls, the
placement of internal boxes in the floor
of preparation is impossible due to
anatomical restrictions.
 Pins and post are indicated.
 Pins and post retained restorations.

LOCATION
 In molars and premolars. This design is
used on the occlusal and sometimes on
the occlusal and/or facial-lingual
surfaces . It also may be used on the
lingual surfaces on anterior teeth.
 INDICATION:-Designed specially for
endodontically treated teeth.
 Confined to occlusal and lingual or
buccal surface of these teeth.

CLASS II CAVITY
PREPARATION
preparation involving the
proximal surface of posterior
teeth are termed class II.

MODIFICATION OF CLASS 2
CAVITY PREPARATION
 CLASS 2, DESIGN 1:
 INVOLVEMENT:
This design is indicated for:
a. A moderate to large size proximal lesion
with the occlusal surface of the affected
tooth involved in a lesion of similar size.
b. A proximal lesion undermining an
adjacent marginal ridge(s) or not
accessible through any other means but
involvement of the occlusal surface .

c. The caries cones occlusally and or
proximally necessitates the cavity width to
exceed one-fourth the intercuspal distance.
d. A class II in stress concentration area(i.e.,
proximal lesion adjacent to a functional
triangular fossa).
e. Patient with high caries index and plaque
indices.
f. An oral environment where local cariogenic
conditions contraindicates a modern design.

CLASS III CAVITY PREPARATION
Preparation involving the proximal surface of
anterior teeth that do not include the incisal
angle are termed as class III.

 CLASS IV CAVITY PREPARATION
Preparation involving the proximal surfaces of
anterior teeth that include the incisal edge are
termed class IV.

CLASS V CAVITY PREPARATION
Preparation on the gingival third of the facial or lingual
surface of all teeth are termed as class V.

 CLASS VI CAVITY
PREPARATION
Preparation on the incisal edges of anterior
teeth or the occlusal cusp tip of posterior
teeth are termed as class VI.

 FINAL STEPS OF PREPARATION

1. Outline Form and Initial
Depth
Definition:
placing the cavity margins in the positions
they will occupy in the final preparation
except for the finishing enamel walls and
margins;
preparing an initial depth of 0.2~0.5mm
pulpally of the dentinoenamel junction and
0.8mm pulpally to the normal root surface.

 Features:
1.Preserving cuspal strength.
2.Preserving marginal ridge strength.
3.Minimizing facio-lingual extension.
4. Connectiong two close (0.5mm apart
)defect or tooth preparation.
6.Restricting depth of penetration into
dentin

1.Preserving cuspal strength
-avoiding termination of the
margin on extreme eminence,
such as cusp height
-if extension of primary groove
includes half / > of cusp incline,
then CUSP CAPPING consider.

2. Preserving marginal ridge
strength
• Remaining Marginal ridge should be
greater than 1.6 mm for premolar & 2mm
for molar If Remaining Marginal ridge
will be less than 1.6 mm there there
may be the chances of
fracture due to undermining
the ridge.

 Direction of mesial & distal walls
 When >1.6 mm
thickness width is
remained at mesial
/distal marginal
ridge , then mesial /
distal wall should
be parallel.
 When less than/=
1.6 mm thickness
width is remained at
mesial /distal
marginal ridge ,
then mesial / distal
wall should be
divergent.

- Minimizing facio –lingual Extension ,which
prevents the weakening of cusp.
- For conservative class I CAVITY
facio-lingual width should be 1 to 1.5 mm

4. Depth of preparation
Restricting depth of penetration into dentin
for pits and fissure-0.2 for smooth surface-0.2
to 0.8
Because,
1.To avoid the seating
of the restoration on
the very sensitive DEJ.
2.To give the bulk of
restoration.
3.To take advantages of
dentin elasticity during
insertion and function.

5. Enameloplasty
 This is the procedure of reshaping the enamel surface
by making it rounded / Saucered ,the area becomes
cleansable and finishable.
 It is indicated when remaining fissure is not greater
than 1/3 rd of enamel thickness.

Outline form for class I
• The outline form varies from one tooth to
another .
• Premolars-
• Upper premolars have “ Dumb- bell “ shape with
their ends triangular.
• In lower premolar –are confined to pit only
but if they involve entire occlusal surface ,then
they resemble like upper premolar.
• In tricuspid lower premolar it will assume Y-
shape

Class I
upper premolar
Class I
lower premolar

Class I & II Outline form for
MOLARS
• Preparation in lower molars have an elongated
shape mesio-distally with three lateral
extensions.
• In upper molars if cavity involves all the occlusal
surfaces ,the preparation elongated mesio-
distally .
• If the oblique ridge is not involved the mesial
preparation will assume kidney shape & distal
will appear as heart shape .
• In class II the shape of proximal box is Inverted
Truncated Cone.

Mandibular Maxillary
ClassⅠoutline form
Occlusal view Proximalview
Class II outline form

Position of Gingival floor
 In class II cavity
preparation ,gingival
margin should be
extended apically of
proximal contact to
provide a minimum of
0.5 mm clearence
between the gingival
margin and djacent
tooth.

Isthmus –
By G.V.Black-
Advocate that class II cavity
preparation with isthmus width
equal to 1/3rd of intercuspal
distance.
By Vale & Brooner-
It should be 1/4th of intercuspal
distance.

 The axio-pulpal line angle should be beveled to reduce the
concentration of stresses and provide grater bulk of material
in the isthmus area, which is liable to fracture.

Final location for the facial and lingual
Walls of proximal box relative to the contact
area
REVERSE CURVE –When viewed
from occlusal outline form of class II cavity
particularly in max . teeth the proximal contact
lies towards the buccal surface whereas the groove
line occurs in the central portion of th occlusal
table. This disparity necessitates occlusal outline
with a REVERSE CURVE.
Advantages
1.It preserve the triangular ridge of cusp
2.Facilitates formation of 90°angle
between proximal wall & the tangent of
proximal surface.

Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

2. Primary Resistance
Form
Definition:
It is defined as that shape and placement
of the cavity walls that best enable both
the restoration and the tooth to withstand,
without fracture, when masticatory forces
delivered principally in the long axis of the
tooth.

Primary Resistance Form
Principles:
To utilize the box shape with a relatively
flat floor to resist occlusal loading by
virtue of being at right angles to
mastication force;
To restrict the extension of the external
walls (keep as small as possible) to allow
strong cusp and ridge areas to remain with
sufficient dentin support;

Principles:
To have a slight rounding of internal line
angles to reduce stress concentration in
tooth structure;
To provide enough thickness of
restorative material to prevent its
fracture under load.

Feature:
Box shape
Relatively flat floors
Inclusion of weakened tooth structure
Preservation of cusps and marginal ridges
Rounded internal line angles
Adequate thickness of restorative materials
Reduction of cusps for capping if indicated

Flat pulpal floor prevents rocking of the restoration which produce
wedging forces

Rounding of line angles prevents stress concentration & provide resistance
form
&
Shows strongrst enamel margin by full length of enamel rods

Silver amalgam needs thickness -1.5 mm
Cast metal needs thickness -1to2mm
Porcelain needs thickness - 2 mm

3. Primary Retention Form
Definition:
primary retention form is the shape or
form of conventional preparation
that resists displacement or removal
of the restoration from tipping or
lifting forces.
In many respects retention and resistance form
are accomplished in the same cutting procedure.

PRINCIPAL MEANS OF
RETENTION
Frictional retention -
1.Greater surface area (length, width,
depth)produces greater frictional component.
2.Parallel walls / convergent wall provide greater
frictional retention
3.Proximity –bringing the restorative material
closer to tooth structure during insertion
provide greater frictional retention component.
4.Elastic deformation of dentin –during
condensation within dentin proportional limit
can add more gripping action.

4.INVERTED TRUNCATED CONES
-In class II cavity preparation , proximal surface have
inverted truncated cones shape
-It prevents the occlusal displacement of restoration in
class II Cavity.

In Class II Cavity
-Dovetail provide retention in class II
cavity .
-It prevents lateral displacement of
restoration in class II cavity.
In Class I Cavity
-In class I ,it is given for the purposeful
modification in outline usually for
‘EXTENSION FOR PREVENTION’

Primary Retention Form
Principles:
 For Amalgam restoration:
-developing external cavity walls that
converge occlusally.
-Adhesive system provide retention by
micromechanically bonding amalgam to
tooth structure.

Primary Retention Form
Principles:
Composite restoration:
a mechanical bond between the material
and conditioned, prepared tooth structure.

4 . Convenience Form
Conception:
The shape or form of the cavity that
provides for adequate observation,
accessibility, and ease of operation in
preparing and restoring the cavity.

Convenience Form
Principles:
 Allow access for caries removal
 Allow access for restoration placement
 Allow access to margins for finishing,
evaluation and cleaning

-IN CLASS II CAST RESTORATION
DIVERGENCE OF
VERTICAL WALL
-EXTENDING PROXIMAL PREPARATION
BEYOND
PROXIMAL CONTACT
-IN CLASS III CAVITY CONVENIENCE FORM
MAINLY
THROUGH LINGUAL SIDE.
- IN CLASS I & V , DIVERGENCE OF WALL
OF CAVITY
IN INLAY

Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin or old restoration, if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

6. Removal of any remaining
infected dentin or old
restoration, if indicated
Definition:
The elimination of any infected carious
tooth structure or faulty restorative
material left in the tooth after initial
cavity preparation.

Removal of dentinal caries using round burs and spoon excavators

Removal of dentin depends on the two
condition
whether it is affected or infected?
• Affected dentin
-Does not contain
micro-organisms
-can be remineralise by
restorative mean.
-it is accepted to allow
affected dentin to
remain in prepared
tooth.
• Infected dentin
-It contain micro-
organisms
-can not be
remineralise by
restorative mean.
-it should be removed
during cavity
preparation.

-SOFT DECAY CAN BE BEST REMOVED
USING SPOON
EXCAVATOR BY FLAKING UP THE CARIES
-HARD DECAY, HEAVILY DISCOLORED
SHOULD
REMOVED USING VERY LOW SPEED BUR.
-CARE SHOULD HAVE TO TAKE DURING
REMOVAL AS
PULP MAY INFECTED BY FORCING
MICRO-
ORGANISMS INTO DENTINAL TUBULES
THROUGH
EXCESSIVE PRESSURE.

dentin if indicated
Step 8 Procedure for finishing external walls

6. Pulp protection
- Using liners or bases
- to protect the pulp or
- to aid pulpal recovery or both.
LINERS-liners are volitile /aquous
suspension /dispersion of zinc oxide or
calcium hydroxide that can be applied to
tooth surface in relatively thin film & are
used to effect a particular pulpal response.
BASES-Are those cements used in thicker
dimensions beneath permanent restoration
to provide for mechanical,
chemical ,thermal protection of the pulp

-Liners are primarily used to provide a barrier to protect
dentin from residual reactants.
-Bases are used to provide thermal protection for the
pulp and to supplement mechanical support for the
restoration by distributing local stresses from
restoration across the underlying dentin surface.
If remaining dentin overlying the pulp is 2mm then no need of liners
But if it is less than 2mm ,pulp protection is mandatory .

Schematic view of needs for pulpal protection below metallic restoration

Schematic examples of liners & bases for amalgam restoration
For shallow tooth
preparation
For moderate
tooth preparation
For very deep
tooth preparation

7. Secondary resistance and
retention forms
Most compound and complex cavity
preparations require additional
resistance and retention form.
The exception being those preparations
that are very conservative.

Secondary resistance and
retention forms
Mechanical forms
Cavity wall conditioning form

Mechanical form:
 Retention locks, grooves, and coves
 Groove extensions
Skirts
Beveled Enamel Margins
Pins, Slots, Steps, Amalgampins

Proximal Grooves for cast restoration
Retention locks for amalgam

Incisal retention coves Incisal & Gingival retention groove

Groove extensions & skirts
When lingual wall
absent or inadequate in
proximal preparation,
then retention form can
be improved by facial skirt
extension.

Pins slots steps & amalgampins
Beveled Enamel margins
-The bevels for cast metal may improve retention form
-Primarily to afford a better junctional relationship
-Beveled margins increases the surface area of etchable enamel
Dentin slots Amalgampins

CAVITY WALL CONDITIONING
FORM
Placement of etchant , Primer , Adhesive on prepared
wall
-in addition to mechanical alteration to tooth structure
certain bonding agents also provide some extent of
retention & resistance form
-such treatment require in bonded restoration like
porcelain , composite , or amalgam materials

Micromechanical retention of bonding system to dental
enamel

dentin if indicated
Step 8 Finishing external walls

8. Finishing the external
walls
Definition:
is the further development of a specific
cavosurface design and degree of
smoothness that produces the
maximum effectiveness of the
restorative material being used.

Finishing the external
walls
Objectives:
 To create the best marginal seal possible
between the restorative material and tooth
structure;
 To afford a smooth marginal junction;
 To provide maximum strength of both the
tooth and the restorative material at and
near the margin.

The strongest enamel margin is that margin
which is composed of full-length enamel rods
that are supported on the cavity side by shorter
enamel rods, all of which extend to sound dentin.

Finishing the external
walls
The design of the cavosurface angle
The degree of smoothness of the wall

The design of the cavosurface angle:
depending on the material
 amalgam: 90°(Cavosurface margin 90°-Butt joint)
Help to minimize the marginal deterioration of
restoration by locating the margins away from the
enamel eminence where occlusal forces may be
concentrated.
composite: beveling 30°~ 40°
Is indicated primarily in larger restoration
because the potential for retention increased by
increasing the surface area of enamel available
for etch.

Occlusal
cavosurface
margin
Proximal
cavosurface
margin

Vertical section of Class II Tooth preparation
-a slight bevel is given to remove unsupported
enamel rods

Gingival Bevel placed with an instrument
Gingival marginal trimmer

Final procedures
 cleaning
 inspecting
 Sealing

Cavity preparation seen after final
procedure

REFERENCES
1.Sturdevants- Art and Science Of Operative Dentistry
2.Marzouk – Modern Theory and Practice
3.G.V. Black –Work on operative dentistry
3.Vimal Sikri- Textbook of Operative Dentistry

FUNDAMENTALS OF TOOTH PREPARATION.pptx

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