Cavity preparation

FUNDAMENTALS IN TOOTH
PREPARATION
GUIDED BY:
DR.RAHUL MARIA
PRESENTED BY:
DR. ANUBHUTI
MDS 3rd year
Conservative Dentistry & Endodontics
Simplicities are enormously complex…

CONTENTS
• Introduction
• Definition
• Objectives
• Terminology
• Armamentarium
• Basic concept of cavity design
• Class I Cavity preparation
• Class II Cavity preparation
3

INTRODUCTION
 In the past, most restorative treatment was due to
caries (decay), and the term cavity was used to
describe a carious lesion in a tooth that had
progressed to the point that part of the tooth
structure had been destroyed.
 Thus the tooth was cavitated and was referred to as a
cavity. Likewise, when the affected tooth was
repaired, the cutting or preparation of the remaining
tooth was referred to as a cavity preparation.
 Now many indications for treatment for teeth are not
due to caries and, therefore, the preparation of the
tooth is no longer referred to as cavity preparation
but as tooth preparation, and the term cavity is used
Art & science of operative dentistry 5th edition page no.282

DEFINITION
5
Its defined as the mechanical
alteration of a defective, injured, or
diseased tooth to best receive a
restorative material that will
reestablish a healthy state for the
tooth, including esthetic
corrections
where indicated, along with normal
form and function.

TERMINOLOGY IN
TOOTH
PREPARATION

TOOTH PREPARATION
WALLS
Internal Wall.
An internal wall is a prepared (cut) surface that
does not extend to the 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 both
perpendicular to the long axis of the tooth and
occlusal of the pulp
External Wal
An external wall is a prepared (cut) surface that
extends to the external tooth surface, and

Floor (or Seat)
A floor (or seat) is a prepared (cut)wall that
is reasonably flat and perpendicular to those
occlusal forces that are directed occluso
gingivally (generally
parallel to the long axis of the tooth
Enamel Wall
The enamel wall is that portion of 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 retention features may
be located
TOOTH PREPARATION
WALLS

TOOTH PREPARATION
ANGLES
Although the junction of
two or more prepared (cut) surfaces is
referred to as an angle, in fact, the junction is
almost always "softened“ so as to present a
slightly rounded configuration

A line angle is the junction of two plane
surfaces of different orientation along a line
An internal line angle –
line angle whose apex points into the tooth
An external line-
angle is a line angle whose apex points away
from the tooth
Line Angle

HOW MANY LINE ANGLES ARE PRESENT IN A
CLASS I CAVITY…….????
1) Mesio buccal
2) Mesio lingual
3) Disto buccal
4) Disto lingual
5) Mesio pulpal
6) Disto pulpal
7) Bucco pulpal
8) Linguo pulpal
Guidebook on preclinical conservative dentistry by K.S.Karthikeyn page no38,39 11

 A point angle is the junction of three plane
surfaces of different orientation.
Point Angle

1. Mesio bucco pulpal
2. Mesio linguo pulpal
3. Disto bucco pulpal
4. Disto linguo pulpal
HOW MANY POINT ANGLES ARE PRESENT IN A CLASS
IICAVITY…….????

HOW MANY POINT ANGLES ARE PRESENT IN A CLASS II
CAVITY…….????
1. Disto bucco pulpal
2. Disto linguo pulpal
3. Bucco axio pulpal
4. Linguo axio pulpal
5. Bucco axio gingival
6. Linguo axio gingival

CAVOSURFACE ANGLE AND
CAVOSURFACE MARGIN.
 The cavosurface angle is the angle of tooth
structure formed by the junction of a prepared
(cut) wall and the external surface of the tooth
The actual junction is referred to as the
cavosurface margin .
 The cavosurface angle may differ with the
location on the tooth, the direction of the
enamel rods on the prepared wall, or the type
of restorative material to be used

NOMENCLATURE
16
Nomenclature refers to a set of terms used in communication by persons in the same profession
that enables them to better understand one another

Location
Primary caries
Its the original carious lesion
of the tooth.
a. Pit & fissure
b. Smooth surface
caries
c. Root caries
Secondary caries
occurs at the junction of a
restoration & the tooth & may
progress under the restoration. caries
Direction
a. Forward caries
is wherever the caries cone in enamel is
larger or at least the same size as that in
dentin
b. Backward caries
When the spread of caries along the DEJ
exceeds the caries in the contiguous enamel
,caries extends into this enamel from the
junction
18
CLASSIFICATION
Art & science of operative dentistry 5th
edition page no.291,292

Extent
Incipient
first evidence of caries activity in the
enamel.
Cavitated
the enamel surface is broken (not intact), and
usually the lesion has advanced into dentin.
Rate
Acute(rampt)
when the disease is rapid in damaging the
tooth. It is usually in the form of many, soft,
light-colored lesions in a mouth and is
infectious
Chronic(arrested )
slow, or it may be arrested following
several active phase
19Art & science of operative dentistry 5th edition page no.293

Histological
depth of
penetration
Enamel
caries
Dental
caries
20strudevant's south asian edition pg no 35

ABRASION
Its abnormal tooth surface loss resulting from
direct friction forces between the teeth &
external objects, or from frictional forces
between contacting teeth components in the
presence of an abrasive medium.
EROSION
Its the wear or loss of tooth surface by
chemico-mechanical action.Regurgitation
of stomach acid can cause this condition
on the lingual surfaces of maxillary teeth
ABFRACTION
Micro fractures occur as the cervical area
of the tooth flexes under such loads.
ATTRITION
is mechanical wear of the incisal or occlusal
surface as a result of functional or
parafunctionalmovements of the mandible
(tooth-to-tooth contacts). Attrition also
includes proximal surface wear at the contact
area because of physiologic tooth movements
22

FRACTURES
NON-HEREDITARY
ENAMEL
HYPOPLASIA
AMELOGENESIS
IMPERFECTA
DENTINOGENESISI
IMPERFECTA
23

Dr. G.V. Black
Chicago, Illinois
1836-1915
"The Grand Old Man of Dentistry"
"The professional man has no right to be
other than a continuous student."

CLASSIFICATION
OF TOOTH
PREPARATION

Simple, Compound, and Complex
Tooth Preparations.
SIMPLE -if only one tooth surface is
involved
COMPOUND- if two surfaces are involved
COMPLEX- if a preparation involving
three (or more) surfaces

CLASS I
RESTORATIONS
All pit-and-fissure restorations are Class I, and
they are assigned to three groups, as follows:
1. Restorations on Occlusal Surface of
Premolars & Molars
2. Restorations on Occlusal Two Thirds of
the Facial & Lingual Surfaces of Molars
3. Restorations on Lingual Surface of
Maxillary Incisors.

CLASS II
RESTORATIONS.
Restorations on the proximal surfaces of
posterior teeth are Class II.

CLASS III
anterior teeth that do not involve the incisal
angle are Class III

CLASS IV
RESTORATIONS
anterior teeth that do involve the incisal
edgeare Class IV.

CLASS V
RESTORATIONS
Restorations on the gingival third of the
facial or lingual surfaces of all teeth (except
pit-and-fissure lesions) are Class V.

CLASS VI
RESTORATIONS
Restorations on the incisal edge of
anterior teeth or the occlusal cusp heights
of posterior teeth are class VI

OBJECTIVES OF TOOTH PREPARATION
remove all defects and provide necessary protection to the pulp
extend the restoration as conservatively as possible
form the tooth preparation so that under the force of mastication the
tooth or the restoration or both will not fracture and the restoration will
not be displaced
allow for the esthetic and functional placement of a restorative material
34

STAGES & STEPS OF TOOTH PREPARATION
Tooth preparation
Initial tooth
preparation
( first stage of tooth
preparation)
Final tooth
preparation
(Second stage of tooth
preparation)
35

Initial tooth
preparation
Step 1: Outline form and initial
depth
Step 2: Primary resistance form
Step 3: Primary retention form
Step 4: Convenience form
Final tooth
preparation
Step 5: Removal of any
remaining infected dentin and/
or old restorative material, if
indicated
Step 6: Pulp protection, if
indicated
Step 7: Secondary resistance
and retention forms
Step 8: Procedures for finishing
external walls
Step 9: Final procedures:
cleaning, inspecting, sealing
36
Art & science of operative dentistry 5th edition page no.298,299

FACTORS AFFECTING TOOTH PREPARATION
General factors
diagnosis
Knowledge
of dental
anatomy
Patient
factors
Conservation of
tooth structure
Restorative
material factor
Amalgam
restoration
Composite
restoration
37

G.V. BLACK’S APPROACH TO
CAVITY PREPARATION
1. Outline form
2. Resistance form
3. Retention form
4. Convenience form
5. Removal of remaining caries
6. Finish enamel walls
7. Clean cavity preparation

1. The dental tissues
2. The disease
3. The properties of the restorative material
WHAT DETERMINES CAVITY DESIGN?

1. THE DENTAL TISSUES -
ENAMEL
Enamel is the hardest tissue in
the body, inelastic and brittle.
Tend to split along the line of
rods

2. THE DENTAL TISSUES -
DENTINE
 Dentine is softer than enamel,
more porous and sensitive.
 Dentine and pulp are considered
one unit.
 Diseases or operative procedures
that affect the dentine may also
affect the pulp

THE DENTAL TISSUES -
PULP
 The preparation is designed to avoid
pulp
 Avoid physical, chemical or thermal
trauma to the pulp during cavity
preparation and placing the
restoration

THE DENTAL TISSUES –
THE GINGIVA
 The cavity design and restoration
should have minimal encroachment
on the gingiva
 The margins of the restoration
should be smooth and not retentive
to plaque
 The margins should be cleansable
as possible

THE DISEASE
Two points to be considered in the
spread of caries: pulpal and lateral
spread

THE PROPERTIES OF
RESTORATIVE MATERIALS
- AMALGAM
 Mechanical retention
 Weak in thin sections
 Is not tooth colored
 corrosion forms at the tooth
amalgam interface
 Needs force to be condensed into
cavity

AMALGAM RESTORATION FOR
CLASS I CAVITY PREPARATION
46

INDICATIONS
Extent of pit &
fissure caries
Incidence of
proximal
surface caries
Age of the
patient
Esthetics Economics
Prophylactic
procedure
47
Art & science of operative dentistry 2nd edition page no.189

CONTRAINDICATIONS
48
Esthetically
prominent areas of
posterior teeth
Small-to-moderate
Classes I and II
restorations that can
be well isolated
Small Class VI
restorations

CONSERVATIVE CAVITY PREPARATION
Conservative tooth preparation
is recommended to protect
the pulp, to preserve the
strength of the tooth, and
reduce deterioration of the
amalgam restoration

INITIAL TOOTH PREPARATION
‘initial tooth preparation is the extension and initial design of
the external walls of the preparation at a specified, limited
depth so as to provide access to the caries or defect, reach
sound tooth structure (except for later removal of infected
dentin on the pulpal or axial walls), resist fracture of
the tooth or restorative material from masticatory forces
principally directed with the long axis of the tooth, and retain
the restorative material in the tooth’Art & science of operative dentistry 5th edition page no.
300

INITIAL TOOTH PREPARATION.
 The preparation is extended internally no deeper than 0.2
mm (0.5 mm when restoring with direct gold) into dentin
for pit-and-fissure lesions and 0.2 to 0.8 mm into dentin for
smooth-surface lesions
 It should include only the faulty, defective occlusal pits &
fissures
 Occasionally the marginal outline for maxillary premolars
is somewhat butterfly shaped, because of extension to
include the developmental fissures facially and lingually.
 The most narrow portion of thepreparation, faciolingually,
is between the cusp heights.
As much of the cusp incline as possible should be preserved
in any preparation involving the occlusal surface

OUTLINE FORM
Establishing the outline form means:
(1) placing the preparation margins in the
positions they will occupy in the final
preparation, except for finishing
enamel walls and margins, and
(2) preparing an initial depth of 0.2 to 0.8
mm pulpally of the DEJ position or
normal root-surface position

FEATURES
preserving cuspal strength,
preserving marginal ridge strength,
minimizing facio lingual extensions,
using enameloplasty,
connecting two close less than 0.5 mm apart) faults or
tooth preparations
Restricting the depth of the preparation intodentin to a maximum of 0.2 mm
for pit-and-fissurecaries and 0.2 to 0.8 mm for the axial wall of smooth
surface caries (the greater depth indicated only for an extension gingivally
onto the root surface).

OUTLINE FORM &
INITIAL DEPTH FOR PIT-
AND FISSURE LESIONS.
Its controlled by three factors:
(1) the extent to which the enamel has been
involved by the carious process
(2) the extensions that must be
(3) the limited bur depth related to the tooth's
original surface while extending the
preparation to sound external walls that have a
pulpal depth of approximately 1.5 to 2 mm and
usually a maximum depth into dentin of 0.2
mm
initial depth is approximately two thirds of 3-mm bur head
length, or 2 mm, as related to prepared facial and lingual walls,
but is half the No. 245 bur head length, or 1.5 mm, as related to
central fissure location.

RULES FOR ESTABLISHING OUTLINE FORM FOR PIT &
FISSURE TOOTH PREPARATION
1.Extend the preparation margin until sound tooth
structure is obtained and no unsupported and/or
weakened enamel remains.
2. Avoid terminating the margin on extreme
eminences such as cusp heights or ridge crests.
3. If the extension from a primary groove includes one
half or more of the cusp incline, consideration should
be given to capping the cusp. If the extension is two-
thirds, the cusp-capping procedure is most often the
proper procedure ,which removes the margin from
the area of masticatory stresses.
Rule for cusp capping: If extension from a primary groove toward the cusp tip is no
more than half the distance, then no cusp capping; if this extension is from one half to two
thirds of the distance, then consider cusp capping; if the extension is more than two thirds
of the distance, then usually cap the cusp.

4. Extend the preparation margin to include all of
the fissure that cannot be eliminated by
appropriate enameloplasty
5. Restrict the pulpal depth of the preparation to
a maximum of 0.2 mm into dentin
6. When two pit-and-fissure preparations have
less than 0.5 mm of sound tooth structure
between them, they should be joined to eliminate
a weak enamel wall between them.
7. Extend the outline form to provide sufficient
access for proper tooth preparation, restoration
placement, & finishing procedures
A,Enameloplasty on area of imperfect coalescence of
enamel.
B, Not more than onet hird of the enamel thickness
should be removed.

RULES FOR ESTABLISHING OUTLINE FORMS FOR
PROXIMAL SURFACE TOOTH PREPARATIONS
The preparation of
class II is divided
into two segments:
Occlusal
Same as
class I
Proximal
Axial wall
Gingival
step
Occlusal
convergence

Axial wall
Restrict the axial wall pulpal depth of
the proximal preparation to a maximum
of 0.2 to 0.8 mm into dentin (the greater
depth when the extension is onto the
root surface; the lesser depth when no
retention grooves will be placed).
Axial wall

 Extended apically of the proximal contact to
provide a minimum clearance of 0.5 mm
between the gingival margin and the adjacent
tooth.
 Its given below the contact area ; at the level of
gingiva.
GINGIVAL
SHEATH
Gingival sheath

External tooth walls converge
Occlusally.
In this way, once the amalgam is placed in the preparation and
hardens, it cannot dislodge without some type of fracture occurring
ADVANTAGES
Produces retention.
It allows slight facial and/or lingual extension of the proximal
portion of the preparation in the gingival area while conserving the
marginal ridge, thus reducing the forces of mastication on critical
areas of the restoration
CAVOSURFACE ANGLE
where the proximal facial and lingual walls meet the marginal ridge
is a desirable 90 degrees because of the occlusal convergence of the
preparation
OCCLUSAL
CONVERGENCE
External walls of proximal &
occlusal portions converging
occlusally
Converge

ENAMELOPLASTY
Sometimes a pit or groove (fissured or not) does
not penetrate to any great depth into the enamel
and does not allow proper preparation of tooth
margins, except by undesirable extension. This is
always true of the end of a fissure. If such a shallow
feature is removed and the convolution of the
enamel is rounded or "saucered," the area
becomes cleanable, finishable, and allows
conservative placement of preparation margins.
This procedure of reshaping the enamel surface
with suitable rotary cutting instruments is termed
enameloplasty
Enameloplasty does not extend the
outline form.

RESISTANCE
FORM
Its defind as ‘Primary resistance form may be
defined as that shape and placement of the
preparation walls that best enable both the
restoration and the tooth to withstand,
without fracture, masticatory forces delivered
principally in thelong axis of the tooth’
Flat pulpal floor
Round internal line angle
Extension of external wall

Resistance forms must consider resistance of tooth to fracture from forces exerted on
restoration.
Flat floor (A) will help prevent restoration movement, whereas rounded pulpal floor
( B) may allow a non bonded restoration rocking action producing a wedging force,
which may result in shearing of tooth structure.

PRINCIPLES
1.to use the box shape with a relatively flat floor, which helps the tooth resist occlusal loading by virtue of being at
right angles to those forces of mastication that are directed in the long axis of the tooth;
2.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;
3.to have a slight rounding (coving) of internal line angles to reduce stress concentrations in tooth
structure;
4. in extensive tooth preparations, to cap weak cusps and envelope or include enough of a weakened tooth
within the restoration to prevent or resist fracture of the tooth by forces both in the long axis and obliquely
directed
5. to provide enough thickness of restorative material to prevent its fracture under load
6. to bond the material to tooth structure when appropriate.

FEATURES
Flat floor
Box shape
Inclusion of
weakened
tooth
structure
Preservation
of cusps and
marginal
ridges
Rounded
internal line
angles
Adequate
thickness of
restorative
material
Reduction
of cusps for
capping
when
indicated

RESISTANCE FORM To achieve this ,the prepared
cavity should possess the
following 4 attributes:
1.Flat Floor, which helps the
tooth to resist occlusal load
2. To restrict the extension of
the walls to allow strong cusp
& ridge areas to remain with
sufficient dentin support
3. To envelope or include
enough of a weakend tooth
within the restoration to
prevent or resist fracture by
lateral forces
4. To provide enough
thickness of restorative
material to prevent its
fracture under load

 The depth should be enough to take
adequate bulk of the restorative material
which can withstand forces of mastication.
 Amalgam thickness should be 1.5 – 2 mm
at least.

69
Resistance principles include:
 Extending around the cusps to conserve tooth structure and prevent the internal line angles
from approaching the pulp horns too closely
 Keeping the facial and lingual margin extensions as minimal as possible between the central
groove and the cusp tips
 Extending the outline to include fissures, thereby placing the margins on relatively smooth,
sound tooth structure
 Minimally extending into the marginal ridges (only enough to include the defect) without
removing dentinal support
 Eliminating a weak wall of enamel by joining two outlines that come close together (i.e., less
than 0.5 mm apart)
 Extending the outline form to include enamel undermined by caries
Art & science of operative dentistry 5th edition page no.672 & 673

RETENTION
FORM
Its defined as ‘Resistance form is the shape
or form of the cavity that best permits the
restoration to resist displacement through
tipping or lifting forces’
Wall should be parallel
Converge occlusally
Cavosurface margin
is 90 Degree

DOVETAIL
 It’s the modification of the outline form
for the sake of additional retention.
 Because the modification looks like a tail
of the dove, its called as dovetail.
Dovetail
Guidebook on preclinical conservative dentistry by K.S.Karthikeyn page no 80

Close
parallelism is
the principal
retention form
for cast
restoration.
In class II ,
occlusal
dovetail aids in
preventing the
tipping of the
restoration by
occlusal forces.
Pins may be
used to provide
additional
retention
Occlusal
convergence
Additional
retention is
affoeded by
enhancing
axiofacial &
axiolingual line
angles in class
II; this is
accomplished
by by placing a
small channel (
e.g- proximal
lock or groove)
bisecting the
line angles.
Other forms
are:small
undercuts at
point angle,
such as incisal
point angle in
class II, or
grooves along
line angles

Its that shape of a cavity that allows adequate
observation, accessibility & ease of operation in
preparing & restoring the cavity.
CONVENIENCE
FORM
Extension of walls
Art & science of operative dentistry 2nd edition page no.99& 5th edition 307

 It needs extension of mesial, facial or lingual walls to gain acces to the deeper
portion of the cavity.
 Only the minimal amount of reduction that will provide the necessary
convenience should be done

Removal of any remaining enamel pit or
fissure, infected dentin, and/or old
restorative material is the elimination of
any infected carious tooth structure or
faulty restorative material left in the tooth
after initial tooth preparation.

Larger areas of soft caries are
best removed by SPOON
EXCAVATERS by flaking up the
caries around the periphery of
the infected mass peeling it off in
layers.
Removal of harder, heavily
discolored dentin
removal process varies by spoon
excavaters, round steel burs at
low speed, round carbide burs
rotating at high speed
Pulpal damage may result from
the creation of frictional heat
with the use of a bur.
Pulp may become infected by
forcing microorganism into the
dentnal tubules through
excessive pressure with a SE
Deeper caries not removed by the initial cavity preparation is now removed. Care must
be exercised as the pulp may be in close proximity.
REMOVAL OF ANY REMAINING ENAMEL PIT OR
FISSURE, INFECTED DENTIN, AND/OR OLD
RESTORATIVE MATERIAL, IF INDICATED

To provide best marginal
seal possible between the
restorative material &
tooth structure, to afford
a smooth marginal
junction & to provide
maximal strength of both
the enamel & restorative
material at the margin
FINISH OF ENAMEL WALLS AND MARGINS

The direction of
the enamel rods
The support of
the enamel rods
both at the
dentinoenamel
junction &
laterally
The type of
restorative
material to be
placed in the
preparation
The location of
the margin
Degree of
smoothness
desired
79Art & science of operative dentistry 2nd edition page no.103

CLEAN THE CAVITY PREPARATION
Rinse away all debris and dry the cavity preparation.

TOOTH PREPARATION
Art & science of operative dentistry 5th edition page
no.672 & 673
 A No. 245 is recommended
 The silhouette of the No. 245 inverted cone bur reveals sides
slightly convergent toward the shank (this produces an
occlusal convergence of the facial and lingual preparation
walls, providing adequate retention form for the tooth
preparation).
 The slightly rounded corners of the end of the No. 245 bur
produce slightly rounded internal line angles that render
the tooth more resistant to fracture from occlusal force."'
 The No. 330 bur is a smaller and pears shaped version of the
No. 245 bur. It is indicated for the most conservative
amalgam preparations
head length of 3 mm
tip diameter of 0.8 mm

punch cut is performed by orienting the bur
so that its long axis parallels the long axis of
the tooth crown
Then the bur is inserted directly into the
faulty pit. When the pits are equally faulty,
enter the distal pit as illustrated.
Entering the distal pit first provides
increased visibility for the mesial extension.
The bur should be positioned so that its
distal aspect is directly over the distal pit,
thereby minimizing extension into the
marginal ridge

As the bur enters the pit, the proper depth of
1.5 mm (one half the length of the cutting
portion of the bur) should be established. The
1.5 mm pulpal depth is measured at the central
fissure.
Depending of the cuspal incline, the depth of the
prepared external walls will be 1.5 to 2 mm. The
desired pulpal depth is usually 0.1 to 0.2 mm
into dentin.
Distal extension into the distal marginal ridge to
include a fissure or caries occasionally requires a
slight tilting of the bur distally (no more than 10
degrees).
This creates a slight occlusal divergence to the
distal wall to prevent undermining the marginal
ridge of its dentin support

Care should be taken not to undermine the marginal
ridge.
when these fissures require extensions of more than a
few tenths of a millimeter, consideration should be given
to changing to a smaller diameter bur, such as a No. 169L
or No. 329, or to using enameloplasty.
The pulpal floor should follow the DEJ to maintain a
more uniform pulpal floor depth When the central
fissure has minimal caries, one pass along the fissure at
the prescribed depth provides the desired minimal
width to the isthmus.
Ideally the width of the isthmus need be no more
than the diameter of the bur. isthmus width of one
fourth the distance between the cusp tips does not
reduce the strength of the tooth."

85
B
However, when operator judges
that extension will l eave only
1.6-mm thickness (two
diameters of No. 245 bur) of
marginal ridge (i.e., premolars)
the mesial and distal walls must
diverge occlusally
to conserve ridge-supporting
dentin
Direction of mesial and distal walls is influenced by remaining
thickness of marginal ridge as measured from mesial or distal
margin
to proximal surface (i.e., imaginary projection of proximal surface)
(b).
A
Mesial and distal walls
should converge occlusally
when distance from a to b is
greater than 1.6 mm
C
Extending mesial or distal wall
to two-diameter limit
without diverging wall
occlusally will undermine
marginal-ridge enamel.

 If the pit-and-fissure remnants are few and small, remove
them with a suitably sized, round carbide bur .
 Removal of the remaining infected dentin is best
accomplished using a discoid type spoon excavator or a
slowly revolving, round carbide bur of appropriate size..
 When removing infected dentin, stop the excavation when
tooth structure feels hard or firm (i.e., the same feel as
sound dentin).
 This often occurs before all lightly stained or discolored
dentin is removed . Ensure that caries is removed from the
peripheral DEJ where it is less visible than on the pulpal floor
86Art & science of operative dentistry 5th edition page no.672 & 673
Removal of dentinal caries is
accomplished with round burs (A) or
spoon excavators

EXTENSIVE CLASS I AMALGAM RESTORATION
Infected dentin and the pulp is judged to be less than 1 mm or
when the facio lingual extent of the defect is up the cuspal inclines
87Art & science of operative dentistry 5th edition page no.687

Initial tooth preparation with extensive caries.
When extending laterally to remove enamel
undermined by caries, alter the bur's long axis to
prepare a 90- to 100-degree cavosurface angle.
A 100-degree cavosurface angle on the cuspal
incline will result in an 80-degree marginal
amalgam angle.

Occlusolingual (OL) amalgam restorations may
be used on maxillary molars when a lingual
fissure connects with the distal oblique fissure
and distal pit on the occlusal surface
CLASS I OCCLUSOLINGUAL AMALGAM
RESTORATIONS
Art & science of operative dentistry 5th edition page no. 731 60

 The tooth preparation should be no wider than
necessary; ideally the mesiodistal width of the
lingual extension should not exceed 1 mm,
except for extension necessary to remove
carious or undermined enamel or to include
unusual fissuring.
 When indicated, the tooth preparation should
be cut more at the expense of the oblique
ridge rather than centering over the fissure
(weakening the small distolingual cusp).
 The margins should extend as little as possible
onto the oblique ridge, distolingual cusp, and
distal marginal ridge.
Enamel cavosurface angles
of 90 to 100 degrees are ideal.
Art & science of operative dentistry 5th edition page no. 732 61

AMALGAM RESTORATION FOR
CLASS II CAVITY PREPARATION
91

CLASS II AMALGAM
RESTORATIONS
INVOLVING ONLY ONE
PROXIMAL SURFACE
Bur position for entry, as viewed
proximally.
Note: slight lingual tilt of bur
Art & science of operative dentistry 5th edition page no. 739

Bur position as viewed lingually.

Enter tooth with punch cut and extend distally
along central fissure at uniform depth of 1.5 to
2 mm (1.5 mm at fissure; because of
inclination of unprepared tooth surface,
corresponding measurement on prepared wall
is greater)

Enter tooth with punch cut and extend
distally along central fissure at uniform
depth of 1.5 to 2 mm (1.5 mm at fissure;
because of inclination of unprepared tooth
surface, corresponding measurement on
prepared wall is greater)

Occlusal view .
Completed occlusal step.

 Reverse curve in occlusal outline is
usually created when mesiofacial enamel
wall is parallel to enamel rod direction.
 Lingually, reverse curve is very slight,
often unnecessary

PROXIMAL OUTLINE
FORM (PROXIMAL BOX)
The objectives for extension of proximal margins
are to:
 Include all caries, faults, or existing restorative
material.
 Create 90-degree cavosurface margins (i.e., butt
joint margins).
 Establish (ideally) not more than 0.5 mm
clearance with the adjacent proximal surface
facially, lingually, & gingivally.
Again visualize the desired final
location of the facial and lingual
walls of the proximal box or
proximal outline form relative to
the contact area.

Bur position to begin proximal ditch cut

Proximal ditch is extended gingivally to
desired level of gingival wall (i.e., floor)

Variance in pulpal depth of axiogingival line
angle as extension of gingival wall varies:
a, at minimal gingival extension;
b, at moderate extension;
c, at extension that places gingival margin in
cementum, whereupon pulpal depth is 0.75
to 0.8 mm and bur may shave side of wedge.

Proximal ditch cut results in axial wall that
follows outside contour of proximal surface

Position of proximal walls (i.e., facial,
lingual, gingival) should not be overextended
with No. 245 bur, considering additional
extension provided by hand instruments
once remaining spurs of enamel are
removed.

When small lesion is prepared, gingival
margin should clear adjacent tooth by only
0.5 mm.
This clearance may be measured with side of
explorer.
The diameter of the tine of a No. 23 explorer
is five tenths millimeter,'/, inch (6.3 mm)
from its tip.

Facio lingual dimension of proximal ditch is
greater at gingival than at occlusal level.

 To further isolate and weaken proximal
enamel, bur is moved toward &
perpendicular to proximal surface (parallel
to direction of enamel rods).
 Side of bur may emerge slightly through
proximal surface at level of gingival floor
(arrow).

Removing isolated enamel., Using spoon
excavator to fracture out weakened proximal
enamel.

Occlusal view with proximal enamel
removed.

Proximal view with proximal
enamel removed.

Round toothpick wedge placed in gingival
embrasure protects gingiva and rubber
dam during preparation of proximal box.

 Triangular wedge is indicated when deep
gingival extension of proximal box is
anticipated, because wedge's greatest
cross-sectional dimension is at its base.
 Consequently, it will more readily engage
the remaining clinical tooth surface.

112
Removing remaining undermined proximal enamel with enamel hatchet on
facial proximal wall (A), lingual proximal wall (B), and gingival wall
Art& science of operative dentistry 5th edition page no. 743

FEATURES OF THE CLASS II PREPARATION:
• open gingival, lingual, buccal contacts;
• dove tail; reverse “S”; convergent walls;
• even depth;
• smooth surfaces;
• no sharp angles.

STANDARD PRINCIPLES
• Margins 90° (perpendicular) to tangent to carvosurface
• Proper clearance: 0.25mm – 0.5mm
• Occlusal, axial and gingival walls in dentin

PREPARATION
Incorporate the reverse-S curve (all walls approx. 90 degrees
to cavosurface)
Black II - MOD

PREPARATION
Proximal box and rounded
axiopulpal angle

PREPARATION
Just open” buccal proximal
wall

BLACK II - CONTACT POINT
Positive contact

MANAGEMENT OF SMALL-TO-MODERATE SIZE
CARIOUS LESION ON PULPAL WALL
119
A, Infected carious dentin extending beyond ideal pulpal wall position.
B, Incorrect lowering of pulpal wall to include infected carious dentin.
C, Correct extension facially and lingually beyond infected carious dentin.
Note excavation below ideal pulpal wall level and facial and lingual seats are at
ideal pulpal wall level.

120
Infected carious dentin on axial wall does not call for preparing axial wall toward pulp
as shown by dotted lines. Infected carious dentin extending pulpally of ideal axial wall
position is removed with round bur.

121
Beveling axiopulpal line angle
Art& science of operative dentistry 5th edition page
no. 705

122
Proximal retention locks.
A, Position of No. 169L bur to prepare retention lock as bur is moved lingually and pulpally. B, Lingual lock.
Note: dentin support of proximal enamel. C, Completed locks. D, Locks prepared with No. '/, bur. E,
Completed locks.

1. Art & science of operative dentistry 5th edition
2. Sturdevent ‘s Art & science of operative dentistry south
asian edition
3. American academy of pediatric dentistry, reference
manual v 34 / no 6 12 / 13
4. Preservation and Restoration of Tooth Structure By G. J.
Mount, W.R.Hume
5. International dentistry sa vol. 12, no. 3
6. Current Concepts and Techniques for Caries Excavation
and Adhesion to Residual Dentin. Vol 13, No 1, 2011
REFERENCES:

7.Interactions between cavity preparation
& restorations events & their effects on
pulp vitality. Vol 26,No 6 2006
8. A clinical evaluation of an Erbium:YAG
laser for dental cavity preparation.
british dental journal, volume 188, no. 12,
june 24 2000
9. Art & science of operative dentistry 2nd
edition

Cavity preparation

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