Principles of tooth preparation

PRINCIPLES OF TOOTH
PREPARATION FOR SILVER
AMALGAM RESTORATIONSAMALGAM RESTORATIONS
Dr. MEENAL ATHARKAR
MDS
DEPT OF ENDODONTICS AND CONSERVATIVE DENTISTRY

CONTENTS
• Introduction
• Definitions
• Objectives of tooth preparation
• Need for restorations• Need for restorations
• Fundamental concepts relating to conventional and
modified tooth preparation
• Principles of tooth preparation according to
Rosensteil
• Factors affecting tooth preparation

• Nomenclature: caries related
noncaries related
tooth preparation related
• Classification for tooth preparation
• Stages and steps of tooth preparation• Stages and steps of tooth preparation
• Initial tooth preparation
• Final tooth preparation
• Additional concepts in tooth preparation
• Clinical consideration
• Summary
• References

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 toothused 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 (a breach in the
surface integrity of the tooth) and was
referred to as a cavity.

• Likewise, when the affected tooth was repaired,
the cutting or preparation of the remaining tooth
structure (to best receive a restorative material)
was referred to as a cavity preparation.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term cavity is used only as a historical reference

DEFINITIONS
According to Sturdevant:
Tooth Preparation is the mechanical
alteration of a defective, injured ,
or diseased tooth to receive aor diseased tooth to receive a
restorative material that re-
establishes a healthy state for the
tooth, including esthetic
corrections where indicated &
normal form & function.

According to M.A. Marzouk :
Tooth Preparation is the mechanical
preparation or the chemical treatment of the
remaining tooth structure, which enables it toremaining tooth structure, which enables it to
accommodate a restorative material without
incurring mechanical/ biological failure.

OBJECTIVES OF TOOTH PREPARATION
 Remove all defects & provide necessary
protection to the pulp.
Extend the restoration as conservatively as
possible.possible.
Form the tooth preparation so that under the
force of mastication, the tooth or the
restoration will not be displaced.
Allow for the esthetic & functional placement
of a restorative material.

NEED FOR RESTORATIONS
• A small or large carious lesion

• Replacement or repair of restorations with
serious defects, such as improper proximal
contact, gingival excess, defective open
margins, or poor esthetics

• To restore proper form and function to
fractured teeth

• A tooth may require a restoration to simply
restore form or function absent as a result of
congenital malformation

• To accomplish an effective preventive program that
places the patient into a low-risk status for developing
future caries or periodontal disease, a complete
assessment must be made ofassessment must be made of
• (1) the type and number of microorganisms present;
• (2) the patient's homecare ability, effectiveness, and
motivation;
• (3) the need for antimicrobial therapy; and
• (4) dietary factors

FUNDAMENTAL CONCEPTS RELATING TO
CONVENTIONAL AND MODIFIED TOOTH
PREPARATION
1. No friable tooth structure can be left
2. The fault ,defect or caries is removed.
3. The remaining tooth structure is left as strong
as possible.
3. The remaining tooth structure is left as strong
as possible.
4. The underlining pulpal tissue is protected.
5. The restorative material is retained in a strong
, esthetic & functional manner.

PRINCIPLES OF TOOTH PREPARATION
ACCORDING TO ROSENSTEIL

FACTORS AFFECTING TOOTH
PREPARATION
• Preparing a tooth to receive a restorative
material is a comprehensive endeavor.
• Many factors affect the appropriate tooth
preparation design for a given tooth.preparation design for a given tooth.
• These factors must be considered for each
restorative procedure contemplated, the end
result being that no two preparations are the
same.

FACTORS AFFECTING TOOTH
PREPARATION
• General factors- 1. diagnosis
2. knowledge of dental
anatomy
3. patient factors.3. patient factors.
• Conservation of tooth structure
• Restorative material factors
• Tooth related factors

• GENERAL FACTORS
1. Diagnosis:
• Before any restorative procedure, a complete and
thorough diagnosis must be made. There must be a
reason to place a restoration in the tooth.reason to place a restoration in the tooth.
• The reasons may include caries, fractured teeth,
esthetic needs, or needs for improved form or
function.
• An assessment of both pulpal and periodontal status
will influence the potential treatment of the tooth,
especially in terms of the choice of restorative material
as well as the design of the tooth preparation.

• Likewise, an assessment of the occlusal
relationships must be made.
• Such knowledge often affects the design of the
tooth preparation and the choice of material.
• The patient's concern for esthetics should be• The patient's concern for esthetics should be
considered when planning the restorative
procedure and will influence the restorative
material selected.
• Esthetic considerations will also influence the
tooth preparation by altering, in some situations,
the extension or design

• The relationship of a specific restorative procedure with
other treatment planned for the patient must be
considered. For example, if the tooth is an abutment for a
fixed or removable partial denture, the design of the
restoration may need to be altered to accommodate
maximum effectiveness of that prosthesis.maximum effectiveness of that prosthesis.
• Lastly, the risk potential of the patient to further dental
disease should be assessed.
• If appropriate, diagnostic tests should be performed to
determine the risk the patient has for further dental caries.
• Also, more conservative, less expensive restorative
procedures may be planned initially until caries factors are
controlled.

• 2.Knowledge of Dental Anatomy:
• Proper tooth preparation is accomplished through
systematic procedures based on definite physical and
mechanical principles.
• A prerequisite for understanding tooth preparation is
knowledge of the anatomy of each tooth and its relatedknowledge of the anatomy of each tooth and its related
parts.
• A gross picture, both internal and external, of the
individual tooth being operated on must be visualized.
• The direction of the enamel rods, the thickness of the
enamel and dentin, the size and position of the pulp, the
relationship of the tooth to supporting tissues, and other
factors must all be known to facilitate accurate judgment in
tooth preparation.

• 3. Patient Factors:
• Patient factors must play an important role in determining
the appropriate restorative treatment rendered.
• A)The patient's knowledge and appreciation of good dental
health influence his or her desire for restorative care and
may influence his or her choice of restorative materials.may influence his or her choice of restorative materials.
• B)Certainly the patient's economic status is a factor in
selecting the type of restorative care selected, and the
patient's input in this regard must be obtained.
• Too often dentists predetermine what they believe is the
patient's best economic alternatives and realize later that
their assessment was incorrect and that other, more
suitable, treatment alternatives should have been pursued.

• C)The patient's age may be a factor in determining the
restorative material and, consequently, the tooth
preparation to be used.
• With increasing numbers of older adults in the population,
their treatment may pose restorative considerations.
• Older adults who have physical or medical complications• Older adults who have physical or medical complications
may require special positioning for restorative treatment as
well as shorter, less stressful appointments.
• Such considerations may influence the type of procedure
planned. Because many older adults will have new or
replacement restorative needs that are completely or
partially on the root surfaces, the treatment of many of
these areas will be more complex.

• CONSERVATION OF TOOTH STRUCTURE:
• While one of the primary objectives of operative
dentistry is to repair the damage from dental caries,
the preservation of the vitality of the tooth is
paramount.
• Although pulp tolerance to insult is usually favorable,• Although pulp tolerance to insult is usually favorable,
the pulp should not be subjected to unnecessary abuse
by the application of poor or careless operative
procedures on the tooth.
• The less tooth structure removed, the less potential
damage that may occur to the pulp.
• Every effort should be made to make restorations as
small as possible.

• The smaller the tooth preparation, the easier it is to
retain the restorative material in the tooth.
• Small tooth preparations result in restorations that
have less effect on both intraarch and interarch
relationships, as well as esthetics. Naturally, the
smaller the tooth preparation, the stronger is thesmaller the tooth preparation, the stronger is the
remaining unprepared tooth structure.
• Examples of conservative tooth preparation features
are concepts relating to: (1) minimal extensions of the
tooth preparations, especially faciolingually and
pulpally; (2) supragingival margins; and (3) rounded
internal line angles.

• RESTORATIVE MATERIAL FACTORS:
• The choice of restorative material affects the
tooth preparation and is made by considering
many factors. The patient's input into the
decision is important. Economic and estheticdecision is important. Economic and esthetic
values are primary patient decisions.
• The ability to isolate the operating area and the
extensiveness of the problem are factors that the
operator must consider in recommending a
material or material options to a patient.

• An amalgam restoration requires a specific tooth
preparation form that ensures:
(1) retention of the material within the tooth
and
(2) strength of material in terms of thickness and(2) strength of material in terms of thickness and
marginal form.
• Adhesive amalgams still require the same tooth
preparation as for nonadhesive amalgam
restorations. Thus the type of tooth preparation
is determined by the restorative material used

• TOOTH RELATED FACTORS:
1. Primary or permanent
2. Occlusal stresses
3. Quality of the tooth3. Quality of the tooth
4. Location of the tooth
5. Type of tooth preparation

NOMENCLATURE
• Nomenclature refers to a set of terms used in
communication by persons in the same
profession that enables them to better
understand one another.understand one another.
• Categorized as:
1. Caries related
2. Non caries related
3. Tooth preparation

• CARIES TERMINOLOGY
• dental caries is an infectious microbiologic
disease that results in localized dissolution anddisease that results in localized dissolution and
destruction of the calcified tissues of the teeth.
• Moreover, caries is episodic with alternating
phases of demineralization and remineralization,
and these processes may be occurring
simultaneously in the same lesion.

• Caries can be described according to location, extent, and
rate .
I] According to location:
A) Primary Caries:
• Primary caries is the original carious lesion of the tooth.
• Accordingly, three morphologic types of primary caries
are evident in clinical observation, namely, carious lesions
originating:
(1) in enamel pits and fissures,
(2) on enamel smooth surfaces, or
(3) on root surfaces.

1) Caries of Pit-and-Fissure Origin.
• Resulting from the imperfect coalescence of
the developmental enamel lobes.
• When such areas are exposed to those oral
conditions conducive to caries formation,
caries usually develops.

• In diagrammatic terms, pit-and-fissure caries
may be represented as two cones, base to
base, with the apex of the enamel cone at the
point of origin and the apex of the dentin
cone directed toward the pulp.

2) Caries of Enamel Smooth-Surface Origin:
• Smooth surface caries does not begin in an enamel
defect, but rather in a smooth area of the enamel
surface that is habitually unclean, and is thereby
continually, or usually, covered by plaque.
• Plaque is necessary for caries, and that additional oral
conditions also must be present for caries to ensue.
• The disintegration in the enamel in smooth-surface
caries also may be pictured as a cone, but with its base
The disintegration in the enamel in smooth-surface
caries also may be pictured as a cone, but with its base
on the enamel surface and the apex at, or directed to,
the DEJ.

• Residual Caries. Residual caries is caries that remains in a completed
tooth preparation, whether by operator intention or by accident. Such
caries is not acceptable if at the DEJ or on the prepared enamel tooth
wall

3)Root-Surface Caries:
• Root-surface caries may occur on the tooth root that has
been both exposed to the environment and habitually
covered with plaque.
• Additional oral conditions conducive for caries also must be
present and often are prevalent in the older population.
• Root caries is usually more rapid than other forms of caries,
and thus should be detected and treated early.
• Root caries is becoming more prevalent because an
increasing number of older persons are retaining more ofincreasing number of older persons are retaining more of
their teeth and experiencing gingival recession, both of
which increase the likelihood of root caries development.
• .

B) Secondary (Recurrent) Caries:
• Secondary caries occurs at the junction of a
restoration and the tooth and may progress
under the restoration. It is often termedunder the restoration. It is often termed
recurrent caries. This condition usually
indicates that microleakage is present, along
with other conditions conducive to caries

II] Extent of Caries:
A) Incipient Caries (Reversible):
• Incipient caries is the first evidence of caries activity in the
enamel.
• On smooth surface enamel, the lesion appears opaque
white when air-dried, and will seem to disappear (not bewhite when air-dried, and will seem to disappear (not be
distinguishable from contiguous unaffected enamel) if
wetted.
• This lesion of demineralized enamel has not extended to
the DEJ, and the enamel surface is fairly hard and still intact
(smooth to the touch).
• The lesion can be remineralized if immediate corrective
measures alter the oral environment, including plaque
removal and control.

• A remineralized lesion usually is either
opaque white, or a shade of brown-to-black
from extrinsic coloration, has a hard surface,
and appears the same whether wet or dry.and appears the same whether wet or dry.
•

B) Cavitated Caries (Nonreversible):
• In cavitated caries, the enamel surface is
broken (not intact), and usually the lesion has
advanced into dentin.
• Usually remineralization is not possible and
treatment by tooth preparation and
restoration is often indicated.
treatment by tooth preparation and
restoration is often indicated.

III] Rate (Speed) of Caries:
1) Acute (Rampant) Caries:
• Acute caries, often termed rampant caries, is
when the disease is rapid in damaging thewhen 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).
• Less time for extrinsic pigmentation explains
the lighter coloration

2)Chronic (Slow or Arrested) Caries:
• Chronic caries is slow, or it may be arrested following
several active phases.
• The slow rate results from periods when demineralized
tooth structure is almost remineralized (the disease istooth structure is almost remineralized (the disease is
episodic over time because of changes in the oral
environment).
• The condition may be in only a few locations in a
mouth, and the lesion is discolored and fairly hard.
• The slow rate of caries allows time for extrinsic
pigmentation.

• ACUTE
• CHRONIC
SLOW
• ARRESTED

• Prophylactic Odontotomy:
• Prophylactic odontotomy is presented only as
a historical concept characterized by
minimally preparing and filling with amalgam,minimally preparing and filling with amalgam,
developmental, structural imperfections of
the enamel, such as pits and fissures, to
prevent caries originating in these sites.
• It is no longer advocated as a preventive
measure.

• NONCARIOUS TOOTH DEFECTS TERMINOLOGY
1)Abrasion.
• Abrasion is abnormal tooth surface loss resulting from direct
friction forces between the teeth and external objects, or from
frictional forces between contacting teeth components in the
presence of an abrasive medium.
• Abrasion may occur from• Abrasion may occur from
• (1) improper brushing techniques,
• (2) habits such as holding a pipe stem by the teeth,
• (3) tobacco chewing, or
• (4) vigorous use of toothpicks between adjacent teeth.
• Toothbrush abrasion is the most common example and is usually
seen as a sharp, V-shaped notch in the gingival portion of the facial
aspect of a tooth.

2)Erosion.
• Erosion is the wear or loss of tooth surface by
chemicomechanical action. Regurgitation of
stomach acid can cause this condition on the
lingual surfaces of maxillary teeth (particularlylingual surfaces of maxillary teeth (particularly
anterior teeth).
• Other examples are the dissolution of the facial
aspects of anterior teeth because of habitual
sucking of lemons or the loss of tooth surface
from ingestion of acidic medicines.

3)Abfraction.
• Recently, it has been proposed that the
predominant causative factor of some of the
cervical, wedge-shaped defects is a strong (heavy)
eccentric occlusal force (shown as an associatedeccentric occlusal force (shown as an associated
wear facet) resulting in microfractures or
abfractures.
• Such microfractures occur as the cervical area of
the tooth flexes under such loads. This defect is
termed idiopathic erosion or abfraction

4)Attrition:
• Attrition is mechanical wear of the incisal or
occlusal surface as a result of functional or
parafunctional movements of the mandible
(tooth-to-tooth contacts). Attrition also
includes proximal surface wear at the contact
area because of physiologic tooth movement.area because of physiologic tooth movement.
.

6)Nonhereditary Enamel Hypoplasia.
• It usually is seen on anterior teeth and first molars in the form of
opaque white or light brown areas with smooth intact, hard
surface, or of pitted or grooved enamel, which is usually hard and
discolored and caused by fluorosis or high fever.
7) Amelogenesis Imperfecta.
• In amelogenesis imperfecta, the enamel is defective either in form• In amelogenesis imperfecta, the enamel is defective either in form
or calcification as a result of heredity and has an appearance
ranging from essentially normal to extremely unsightly
8) Dentinogenesis Imperfecta.
• Dentinogenesis imperfecta is a hereditary condition in which only
the dentin is defective. Normal enamel is weakly attached and lost
early.

• TOOTH PREPARATION TERMINOLOGY:
• Simple, Compound, and Complex Tooth
Preparations.
• A tooth preparation is termed simple if only• A tooth preparation is termed simple if only
one tooth surface is involved,
• compound if two surfaces are involved, and
• complex for a preparation involving three (or
more) surfaces

• TOOTH PREPARATION TERMINOLOGY
• Tooth preparation walls:
• Internal wall –An internal wall is prepared surface
that does not extend to external tooth 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 of the tooth and
occlusal of the pulp.

• External Wall- An external wall is a prepared
(cut) surface that extends to the external tooth
surface. Such a wall takes the name of the tooth
surface (or aspect) that the wall is towardsurface (or aspect) that the wall is toward
• Enamel Wall- The 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 retention features may be
located.

• Floor (or Seat)- A floor (or seat) is a prepared
wall that is reasonably flat and perpendicular
to the occlusal forces that are directed
occlusogingivally (generally parallel to the longocclusogingivally (generally parallel to the long
axis of the tooth Examples are the pulpal and
gingival walls.

• TOOTH PREPARATION ANGLES
1)Line angle. A line angle is the junction of two
planal surfaces of different orientation along a
line.An internal line angle is a line angleline.An internal line angle is a line angle
whose apex points into the tooth. An external
line angle is a line angle whose apex points
away from the tooth
2)Point angle – a point angle is the junction of
three planal surface of different orientation

3) 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, theangle 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.
• For better visualization, these imaginary projections
can be formed by using two periodontal probes, one
lying on the unprepared surface and the other on the
prepared external tooth wall

• Enamel Margin Strength:
• One of the more important principles in tooth preparation is the
concept of the strongest enamel margin.
• This margin has two significant features:
• (1) it is formed by full-length enamel rods whose inner ends are on
sound dentin, andsound dentin, and
• (2) these enamel rods are buttressed on the preparation side by
progressively shorter rods whose outer ends have been cut off but
whose inner ends are on sound dentin.
• Because enamel rods usually are perpendicular to the enamel
surface, the strongest enamel margin results in a cavosurface angle
greater than 90 degrees An enamel margin composed of full-length
rods that are on sound dentin but are not buttressed tooth-side by
shorter rods also on sound dentin is termed strong but not the
strongest.

• Generally, this margin will result in a 90-degree
cavosurface angle. An enamel margin composed
of rods that do not run uninterrupted from the
surface to sound dentin is termed unsupported,
and this marginal enamel tends to split orand this marginal enamel tends to split or
fracture off, leaving a V-shaped ditch along the
margin of a restoration.
• Usually, this weak enamel margin either has a
cavosurface angle less than 90 degrees or no
dentinal support

• Intracoronal tooth
preparation
• Boxlike
• Has both internal and
• Extracoronal tooth
preparation
• Stumplike
• Has walls or surfaces that• Has both internal and
external preparation walls
• Much of the tooth crown
and surface is not involved
• Remaining tooth is usually
weakened
• Restoration may or may not
restore the tooth strength
• Has walls or surfaces that
result from removal of most
to all of enamel.
• Also termed as crown
envelops the remaining
tooth crown and thereby
usually restores some of its
strength.

• Anatomic Tooth Crown and Clinical Tooth
Crown.
• The anatomic tooth crown is the portion of
the tooth covered by enamel.
• The clinical tooth crown is the portion of the
tooth exposed to the oral cavity.tooth exposed to the oral cavity.

CLASSIFICATION
• The more historical tooth preparation
(conventional) and alterations from that type
of preparation.
• The altered preparation designs are referred• The altered preparation designs are referred
to as:
• (1) bevelled conventional preparations and
• (2) modified preparations.

• Bevelled conventional designs are characterized
as conventional preparations with beveling of
some accessible enamel margins.
• Modified preparation designs may not have
uniform axial or pulpal depths or occlusallyuniform axial or pulpal depths or occlusally
converging vertical walls.
• Furthermore, thin cavosurface margins may
result in more acute angles in the restoration.
• Amalgam tooth preparations only use
conventional designs, whereas composite
preparations may be any of the three designs

CLASSIFICATION
• The conventional design preparation is typical
for an amalgam restoration and includes the
following characteristics:
• (1) uniform pulpal and/or axial wall depths,• (1) uniform pulpal and/or axial wall depths,
• (2) cavosurface margin design that results in a
90-degree restoration margin, and
• (3) primary retention form derived from
occlusally converging vertical walls..

CLASSIFICATION FOR CAVITY
PREPARATION
A) Black’s Classification
B) Modifications
- Charbeneu’s Modification- Charbeneu’s Modification
- Sturdevant’s Classification
C) Baume’s Classification
D) Mount and Hume’s Classification

CLASSIFICATION FOR TOOTH
PREPARATION
CLASS I
CLASS II
BLACK’S CLASSIFICATION
CLASS IV
CLASS V
CLASS VI
CLASS II
CLASS III

G V BLACKS Classification
First classification
universally accepted
based on type of treatment & areas involved

MODIFICATIONS
CHARBENEU’S MODIFICATION:
Class II: cavities on the single proximal surface of
bicuspids and molarsbicuspids and molars

• Class VI: cavities on both
mesial and distal proximal
surfaces of posterior teeth that
will share a common occlusalwill share a common occlusal
isthumus; lingual surface of
upper anterior teeth; any other
unusally located pit or fissure
involved with decay.

STURDEVANT’S CLASSIFICATION:
Simple Compound Complex

BAUM’S CLASSIFICATION
a) Pit and fissure cavities
b) Smooth surfaceb) Smooth surface
cavities

MOUNT &HUME CLASSIFICATION
SITE 1: pit, fissure and enamel defects on
occlusal surface of posterior teeth or other
smooth surface
SITE 2: proximal enamel immediately below areas inSITE 2: proximal enamel immediately below areas in
contact with adjacent teeth
SITE 3: the cervical one-third of the crown or,
following gingival recession, the exposed root.

Size 1: Minimal involvement of dentin
treated by remineralisation alone.
Size 2:Size 2:
• – moderate involvement of dentin.
Following cavity preparation,
remaining enamel is sound, well
supported by dentin and not likely
to fail under normal occlusal load.
The tooth is sufficiently strong to
support the restoration

Size 3: the cavity is enlarged
beyond moderate involvement.
Remaining tooth structure is
weakened to the extent that
cusps or incisal edges are split or
are likely to fail if left exposed
to occlusal load. The cavity
needs to be further enlarged soneeds to be further enlarged so
that the restoration can be
designed to provide support to
the remaining tooth structure.
Size 4: Extensive caries; bulk loss of
tooth structure

MOUNT AND HUME’s
CLASSIFICATION
SITE SIZE
MINIMAL
(1)
MODERATE (2) ENLARGED
(3)
EXTENSIVE (4)
(1) (3)
PIT/FISSURE
(1)
1.1 1.2 1.3 1.4
CONTACT AREA
(2)
2.1 2.2 2.3 2.4
CERVICAL
(3)
3.1 3. 2 3.3 3.4

STAGES OF TOOTH PREPARATION
• The preparation procedure is divided into two
stages (initial and final), primarily to allow
assessment of the beginning operator's
knowledge and abilityknowledge and ability

• 1) The first stage of tooth preparation is referred
to as the initial tooth preparation stage.
• In this stage, the mechanical alterations of the
tooth are extended to sound tooth structure in
all directions.all directions.
• 2) Final tooth preparation, the second stage of
tooth preparation, is the completion of the tooth
preparation.

STAGES AND STEPS IN TOOTH
PREPARATION
• INITIAL TOOTH PREPARATION STAGE:
Step 1: Outline form and initial depth
Step 2: Primary resistance form
Step 3: Primary retention form
Step 4: Convenience formStep 4: Convenience form
• FINAL TOOTH PREPARATION STAGE :
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

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 orfor 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.’
• Sturdevant

STEP 1: OUTLINE FORM AND INITIAL DEPTH
• Definition:
Establishing the outline form means
(1) placing the preparation margins in the positions(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 Postion or root-surface
position

• The greater depth is for extensions onto the
root surface. Otherwise, the depth into dentin
is not to exceed 0.2 to 0.5 mm, the deeper
dimension necessary when placing secondarydimension necessary when placing secondary
retention.

• Principle:
(1) all friable or weakened enamel should be
removed
(2) all faults should be included and(2) all faults should be included and
(3) all margins should be in a position to afford
good finishing of the margin of the
restoration.

• Factors:
• In determining the outline form of a proposed tooth
preparation, certain conditions or factors must first be
assessed.
1)Extent of the carious lesion, defect, or faulty old
restoration.
1)Extent of the carious lesion, defect, or faulty old
restoration.
• There is one extension exception: occasionally, a tooth
preparation outline for a new restoration will contact
or extend slightly into a sound, existing restoration.
• This is sometimes an acceptable practice (i.e, to have a
margin of a new restoration placed into an existing,
sound restoration).

2) Esthetic and occlusal conditions affect the proposed preparation.
• Esthetic considerations not only affect the choice of restorative
material, but also the design of the tooth preparation in an effort to
maximize the esthetic result of the restoration.
3)Correcting or improving occlusal relationships also may necessitate
altering the tooth preparation to accommodate such changes, even
when the involved tooth structure is not faulty (i.e., perhaps awhen the involved tooth structure is not faulty (i.e., perhaps a
cuspal form must be altered to effect better occlusal relationships).
4) The adjacent tooth contour may dictate specific preparation
extensions that both secure appropriate proximal relationships and
provide the restored tooth with optimal form and strength.
5) The desired cavosurface marginal configuration of the proposed
restoration affects the outline form.

• Features:
Generally the six specific, typical features of establishing proper
outline form and initial depth are:
(1) preserving cuspal strength,
(2) preserving marginal ridge strength,
(3) minimizing faciolingual extensions,(3) minimizing faciolingual extensions,
(4) using enameloplasty,
(5) connecting two close (less than 0.5 mm apart) faults or tooth
preparations, and
(6) restricting the depth of the preparation into dentin to a maximum
of 0.2 mm for pit-and-fissure caries and 0.2 to 0.8 mm for the axial
wall of smoothsurface caries (the greater depth indicated only for
an extension gingivally onto the root surface).

• Rules for establishing outline form for pit and 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• 2. Avoid terminating the margin on extreme eminences
such as cusp heights or ridge crests.
• 3. If the extension from a primary groove includes onehalf
or more of the cusp incline, consideration should be given
to capping the cusp. If the extension is twothirds, the cusp-
capping procedure is most often the proper procedure,
which removes the margin from the area of masticatory
stresses.

• 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 except when (1) preparing
a tooth for a gold foil restoration, in which case the initiala tooth for a gold foil restoration, in which case the initial
depth is 0.5 mm into dentin or (2) when the occlusal
enamel has been worn thin.
• To be as conservative as possible, the preparation for an
occlusal surface pit-and-fissure lesion is first prepared to a
depth of 1.5 mm, as measured at the central fissure.
Depending on the cuspal steepness angles, the facial and
lingual prepared walls usually will be greater than 1.5 mm.

• If the amount of pit or fissure remaining is greater
than 50% of the pulpal floor, the entire pulpal floor is
deepened (at this time of preparing outline form) to a
maximum initial depth of 0.2 mm into dentin. This will
mean 0.2 mm into dentin when extension is to soundmean 0.2 mm into dentin when extension is to sound
tooth structure (i.e., a 0.2-mm dentinal wall, with the
remainder of the wall formed in enamel).
• Thus, the actual depth of the preparation may vary
from 1.5 mm, depending on the thickness of the
enamel and the steepness of the cuspal inclines.

• 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, and finishing procedures.

• Rules for establishing outline forms for proximal
surface tooth preparations
• 1. Extend the preparation margins until sound
tooth structure is obtained and no unsupported
and/or weakened enamel remains. (Sometimes,
unsupported but not friable enamel may remain
in tooth preparations for bonded restorations.)in tooth preparations for bonded restorations.)
• 2. Avoid terminating the margin on extreme
eminences such as cusp heights or ridge crests.
• 3. Extend the margins to allow sufficient access
for proper manipulative procedures.
•

• 4. 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).
• Typically, in this stage of tooth preparation for Class II• Typically, in this stage of tooth preparation for Class II
amalgam restorations, which will have proximal
retention locks, the cutting instrument (No. 245 bur) is
positioned by being held parallel to the DEJ and
thereby creating a cut approximately 0.3 mm into
enamel with the remainder of the instrument diameter
(approximately 0.5 mm) into dentin.

• During this initial cutting, portions of the instrument may
be in air (from a void caused by deeper caries) but it should
not remove dentin caries that is deeper pulpally than 0.5
mm from the DEJ.
• 5. Usually, gingival margins of tooth preparations are
extended apically of the proximal contact to provide aextended apically of the proximal contact to provide a
minimum clearance of 0.5 mm between the gingival margin
and the adjacent tooth.
• 6. Likewise, the facial and lingual margins in proximal tooth
preparations usually are extended into the respective
embrasures to provide specified clearance between the
prepared margins and the adjacent tooth.
• The purpose of this clearance is to place the margins away
from close contact with the adjacent tooth so that the
margins can be better visualized, instrumented, and
restored.

• Rules for establishing outline form for the
Gingival Portion of Facial and Lingual Surfaces
(Class V):
• The outline form of Class V tooth preparations is
governed ordinarily only by the extent of the
lesion, except pulpally.
• Therefore extension mesially, gingivally, distally,• Therefore extension mesially, gingivally, distally,
and occlusally (incisally) is limited to reaching
sound tooth structure; and during this initial
tooth preparation, the bur depth is usually no
deeper than 0.8 to 1.25 mm pulpally from the
original (when unaffected) tooth surface.

• The lesser axial wall depth (0.8 mm) is at a
gingival wall without an enamel portion.
• The correct axial wall pulpal depth at the occlusal
(incisal) wall is that which provides a 0.5 mm(incisal) wall is that which provides a 0.5 mm
extension into dentin (the remainder being
enamel).
• Infected caries deeper than these described
depths should not be removed by the cutting
instrument during this initial preparation stage.

• Restricted and Increased Extensions:
• Conditions that may warrant consideration of restricted or reduced
extensions for smooth-surface tooth preparations are:
(1) proximal contours and root proximity,
(2) esthetic requirements, and
(3) the use of some tooth preparations for composite restorations.
• Some conditions that may necessitate increased extensions for smooth-
surface tooth preparations are:
(1) mental or physical handicaps,
(2) advanced age of the patient,
(3) restoration of teeth as partial denture abutments or as units of a splint,
(4) need for additional measures for retention and resistance form, and
(5) need to adjust tooth contours.

Step 2: Primary Resistance Form:
• Definition:
Primary resistance form may be defined as
that shape and placement of the preparationthat 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 the
long axis of tooth

• Principles:
• The fundamental principles involved in obtaining
primary resistance form are:
• (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 masticationof 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
(laterally) directed (most resistance to oblique or(laterally) directed (most resistance to oblique or
lateral forces is attained later in the final tooth
preparation stage);
• (5) to provide enough thickness of restorative material
to prevent its fracture under load; and
• (6) to bond the material to tooth structure when
appropriate.

• Conventional and beveled conventional
preparation designs provide these resistance
form principles.form principles.
• Modified tooth preparation designs are for
small-to-moderate size composite restorations
and may not provide uniform pulpal or axial
depths or minimal thickness for the material.

• During extension of external walls to sound tooth
in developing outline form in conventional
Classes I and II preparations, the end of the
cutting instrument prepares a relatively flatcutting instrument prepares a relatively flat
pulpal wall of uniform depth into the tooth (1.5
to 2 mm overall depth or 0.2 mm into dentin).
• The pulpal wall, therefore, is as flat as the original
occlusal surface and the DEJ (these roughly
paralleling each other).

• This resemblance of flatness is perpendicular to those
masticatory forces directed nearly in the long axis of
the tooth, and thus is ideal for the stable seating of a
restoration that can best resist such forces without
fracture of the tooth (both wedging forces on the toothfracture of the tooth (both wedging forces on the tooth
or tilting forces on the restoration are unlikely).
• Following the same principle, in the proximal portion
of conventional Class II preparations, the end of the
cutting instrument prepares a gingival wall (floor) that
is flat and relatively perpendicular to these forces.

• Minimally extended facial and lingual walls
conserve dentin supporting the cusps as well
as facial and lingual ridges, thereby
maintaining as much strength of themaintaining as much strength of the
remaining tooth structure as possible.
• This resistance is against obliquely delivered
forces, as well as those in the tooth's long axis

• Internal and external angles within the tooth
preparation are slightly rounded (coved) so that
stresses in the tooth and restoration from masticatory
forces will not be as concentrated at these line angles.
• Rounding internal line angles (those with apices
directed internally) reduces the stress on the tooth,directed internally) reduces the stress on the tooth,
thus resistance to fracture of the tooth is increased.
• Rounding external angles (those with apices directed
externally [e.g., axiopulpal line angles]) reduces the
stress on some restorative materials (amalgam and
porcelain), thus increasing resistance to fracture of the
restorative material.

• Restorative material thickness affects the
ability of a material to resist fracture.
• The minimal occlusal thickness for amalgam
for appropriate resistance to fracture is 1.5for appropriate resistance to fracture is 1.5
mm, cast metal 1 to 2 mm (depending on the
region), and porcelain 2 mm.
• Most composite restorations are 1-2 mm
thick.

• Factors affecting resistance form
• Assessment of the occlusal contact on the
restoration and remaining tooth structure.
• Amount of remaining tooth structure ( eg. In
class IV restorations , the cavity is kept narrowclass IV restorations , the cavity is kept narrow
faciolingually to obtain resistance form)
• All weakened , friable tooth structure should
always be removed.

• Occlusal stresses on the tooth ( Greater the occlusal
force , the greater is the potential for future fracture)
• The last factor relates to the enhancement of
resistance form simply by bonding a restoration to theresistance form simply by bonding a restoration to the
tooth. Bonding amalgam, composite, or ceramic to
prepared tooth structure increases the strength of the
remaining unprepared tooth, thereby reducing the
potential for fracture.-' In fact, the benefits of bonding
procedures may permit the operator to leave a portion
of the tooth in a more weakened state than usual or
not to cap a cusp

• FEATURES
• 1. Relatively flat floor
• 2. Box shape
• 3. Inclusion of weakened tooth structure• 3. Inclusion of weakened tooth structure
• 4. Preservation of cusps and marginal ridges
• 5. Rounded internal line angles
• 6. Adequate thickness of restorative material
• 7. Reduction of cusps for capping when indicated

STEP 3:Primary retention form
• DEFINITION (Sturdevant)
• Primary retention form is the shape or form of
the conventional preparation that resists
displacement or removal of the restoration bydisplacement or removal of the restoration by
tipping or lifting forces.
• Although they are separate entities,the same
prepared form may contribute to both
resistance and retention qualities of the
preparation

• Principles:
• Because retention needs are related to the restorative material used, the
principles of primary retention form vary depending on the material.
1) For amalgam restorations in most Class I and all Class II conventional
preparations:
• The material is retained in the tooth by developing external tooth walls
that converge occlusally.that converge occlusally.
• In this way, once the amalgam is placed in the preparation and hardens, it
cannot dislodge without some type of fracture occurring.
• In these preparations, the facial and lingual walls of the occlusal portion of
the preparation, as well as the proximal portion, converge toward the
occlusal surface.
• This convergence should not be overdone for fear of leaving unsupported
enamel rods on the cavosurface margin of the occlusal surface.

• The occlusal convergence of the proximal portion has
several advantages in addition to producing retention.
• Advantages:
• 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
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.
• The 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.

2) In other conventional preparations for
amalgam (such as Classes III and V), the
external walls diverge outwardly to provide
strong enamel margins, and thereforestrong enamel margins, and therefore
retention coves or grooves are prepared in the
dentinal walls to provide the retention form

3) In Class II preparations involving only one of the two
proximal surfaces, an occlusal dovetail may aid in
preventing the tipping of the restoration by occlusal
forces.
• When an unusually large amount of retention form is
required, the occlusal dovetail may be placed whether
or not caries is on the occlusal surface.
• The dovetail simulates a Class I occlusal preparation in• The dovetail simulates a Class I occlusal preparation in
the area opposite the proximal involvement.
4) Another consideration in obtaining retention form, in
addition to compensating for the forces of mastication,
is the pull of sticky foods.
• In all cases, the preparation design must provide for
the retention of the restorative material in the tooth. .

• Factors affecting retention form:
• Amount of the masticatory stresses falling on
the restoration
• Thickness of the restoration• Thickness of the restoration
• Total surface area of the restoration exposed
to the masticatory forces
• The amount of remaining tooth structure

• Retention form for Amalgam restorations:
• Retention is increased in amalgam restoration by
the following:
• – Providing occlusal convergence (about 2–5%)
of the dentinal walls towards the tooth surface
• – Providing occlusal convergence (about 2–5%)
of the dentinal walls towards the tooth surface
• – Giving slight undercut in dentin near the pulpal
wall
• – Conserving the marginal ridges
• – Providing occlusal dovetail

STEP 4:Convenience form
• Definition:
The convenience form is that form which
facilitates and provides adequate visibility,
accessibility and ease of operation duringaccessibility and ease of operation during
preparation and restoration of the tooth

• Features of convenience form
• Sufficient extension of distal, mesial, facial or
lingual walls to gain adequate access to the
deeper portion of the preparation.
The cavosurface margin of the preparation• The cavosurface margin of the preparation
should be related to the selected restorative
material for the purpose of convenience to
marginal adaptation.
• In class II preparations access is made through
occlusal surface for convenience form

• Proximal clearance is provided from the
adjoining tooth during class II tooth
preparation.
• In tooth preparation for cast gold restorations• In tooth preparation for cast gold restorations
occlusal divergence is one of the feature of
convenience form

• On occasion, obtaining this form may necessitate
extension of distal, mesial, facial, or lingual walls
to gain adequate access to the deeper portion of
the preparation. An example of this is thethe preparation. An example of this is the
preparation and restoration of a mesial (or distal)
root surface carious lesion.
• However, the arbitrary extension of facial margins
on anterior teeth usually is contraindicated for
esthetic reasons

FINAL TOOTH PREPARATION
• With conservative amalgam or composite
restorations, the preparation may be complete
after initial tooth preparation except for:
• (1) sealing the prepared walls for amalgam or• (1) sealing the prepared walls for amalgam or
• (2) etching and priming the prepared walls for
the bonding agent(s) for amalgam or
composite.
• Often, however, additional steps are needed
in the final tooth preparation stage.

Final stage of tooth preparation
• After initial stages of the preparation, the
prepared tooth should be carefully examined
• The remaining carious portion should be
removed only after the initial tooth preparation
has been completed. It provides two advantages:has been completed. It provides two advantages:
1. It allows optimal visibility and convenience form
for removal of remaining carious lesion.
2. Completion of the initial preparation permits
immediate placement of a base and the
restoration.

• Step 5: Removal of Any Remaining Enamel Pit
or Fissure, Infected Dentin, and/or Old
Restorative Material, if Indicated
• Definition- Removal of any remaining enamel pit
or fissure, infected dentin, and/or old restorativeor 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.
• The exception to the removal of infected carious
tooth structure is when it is decided to perform
an indirect pulp cap

• Removal of remaining enamel pit or fissure typically occurs
as small, minimally extended excavations on isolated faulty
areas of the pulpal floor.
• Removal of defective old restorative material is addressed
later in this section. However, in dentin, as caries
progresses, an area of decalcification precedes theprogresses, an area of decalcification precedes the
penetration of microorganisms.
• This area of decalcification often appears discolored in
comparison with undisturbed dentin, yet it does not exhibit
the soft texture of caries.
• This dentin condition may be termed affected dentin and
differs from infected dentin in that it has not been
significantly invaded by microorganisms. It is accepted and
appropriate practice to allow affected dentin to remain in a
prepared tooth

• Any remaining old restorative material should be removed if any of
the following conditions are present:
(1) the old material may affect negatively the esthetic result of the
new restoration (i.e., old amalgam material left under a new
composite restoration),
(2) the old material may compromise the amount of anticipated
needed retention (i.e., old glass-ionomer material having a weakerneeded retention (i.e., old glass-ionomer material having a weaker
bond to the tooth than the new composite restoration using
enamel and dentin bonding),
(3) radiographic evidence indicates caries is under the old material,
(4) the tooth pulp was symptomatic preoperatively, or
(5) the periphery of the remaining old restorative material is not intact
(i.e., there is some breach in the junction of the material with the
adjacent tooth structure that may indicate caries under the old
material).

• If none of these conditions is present, the
operator may elect to leave the remaining old
restorative material to serve as a base, rather
than risk unnecessary excavation nearer to thethan risk unnecessary excavation nearer to the
pulp, which may result in pulpal irritation or
exposure.

• Techniques: When a pulpal or axial wall has
been established at the proper initial tooth
preparation position and a small amount of
infected carious material remains, only thisinfected carious material remains, only this
material should be removed, leaving a
rounded, concave area in the wall. The level or
position of the wall peripheral to the caries
removal depression should not be altered

• Another instance in which the removal of caries is
indicated early in tooth preparation is when a
patient has numerous teeth with extensive caries.
• In one appointment, infected dentin is removed
from several teeth and temporary restorationsfrom several teeth and temporary restorations
are placed.
• After all the teeth containing extensive caries are
so treated, then individual teeth are restored
definitively.
• This procedure stops the progress of caries and is
often referred to as the caries control technique.

STEP 6: Pulp Protection
• Although the placement of liners and bases is not a step in
tooth preparation in the strict sense of the word, it is a step
in adapting the preparation for receiving the final
• The reason for using traditional liners or bases is to either• The reason for using traditional liners or bases is to either
protect the pulp or to aid pulpal recovery or both.
• However, often, neither liners nor bases are needed.
• When the thickness of the remaining dentin is minimal,
heat generated by injudicious cutting can result in a pulpal
burn lesion, an abscess formation, or pulpal necrosis.

• Thus a water or air-water spray coolant must be used with
the highspeed rotary instrument.
• Cutting the dentinal odontoblastic fibrils that previously
have not been exposed to any irritating episode such as
caries or tooth wear will result in degeneration and death
of the affected primary odontoblasts and their extensions.of the affected primary odontoblasts and their extensions.
• The involved tubules become open, dead tracts.
• Worse still, if the remaining dentin thickness is 1.5 mm or
more and the cutting was done atraumatically using high
speed with water or airwater spray, the pulp is not irritated
enough to form replacement odontoblasts and therefore
no reparative dentin is formed to seal the pulpal side of the
dead tracts.

• Other pulpal irritants that affect operative
procedures are:
• (1) some ingredients of various materials;
• (2) thermal changes conducted through
restorative materials;restorative materials;
• (3) forces transmitted through materials to the
dentin;
• (4) galvanic shock; and, most importantly,
• (5) the ingress of noxious products and bacteria
through microleakage.

LINERS
• Liner is reserved for those volatile or aqueous
suspensions or dispersions of zinc oxide or
calcium hydroxide that can be applied to a tooth
surface in a relatively thin films' and are used to
affect a particular pulpal response.affect a particular pulpal response.
• Liners also may provide:
• (1) a barrier that protects the dentin from
noxious agents from either the restorative
material or oral fluids,
• (2) initial electrical insulation, and/or
• (3) some thermal protection.

LINERS
• A traditional liner is used to medicate the pulp
when suspected trauma has occurred.
• The desired pulpal effects include both sedation
and stimulation, the latter resulting in reparative
dentin formation.dentin formation.
• The specific pulpal response desired dictates the
choice of liner.
• If the removal of infected dentin does not extend
deeper than 1 to 2 mm from the initially
prepared pulpal or axial wall, usually no liner is
indicated

LINERS
• If the excavation extends into or very close to the
pulpal tissue, a calcium hydroxide liner is usually
selected to stimulate reparative dentin.
• In the past, if the excavation depth was between
the above examples, a zinc oxide-eugenol linerthe above examples, a zinc oxide-eugenol liner
may have been selected (except for composite
restorations, for which it could impede the
polymerization process) to provide a palliative,
sedative pulpal response, thus decreasing the
potential for postoperative sensitivity.

LINERS
• For amalgam- zinc oxide eugenol, glass
ionomer cement, calcium hydroxide liner.
• For composites- calcium hydroxide liner.

BASES
• Bases are considered those cements
commonly used in thicker dimensions beneath
permanent restorations to provide for
mechanical, chemical, and thermal protection
of the pulp.of the pulp.
• Examples of bases include zinc phosphate;
zinc oxide-eugenol; calcium hydroxide;
polycarboxylate; and the most common, some
type of glass ionomer.

• No liner or base exhibits the crushing strength of
amalgam. Therefore, in the placement of large
amounts of these materials, ideally there should be at
least three seats, tripodally distributed, for the
amalgam on sound dentin at the prescribed level of theamalgam on sound dentin at the prescribed level of the
pulpal wall in initial tooth preparation .
• This will allow the restoration and the tooth structure,
rather than the liner or base, to bear the load after the
amalgam has set. However, when a bonded material is
used, tripodal seats are less necessary.

TOOTH VARNISH
• Tooth varnish is a solution liner that was used in the past to
seal dentinal tubules and was placed on all tooth
preparation walls for amalgam and on dentinal walls of
tooth preparations for cast gold, but was not used for
composites.
• Tooth varnish usually was applied just before the insertion• Tooth varnish usually was applied just before the insertion
of an amalgam or cementation of a cast gold restoration.
• Two coats of tooth varnish were applied to the prepared
surfaces for amalgams.
• Tooth varnish was the only material necessary for shallow
excavations in such preparations.
• The varnish prevented penetration of materials into the
dentin and helped prevent microleakage

• Varnishes also helped reduce postoperative
sensitivity by reducing the infiltration of
• fluids and salivary components at the margins
of newly placed restorations." Two coats ofof newly placed restorations." Two coats of
tooth varnish were applied to dentin surfaces
(not on enamel walls) of tooth preparations
for cast gold restorations.
• The varnish barrier helped reduce pulpal
irritation from the luting cement

• Although varnishes were valuable in reducing
postoperative sensitivity, their thin film thickness
was insufficient to provide thermal insulation
even when applied in two coats .
• However, their presence significantly reduced the• However, their presence significantly reduced the
diffusion of acid from cements into dentin.
• Tooth varnishes are not used under composites
because the solvent in the varnish could react
with or soften the resin component in the
composite, adversely affecting polymerization.

Step 7: Secondary Resistance and
Retention Forms
• After removal of any remaining enamel pit or
fissure, infected dentin, and/or old restorative
material (if indicated) and pulpal protection
has been provided by appropriate liners and
bases, additional resistance and retentionbases, additional resistance and retention
features may be deemed necessary for the
preparation.
• Many compound and complex preparations
require these additional features.

• Features:
• For amalgam, 90 degree cavosurface angle or
butt joint is recommended to compensate for the
low edge strength of the material.
For composite and cast metal- bevels- to allow• For composite and cast metal- bevels- to allow
better marginal sealing and improved bonding.
• Cast metal restoration- very smooth surface
• Amalgam, direct gold and composite- roughened
surface.

• The secondary retention and resistance forms
are of two types:
• (1) mechanical preparation features and
• (2) treatments of the preparation walls with• (2) treatments of the preparation walls with
etching, priming, and adhesive materials.

1)Mechanical preparation features:
1] Retention locks, grooves, and coves.
• Vertically oriented retention locks and retention
grooves are used to provide additional retention
for proximal portions of some tooth preparations
• the locks are for amalgams and the grooves are• the locks are for amalgams and the grooves are
for cast metal restorations .
• Horizontally oriented retention grooves are
prepared in most Classes III and V preparations
for amalgam and in some root surface tooth
preparations for composite.
•

• Retention locks in Class II preparations for
amalgam restorations are generally thought to
increase retention of the proximal portion against
movement proximally due to creep.
• Also, they are believed to increase the resistance• Also, they are believed to increase the resistance
form of the restoration against fracture at the
junction of the proximal and occlusal portions.
• However, they are recommended for extensive
tooth preparations for amalgam involving, for
example, wide faciolingual proximal boxes and/or
cusp capping.

2] Retention coves:
• are appropriately placed undercuts for the
incisal retention of Class III amalgams occlusal
portion of some amalgam restorations, someportion of some amalgam restorations, some
Class V amalgams, and occasionally for
facilitating the start of insertion of certain gold
foil restorations.

3] Groove extensions:
• Additional retention of the restorative material
may be obtained by arbitrarily extending the
preparation for molars onto the facial or lingual
surface to include a facial or lingual groove.surface to include a facial or lingual groove.
• Such an extension when performed for cast metal
restorations, results in additional vertical
(longitudinal), almost-parallel walls for retention.
• This feature also enhances resistance for the
remaining tooth due to envelopment

4] Skirts:
• Skirts are preparation features used in cast
gold restorations that extend the preparation
around some, if not all, of the line angles ofaround some, if not all, of the line angles of
the tooth.
• .

5] Bevelled enamel margins:
• Both cast gold/metal and composite restorations
include beveled marginal configurations.
• The bevels for cast metal may slightly improve
retention form when there are opposing bevels, but
are used primarily to afford a better junctional
retention form when there are opposing bevels, but
are used primarily to afford a better junctional
relationship between the metal and the tooth.
• Many enamel margins of composite restorations have a
beveled or flared configuration to increase both the
surface area of etchable enamel and to maximize the
effectiveness of the bond by etching more enamel rod
ends

6] Pins, slots, steps, and amalgampins:
• When the need for increased retention form is
unusually great, especially for amalgam
restorations, several other features may be
incorporated into the preparation.incorporated into the preparation.
• The use of pins and slots increases both
retention and resistance forms.
• Amalgampins and properly positioned steps also
improve retention form, but not to the extent of
pins or slots.

2)Conditioning procedure:
• Enamel wall etching:
• Enamel walls are etched for bonded
restorations that use porcelain, composite, or
amalgam materials.amalgam materials.
• This procedure consists of etching the enamel
by an appropriate acid, resulting in a
microscopically roughened surface to which
the bonding material is mechanically bound.

• Dentin treatment:
• Dentinal surfaces may require etching and
priming when using bonded porcelain,
composite, or amalgam restorations.
• The actual treatment varies with the restorative• The actual treatment varies with the restorative
material used, but foremost composite
restorations, a dentin bonding agent is
recommended.
• Sometimes a glass-ionomer material is used as a
base before the restoration of the tooth with
another restorative material, usually amalgam

Step 8: Procedures for Finishing the
External Walls of the Tooth Preparation
• Definition:
Finishing the preparation walls is the further
development, when indicated, of a specific
cavosurface design and degree of smoothnesscavosurface design and degree of smoothness
or roughness that produces the maximum
effectiveness of the restorative material being
used

• Objectives. The objectives of finishing the
prepared walls are to:
• (1) create the best marginal seal possible
between the restorative material and the toothbetween the restorative material and the tooth
structure,
• (2) afford a smooth marginal junction, and
• (3) provide maximum strength of both the tooth
and the restorative material at and near the
margin.

• The following factors must be considered in the
finishing of enamel walls and margins:
• (1) the direction of the enamel rods,
• (2) the support of the enamel rods both at the
DEJ and laterally (preparation side),DEJ and laterally (preparation side),
• (3) the type of restorative material to be placed in
the preparation,
• (4) the location of the margin, and
• (5) the degree of smoothness or roughness
desired.

• Theoretically, the enamel rods radiate from the DEJ to the
external surface of the enamel and are perpendicular to
the tooth surface.
• All rods extend full length from the dentin to the enamel
surface.
• The rods converge from the DEJ toward concave enamel• The rods converge from the DEJ toward concave enamel
surfaces and diverge outwardly toward convex surfaces.
• In general, therefore, the rods converge toward the center
of developmental grooves and diverge toward the height of
cusps and ridges.
• In the gingival third of enamel of the smooth surfaces in
the permanent dentition, the rods incline slightly apically.

Step 9: Final Procedures: Cleaning,
Inspecting, and Sealing
• Final procedures in tooth preparation include the cleaning of the
preparation, inspecting the preparation, and applying a sealer when
indicated.
• The first procedure includes removing all chips and loose debris
that have accumulated, drying the preparation (do not desiccate),
and making a final complete inspection of the preparation for anyand making a final complete inspection of the preparation for any
remaining infected dentin, unsound enamel margins, or any
condition that renders the preparation unacceptable to receive the
• Naturally, most of the gross debris has been removed during the
preparation steps, but some fine debris usually remains on the
prepared walls after all cutting is completed

Amalgam Box- Only Tooth Restoration
• This is advocated for some
posterior teeth in which a proximal
surface requires restoration, but
the occlusal surface is not faulty.
• Proximal box is prepared & specific
retention form is provided ,but noretention form is provided ,but no
occlusal step is included.
• Such restorations obviously are
more conservative, in that less
tooth structure is removed.

Amalgam Tunnel Tooth Preparation
• This preparation joins an occlusal lesion with a
proximal lesion by means of a prepared tunnel
under the involved marginal ridge.
• In this way, marginal ridge remains intact.

BONDED AMALGAM
• There is use of various materials to bind amalgam
material to tooth surface.
• Procedure : prepare tooth similar to typical amalgam
cavity preparation except that more weakened toothcavity preparation except that more weakened tooth
structures may be retained. Cavity wall are covered
with adhesive liner material which bond both tooth
& amalgam. Amalgam is condensed into this & bond
develops between liner & amalgam.

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 theshallow 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 .

• The operator must be selective in the choice of
areas on which enameloplasty is performed.
• Usually a fissure should be removed by normal
preparation procedures if it penetrates to more
than one-third the thickness of the enamel in thethan one-third the thickness of the enamel in the
area.
• If one-third or less of the enamel depth is
involved, the fissure may be removed by
enameloplasty without preparing or extending
the tooth preparation.

CLINICAL CONSIDERATION
• Whenever possible margins of the restoration should be
placed coronal to the gingival margin.
• Placement of the margin subgingivally,particularly with
resin & silicate restoration, is to be avoided.(glazeresin & silicate restoration, is to be avoided.(glaze
porcelain, polished gold,resin restorations are better
tolerated)
• Avoid overhangs- conductive to periodontal destruction.
• Open contact is deleterious as it leads to food impaction
& encourage plaque accumulation.
• Avoid over countering & under countering of restoration.

Conclusion
• An effective operative dentist must possess a
thorough understanding of the principle & concept of
tooth preparation.
• Applying this understanding to a specific restorative• Applying this understanding to a specific restorative
procedure , combined with appropriate operating skill
& proper handling of the restorative materials ,results
in successful treatment.

REFEREEFERENCES
 Sturdevant’s Art and Science of Operative Dentistry, (5thSturdevant’s Art and Science of Operative Dentistry, (5th eded):):
Theodore M. Roberson,Theodore M. Roberson, HaraldHarald O.O. HeymannHeymann, Edward J. Swift, Edward J. Swift
 Operative dentistry, Modern theory andOperative dentistry, Modern theory and
practice:M.A.Marzouk,A.L.Simonton,R.D.Grosspractice:M.A.Marzouk,A.L.Simonton,R.D.Gross

Principles of tooth preparation

Principles of tooth preparation

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Principles of tooth preparation

Similar to Principles of tooth preparation (20)

More from Dr. Meenal Atharkar

More from Dr. Meenal Atharkar (20)

Recently uploaded

Recently uploaded (20)

Principles of tooth preparation