Fundamentals of Class I Amalgam Cavity Preparation

Fundamentals of cavity
preparation for class I Amalgam
restoration
Simplicities are enormously complex…
PRESENTED BY:
DR. ANUBHUTI
BDS,MDS
Dept. of Conservative Dentistry &
Endodontics
DENTAL INSTITUTE 1

Art & science of operative dentistry 5th edition page no.283 2

Class I cavity is routinely restored with composite restoration ,
but it can also be restored with amalgam
Overview
Why to choose amalgam????
• Strength
• Longevity
• Ease of use
• Clinical proven success
• It’s the only restorative material that its external
surface improve over time

Definition
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

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

Art & science of operative dentistry 5th edition page no.287
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

Tooth
preparation
Initial tooth
preparation
( first stage of tooth
preparation)
Final tooth
preparation
(Second stage of tooth
preparation)
7

Initial tooth
preparation
Step 1: Outline form &
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
8
Art & science of operative dentistry 5th edition page no.298,299

9
Avoid cutting into cups-it saves
more tooth structure & to avoid
exposing pulp horns which lies
beneath the cusps.
Keep the width of the preparation
as conservative as possible
Try to avoid cutting marginal ridges
,avoid cutting and weakening the
tooth structure as much as possible

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 the preparation, 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

Outline form
Pulpal floor
is always in
dentin

Resistance & Retention form

Resistance form
Resistance principal allows margins to be positioned
in areas that are sound and subject to minimal forces
while conserving structures to maintain the strength &
health of the tooth

Art & science of operative dentistry south Asian edition page no.362
18
Resistance form
i. Flat pulpal
floor in sound
ctooth
structure
To resist forces
directed in the long
axis of the tooth &
to provide a strong
,stable seat for the
restoration

Resistance form
i. Minimal
extension of
external walls

iii. Strong ideal
enamel
margins
Resistance form

iv. Sufficient depth
(1.5-2.0) that result in
adequate thickness of
the restoration
,providing resistance to
fracture and wear

Prevents stress
concentration
Resistance form

Flat pulpal floor
Round internal line angle
Extension of external wall

Retention form
Primary retention form is that form, shape and configuration
of the tooth preparation that resists the displacement or
removal of restoration from the preparation under lifting &
tipping masticatory forces. Usually, resistance and retention
forms are obtained by providing same features, hence they
are sometimes described together.

Resistance form
Retention form

Slight occlusal
convergence of
external walls provides
retention
Retention form

Convenience form
Its that shape of a cavity that
allows adequate observation,
accessibility & ease of
operation in preparing &
restoring the cavity.
27
Extension
of walls
Art & science of operative dentistry 2nd edition page no.99& 5th edition 307

Initial tooth
preparation
Step 1: Outline form &
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
31
Art & science of operative dentistry 5th edition page no.298,299

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.

Removal of Any Remaining Enamel Pit or
Fissure, Infected Dentin, and/or Old Restorative
Material, if Indicated
Deeper caries not removed by the
initial cavity preparation is now
removed. Care must be exercised as
the pulp may be in close proximity.

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 excavators, 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 dentinal tubules
through excessive pressure with a SE

Pulp protectionIf the tooth
preparation is of
ideal or shallow
depth, no liner or
base is indicated
In deep preparations (RDT-0.5-2mm) a
thin layer (0.5-.75 mm) of light
activated, resin modified glass
ionomer (RMGI) should be placed.

RMGI insulates the pulp from thermal changes,
bonds to dentin, releases fluoride
Applied only over the excavation . Entire dentin
surface should not be covered
In very deep preparations (RDT-0.5mm), a
calcium hydroxide liner is indicated.
RMGI base is applied over this liner

To provide best marginal
seal possible between the
restorative material &
tooth structure, to afford a
smooth marginal junction
& to provide maximal
strength to both the
enamel & restorative
material at the margin
Art & science of operative dentistry 2nd edition page no.103
Finish of enamel walls and margins

An occlusal
convergence bevel is
contraindicated in
amalgam restoration .
Butt joint margins of
enamel and amalgam
is the strongest for
both.

Rinse away all debris and dry
the cavity preparation.
Final procedures: cleaning, inspecting, sealing

Fascial pit of the mandibular molar
Lingual pit of the maxillary lateral incisors
Occlusal pits of the mandibular 1st premolar
Occlusal pits & fissure of the maxillary 1st molar
Occlusal pits & fissure of the maxillary 2nd molar
Other conservative class I Amalgam
preparations

Fundamentals of Class I Amalgam Cavity Preparation

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