Presented By:
Rahul Mishra,
Junior Resident-I,
UP Dental College &
Research Centre,
Lucknow.
1
DEFINITION OF CAVITY
PREPARATION
Cavity preparation is the mechanical alternation of a
tooth to receive a restorative material, which will return
the tooth to proper anatomical form, function, and
esthetics. The procedure of the preparing the tooth is
the removal of the defective or friable tooth structure.
Any remaining infected or friable tooth structure may
result of further carious progression, sensitivity or pain
or fracture of the tooth and / restoration.
2
Cavity preparation is the mechanical alternation of
defective, injured or diseased tooth in order to best
receive a restorative material that will reestablish a
healthy state for the tooth including esthetic correction
when indicated, along with normal form and function.
The reason of the need for restoration as follow:
• To restore the integrity of the tooth surface.
• To restore the function of the tooth.
• To restore the appearance of the tooth.
• To remove the diseased tissue from the tooth.
3
OBJECTIVES OF CAVITY
PREPARATION
• To remove diseased tissue as necessary and at the
same time provides the protection to the pulp.
• To locate the margins of the restoration as
conservative as possible.
• To ensure the cavity form, it should not be under the
force of mastication of the tooth.
• To allow the functional placement of the restorative
material.
4
PRINCIPLES OF CAVITY PREPARATION
•Gain access to caries.
•Removal of all carious lesions.
•Cut away all significantly unsupported enamel.
•Extended margins so that they are accessible for
instrumentation and Cleaning.
5
CLASSIFICATION
(G.V. BLACK CLASSIFICATION)
Black suggested that it was necessary to
•Remove additional tooth structure to gain access and
visibility .
•Remove all trace of demineralized enamel and dentin
from the floor, walls and margins of the cavity.
•Make room for the insertion of the restorative material in
sufficient bulk to provide strength.
•Provide mechanical interlocking retentive designs.
•Extend the cavity to self-cleansing areas to avoid
recurrent caries.
6
CLASS I
The lesions involving the occlusal surfaces of
molars and premolars, the occlusal 2/3 of buccal and
lingual surfaces of molars, and the palatal pits in anterior
teeth.
CLASS II
The lesions involving the proximal surfaces of
the posterior teeth with access established from the occlusal
surface.
CLASS III
The lesions involving the proximal surfaces of
anterior teeth which may or may not involve a labial or a
lingual extension & not involving incisal edge.
7
CLASS IV
The lesions involving all proximal surfaces of
anterior teeth which involves the incisal edge.
CLASS V
The lesions involving the cervical third of all
teeth, including the proximal surface of posterior teeth
where the marginal ridge is not included in the cavity
preparation.
8
ACCORDING TO SITE INVOLVED
Site 1 . Pits, fissures and enamel defects on occlusal
surfaces of posterior teeth or other smooth surfaces.
Site 2 . Approximal enamel in relation to areas in contact
with adjacent teeth.
Site 3 . The cervical one third of the crown or, following
gingival recession, the exposed root surface.
9
ACCORDING TO THE SIZE AND EXTENT OF THE LESION AT
THE TIME OF IDENTIFICATION
Size 0 . The earliest lesion that can be identified as the initial
stages of demineralisation. This needs to be recorded but will be
treated by eliminating the cause and should therefore not require
further treatment,
Size 1 . Minimal surface cavitation with involvement of dentine
just beyond treatment by remineralisation alone. Some form of
restoration is required to restore the smooth surface and prevent
further plaque accumulation,
Size 2 . Moderate involvement of dentine following cavity
preparation. Remaining enamel is sound, well supported by
dentine and not likely to fail under normal occlusal load. The
remaining tooth is sufficiently strong to support the restoration,
10
Size 3 . The lesion is enlarged beyond moderate. 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 so that the
restoration can be designed to provide support to the remaining
tooth structure,
Size 4 . Extensive caries or bulk loss of tooth structure e.g. loss
of a complete cusp or incisal edge has already occurred.
11
DESIGN AND PREPARATION OF
CAVITIES
• The design and preparation of cavities are based on
Black’s principles that have been determined and reapplied with importance directed towards protection
of tooth in preparation rather than only on the
material.
• Each diseased tooth has an individual cavity form
determined by caries involvement, morphology of
tooth and its location in oral cavity – leading to new
conservative cavity designs.
12
STEPS IN THE CAVITY PREPARATION
(Given by G V Black)
Obtaining Outline Form
Obtaining Primary Resistance Form
Obtaining Primary Retention Form
Obtaining Convenience Form
Removal of Remaining Carious Dentin
Obtaining Secondary Resistance & Retention Form
Providing Pulp Protection
Finishing of Enamel Walls & Margins
Performing the Toilet of the Cavity
13
ARMAMENTARIUM
• Basic Instruments – mouth mirror, explorer, tweezer,
etc.
• Hand Instruments – Excavators, enamel hatchet,
monoangle or biangle chisels, Gingival Marginal
Trimmer.
• Rotary Instruments –
•Burs No.-carbide burs 55, 56, 57.
• Ultraspeed and conventional speed contrangle
handpiece.
• Safety glasses.
14
Definition:
These are pit and fissure type cavities
that involve the occlusal surfaces of
molars and premolars, the occlusal 2/3
of buccal and lingual surfaces of molars,
and the palatal pits in anterior teeth.
15
 These are self-cleansable areas.
However, they may get involved by
caries due to their inherent defective
structure. These areas are retentive
for food and thus invite caries.
16
These lesions are
clinically characterized
by:
1. A small surface opening which may
remain unnoticed until the lesion
becomes of a considerable size.
2. A conical spread in both enamel and
dentin, with the bases of cones at the
Dentinoenamel Junction.
3. It is rapid burrowing at the dentinoenamel
junction. These lesions may involve one
or more surfaces and hence a simple or
compound cavity should be prepared.
17
Simple occlusal
cavities
Designing the Outline Form
The outline form of a routine class I cavity should
describe a symmetrical design running in sweeping
curves along all pits, fissures, and angular grooves
between the cusps and with a minimum width.
18
Marginal ridge walls should be 1/2 distance from
mesial and distal pit to the crest of each marginal
ridge and in a direction parallel to these ridges.
 The mesial and distal wall should
have a slant or slight divergence
from the pulpal floor outward to
avoid undermining the marginal
ridges.
20
PERPENDICULAR IN MESIALDISTAL DIRECTION
•Pulpal Floor mesio-distally is flat and
perpendicular to the long axis of the tooth
In a bucco-lingual direction, the cavity
is extended just sufficient to eliminate
the defective and susceptible tissues.
The lingual and the buccal wall should
be parallel to the respective tooth
surface.
23
•INTERNAL FORM
•Buccal and Lingual Walls
are Parallel to each other
and to the Long Axis of the
Crown (Provides retention)
•Buccal, Lingual, and
Proximal Walls meet Pulpal
Floor at sharp angle
•Buccal and Lingual Walls
meet Proximal in smooth,
rounded form.
BUCCO-LINGUAL VIEW
LONG AXIS
OF
THE
TOOTH
LONG
AXIS OF
THE
CROWN
 It must be reemphasized that the
outline form for class 1 cavities
should be very conservative since
they involve cleansable areas.
It is governed only by the extent of
caries in both enamel and dentin and
the amount of extension or need to
eliminate pits and fissures to secure
smooth margins.
27
Isthmus just wide enough to accept
instrumentation
1/4th intercuspal
distance
29
CORRECT OUTLINE FORM
30
Obtaining the Resistance
and Retention Forms
 The resistance form here consists
chiefly of a pulpal wall parallel to
the occlusal plane with dentin walls
at right angles to it., i.e. Boxing the
preparation.
 The form of this cavity provides
automatically for effective retention
and, therefore, no special retentive
features are required.
31
Removal of remaining
Carious Dentin
 In small size cavities, the carious dentin
should have been removed during making the
cavity extensions.
 In moderately deep and deep cavities, the
carious dentin is peeled off carefully at the
sides using large spoon excavators, and then
scooped out in few and large pieces.
 Only light pressure in a direction parallel to
that of the pulp is utilized. This is continued
until a sound dentin floor is reached.
32
Planning of Enamel
Walls
The enamel walls of the cavity should be
finished free from any loose, short, or
undermined enamel, and trimmed to meet the
tooth surface at a right cavo-surface angle.
This may be done by sharp and regular edged
chisels and hatchets, plane fissure burs,
stones, or sand-paper discs.
All sharp corners in enamel must be rounded,
as they may contain short enamel rods.
33
Performing of the toilet
of the cavity
A sharp explorer is then used to check
the details of the prepared cavity and to
loosen the tooth debris which are then
blasted out with warm air.
34
Procedure
The outline form is performed by first
gaining access through the enamel to
the carious dentin floor of the cavity
followed by making the necessary
cavity extensions.
35
• In case of initial carious lesions, access is
obtained by employing a small round bur #330.
• In big carious lesions, access is obtained easily
by breaking down the undermined enamel
overlying the carious dentin, using a suitable size
chisel.
• In either case, access is started at the most
defective area of enamel, i.e., a carious pit or
fissure.
36

The bur is held at a right angle to the
involved surface of the tooth and light
pressure in an in-and-out direction is
exerted. Cutting is continued until the
Dentinoenamel Junction is reached.
37
 The necessary cavity extensions through
pits, fissures, and deep developmental
grooves are made using a
#330 round bur held at
Right Angle To The
Surface Of The Crown.
The
bur is rotated, and carefully
introduced through the opening just
obtained, so that its weak corners do not
touch the enamel and get dulled.
38
With the bur seated in the cavity just
below the dentinoenamel junction 1/2-1 mm.
Gentle pressure is applied in the direction
of required extension.
During cutting, the bur should be kept
moving in-and-out of the cavity and at
right angle to the tooth surface. In this
way, the bur will undermine and lift the
cut enamel, and at the same time unclog
itself.
39
Provision of ample resistance and
adequate retention through boxing of
the preparation could be obtained.
This is obtained by using a #56 fissure
bur held perpendicular to the surface of
the tooth. All the line angle in dentin
must be squared up by help of the HOE
Excavators.
40
•Deepest or most carious pit entered with a
punch cut using No. ½ round bur or No.245
inverted cone bur oriented perpendicular to
long axis of tooth.
•Depending on cuspal incline, depth of
prepared external walls is 1.5 – 2 mm and
1.5mm pulpal depth measured at central
fissure.
•Desired pulpal depth – 0.1 to 0.2 mm into
dentin.
41
•Maintaining depth, cavity extended to include all
defective supplemental and developmental
grooves (No.57 plain St. fissures carbide bur).
•Isthmus width of 1/4th intercuspal distance so
that it does not reduces the strength of tooth
(Diameter of bur should be considered).
•If fissure extends farther into marginal ridge,
slight occlusal divergence is given, to prevent
undermining of marginal ridge & to provide
dentinal support.
42
•Pulpal floor remains at initial ideal depth,
relatively flat, in dentin and provides a strong
stable seat for restoration.
•Enameloplasty done on terminal ends of
shallow fissures to conserve tooth structure.
•Final tooth preparation includes removal of
remaining defective enamel / infected dentin,
pulp protection and finishing of external walls
accomplished with hand instruments.
43
44
45
Buccal Pit Cavities
•The outline of these cavities usually
describes a triangle with its base facing
the gingival wall and its sides forming
the mesial and distal walls.
•The gingival wall is placed at or slightly
occlusal to the height of contour of the
tooth.
46
OUTLINE FORM FOR PIT RESTORATIONS
47
All walls are extended just enough
to eliminate defective enamel and
dentin.
The enamel walls are planed in the
direction of enamel rods
perpendicular to the axial wall.
and
48
Hoe excavators are used to smooth
the axial wall and make it parallel with
the external surface of the tooth.
It should be re-emphasize that the
shape of the cavity will be governed by
the extension of caries, accordingly
the outline of these cavities may be a
rounded or oval in shape.
49
Buccal and Lingual
Extensions
In case of occluso-buccal and occlusolingual cavities extensions are made
through the fissures and towards the
respective surfaces.
The cutting is done in dentin at the
dentinoenamel junction using a #56 bur
until the occlusal ridge is undermined
and removed.
50
If the caries is still gingival to the
level of the pulpal seat, a step is
indicated: a #330 or 56 bur is used
to cut the dentin at the
dentinoenamel junction, applying
pressure in a gingival direction and
at the same time moving the bur
mesio-distally.
51
The enamel thus undermined, is broken
down with chisels.
Retentive grooves are then made in
dentin along the axio-mesial and axiodistal line angles. The cavity walls and
margins are finished as previously
described.
52
In case of deeply-seated caries,
where removal of the carious dentin
will leave a round cavity floor,
flattening of which to obtain the
required resistance form, will
expose the pulp.
53
The following technique is
used:
a) The cavity floor is covered with
a sub base followed by a base or
base alone which fills it to the
routine cavity depth.
54
b) A ledge is cut on the expense of
the buccal and lingual side walls
of the cavity for obtaining the
required resistance in sound
dentin.
55
56
Principles
I. OUTLINE FORM –
Smooth flowing,
regular curves.
Rationale
Angular irregularities in
the outline are
susceptible to fracture
during condensation – a
smooth flowing outline is
easier to visualize and
carve following
condensation.
57
II. EXTENSIONS (Extension for Prevention)
Conservation of tooth structure is the basis for
all cavity preparations in order to preserve the
strength of the tooth.
However, sufficient extension of cavity
preparations is necessary to ensure access
(convenience form) for instrumentation, removal
of defective tooth structure, insertion and
finish of the restorative material, and
maintenance of the restoration (prevention).
58
Principles
Rationale
A. Extensions consist of:
a.
Caries and
decalcifications
b. Enamel unsupported by
sound dentin
c.
Pits and fossae
d. Major fissures and
grooves
e. Existing restorations
eliminates defective
tooth structure and
eliminates areas (pits,
fissures, etc.) which are
susceptible to recurrent
caries and facilities oral
hygiene procedures
(extension for
prevention).
59
Principles
Rationale
B. Bucco – lingual extension
1. Extend fully in areas of
buccal and lingual grooves
to terminate on smooth
surfaces.
to allow a smooth
tooth-restoration
margin to be created
(easier to finish and
keep clean).
60
Principles
2. Extend minimally in
areas of triangular
ridges (optimal isthmus
width is ¼ intercuspal
distance or less)
terminating on smooth
surfaces.
Rationale
to preserve the
strength and function
of the cusps while
eliminating susceptible
grooves or defective
tooth structure (must
be wide enough to allow
condensation).
61
Principles
Rationale
C. Mesio-distal extension
1. Stop short of the
marginal ridge crest
to preserve strength of
marginal ridges.
Marginal ridge walls should
be 1/2 distance from mesial
and distal pit to the crest of
each marginal.
2. Parallel to the contour of
the marginal ridge.
to preserve a uniform
bulk (strength) to the
mariginal ridges.
62
Principles
3. Groove extensions are
kept narrow (mesiodistally) where possible
terminating on smooth
tooth structure.
Rationale
to preserve strength of
cusps while eliminating
susceptible grooves
and/or defective tooth
structure (must be at
least as wide as the
narrowest condenser).
63
Principles
4. If marginal ridge is
unsupported or very
thin it should be
included, resulting in
a Class II
preparation.
Rationale
If not included the
marginal ridge may
fracture. (amalgam will
be stronger than the
unsupported enamel)
64
Principles
Rationale
III. RESISTANCE/ RETENTION FORM
A. Depth = 0.1-0.2mm into
dentin (approx. 2 mm
measured at triangular
ridges).
Minimum depth is
required to provide
sufficient bulk to
prevent fracture and
retain the amalgam.
65
Principles
Rationale
B. Pulpal floor
1. Smooth and flat
2. Parallel to the occlusal
plane
Uniform thickness of
restorative material.
resists occlusal stress
(resistance form) and
forces of condensation.
66
Principles
Rationale
C. Buccal and lingual walls
1. Smooth and curved
mesio-distally.
2. Smooth and straight
pulpo-occlusally.
Facilitates adaptation
of amalgam and
elimination of weak
tooth structure.
67
Principles
3. Converge slightly
pulpo-occlusally in
areas of triangular
ridges (60).
Rationale
To provide mechanical
lock or retention to the
occlusal portion and
create bulk at the
margins.
68
Principles
4.Diverge slightly
pulpo-occlusally in
buccal and lingual
groove extensions
(60).
Rationale
protects buccal and lingual
surfaces from being
undermined (RESISTANCE
FORM).
69
Principles
Rationale
D. Mesial and distal wall
1. Smooth and straight
facilitates adaptation
of amalgam and
elimination of weak
tooth structure.
70
Principles
2. Diverges slightly
pulpo-occlusally
(forms an obtuse
angle with pulpal
floor).
Rationale
protects marginal ridge
from being undermined or
weakened (enamel must
be supported by dentin)
71
72
Principles
Rationale
IV. CAVITY FINISH
A. Pulpo-occlusal line
angle is well defined
(no point angles are
present) and follows
general
configuration of
cavosurface outline.
increases retention of the
amalgam restoration and
preparation is more easily
visualized.
73
Principles
Rationale
B. Cavosurface margins
1. Sharp (well defined)
2. Sound (well supported)
easier to visualize and
carve.
provides marginal
integrity.
74
Principles
C. Cleanliness – cavity
is free of debris
and moisture.
Rationale
facilitates adaptation of
amalgam to the cavity and
improves the physical
properties of the
restoration by elimination of
void or foreign material.
75
Principles
Rationale
V. TISSUE RESERVATION
A. Rubber dam is intact
preserves isolation,
eliminates moisture.
B. Adjacent tooth structure
and restorations are
intact
conservation of tooth
structure.
C. Adjacent soft tissue
(periodontium) is intact
prevention of postoperative pain and
inflammation.
76
REFERENCES
1.
2.
3.
4.
5.
6.
ART & SCIENCE OF OPERATIVE DENTISTRY- STURDEVANT.
OPERATIVE DENTISTRY- WEINE
OPERATIVE DENTISTRY- MARZOUK
DENTISTRY FOR THE CHILD AND ADOLESCENT- MCDONALD.
ESTHETICS IN DENTISTRY- GOLDSTEIN.
CLASSIFICATION & CAVITY PREPARATION FOR CARIOUS
LESION- G J MOUNT & W R HUME.
7. MINIMALLY INVASIVE DENTISTRY- JADA, Vol. 134, January 2003
8. CARIES
PREVENTION
CURRENT
STRATEGIESNEW
DIRECTIONS- JADA, Vol. 127, October 1996
77