UP Dental College &
DEFINITION OF CAVITY
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.
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.
OBJECTIVES OF CAVITY
• 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
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.
(G.V. BLACK CLASSIFICATION)
Black suggested that it was necessary to
•Remove additional tooth structure to gain access and
•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
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
The lesions involving the proximal surfaces of
the posterior teeth with access established from the occlusal
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
The lesions involving all proximal surfaces of
anterior teeth which involves the incisal edge.
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
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.
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
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,
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
Size 4 . Extensive caries or bulk loss of tooth structure e.g. loss
of a complete cusp or incisal edge has already occurred.
DESIGN AND PREPARATION OF
• The design and preparation of cavities are based on
Black’s principles that have been determined and re-
applied with importance directed towards protection
of tooth in preparation rather than only on the
• 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.
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
• Basic Instruments – mouth mirror, explorer, tweezer,
• Hand Instruments – Excavators, enamel hatchet,
monoangle or biangle chisels, Gingival Marginal
• Rotary Instruments –
•Burs No.-carbide burs 55, 56, 57.
• Ultraspeed and conventional speed contrangle
• Safety glasses.
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.
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.
These lesions are
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
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.
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.
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
PERPENDICULAR IN MESIAL-
•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
•INTERNAL FORM BUCCO-LINGUAL VIEW
•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,
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
Isthmus just wide enough to accept
CORRECT OUTLINE FORM
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
The form of this cavity provides
automatically for effective retention
and, therefore, no special retentive
features are required.
Removal of remaining
In small size cavities, the carious dentin
should have been removed during making the
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.
Planning of Enamel
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.
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.
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
• 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
• In either case, access is started at the most
defective area of enamel, i.e., a carious pit or
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.
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
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
•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
•Desired pulpal depth – 0.1 to 0.2 mm into
•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
•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
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
OUTLINE FORM FOR PIT RESTORATIONS
All walls are extended just enough
to eliminate defective enamel and
The enamel walls are planed in the
direction of enamel rods and
perpendicular to the axial wall.
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.
Buccal and Lingual
In case of occluso-buccal and occluso-
lingual cavities extensions are made
through the fissures and towards the
The cutting is done in dentin at the
dentinoenamel junction using a #56 bur
until the occlusal ridge is undermined
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
The enamel thus undermined, is broken
down with chisels.
Retentive grooves are then made in
dentin along the axio-mesial and axio-
distal line angles. The cavity walls and
margins are finished as previously
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.
The following technique is
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.
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
I. OUTLINE FORM – Angular irregularities in
Smooth flowing, the outline are
regular curves. susceptible to fracture
during condensation – a
smooth flowing outline is
easier to visualize and
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).
A. Extensions consist of:
a. Caries and eliminates defective
decalcifications tooth structure and
b. Enamel unsupported by eliminates areas (pits,
sound dentin fissures, etc.) which are
susceptible to recurrent
c. Pits and fossae caries and facilities oral
d. Major fissures and hygiene procedures
grooves (extension for
e. Existing restorations
B. Bucco – lingual extension
1. Extend fully in areas of to allow a smooth
buccal and lingual grooves tooth-restoration
to terminate on smooth margin to be created
surfaces. (easier to finish and
2. Extend minimally in to preserve the
areas of triangular strength and function
ridges (optimal isthmus of the cusps while
width is ¼ intercuspal eliminating susceptible
distance or less) grooves or defective
terminating on smooth tooth structure (must
surfaces. be wide enough to allow
C. Mesio-distal extension
1. Stop short of the to preserve strength of
marginal ridge crest marginal ridges.
Marginal ridge walls should
be 1/2 distance from mesial
and distal pit to the crest of
2. Parallel to the contour of to preserve a uniform
the marginal ridge. bulk (strength) to the
3. Groove extensions are to preserve strength of
kept narrow (mesio- cusps while eliminating
distally) where possible susceptible grooves
terminating on smooth and/or defective tooth
tooth structure. structure (must be at
least as wide as the
4. If marginal ridge is If not included the
unsupported or very marginal ridge may
thin it should be fracture. (amalgam will
included, resulting in be stronger than the
a Class II unsupported enamel)
III. RESISTANCE/ RETENTION FORM
A. Depth = 0.1-0.2mm into Minimum depth is
dentin (approx. 2 mm required to provide
measured at triangular sufficient bulk to
ridges). prevent fracture and
retain the amalgam.
B. Pulpal floor
Uniform thickness of
1. Smooth and flat restorative material.
2. Parallel to the occlusal resists occlusal stress
plane (resistance form) and
forces of condensation.
C. Buccal and lingual walls
1. Smooth and curved Facilitates adaptation
mesio-distally. of amalgam and
elimination of weak
2. Smooth and straight
3. Converge slightly To provide mechanical
pulpo-occlusally in lock or retention to the
areas of triangular occlusal portion and
ridges (60). create bulk at the
4.Diverge slightly protects buccal and lingual
pulpo-occlusally in surfaces from being
buccal and lingual undermined (RESISTANCE
groove extensions FORM).
D. Mesial and distal wall
1. Smooth and straight facilitates adaptation
of amalgam and
elimination of weak
2. Diverges slightly protects marginal ridge
pulpo-occlusally from being undermined or
(forms an obtuse weakened (enamel must
angle with pulpal be supported by dentin)
IV. CAVITY FINISH
A. Pulpo-occlusal line increases retention of the
angle is well defined amalgam restoration and
(no point angles are preparation is more easily
present) and follows visualized.
B. Cavosurface margins
easier to visualize and
1. Sharp (well defined) carve.
2. Sound (well supported) provides marginal
C. Cleanliness – cavity facilitates adaptation of
is free of debris amalgam to the cavity and
and moisture. improves the physical
properties of the
restoration by elimination of
void or foreign material.
V. TISSUE RESERVATION
A. Rubber dam is intact eliminates moisture.
B. Adjacent tooth structure conservation of tooth
and restorations are structure.
prevention of post-
C. Adjacent soft tissue operative pain and
(periodontium) is intact inflammation.
1. ART & SCIENCE OF OPERATIVE DENTISTRY- STURDEVANT.
2. OPERATIVE DENTISTRY- WEINE
3. OPERATIVE DENTISTRY- MARZOUK
4. DENTISTRY FOR THE CHILD AND ADOLESCENT- MCDONALD.
5. ESTHETICS IN DENTISTRY- GOLDSTEIN.
6. 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 STRATEGIES- NEW
DIRECTIONS- JADA, Vol. 127, October 1996