Modifications of Class 2 Cavity preparations

MODIFICATION OF CLASS 2
CAVITY PREPARATION
Presented By: Shashank Mishra Guided By : Dr. Sandip Metgud
Dr. Deepali Agarwal

INDICATION
 Moderate to small size proximal
caries.

 Cavity not exceeding one fourth the
intercuspal distance.

 A class 2 in stress concentration area.

 A patient with good oral hygiene, low
plaque and caries index.

 A lesion where after removal of carious
dentin sufficient bulk in the buccal and
lingual wall present.

GENERAL SHAPE :
 OCCLUSAL PORTION :
 Outline resembles class 1 design 1 or 2
, except they should have some dovetail
formation which may be toward one side
only.

PROXIMAL PORTION:
 These preparation assume an only
unilateral inverted truncated cone
shape

LOCATION OF MARGIN
 OCCLUSAL PORTION :
Resemble those seen in class1 design 1

Proximal portion
 Gingival margin may be located anywhere on the
proximal surface,provided
1. It is gingival to the contact area

2. Cavity preparation include all carious
and undermined tooth structure.

ISTHMUS PORTION
 facial and lingual margins at the isthmus are placed on
corresponding surfaces of inclined plane and the remaining
areas of marginal ridge. Because of the limited cavity width ,
the universal sweeping curves of facial and lingual margins
occlusally will always reverse in isthmus portion (in S-shaped
form) to include contact area.

INTERNAL ANATOMY
 A. occlusal portion : similar to class 1
design 1.

Proximal portion
Mesio-distal cross-section :
Similar to the conventional design, except that rarely gingival
margin may be located on cementum. All line angles are
rounded, with exception of gingivo-axial line angle, which
should be kept sharp.

facio – lingual cross section
It is very similar to the conventional design
 With following variations --
 Buccal and lingual dentinal retention grooves will
be present

 The axial depth of modern design
cavity is much less than that of the
conventional design .

 Preparation modifications:
In tapered teeth (bell shaped teeth )
in line with the axio-pulpal line angle
facially and lingually a groove is prepared
on each of the facial and lingual walls
respectively.

 . After preparing a Class II cavity preparation, if
there presents an intact marginal ridge, crossed by
a fissure, or carious groove, all that is needed is a
proximal extension in the form of slit .

 Slit : a long, narrow cut or opening.

 This “ slit “ may open proximally on
the same level as the pulpal floor , or
with an occlusal step .

Instrumentation for Class II , Design 2
Procedure
Procedural steps are similar to those described for Design 1,
with exception that smaller instruments are used.
Eg. In gaining access and gross removal use a 168 bur, instead
of a 699 bur. In preliminary and final shaping use the
smallest sizes of chisels . The proximal retention grooves ,
which are mandatory here, are created with smaller gingival
marginal trimmers or angle former.

○CLASS II , DESIGN 3
(CONSERVATIVE
DESIGN)

 Involvement
 This preparation is designed to involve
primarily the proximal surface(s) and a very
limited part of the occlusal surface , not
extending beyond the adjacent triangular
fossa .

Indication
 The decay is restricted to the proximal
surface only and the occlusal surface
is completely sound.

• Low stress bearing area .
• There is sufficient bulk of
remaining tooth structure to
place substantial buccal ,
lingual and gingival retentive
grooves .
• Patient exhibits good oral
hygiene and low caries and
plaque indices

General shape
These preparations appear proximally
as a one-sided inverted truncated cone
which is located totally proximally
with the exception of its tip, which
involves part of the adjacent occlusal
triangular fossa

LOCATION OF MARGIN
 OCCLUSAL PORTION
located on the occlusal
inclined planes of the
involved marginal ridge

Proximal portion :
 Appear exactly like modern design .

Internal anatomy :
1. Mesio-distal cross section
The gingival floor may assume one of two forms
a. If the gingival margin is present at the
gingival third of the proximal surface , the
floor will be formed of 3 planes –
1. an inner dentinal plane in the form of a
groove.
2. middle transistional dentinal phase
3. an outer enamelo-dentinal plane
following the direction of the enamel rods
and inclining gingivo-proximally.

. If the gingival margin is located at the middle third
proximally the gingival floor will be formed of 2
planes –
1. an inner dentinal plane in the form of a groove.
2. straight plane formed of enamel and dentin

Facio-lingual cross section
This view shows the axial wall to be
perfectly convex.
The facial and lingual walls , If their margins
are at the facial or lingual thirds of the
proximal surface ,
It will be formed of 3 planes : 1. an inner
dentinal plane in form of groove . 2. a
transitional dentinal plane. 3. an outer enamel
–dentinal plane following the direction of
enamel rods proximo-buccally and lingually.

If their wall ends at middle
third it will be composed of
2 planes : 1. inner dentinal
groove plane . 2. outer ,
straight enamel –dentinal
plane , perpendicular to the
tangent of the axial wall

INSTRUMENTATION
 PROCEDURES:
 Using a ¼ round bur , start a tunnel on the occlusal inclined
planes of the marginal ridge to be involved in the
preparation, connecting this tunnel with the lesion, widening
and breaking it in the same way as was done in preparation
of previous 2 designs.

 If part of the marginal ridge is lost , two
lateral grooves may be prepared on the
buccal and lingual behind the portion of
marginal ridge to be removed

CLASS 2 DESIGN 4( SIMPLE
DESIGN)

 Involvement :
 The proximal surfaces only

Indications
 The decay is restricted to contacting
or proximal surfaces without
undermining the corresponding
marginal ridges

 There is a diastema
• the adjacent tooth is
missing facilitating
direct access to the
lesion.

 The affected tooth is rotated or
inclined.
• The proximal lesion occurs on tapered
teeth with wide gingival embrasures
facilitating facial or lingual access to the
lesion

 The proximal lesion is located very
gingivally at or apical to, the CEJ,
accompanied by gingival recession(senile
decay), making accessibility to the lesion
from the facial or lingual direction possible

General Shape
 Generally, it should follow the shape of
the contact area and the proximal
surface. Usually it will assume a
trapezoidal or rhomboidal shape.

Locations of margins
 If there is no proximally contacting tooth
(diestema) , there is no specific location
of margins , for the entire proximal
surface is essential self-cleansable.

 If the lesion is apical to the contact
area(senile decay ), the occlusal and
gingival margins will be in the gingival
embrasures.

Internal anatomy
a. Facio –lingual cross section
The axial wall is seen to be flat to
slightly convex facio-lingually .
(interrupted line)
The buccal or lingual wall , on the
access side will be a one-planed
enamel dentinal wall
following the directions of the
enamel rods.

Occlusogingival cross section
 The gingival floor may be seen to occur in one of
the two ways
 If the gingival margin is located on cementum ,
cementum should be removed
 gingival floor should be completely formed of
dentin and in 2 planes : an inner one formed of a
groove and an outer one perfectly straight and
flat

 If the gingival margin is present on
enamel, it will be formed of 3 planes :
inner dentinal groove , a dentinal
transistional plane and an outer plane
of enamel and dentin

Instrumentation for class II design 4
Prerequisites :
 These are similar to previous designs , with the exception that
wedges are used if they will interfere with access.
Procedures :
a. Gaining access and gross removal
 From the access side, using a round bur ¼ the size of the proximal
preparation with axial pressure and lateral dragging. Remove decayed and
sound tooth structure within the outline.


b Preliminary shaping
 This is done using the base of an inverted cone
bur . With buccal access ,at the future location of
the lingual wall ,form the lingual wall in gingivo-occlusal
movements .

• At the gingival floor location ,use the
same part of the bur moving it in a bucco-lingual
direction to form the gingival floor .

• Then using the side of the bur , in an occluso-apical
direction , form the buccal wall .

 The occlusal wall could be formed
with a tapered fissure bur , using
bucco-lingual strokes.

 If access is from the lingual, the exact reverse of the previous
steps are followed.
 Final shaping is accompanished in several steps.
 The different planes for the buccal and lingual walls can be
formed using a hatchet and wedelstaedt chisel .

Similarly different planes for the gingival and
occlusal walls could be formed using a
Wedelstaedt chisel from buccal or hatchet
from lingual

CLASS II DESIGN 5
Involvement : Part of the proximal surface, with a very limited
access area on the facial or lingual surface .
Indications
There are two shapes for this design , each with certain
indications.
Shape A– facial and lingual surface will not have dovetail form.
1. The cavity will have 4 walls , with retentive grooves in atleast
2 of them.
2. Small to medium sized proximal lesions.
3. Restoration subjected to normal displacing forces.
4. Marginal ridge is intact.
5. Lesion does not involve the contact area.
6. Good oral hygiene.

In shape B - the facial or lingual access will have a
locking feature in the form of a dovetail, unilaterally
cut in the occlusal direction.
1. Final cavity preparation will not have 4 surrounding
walls and either one wall or no wall is bulky enough
to accommodate a groove.
2. For medium to large sized proximal lesion.

General shape
The proximal part of this cavity will have no specific shape , however , it
will appear either trapezoidal .
One- sided
dovetailed
shapedovetailed
shape
a box or
rectangular shape

Occlusal margin
located in gingival
embrasure
Gingival margin
present in gingival
embrasure
The proximal
margins are far
enough onto the
facial or lingual
surface to include
the axial angle and
¼ th of the facial or
lingual surface.

Internal Anatomy
Occluso –gingival cross section
The axial wall will
appear flat
occlusogingivally
The occlusal and gingival walls , if both are
located on cementum or dentin, will be formed of 2
planes – an internal dentinal grooved plane and an
external dentinal plane which is perfectly flat and
opening straight proximally.
If the occlusal
margin is located on
enamel it is always
at the gingival third
of the surface .The
resultant inclination
axio-gingivally
creates a needed
undercut.

Two distinct axial walls ,
i.e. One proximal
and another facial or
lingual (access side).
Both are perfectly flat
.
If the facial or lingual wall on the
non-access side has its margin
on enamel, it will be composed
of 2 planes: an inner dentinal
plane at right angle to proximal
axial wall for resistance and
retention and outer enamel-dentin
plane in direction of
enamel rods

In a very apically located
lesion, part or all of this
facial or lingual walls
will be completely
formed of dentin,
always at a right angle
to the axial wall.
The mesial and distal
wall on the access
side is always one
planed. It is formed
of enamel and
dentin following the
direction of enamel
rods.

Instrumentation
a. Gaining access and gross removal :
with a tapered fissure bur using axial pressure and lateral
dragging , on the access side, cut the access window
which usually will be in sound tooth structures.
Access window
in the sound
tooth structure

 From this access preparation
introduce the same tapered fissure
bur proximally using axial and lingual
pressure and occluso-gingival
dragging.
Axial and
lingual
pressure
Bucco
lingual
direction

a. Preliminary shaping : this is done using the tip and side of a
700 or a 169 bur which creates definite surrounding walls,
and to formulate the proximal axial wall. Retention grooves if
indicated , may be cut using a ¼ round bur, dragged along
the axio-gingival and sometimes axio-occlusal line angle
with pressure gingivally and occlusally.
.

a. Final shaping occurs when the different
planes of surrounding walls are formed
using a hatchet for the access cavity and
axial wall and a gingival marginal trimmer
for the non-access side walls and gingival
walls . Defining and rounding of line and
point angles is done using a Wedelstaedt
or hatchet chisels.
hatchet GMT Wedelstaedt

 Cavity finish is accomplished using
the same instruments but with lighter
and more frequent applications

CLASS II , DESIGN 6
Involvement : The occlusal, proximal(s) and
part of the facial and/or lingual surfaces.

Indications:
1. The cusp length is double or more its width ,
either throughout or at certain portions of
cusp.
2. A cusp is completely missing .
3. A foundation for cast restoration is required.
4. Teeth have a doubtful prognosis
endodontically and periodontically.
5. A badly broken down tooth needs to be
prepared prior to endodontic or orthodontic
treatment

General shape
 The occlusal and proximal portions have the
same locations of margins as in designs 1 or
2 . The facial and/or lingual parts are
rectangular in outline.
RECTANGULAR
IN OUTLINE

 The occlusal and proximal portions have
same location of margins as design 1or 2.
 With only partial mesio-distal replacement
of cusp, the margin should not end at the
tip of cusp rather it should be located
mesial or distal to it.
• Similarly if margins come near groove , the groove
is involved in cavity preparation

Cuspal elements , or parts
of them , which will
accomodate amalgam
must be cut flat, i.e. In the
form of a table with right
angled cavosurface
margins.
Reduce cusps or parts of a
cusp until there is minimum
length:width ratio of 1:1. If
length:width ratio is
different at different levels
tables can be prepared at
these different levels.
The junction between tables
should be rounded.
Cusps or parts of it to be replaced or covered with amalgam should be
reduced at least 1.5-2 mm from the opposing cuspal elements in both
static and dynamic contacts. This will accomodate sufficient amalgam
bulk to resist loading.
Internal Anatomy

It is always advisable to
have a retention form ,
for e.g. External box or
groove, adjacent to the
tabled cusp
• Undermined or
thinned enamel
should be tabled .
• Never place pins on
tables which will
accommodate
amalgam cusps.

Class II Design 7 (Combination of Class II with Class V)
Shape A
The junction between the Class II and Class V via the proximal,
crossing the axial angles.
Involvement
The occlusal, proximal and part or all of the gingival third of the
facial and/or lingual surfaces with the intervening part of the
axial angles

Indications
a. When at a location apical to the contact area, an
occluso-proximal lesion joins a senile decay lesion via
decalcification, or a defect that has spread laterally
beyond the regular cavity preparation.
b. A class V lesion undermines enamel or directly
involves tooth structure of the adjacent axial angles in
a tooth having a proximo-occlusal lesion.
c. Surface defects or decalcifications at the axial angles
of the tooth are continous with a proximo-occlusal
cavity preparation apical to contact area.

If the cavity extension will
unilaterally involve the facial or
lingual axial angle only, will be
“L shaped”.
If cavity extension is
bilateral it will be “invered
T-shaped”.
General shape

Location of margins
The occlusal margins and main parts of the proximal
margins will be exactly like Design 1 and 2.
In the extensions, facially
and/or lingually the
gingival margin will
seldom be located
subgingivally but will be
even with free gingiva or
supragingival.
•The occlusal margin in the
extension will be apical to the contact
area.
• In unilateral L shaped design there
is one occlusal wall.
The facial and/or lingual margins of the
extensions will be located past the axial angle on
facial or lingual surfaces.

In bilateral inverted T design there are
2 occlusal walls.

Shape B
The junction between class II and class V is through the occlusal via the buccal
and/or lingual grooves.
Involvement : the proximal, occlusal , facial and/or lingual surfaces.
Indications
1. Class V lesion connects with an occluso-proximal lesion via a facial or
lingual fissured groove.
2. Surface defects or decalcifications on facial or lingual surface .
3. Class V is continuous with Class 1.

General shape
Occlusal and proximal
portions are exactly as design
1 and 2. The facial and / or
lingual parts are inverted T-shaped.
Internal Anatomy
The connection between the occlusal
and facial or lingual portion is in the form
of long arm of inverted T.

Class II Design 8
Involvement
Two or more surfaces of an endodontically treated that
does not require post retention .
Indications
1. The remaining tooth structure after endodontics can
support and retain an amalgam restoration.
2. The tooth has a sufficient pulp chamber to accomodate
retaining self – resisting amalgam bulk i.e. A minimum 2
mm thickness in three dimensions.
3. The post-endodontics pulp chamber has at least two
opposing intact walls.
4. The tooth contains sufficiently large root canals to
accomodate retaining resisting amalgam bulk at its
occlusal 1/3rd (i.e. Minimum 1.5 mm thickness )
5. A foundations is needed for a reinforcing restorations
(cast restoration)

6. There is sufficient remaining tooth structure to permit the
preparation of flat planes at right angles to occluding forces.
7. There has been successful root canal therapy leaving an intact
subpulpal floor.
8. The tooth does not show any signs of cracking or crazing.

Excavate from the entire pulp
chamber any residual root canal
filling materials or debris. Bare
dentin should be exposed on
the surrounding walls and
subpulpal floor
Large root canals that
can accomodate an
amalgam thickness of
1.5 mm should have
the root canal filling
removed to a 3-4 mm
depth .
General shape
The outline will appear exactly as
described for Design 6.
Internal anatomy

Each flat portions of the tooth
preparation eg. Tables or ledges should
be opposed by a similar flat component
for proper reciprocation, to immobilize
the restoration and evenly distribute
stresses.
•Any external boxes for retention should not perforate to the pulp chamber or
cause thinning in the intervening walls.
• In preparing tables and ledges allow sufficient reduction depths to provide
enough thickness of amalgam to serve as a foundation for a reinforcing cast
restoration.

In the bulky portion of the
surrounding walls of the
pulp chamber, cut flat
ledges to receive most of
the occlusal loading ,
thereby minimizing
stresses on the subpulpal
floor during such loading .

If possible “square up” surrounding walls provided this
action will not perforate to the surface , furcation , or
thin tooth structure to the extent of making these
areas non-resistant .
Retain any residual
pulpal floor , placing
ledges in it and
making it as flat as
possible.

Instrumentation for Class II, Design 8
 The occluso-proximal cavity preparation and capping of cusps , short of pulp
chamber and root canal preparation, is done in same way as described for Designs
1 and 6 .
For intrapulpal and intraradicular prepartion the following procedure may be done :
 Ledges and shelves may be prepared using 555 and 556 burs in apical pressure
and lateral dragging .
APICAL
PRESURE

 Intraradicular preparation is started by removing
the specified lengths of the indicated root canal
material using hot gutta-percha pluggers,peeso
reamers or bibevelled-sided reamers.

Then the specified length of the canal is
widened and side-paralleled using large
tapered, then cylindrical fissure burs
(704,558).

Following this , the junction between pulp
chamber and root canal preparations
should be rounded using round burs.
Finally , all junctional parts of the cavity
preparations are rounded using a round
bur or a very sharp gingival marginal
trimmer

References
Operative Dentistry – Modern theory and Practice –
Marzouk.
Art and Science of Operative Dentistry – Sturdevant.
Fundamental of operative dentistry – j.summit
Textbook of endodontics- Nisha garg

Modifications of Class 2 Cavity preparations

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