Principles of cavity
preparation (outline form)
UNDER THE SUPERVISION OF DR. RAWDA
Presented by: Mahmoud
Ismael
Lina Mostafa
Wessal Essam
Merna Ezzat
Mohammed
Hassan

Intended learning outcomes
! 1) Surgical outline form
! 2) Conservative outline form
! 3) Outline form for occlusal cavity preparation
! 4) Outline form for proximal
cavity preparation
! 5) Outline form for cervical cavity preparation

Steps of cavity preparation according to G.V black
Outline form
External outline Internal outline
the marginal boundaries shape of the internal
form of the preparation
An outline form defined as the shape of boundaries of the
completed cavity.

General factors affecting the outline
form ( surgical oultline form):
I- Extension of the carious defect in enamel
and its lateral spread in dentin
! - Some principles should be considered
during caries removal. The access or
! starting point of the preparation must be
initiated at area nearest to the
pathology.
! - All carious enamel and dentin must be
included in the outline, with
consideration to the lateral spread of
decay at the dentino-enamel junction.

General factors affecting the
outline form ( surgical oultline form):
II- All enamel which is weak or undermined
by caries must be eliminated (quality of
enamel rods).
! If such enamel is left at a cavity margin,
it will break easily under mastication
forces leaving a “marginal ditch” since
its brittle and depends on the relative
elasticity of the sound dentin for support.
! * All short, loose and undermined
enamel rod should be eliminated, to
avoid marginal ditch.

General factors affecting the
outline form ( surgical oultline form):
III- Adjacent cavities, closely
approaching to each other, should
not be joined into single cavity
unless if the intervening enamel is
carious, undermined or weak (less
than 0.5mm). separate spot
preparations are preferable
because this preserves the structural
continuity and strength of the tooth.

General factors affecting the
outline form ( surgical oultline form):
IV- Cusps and ridges that are
severely weakened and subjected
to occlusal forces must be reduced
and restored with appropriate
restoration (cusp capping).

General factors affecting the
outline form ( surgical oultline form):
V- The outline form must be in the form of
harmonious sweeping curves in order to
avoid stress concentration and provide
better esthetic.

General factors affecting the outline form
( surgical oultline form):
VI- The pulp should be protected against, cutting of
dentin, thermogenesis, pressure and desiccation.
Depth penetration into dentin should be kept to a
minimum (0.2 to 0.8mm beyond the DEJ) dictated by
the strength requirements, establishment of retention or
removal of carious tissues.

General factors affecting the
outline form ( surgical oultline form):
VII- The cavo-surface angle should be given
correct angulation according to physical
properties of the restorative material.
Moreover, it should be located in dentin areas
that are less liable to caries recurrence and
less stress bearing.
* CSA for amalgam is 90 degree.

General factors affecting
the outline form
( surgical oultline form):
VIII- Age consideration; old patient having
occlusal attrition with shallow grooves and
broader proximal contacts are expected to
have different outline forms.

General factors affecting the
outline form ( surgical oultline form):
IX- Contact area in proximal cavities
should be eliminated “cavity
margins must be pass contact area”

General factors affecting the
outline form (surgical oultline form):
X- Extension for prevention “old concept”:
- Defined as extension of cavity margin into
areas which are considered to be
caries resistant (caries immune areas) and
these are:
1) 2/3 cusp inclines toward the cusp tip
occlusally
2) axial line angles of the tooth
3) areas of buccal and lingual surfaces
occlusal to be height of contour 4) below
the healthy gum margins.
* This concept was previously thought by
G.V black to prevent caries recurrence.

Objections for G.V black
concept:
1) Weaking of sound tooth structure.
2) Increase pulp irritation.
3) Increase gingival and periodontal
irritation.
4) There are no caries immune areas.

- So, now the old concept termed
“cutting for destruction”
- Extension for prevention had been
replaced by necessary extension
without
undue destruction of the tooth which
is called “conservative cavity design”
* IT IS IMPORTANT TO NOTE THAT SOME
MODIFICATION COULD BE APPLIED TO THE
CLASSICAL OUTLINE OF DIFFERENT CAVITY
DESIGNS FOR SAKE OF CONSERVATION,
ESTHETICS AND CONVENIENCE
APPROACHES.

General factors affecting the
outline form
conservative oultline
form

1) Defective retentive enamel
nonremineralizable , such as
pits, fissures and angular
groove which are deeper
than one third the enamel
thickness and are continuous
with cavity outline should be
included in the outline

WHY ?
!retentive for
food
!More susceptible to
caries

enamel at these
locations is not
smooth
ADAPTATION OF
RESTORATION
,# ❌

2). The cavo-surface
angle should be given
correct angulation
according to
physical properties of
the restorative
material.

* CSA for amalgum 90 degree

Moreover, it should
be located in
dentin areas that are
less liable to caries
recurrence and less
stress bearing.

3) Age consideration;
old patient having occlusal attrition with shallow
grooves and broader proximal contacts are
expected to have different outline forms

Supplement Grooves and fissures

4) supplementary fissures 🤔🤔🤔🤔🤔🤔🤔🤔🤔🤔🤔
Non Carious Carious but not more
than 2/3 enamel

To achieve conservative approach:
supplementary fissures are
preferably
considered for
Enameloplasty❓
Slanting!
OR
fissure sealing. !

Enameloplasty:

the procedure is
simply reshaping of
the fissures and
angular
grooves to make them
non-retentive and less
prone to caries

• It is indicated as a
* preventive method *
. for treatment of early carious lesions
involving the outer third of enamel .
. for supplementary fissures which
approximates the outline of a
cavity preparation.

For brittle material,
the cavosurface
angle should be not
exceed 100 degrees and
the restorative angle
should not less than 80
degree.

During
carving, brittle restorative
materials should be removed
from areas of
enameloplasty otherwise thin
edged restorations left at this
areas will be prone to fracture.

* Slanting bur
technique

is a conservative way
to include
supplementary or
defective fissures that
approximate the
outline of the cavity
preparation

The fissure bur is placed
on the wall of the
preparation and slanted
or tilted to 110
degree to include fissure.
The prepared area is
usually included in the
restoration.

IS thiS A CONSERVATIVE
TECHNIQUE

However, this technique achieves
conservation of tooth structure at
the expense of mechanical
retention and resistance at this area

Pit and fissure sealing:

it is primarily indicated in case of
deep angular grooves
liable to stagnation and difficult to clean as
in recently erupted permanent molars.

WHAt IF It Used IN conjunction
with restorations In cavity
prepration ?
Sealants. +. Composite Resin
.

These procedure is termed
preventive resin restoration (PRR)
and is used with resin composite
restorations and the restorations will
chemically bond to the tooth structure

CONCLUSION
Extent of the carious lesion.
Extend the cavity margin until sound tooth structures
obtained and no unsupported enamel remains.
Margins should be paced in easily cleansable areas.
Average depth of the cavity should be 0.5 mm into
dentin.
Extend the cavity margins into fissures that cannot
be eliminated by appropriate enameloplasty.

OCCLUSAL OUTLINE
FORM
WESSAL ESSAM SEYAM

TWO OUTLINE FORMS:
• External outline form:
refers to the marginal bounderies.
• Internal outline form :
dictates the inner dimensions the
details of the cavity.

FACTORS AFFECTING THE OUTLINE FORM
OF THE OCCLUSAL CAVITY PREPARATION:

Occlusal
contact
Occlusal
anatomy

Cavity margins should not be placed in
centric holding areas
Occlusal
contact

what are the centric holding areas?

• The points where the
opposing teeth touch in
centric occlusion ,
which are the functional
cups : the palatal cusps
in the upper teeh, The
buccal cusp in the lower
teeth .

CRITERIA FOR PERFECT CAVITY
MARGIN ACCORDING TO GV BLACK
CONCEPT :
• At contact free areas with
minimal stresses
• defect free
• Smooth
• Run symmetrically through
the anatomical defects and
around the cusps & ridges .

Occlusal
anatomy
Every tooth has an occlusal
anatomy which differs
according to whether it is
in the upper or the lower
jaw
& also differs from any
other tooth in the same

Such difference affects the final shape of the
obtained cavity preparation.
Unusual anatomy, mal-alignment and steep cusp
will change the locations and the extend of the
outline form

PROXIMAL CAVITY
OUTLINE

PRINCIPLES OF CAVITY PREPARATIONS :
Factors affecting outline form of proximal cavities :
1- site and size of contact area
2- width of embrassures
3- position of free gingival margin

PROXIMAL CAVITY OUTLINE

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH
Flaring the margins
this is done to make the cavity more
accessible for carving and finshing
of the restoration

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS II IN POSTERIOR TEETH

CLASS III IN ANTERIOR TEETH

Outline Form Of Cervical Cavity
Preparations

Class V

The outline of Class V cavity is determined gingivally
by the position of gingival tissues

According to convntional outline form, the gingival
margin is placed supra-gingivally

But in some cases for esthetic demands, the
gingival margin should be placed subgingivally

In case of treating anterior teeth, the outline form is
limited to the extent of caries due to the use of tooth-
colored restorations

Also in the anterior region, the incisal wall of the
outline is beveled to enhance esthetics through
color degradation

• At the end, it should be obvious that the extent of
caries is the deciding factor of the extent and form
of cavity outline.
• So, our main goal is to preserve as much sound
tooth structure as possible.
• This could be achieved by preventing over-
cutting of sound tooth structure.

Thank you!