Class I , II Composites Cavity preparations

DR. PALANI SELVI. K
POSTGRADUATE STUDENT
DEPARTMENT OF CONSERVATIVE DENTISTRY AND
ENDODONTICS

TOOTH PREPARATION
• The mechanical alteration of a defective,
injured, or diseased tooth in order to best
receive a restorative material which will re-
establish a healthy state for the tooth
including esthetic corrections where indicated,
along with normal form and function.

OBJECTIVES OF TOOTH PREPARATION
 Remove all defects and provide
necessary protection to the pulp.
 Extend the restoration as
conservatively as possible .
 Tooth prepration such that under
mastication both the tooth and
restoration will not fracture or
displace.
 Allow the functional and esthetic
placement of a restorative material.

FACTORS AFFECTING TOOTH PREPARATION
1.General Factors
 Pulpal & periodontal
status
 Occlusal relationship
2.Dental anatomy
Direction of enamel rods
Thichness of enamel /dentin
Size and positionof pulp
Relationship of tooth to its
supporting tissues
3.Patient factors
Age
Esthetic consideration
Economic status
Patients with high risk caries
4.Affected & infected Dentine
5. Restorative material factors

 Simple cavity: only one tooth surface is involved.  Compound cavity: two surfaces are involved.
Complex cavity: three or more surfaces are involved

INITIAL CAVITY PREPARATION STAGE
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

Final cavity preparation stage
• Step 5 Removal of any remaining infected dentin if indicated
• Step 6 Pulp protection
• Step 7 Secondary resistance & retention form
• Step 8 Procedure for finishing external walls
• Step 9 Final procedures

INDICATIONS:
1. Small, moderate restorations, enamel margins
2. Most premolars or 1st molars, esthetics
3. Does not provide all of the occlusal contacts
4. Does not have heavy occlusal contacts
5. Proper isolation is possible
6. Foundation for crowns
7. Large restorations, economic or interim use
CLASS I COMPOSITE PREPARATION

Contraindications
1. Operating site cannot be appropriately isolated
2. When heavy occlusal stresses are present
3. When all occlusal contacts are on composite only
4. In restorations that extend to the root surface

ADVANTAGES
1. Esthetics
2. Conservative
3. Easier, less complex tooth preparation
4. Economics
5. Insulation
6. Bonding benefits

DISADVANTAGES
2. Time consuming
3. Technique sensitive:
4. More expensive than amalgam

Clinical Techniques for Direct Class I Composite Restoration
• Isolation of the operative field
• Shade selection

Selecting a cutting instrument:
– Carbide burs: 330 pear shaped bur
– Diamond burs

Three typical composite preparation
1: Conventional (need to provide increased resistance)
2: Beveled conventional (rarely used)
3: Modified

• Boxlike form
• Some flat walls –perpendicular to occlusal forces
• Strong tooth marginal configurations
CLASS I PREPARATION CONVENTIONAL, BEVELED
CONVENTIONAL DESIGN

• Need to provide increased resistance: Resistance to
fracture of the tooth or composite
• Amalgam like preparation
• For large preparation or restorations subjected to heavy
occlusal forces
CLASS I PREPARATION - CONVENTIONAL

• Enter the tooth in the distal pit area
(inverted cone diamond –parallel with the
long axis of the crown) –permits better
vision.
• The mesio-distal length will be prepared.
Class I preparation- Conventional

• Pulpal floor initial depth 1.5mm (from
the central groove) –0.2mm inside DEJ
• Lingual facial depth could be greater
1.75mm (depends on the steepness of
the cuspal inclines)

• Facial and lingual extension and width are dictated by the
caries, old restorative material or fault.
• Cuspal and marginal ridge area preservation as much as
possible
• Outline form should be as conservative as possible
• Extensions towards cusp tips should be as minimal as
possible

• 1.6 mm thickness of remaining marginal ridge
for premolars, 2 mm for molars
• Extending the outline form to sound tooth
structure, remaining caries should be removed
• No additional bevelling on the occlusal margin
• Inverted cone diamond results in occlusal
convergency

• Marginal form of groove extension on
the facial or lingual surface may be
beveled with diamond 0.25-0.5 mm with
bevel at a 45 degree angle to the
prepared wall
• Large class I cavity with facial or lingual
groove resulted a combination of
conventional and beveled conventional
preparation

Box form
• Beneficial effect on retention and resistance
• Negative effects on C-factor

• Associated with polimerization shrinkage for
different situations using dental restorative materials
• The ratio of bound-to-unbound surface areas on
restoration
• May be estimated as the ratio of the number of
bound-to-unbound surfaces
• Range from 0.1 to 5.0
C-factor

• The higher the C-
factor, the greater
the potential for
bond disruption
from polymerization
effect.
C-factor

• Cavity class I:
-five bonded surface (mesial, distal, facial,
lingual, pulpal)
-occlusal surface is unbonded (free)
• Ratio between the number of bonded and
unbonded surfaces is 5.
• Flow (stress relief is limited) can occure only
from the single free surface.
C-factor

• Small-to moderate restoration
• Not involve the characteristic of resistance
form features
• Less specific in form
• Utilizes more flared cavo-surface forms
• No uniform or flat pulpal or axial walls
• As conservative as possible in tooth structure
removal
CLASS I PREPARATION MODIFIED DESIGN

DESIGN, CUTTING INSTRUMENTS
• More rounded and smaller cutting instruments
• Size: dictated by the size of the lesion or fault
• Shape: depending on the retention and resistance forms
needed
• Diamond instruments are preferred:
- roughens the surface area
- increase the surface area and retention

• Extensive occlusal portion
• Flat tipped bur or diamond
• Inverted cone with rounded corners:
- provide flat floors
- result in occlusal marginal configurations, more
representative of the strongest enamel margin
• Enhance retention form (occlusal convergency)
• More conservative faciolingual preparation width

• Small round or inverted cone diamond bur
• Initial pulpal depth 1.5mm (0.2 mm inside the DEJ) but may
not be uniform
• Round bur results more flared (obtuse) cavosurface margin
angle than inverted cone

Two separate faulty occlusal pits:
• The bur is as small in diameter and as
shallow in depth as possible
• Small round bur, or diamond (size
depends on the lesion)
• Oriented perpendicular to the surface
• Extend pulpally to eliminate the lesion
• Complete the prep with flame shape
or round diamond to roughen the
prepared surface

• Any shallow fissure that extends laterally
from the pit is incorporated in the preparation
by an extended cavosurface bevel or flare
(like enameloplasty procedure)

Controversial effects of bevelling on the surface:
• Main goal: to maximize the exposure of end-cut enamel prisms
• Normal preparation results in end-cut enamel prisms
(orientation of the enamel rods in cuspal inclines)
OCCLUSAL CAVOSURFACE MARGIN BEVELLING

Benefits from no extra bevelling:
• Prevents the loss of sound tooth structure
• Decreases the surface area of the final restoration
• Lessens the chance of the occlusal contact on the restoration
• Eliminates the thin area of composite: -more susceptible to fracture
• Presents well-demarkated marginal periphery –more precise
finishing is possible
OCCLUSAL CAVOSURFACE MARGIN BEVELLING

Similarities
2. All angles must be rounded to prevent stress
magnitude on the tooth structure.
3. The walls must be either parallel or
perpendicular to the long axis of the teeth to
decreases the forces.
Incorrect
Correct

•Amalgam
all pits &
fissures
•Composite
Limited to defected
areas

• Amalgam
requires
bulkiness
•Composite
depends on extent of
defect
1. pulpal depth: not necessarily
uniform but usually 1 – 2 mm
1. Pulpal depth = min. 1.5 mm (floor
must consist of dentin)
2. Axial wall: Should be uniform
= 0.2 – 0.5 mm inside DEJ 2. Axial wall: Not necessarily
uniform
3. If caries extends deeper than
pulpal depth of 1.5 mm, only
the carious area is excavated
and a flat seat is established
around to not affect retention
form

Modified Class I
Amalgam vs. Composite

Amalgam
1. Box shaped appearance
Composite
1. Scooped out appearance
3. occlusolingual
restoration used when
lingual fissure is connected
w/ the distal oblique groove
& distal pit on occlusal
aspect
2. bur must be slightly
inclined distally to
conserve the dentinal
support & strength of
marginal ridges &
distolingual cusp
2. Undermined marginal
ridge can be left in extensive
preparation & strengthened by
composite bonding
Amalgam Composite

Decision making:
• Expected presence of enamel periphery –IDEAL
• Preparation is expected to extend onto the root
surface –potential problems of isolation and gap
formation -good technique will be needed
• Occlusal relationship -heavy occlusal contact
problems
• Preoperative wedging before preparation –
separation, beneficial effect on the reestablishment
of the proximal contact
CLASS II - COMPOSITE CAVITY PREPARATION

Conventional
Modified design

OBJECTIVES
• Remove the fault, defect, caries or old
material
• Remove friable tooth structure
• 90 degree or greater cavosurface angles
• Two components:
-occlusal step portion (like class I)
-proximal box portion

• Moderate to very large decay
• Inverted cone diamond bur
• More boxlike form
• More uniform pulpal and axial depth
• Walls prepared perpendicular to occlusal forces
(enhance resistance form)
• No secondary retention features
• Roughened preparation walls
CAVITY CLASS II CONVENTIONAL DESIGN

Occlusal step
-similarly like class I
-propose the facial and lingual proximal
extensions
-conservative connection between
occlusal and proximal portion
-1.5 mm initial occlusal depth

CAVITY CLASS II
CONVENTIONAL
DESIGN

Occlusal step
• Initial extension toward the proximal area
• Go trough the marginal ridge, initial pulpal floor
depth, exposing the DEJ
• DEJ serves a guide for preparation
• Inverted cone diamond, parallel with the long
axis of the tooth crown –occclusal convergency
• Only faulty central groove area are prepared

PROXIMAL BOX
• Faciolingual width as narrow as possible
• Initial depth 1.5 mm than follows the rise
and fall of the underlying DEJ
• Pulpal floor relatively flat, may rise and
fall slightly in a mesiodistal plane.
• Preservation of the cuspal area
• Typical caries localisation: Gingivally to
the proximal contact

PROXIMAL BOX
• Not to cut the adjacent tooth
• Ideally there is no preparation beyond the proximal contact
• Gingival cut 0.2 mm inside the DEJ
• Facio-lingual, gingival extension include all fault, caries or old
material –follow the DEJ
• Bur always paralell with the long axis of the crown
• Facial, lingual margins have 90-degree or more obtuse
• Gingival floor prepared flat with 90 degree cavosurface margin

PROXIMAL BOX
• Axial wall 0.2 mm inside DEJ, slight outward
convexity
• Finally remaining caries excavation
• No secondary retention features are needed
• Inverted cone diamond resulted occlusal
convergency
• Remove gingivally any unsupported enamel
margins

PROXIMAL BOX
• Preparation on the root:
-90 degree cavosurface margin
-depth is 0.75 –1 mm

BEVELLING
• No occlusal bevelling
• No facial, lingual, gingival bevelling
• Bevelling may be placed on facial, lingual
margin if the box is wide
• No gingival bevelling -preservation of the
thin enamel

BEVELS OF THE PROXIMAL BOX
• Conservative bevels 0.5-1.0 mm
• On the facial and lingual cavosurface margins
• Provide more accessible location for finishing and polishing
CAVITY CLASS II MODIFIED DESIGN

• Gingival margin bevel requires clinical judgment
• Near the cementoenamel junction
-thin enamel layer –beveling can remove the little enamel
layer
-presence of the prismless enamel layer-less effective acid
ecthing

Beveling is indicated
• Gingival margin is above the CEJ
• Adequate band of enamel remains
• Groove at the gingivoaxial line angle can reduce the
microleakage if the gingival margin is below the CEJ.

• For smaller restorations
• Round or inverted cone diamond bur
• More rounded
• Less boxlike
• Less uniform extension or depth dictated by the
lesion
• Possible to save considerably more tooth
structure by using a conservative approach.
Indications

• Walls are 90 degree or greater
• Proximal box is narrower than that associated with
conventional amalgam cavity preparations
• Proximal box is not extended onto the occlusal surface by
more than 2 to 2.5mm beyond the location of the proximal
marginal ridge
• Gingival margin should be at least 2mm from the cervical
line
• Remove friable tooth structure

• A small round or inverted cone diamond may be used for this preparation
to scoop out the carious or faulty material.
• This scooped appearance occurs on both the occlusal and proximal
portions.
• The pulpal and axial depths are dictated only by the depth of the lesion
and are not necessarily uniform.
• The proximal extensions likewise are dictated only by the extent of the
lesion, but may require the use of another diamond with straight sides to
prepare walls that are 90 degrees or greater .
• The objectives are to conservatively remove the fault, create 90-degree
cavo surface margins or greater, and remove friable tooth structure.

BOX ONLY PREPARATION

BOX ONLY PREPARATION
• Indicated when only the proximal surface is faulty, with no lesions on the occlusal
surface.
• An inverted cone or round diamond, held parallel to the long axis of the tooth crown.
The diamond is extended through the marginal ridge in a gingival direction.
• The axial depth is prepared 0.2 mm inside the DEJ.
• The more box-like with the inverted cone, and the more scooped with the round
diamond.
• The facial, lingual, and gingival extensions are dictated by the fault or caries.
• No beveling or secondary retention is indicated

• These preparation designs have been
described as minimally invasive and
relatively successful with a reported 70%
success rate over an average of 7 years.
MINIBOX OR “SLOT” PREPARATIONS

• The lesion on the proximal surface but access can be obtained from
either a facial or lingual direction, rather than through the marginal
ridge in a gingival direction.
• Usually a small round diamond is used to gain access to the lesion.
• The diamond is oriented at the correct occlusogingival position and the
entry is made with the diamond as close to the adjacent tooth as
possible, preserving the facial or lingual surface.

• The preparation is extended occlusally, facially, and gingivally enough
to remove the lesion.
•
The axial depth is 0.2 mm inside the DEJ.
• The occlusal, facial, and gingival cavosurface margins are 90 degrees
or greater. This preparation is similar to a Class III preparation for an anterior
tooth

Class II
Amalgam vs. Composite

Class II
Amalgam Composite
Conventional Modified

1. Outline
Amalgam
 The occlusal
outline form of
proximal box is
determined
primarily by:
1. bucco-lingual
position of the
contact
2. extent of the
carious lesion
Conventional Composite
 used for moderate to very
large Class II composite
restoration
Occlusal outline Occlusal outline
Same principles in Class I cavity preparation except that external
outline is extended proximally toward defective proximal surface

…Outline
Amalgam
 Bucco proximal
margin, linguo
proximal margin
& gingival floor
should be
extended to
include caries
& break the
contact with
the adjacent
tooth
 What dictates the facial,
lingual, and gingival
extension of the proximal
box?
1. The extent of the
carious lesion
2. Amount of old
restorative materiaL
 not required to extend the
proximal box beyond
contact with the adjacent
tooth
Proximal boxProximal box

Amalgam
 Slot preparation:
Modified class II
cavity for
placement of
RMGIs (Resin
Modified Glass
Ionomer)
• Presence of infected carious dentin
on portion of either pulpal floor or
axial doesn’t indicate deepening
entire wall.

2. Retention
Amalgam
 Rounded grooves within dentin at bucco
and linguo- proximal walls and gingival
floor
1. No dovetail
3. Gingival bevel
2. Cavosurface bevel to
increase surface area
• Gingival divergence faciolingual
width at gingiva greater than the
occlusal
3. No gingival bevel
2. No cavosurface bevel
1. Occlusal dovetail required for retention

 for smaller restorations
 preparation design: more rounded, less boxlike, & less uniform
in extension or depth compared to conventional
Composite Modified Class II
conservatively
remove the fault
create 90-degree
cavosurface margins
or greater
remove friable tooth
structure

when only proximal surface is faulty, with
no lesions on the occlusal surface
No beveling or secondary retention
indicated
proximal box not extended onto occlusal
surface by more than 2 - 2.5 mm beyond
location of the proximal marginal ridge
 lesion on proximal surface but access
to lesion is possible through
facial/lingual surface rather than
through the marginal ridge in a
gingival direction
 Direct access for caries removal
Box-only tooth preparation Facial/Lingual Slot Preparation
Composite Modified Class II

 Roberson, T. (2006). Sturdevant's art and science of operative dentistry (5th ed.). St. Louis, Mo.:
Mosby.
 http://iust.edu.sy/courses/class%20i%20and%20ii%20direct%20composite%20and%20other%20t
ooth-colored%20restorations%20(1).pdf
 http://ccnmtl.columbia.edu/projects/virtechs2006/pdfs/opclass2prephandout.pdf

Class I , II Composites Cavity preparations

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