1. The document compares amalgam and composite for Class I and Class II cavity preparations. Amalgam is more durable but less esthetic, while composite is more technique sensitive but offers better esthetics. 2. For Class I cavities, amalgam preparations include all pits and fissures while composite only replaces defective areas. Retention forms also differ between the materials. 3. For Class II cavities, the outline and retention forms for amalgam and composite preparations depend on factors like the extent of decay and location of contacts or fractures. Modified preparations are also described that are more conservative.

1. Difference Between Amalgam
& Composite Class I & II
Cavity Preparation
Ibtissam Itani
Maya Kabbara
Nancy Itani
Sana Jardali
Yara Ismail

2. vs.

3. Content
1. General comparison between amalgam and composite
2. Class I cavity preparation
a. Modified class I
3. Class II cavity preparation
1.Outline
2.Retention
3.Resistance

4. Amalgam Composite
Esthetics Contraindicated Highly esthetic
Technique Sensitivity &
Isolation
Restorations that cannot be well isolated More technique sensitive & restoration
that can be appropriately isolated
Durability Long-lasting if handled well According to the ADA, expected lifetime
can be comparable to that of amalgam in
Class I & II if material’s handled well
Location Posterior teeth Anteriors & esthetically prominent areas
in posterior teeth
Cavity size more extensive (moderate-to-large) Class I
restorations
most small Class I restorations
Mechanical properties Higher mechanical properties Less mechanical properties  more
subjected to wear
Caries Risk Patients w/ bad oral hygiene  less risk of
recurrent caries due to self-sealing
properties
Patients w/ good oral hygiene  high rate
of recurrent caries due to polymerization
shrinkage
Hazards on practitioner More hazardous due to mercury Hazardless
Repair Can’t be repaired Can be repaired

5. Class I
Amalgam vs. Composite

6. 1. The enamel must be supported with dentin to over
come the fracture.
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

7. 1. Outline
Amalgam
• Includes all pits &
fissures and other
areas prone to caries
• width cavity within
1/4 to 1/3 intercuspal
distance
Composite
Limited to defected
areas and does not
have to extend to all
pits & fissures
 Most conservative
manner

8. 2. Retention
Amalgam
• Macromechanical retention
 undercuts: diverging
mesial & distal walls
smoother prepared walls
• Retention is dependent on
design of cavity
Composite
• micromechanical retention
Rough surfaces of prepared
walls
• Sometimes, a dentinal retention
groove or enamel bevel  to
enhance the retention form

9. 3. Resistance Form
Amalgam
 Resistance requires
bulkiness of cavity
Composite
3. Depth depends on extent of
defect  can be stopped short
of the dentinal-enamel
junction if the caries process
also stops before the dentin is
reached
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

10. Resistance Form
Amalgam
• Cavosurface Angle = 90° to
protect enamel rods
 occlusal cavosurface bevel
is contraindicated
Composite
• Cavosurface Angle ≥ 90° to:
1. Increase surface area of enamel to be etched to
strengthen micromechanical bond
2. Esthetic blending of composite w/ tooth
structure
3. Ends of enamel rods are more effectively
etched, producing deeper microundercuts than
when only the sides of the rods are etched

11. Modified Class I
Amalgam vs. Composite

12. 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

13. Class II
Amalgam vs. Composite

14. Class II
Amalgam Composite
Conventional Modified

15. 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

16. …Outline
Amalgam
• Bucco proximal
margin, linguo
proximal
margin &
gingival floor
should be
extended to
include caries
& break the
contact with
the adjacent
tooth
Conventional Composite
• 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

17. 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.

18. 2. Retention
Amalgam
• Rounded grooves within dentin at bucco
and linguo- proximal walls and gingival
floor
Conventional Composite
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

19. • 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

20. • 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

22. References:
• 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%20comp
osite%20and%20other%20tooth-colored%20restorations%20(1).pdf
• http://ccnmtl.columbia.edu/projects/virtechs2006/pdfs/opclass2prepha
ndout.pdf