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CLASS V AMALGAM
Design Principles
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CLASS V
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DISTAL
WALL
GINGIVAL WALL
OCCLUSAL WALL
MESAL
WALL
DC
DBC
MBC
DBC
MBC
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AXIAL WALL
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OUTLINE FORMPRINCIPLE
rounded trapezoid in
gingival third G & O outline
straight & parallel to
occlusal table
RATIONALE
conforms to usual
lesion location provides retention
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EXTENSION
a balance between
conservation oftooth structure and
the need for access
and to remove
defective tooth
structure
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EXTENSIONPRINCIPLE
encompasses carioustissue
eliminates unsupportedenamel
encompasses contiguousrestorations
RATIONALE
eliminates infected tissue
eliminates weakenedtooth structure
maximizes restoration
lifespan
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OCCLUSO-GINGIVAL EXTENSION
PRINCIPLE
occlusally to height of
contour or extent oflesion
gingivally to extent of
lesion (frequentlysubgingival)
RATIONALE
provides access
(convenience form)
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MESIO-DISTAL EXTENSIONPRINCIPLE
to line angles of tooth or
extent of lesion
RATIONALE
provides access
(convenience form)
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AXIAL DEPTH
PRINCIPLE
depth 0.5mm into
dentin (1-1.25mmgingivally, 1.5-
1.75mm occlusally)
RATIONALE
suf ficient bulk of
amalgam to preventfracture
suf ficient O & G walllength for retention
1-1.25mm
1.5-1.75mm
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AXIAL WALL
PRINCIPLE
smooth
curved M-D
straight O-G
parallels surface
RATIONALE
optimize adapatation of
amalgam to wall uniform bulk of amalgam to
prevent fracture
maximum pulpal protection
A
B
B
A
A-A
B-B
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MESIAL & DISTAL WALLS
PRINCIPLE
smooth
diverge creating 90
cavosurface angle
RATIONALE
optimize adaptation
of amalgam to walls optimizes strength of
both amalgam and
enamel at margin
B
B
B-B
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OPTIMUM CAVOSURFACE
ANGLE FOR AMALGAM
cross-section ofamalgam restoration
margin
amalgam enamel
90 butt joint
weak amalgam margin weak enamel margin
surface of tooth
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OPTIMUM CAVOSURFACE
ANGLE FOR AMALGAM
cross-section ofamalgam restoration
margin
amalgam enamel
90 butt joint
weak amalgam margin weak enamel margin
surface of tooth
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OCCLUSAL WALL
PRINCIPLE
smooth
straight mesio-distally
90 cavosurface angle
RATIONALE
optimize adaptation of
amalgam to walls easier to visualize &
carve followingcondensation
optimizes strength ofboth amalgam andenamel at margin
opposes G-wall(retention)
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OCCLUSAL RETENTION
PRINCIPLE
retention groove 0.5mm
deep placed in occlusalwall 0.5mm deep to DEJ
RATIONALE
only required when
preparation is over-extended occlusallybecause occlusal &gingival walls will be
divergent
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GINGIVAL WALL
PRINCIPLE
smooth
straight mesio-distally
70 axio-gingival angle
plane enamel at cavo-
surface margin to 90
RATIONALE
optimize adaptation ofamalgam to walls
easier to visualize &carve followingcondensation
helps lock restoration in
tooth (retention)
elimination of weak toothstructure
70
90
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70
angles of
gingival wall
90
gingival wall
cavosurface angle
axio-gingival angle
axial wall
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plane enamel at cavo-
surface margin to 90
90
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CAVITY REFINEMENT
PRINCIPLE
internal line angles well-
defined but not sharp
RATIONALE
maximizes amalgam
resistance todislodgement
reduces stressconcentration & risk
of subsequent toothfracture
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CAVITY REFINEMENT
PRINCIPLE
angles between O, M, G,
& D walls rounded
RATIONALE
reduces stressconcentration & riskof subsequent toothfracture
dif ficult to condense
viscous amalgam intosharp external angles
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CAVITY REFINEMENT
PRINCIPLE
cavosurface margins
regular, well-defined,well-supported
RATIONALE
easier to visualize & carvefollowing condensation
optimize adaptation ofamalgam to margins
eliminates weak toothstructure
maximizes marginalintegrity
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CLEANLINESSPRINCIPLE cavity is free of debris
& moisture
RATIONALE
facilitates adaptation
of amalgam to thecavity
improves physical
properties of therestoration by
elimination of voids
& foreign material
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CLASS V AMALGAM
Preparation Technique
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CEJ
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#245
rounded straight fissure bur
3.5mm head length
t t h O li
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create trench near O-line
i t i d th
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maintain even depth
just shy of bur head length (3mm)
as trench follows curvature of surfacefrom M to D
k b di l t f
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keep bur perpendicular to surface
as it curves from M to D
this creates a flat
occlusal wall and a
curved axial wall
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i h f 3
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starting shy of 3 mm
allows room for refining
the axial wall later
create a second trench near the G-line
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create a second trench near the G-line
this one is less than 2mm deep
(1/2 length of bur head)
t ti t h
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cut connecting trenches
with matching depths
remove intervening plaster
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remove intervening plaster
rough out axial wall
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rough out axial wall
maintain curvature
& O-G depth change
begin M & D walls just shy of pencil line
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begin M & D walls just shy of pencil line
keep bur perpendicular to surface of tooth
M & D walls should be divergent
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M & D walls should be divergent
axial wall should curve from M to D
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the target axial depth is
3mm occlusally
2mm gingivally
being slightly shy of thesemeasures is preferable at
this point to allow room
for smoothing
finishing with the primary & secondary cutting edges of a hatchet
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finishing with the primary cutting edges of a chisel
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finishing with the primary cutting edges of a chisel
plane gingivo-axial angle to 70 with gingival margin trimmer
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plane gingivo axial angle to 70 with gingival margin trimmer
plane the gingival cavosurface margin enamel
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finished walls should just reach the pencil line
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j p
self-evaluate beforeseeking instructor evaluation
accomplished: 30-O Class I cavity preparation for amalgam
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planned: 30-F Class V cavity preparation for amalgam
p y p p g
imagine there is a Class V caries lesion
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draw outline with gingival line at FGM
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bench instructor approval recommended
Bow
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Double-Bowed
212 Retainer
For
gingivalretraction
Li beak
Fa beak
Bow
To increase g ing iva l re t rac t ion fac ia l ly , bend l ingual beak inc isa l ly
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212 retainer used to retract the gingiva
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begin 1.5mm deep (
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extend mesially & distally
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axial wall depth approx. 1.5mm--
l ll l i i ll
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more occlusally, less gingivally
extend walls to pencil lines
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may need to remove 212
to create divergent M & D walls
finish walls with
chisel 111 hoe or
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chisel, 111 hoe, or
hatchet
Wedelstaedt chisel
111 hoe
set gingival wall to 70 with gingival margin trimmer
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self-evaluate before
seeking instructor evaluation
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seeking instructor evaluation
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