8/17/2019 14.Cl2 amal.principles2.08.pdf
1/50
CLASS II AMALGAM
Design Principles
8/17/2019 14.Cl2 amal.principles2.08.pdf
2/50
CLASS II
8/17/2019 14.Cl2 amal.principles2.08.pdf
3/50
Class II cavitated caries lesions
8/17/2019 14.Cl2 amal.principles2.08.pdf
4/50
opaque white haloes identify areas of
enamel undermining and decalcificationfrom within
Class II cavitated caries lesions
8/17/2019 14.Cl2 amal.principles2.08.pdf
5/50
radiographic appearance of
the Class II caries lesion
8/17/2019 14.Cl2 amal.principles2.08.pdf
6/50
A
E1 lesion
confined to outer
half of enamel
8/17/2019 14.Cl2 amal.principles2.08.pdf
7/50
B
E2 lesion
reaches into inner
half of enamel
8/17/2019 14.Cl2 amal.principles2.08.pdf
8/50
C
cavitated lesion
spreading radiolucency
at DEJ
8/17/2019 14.Cl2 amal.principles2.08.pdf
9/50
Primary Caries
D1E2
8/17/2019 14.Cl2 amal.principles2.08.pdf
10/50
Primary Caries
D1D2
D3
8/17/2019 14.Cl2 amal.principles2.08.pdf
11/50
Accepted Terminology
extending into proximal
extending gingivally
preparing a proximal box
Jargondropping a box
deepening cervically
8/17/2019 14.Cl2 amal.principles2.08.pdf
12/50
The Class II cavity prepared to receive amalgam has two parts
8/17/2019 14.Cl2 amal.principles2.08.pdf
13/50
the occlusal portion
design principles are the same as for the Class I cavity
8/17/2019 14.Cl2 amal.principles2.08.pdf
14/50
the proximal portion or proximal box
design principles will be presented now
8/17/2019 14.Cl2 amal.principles2.08.pdf
15/50
names of walls for the the occlusal portion of the Class II cavity
are similar to the Class I
Class IClass II
8/17/2019 14.Cl2 amal.principles2.08.pdf
16/50
DISTAL
WALL
LINGUAL WALL
BUCCAL WALL
MESIAL
WALL
DISTAL
WALL
LINGUAL WALL
BUCCAL WALL
Class I
Class II
8/17/2019 14.Cl2 amal.principles2.08.pdf
17/50
PULPAL FLOOR
PULPAL FLOOR
Class I
Class II
8/17/2019 14.Cl2 amal.principles2.08.pdf
18/50
names of walls for proximal portion of Class II cavity
8/17/2019 14.Cl2 amal.principles2.08.pdf
19/50
GINGIVAL SEAT
LINGUAL
WALL
BUCCAL
WALL
DISTAL WALL
8/17/2019 14.Cl2 amal.principles2.08.pdf
20/50
LINGUAL
WALL
BUCCAL
WALL
8/17/2019 14.Cl2 amal.principles2.08.pdf
21/50
LINGUAL
PROXIMAL
WALL
BUCCAL
PROXIMAL
WALL
BUCCAL
OCCLUSAL
WALL
LINGUAL
OCCLUSAL
WALL
8/17/2019 14.Cl2 amal.principles2.08.pdf
22/50
AXIAL
WALL
8/17/2019 14.Cl2 amal.principles2.08.pdf
23/50
names of line angles for proximal portion of Class II cavity
LINGUO-GINGIVAL
LINE ANGLE
AXIO-BUCCAL
LINE ANGLE
AXIO-PULPAL
LINE ANGLE
AXIO-LINGUAL
LINE ANGLE
AXIO-GINGIVAL
LINE ANGLE
BUCCO-GINGIVAL
LINE ANGLE
8/17/2019 14.Cl2 amal.principles2.08.pdf
24/50
names of cavosurface margins for proximal portion of Class II cavity
BUCCAL
PROXIMAL
CAVOSURFACE
MARGIN
LINGUAL
PROXIMAL
CAVOSURFACE
MARGIN
GINGIVAL
CAVOSURFACE MARGIN
8/17/2019 14.Cl2 amal.principles2.08.pdf
25/50
names of point angles for proximal portion of Class II cavity
AXIO-
BUCCO-
GINGIVAL
POINT ANGLE
AXIO-
LINGUO-GINGIVAL
POINT ANGLE
BUCCO-
GINGIVO-
CAVOSURFACE
POINT ANGLE
LINGUO-
GINGIVO-
CAVOSURFACE
POINT ANGLE
8/17/2019 14.Cl2 amal.principles2.08.pdf
26/50
PROXIMAL OUTLINE FORMPRINCIPLE
• straight
• B & L outlines near
parallel to long axis of tooth
• gingival outlineperpendicular to long axis
of tooth
RATIONALE
• conservative of toothstructure
• resists forces of occlusion
8/17/2019 14.Cl2 amal.principles2.08.pdf
27/50
EXTENSION
a balance between
conservation of
tooth structure and
the need for access
and to removedefective tooth
structure
8/17/2019 14.Cl2 amal.principles2.08.pdf
28/50
PROXIMAL EXTENSIONPRINCIPLE• encompasses carious
tissue
• eliminatesunsupported enamel
• encompassescontiguous fissures
• encompassescontiguous
restorations
RATIONALE
• eliminates infectedtissue
• eliminates weakenedtooth structure
• reduces risk of secondary caries
• maximizes restorationlifespan
8/17/2019 14.Cl2 amal.principles2.08.pdf
29/50
PROXIMAL EXTENSION
PRINCIPLE
• clears adjacent tooth by
0.5mm (0.3 - 0.65mm)
RATIONALE
• access for matrix band
• allows inspection of restoration margin
• access for finishing
8/17/2019 14.Cl2 amal.principles2.08.pdf
30/50
PROXIMAL DEPTH
• proximal depth is M-D dimension of proximal box
8/17/2019 14.Cl2 amal.principles2.08.pdf
31/50
PROXIMAL DEPTH
• proximal depth is M-D dimension of proximal box
Syn: axial depth
NOT pulpal depth
8/17/2019 14.Cl2 amal.principles2.08.pdf
32/50
PROXIMAL DEPTH
PRINCIPLE
• 0.5mm into dentin
• 1.25 - 1.5 mm measuredat level of gingival seat
RATIONALE
• suf ficient bulk of amalgam to preventfracture
• maximum thickness of dentin protecting pulp
8/17/2019 14.Cl2 amal.principles2.08.pdf
33/50
AXIAL WALL
PRINCIPLE
• smooth
• straight O-G, parallel tolong axis of tooth
• parallels curvature of
tooth surface B-L
RATIONALE
• optimize adapatationof amalgam to wall
• uniform bulk of amalgam to preventfracture
• maximum pulpalprotection
8/17/2019 14.Cl2 amal.principles2.08.pdf
34/50
AXIO-PULPAL LINE ANGEL
PRINCIPLE
• rounded or beveled
RATIONALE
• reduces risk of amalgam fracture
8/17/2019 14.Cl2 amal.principles2.08.pdf
35/50
GINGIVAL SEAT
PRINCIPLE
• smooth, flat, straight
• perpendicular to longaxis of tooth M-D & B-L
• enamel planed at margin
RATIONALE
• optimize adaptation of amalgam to walls
• resists forces of occlusion
• elimination of friableenamel
A
A’
A-A’
plane margin enamel
8/17/2019 14.Cl2 amal.principles2.08.pdf
36/50
BUCCAL & LINGUAL WALLS
PRINCIPLE
• smooth, straight G-O
• wall nearest functionalcusp convergent 6° G-O
• wall nearest non-
functional cusp parallelslong axis of tooth
RATIONALE
• optimize adaptationof amalgam to walls
• helps lock restoration intooth (retention)
• preserves strength of
cusps (resistance form)
FC NFC
8/17/2019 14.Cl2 amal.principles2.08.pdf
37/50
tangent
8/17/2019 14.Cl2 amal.principles2.08.pdf
38/50
BUCCAL & LINGUAL WALLS
PRINCIPLE
• angle with proximal
cavosurface 90-110°(measured to tangent)
RATIONALE
• optimizes strength of both amalgam and
enamel at margin
t a n g e n
t t a n g e n t
90°110°
8/17/2019 14.Cl2 amal.principles2.08.pdf
39/50
the cavosurface angle is defined as the anglein metal at the margin of a restoration
90° 70°
8/17/2019 14.Cl2 amal.principles2.08.pdf
40/50
BUCCAL & LINGUAL WALLS
PRINCIPLE
• proximal cavosurface
angle is 70-90°(measured to tangent)
RATIONALE
• optimizes strength of both amalgam and
enamel at margin
90°90° 110°
70°
8/17/2019 14.Cl2 amal.principles2.08.pdf
41/50
PROXIMAL RETENTION GROOVES
PRINCIPLE
• placed in B&L proximalwalls 0.5mm deep to DEJ
• directed laterally, not pulpally• extending from G seat to A-P
line angle
• 0.5mm deep gingivally,
fading away occlusally• rounded cross-section
RATIONALE
• provides mechanical lockagainst displacement
proximally• prevents encroachment on
pulp
• prevents undermining
enamel• maximizes retention while
minimizing weakening of tooth
8/17/2019 14.Cl2 amal.principles2.08.pdf
42/50
CAVITY REFINEMENT
PRINCIPLE
• internal line angles well-
defi
ned but not sharp
RATIONALE
• maximizes amalgamresistance todislodgement
• reduces stressconcentration & risk
of subsequent toothfracture
cusp fracture
8/17/2019 14.Cl2 amal.principles2.08.pdf
43/50
cusp f racture
8/17/2019 14.Cl2 amal.principles2.08.pdf
44/50
CAVITY REFINEMENT
PRINCIPLE
• B-G and L-G line angles
have slight radius
RATIONALE
• reduces stress
concentration & riskof subsequent tooth
fracture
• dif fi
cult to condensethick amalgam into
sharp point angles
8/17/2019 14.Cl2 amal.principles2.08.pdf
45/50
CAVITY REFINEMENT
PRINCIPLE
• cavosurface margins
well-defi
ned & well-supported
RATIONALE
• easier to visualize &carve following
condensation• optimize adaptation of
amalgam to margins
• eliminates weak tooth
structure• maximizes marginal
integrity
CAVOSURFACE MARGINS
8/17/2019 14.Cl2 amal.principles2.08.pdf
46/50
enamel
cavosurface marginunsupported, rough poorly defined
CAVOSURFACE MARGINS
tooth surface
CAVOSURFACE MARGINS
8/17/2019 14.Cl2 amal.principles2.08.pdf
47/50
amalgam enamel
cavosurface marginunsupported, rough poorly defined
CAVOSURFACE MARGINS
tooth surface
ditching
8/17/2019 14.Cl2 amal.principles2.08.pdf
48/50
ditching
8/17/2019 14.Cl2 amal.principles2.08.pdf
49/50
CLEANLINESSPRINCIPLE
• cavity is free of debris
& moisture
RATIONALE
• facilitates adaptation
of amalgam to the
cavity
• improves physical
properties of the
restoration by
elimination of voids
& foreign material
8/17/2019 14.Cl2 amal.principles2.08.pdf
50/50
TISSUE PRESERVATIONPRINCIPLE
• rubber dam intact
• adjacent toothundamaged
• gingival soft tissues
not undulytraumatized
RATIONALE
• isolation important to
quality of result
• prevention of post-
operative sensitivity,
inflammation, &
nidus for further
caries attack