14.Cl2 Amal.principles2.08

7/29/2019 14.Cl2 Amal.principles2.08

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CLASS II AMALGAM

Design Principles


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CLASS II


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Class II cavitated caries lesions


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opaque white haloes identify areas of

enamel undermining and decalcificationfrom within

Class II cavitated caries lesions


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radiographic appearance of

the Class II caries lesion


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A

E1 lesion

confined to outer

half of enamel


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B

E2 lesion

reaches into inner

half of enamel


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C

cavitated lesion

spreading radiolucency

at DEJ


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Primary Caries

D1E2


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Primary Caries

D1D2

D3


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Accepted Terminology

extending into proximal

extending gingivally

preparing a proximal box

Jargondropping a box

deepening cervically


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The Class II cavity prepared to receive amalgam has two parts


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the occlusal portion

design principles are the same as for the Class I cavity


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the proximal portion orproximal box

design principles will be presented now


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names of walls for the the occlusal portion of the Class II cavity

are similar to the Class I

Class IClass II


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DISTAL

WALL

LINGUAL WALL

BUCCAL WALL

MESIAL

WALL

DISTAL

WALL

LINGUAL WALL

BUCCAL WALL

Class I

Class II


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PULPAL FLOOR

PULPAL FLOOR

Class I

Class II


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names of walls for proximal portion of Class II cavity


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GINGIVAL SEAT

LINGUAL

WALL

BUCCAL

WALL

DISTAL WALL


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LINGUAL

WALL

BUCCAL

WALL


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LINGUAL

PROXIMAL

WALL

BUCCAL

PROXIMAL

WALL

BUCCAL

OCCLUSAL

WALL

LINGUAL

OCCLUSAL

WALL


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AXIAL

WALL


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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


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names of cavosurface margins for proximal portion of Class II cavity

BUCCAL

PROXIMAL

CAVOSURFACE

MARGIN

LINGUAL

PROXIMAL

CAVOSURFACE

MARGIN

GINGIVAL

CAVOSURFACE MARGIN


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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


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PROXIMAL OUTLINE FORMPRINCIPLE

straight

B & L outlines near

parallel to long axis oftooth

gingival outlineperpendicular to long axis

of tooth

RATIONALE

conservative of toothstructure

resists forces of occlusion


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EXTENSION

a balance between

conservation of

tooth structure and

the need for access

and to removedefective tooth

structure


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PROXIMAL EXTENSIONPRINCIPLE encompasses carious

tissue

eliminatesunsupported enamel

encompassescontiguous fissures

encompassescontiguous

restorations

RATIONALE

eliminates infectedtissue

eliminates weakenedtooth structure

reduces risk ofsecondary caries

maximizes restorationlifespan


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PROXIMAL EXTENSION

PRINCIPLE

clears adjacent tooth by

0.5mm (0.3 - 0.65mm)

RATIONALE

access for matrix band

allows inspection ofrestoration margin

access for finishing


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PROXIMAL DEPTH

proximal depth is M-D dimension of proximal box


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PROXIMAL DEPTH

proximal depth is M-D dimension of proximal box

Syn: axial depth

NOT pulpal depth


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PROXIMAL DEPTH

PRINCIPLE

0.5mm into dentin

1.25 - 1.5 mm measuredat level of gingival seat

RATIONALE

suf ficient bulk ofamalgam to preventfracture

maximum thickness ofdentin protecting pulp


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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 ofamalgam to preventfracture

maximum pulpalprotection


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AXIO-PULPAL LINE ANGEL

PRINCIPLE

rounded or beveled

RATIONALE

reduces risk ofamalgam fracture


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GINGIVAL SEAT

PRINCIPLE

smooth, flat, straight

perpendicular to longaxis of tooth M-D & B-L

enamel planed at margin

RATIONALE

optimize adaptation ofamalgam to walls

resists forces of occlusion

elimination of friableenamel

A

A

A-A

plane margin enamel


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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


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tangent


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PRINCIPLE

angle with proximal

cavosurface 90-110(measured to tangent)

RATIONALE

optimizes strength ofboth amalgam and

enamel at margin

tangen

ttangent

90110


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the cavosurface angle is defined as the anglein metal at the margin of a restoration

9070


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PRINCIPLE

proximal cavosurface

angle is 70-90(measured to tangent)

RATIONALE

optimizes strength ofboth amalgam and

enamel at margin

9090 110

70


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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 oftooth


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CAVITY REFINEMENT

PRINCIPLE

internal line angles well-

defi

ned but not sharp

RATIONALE

maximizes amalgamresistance todislodgement

reduces stressconcentration & risk

of subsequent toothfracture

cusp fracture


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cuspfracture


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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


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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


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enamel

cavosurface marginunsupported, rough poorly defined

CAVOSURFACE MARGINS

tooth surface

CAVOSURFACE MARGINS


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amalgam enamel

cavosurface marginunsupported, rough poorly defined

CAVOSURFACE MARGINS

tooth surface

ditching


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ditching


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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


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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

Date post:	03-Apr-2018
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14.Cl2 Amal.principles2.08

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