14.Cl2 amal.principles2.08.pdf

8/17/2019 14.Cl2 amal.principles2.08.pdf

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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 or proximal 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 of tooth

• 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 of secondary 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 of restoration 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 of amalgam to preventfracture

• maximum thickness of dentin 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 of amalgam to preventfracture

• maximum pulpalprotection


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AXIO-PULPAL LINE ANGEL

PRINCIPLE

• rounded or beveled

RATIONALE

• reduces risk of amalgam 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 of amalgam 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 of both amalgam and

enamel at margin

t a n g e n

t t a n g e n t

90°110°


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

90° 70°


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PRINCIPLE

• proximal cavosurface

angle is 70-90°(measured to tangent)

RATIONALE

• optimizes strength of both amalgam and

enamel at margin

90°90° 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 of tooth


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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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cusp f racture


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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

14.Cl2 amal.principles2.08.pdf

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