Class v Cavity Preparation for Amalgam [Compatibility Mode]

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CARIES may not be the only reasonCARIES may not be the only reasonCARIES may not be the only reasonCARIES may not be the only reason

Causative factor

Abrasion , Erosion & AbfractionAbrasion , Erosion & AbfractionAbrasion , Erosion & AbfractionAbrasion , Erosion & Abfraction couldcouldcouldcouldALSO be responsible for class V lesionsALSO be responsible for class V lesionsALSO be responsible for class V lesionsALSO be responsible for class V lesions

1.1.1.1. The carious lesion usually starts as aThe carious lesion usually starts as aThe carious lesion usually starts as aThe carious lesion usually starts as awhite or chalky line at the gingivalwhite or chalky line at the gingivalwhite or chalky line at the gingivalwhite or chalky line at the gingival 1/31/31/31/3 ofofofof

clinical characteristics

yyyythe labial or buccal surfacesthe labial or buccal surfacesthe labial or buccal surfacesthe labial or buccal surfaces

2.2.2.2. Usually affects multiple teethUsually affects multiple teethUsually affects multiple teethUsually affects multiple teeth( high caries susceptibility )( high caries susceptibility )( high caries susceptibility )( high caries susceptibility )

3.3.3.3. Spread mesially & distally to the axialSpread mesially & distally to the axialSpread mesially & distally to the axialSpread mesially & distally to the axialangles of teethangles of teethangles of teethangles of teeth

4.4.4.4. Causes Cervical sensitivityCauses Cervical sensitivityCauses Cervical sensitivityCauses Cervical sensitivityTh h fTh h fTh h fTh h f5.5.5.5. The more convex is the surfaceThe more convex is the surfaceThe more convex is the surfaceThe more convex is the surface

more liable tomore liable tomore liable tomore liable tocervical cariescervical cariescervical cariescervical caries

6. More frequent among old6. More frequent among old6. More frequent among old6. More frequent among old----aged patientsaged patientsaged patientsaged patients(senile caries)(senile caries)(senile caries)(senile caries)

The Outline Form

• Class V cavity usuallyClass V cavity usuallyClass V cavity usuallyClass V cavity usuallyTrapezoidalTrapezoidalTrapezoidalTrapezoidal outlineoutlineoutlineoutline withwithwithwith straightstraightstraightstraight

marginsmarginsmarginsmargins andandandand round cornersround cornersround cornersround corners,,,,marginsmarginsmarginsmargins andandandand round cornersround cornersround cornersround corners,,,,

with thewith thewith thewith the short armshort armshort armshort arm being thebeing thebeing thebeing the gingivalgingivalgingivalgingival

• Mesial & distal wallsextended to but not encroaching onaxial line angles & Parallel to the M &D tooth outline

Location of marginsLocation of marginsLocation of marginsLocation of margins

D tooth outline

• Occlusal wall located at but notincluding the height of contour

• Gingival wall straight & parallel toocclusal plane at the gum margin

• Axial wall in dentin (0.5 mmunder DEJ)

• convex outwards Mesiodistally &occlusogingival following contour offacial surface……………

provides resistance& maximal pulp

protection protection

Internal anatomy• M & D walls are divergent outwards

(flare mesially & distally )……..tofollow the direction of enamel rods………& to form 9090°° cavo-surface angle………& to form 9090 cavo surface angle

• provide strength for the tooth & amalgam• & prevent undermined enamel walls

• Occlusal & gingival walls formedof 2 planes:

a. Grooved internal dentin plane(mechanical retention lock)

b O t l l f ll i

Internal anatomyInternal anatomyInternal anatomyInternal anatomy

b. Outer enamel plane followingthe direction of enamel rodsTo form 9090°° cavo-surfaceangle ………..resistance

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� If the gingival wall is located oncementum at the root, it is alsoformed of two planes

* internal grooved plane made* internal grooved plane madeof dentin &

* an outer flat plane made ofdentin & cementum

Resistance andRetention

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