amalgam class ii prep

8/17/2019 Amalgam Class II Prep

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CLASS IICLASS IICLASS IICLASS II(pp(pp(pp(pp 658658658658----664664664664,,,, 696696696696----708708708708))))

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Seven Steps of Cavity PreparationSeven Steps of Cavity PreparationSeven Steps of Cavity PreparationSeven Steps of Cavity Preparation

1) Establish the outline form2) Establish resistance form

3) Establish retention form

4) Provide convenience form

5) Removal of remaining caries

6) Finish the cavity walls andmargins

7) Toilet of the cavity preparation


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StepStepStepStep 1111

Outline Form Outline Form Outline Form Outline Form Considerations

– Visualize outline pre-operatively – Gentle sweeping curves - “fluidity”

– Remove undermined enamel

– Extend for preventionMargins on smooth surfaces and self

cleansing accessible areas


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Outline Form Outline Form Outline Form Outline Form Preparation shape

Encompasses carious lesion and caries

susceptible areas


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Ideal PreparationIdeal PreparationIdeal PreparationIdeal Preparation

Fishtail versus dovetail

Dovetails parallel ridges

Outline follows fissures


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– Visualize outline pre-operatively


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– Gentle sweeping curves - “fluidity”


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– Gentle sweeping curves - “fluidity”


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– Remove undermined enamel


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Outline Form Outline Form Outline Form Outline Form

Considerations

– Extend for prevention Margins on smooth surfaces and self cleansing accessible areas


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Outline Form Outline Form Outline Form Outline Form

Considerations

– Extend for prevention Margins on smooth surfaces and self cleansing accessible areas


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Class II Outline Form Class II Outline Form Class II Outline Form Class II Outline Form

Smooth flowing outline (occlusal view)

Include carious pits/fissures and non-coalesced areas (extension for

prevention) Include all of the proximal contact area

90° “exit angles” (occlusal view of box)

Follow tooth contours (proximal view)


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Rounded proximal

Flat proximal contour

BUCCOPROXIMAL WALLand

LINGUOPROXIMAL WALL

- are straight and flat to theaxial wall

- exits 90° at cavosurface

- blend into the isthmus,

preserving the cusps- may or may not use an

“s-curve”


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Rounded proximal Flat proximal contour

S-curve: Transition from proximal wall to buccalor lingual walls; used only as needed


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Class II Outline FormClass II Outline FormClass II Outline FormClass II Outline Form ---- Proximal ExtensionsProximal ExtensionsProximal ExtensionsProximal Extensions

Remove proximalcontact area and

extend the gingival wallto provide 0.5 mm fromthe adjacent tooth

Include all enamel caries and extend forprevention to caries-susceptible areas


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Class II Outline FormClass II Outline FormClass II Outline FormClass II Outline Form

Proximal ExtensionsProximal ExtensionsProximal ExtensionsProximal ExtensionsBuccal and lingual walls are extended,

following adjacent tooth contours, to

provide 0.3 - 0.5 mm clearance

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RGS 1 10-7-14 Hatchet


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Class II Outline FormClass II Outline FormClass II Outline FormClass II Outline Form

Proximal ExtensionsProximal ExtensionsProximal ExtensionsProximal ExtensionsExtensions follow proximalcontours and allow access

for:

finishing and polishing torefine margins

brushing & flossing toreduce caries recurrence

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Resistance Form Resistance Form Resistance Form Resistance Form Flat walls (pulpal, gingival)

Restricted extension(conserve tooth structure)

Adequate bulk (of restorative material)

Failure of resistance form

– Fractured restoration

– Fractured tooth


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Resistance Form Resistance Form Resistance Form Resistance Form Flat walls (pulpal, axial, gingival, etc.)


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Resistance Form Resistance Form Resistance Form Resistance Form Restricted extension = conserve tooth structure


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Resistance Form Resistance Form Resistance Form Resistance Form Restricted extension

Preserve bulk of marginal ridge


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Resistance Form Resistance Form Resistance Form Resistance Form Adequate bulk (of restorative material)

StStStSt 2222


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Resistance Form Resistance Form Resistance Form Resistance Form

Failure of resistance form

– Fractured restoration – Fractured tooth

Cl II R i FCl II R i FCl II R i FCl II R i F


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Class II Resistance Form Class II Resistance Form Class II Resistance Form Class II Resistance Form

1. Flat pulpal wall

2. 1.5 mm minimum pulpal

depth (RGS 1)3. Flat gingival wall (B-L)

4. Axial depth 1.0 mm min.

(0.5 mm into dentin)5. Rounded axiopulpal line

angle

6. Gingival “bevel” followsenamel rods

1

2

3

4

5

6


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Errors in the Proximal Box Errors in the Proximal Box Errors in the Proximal Box Errors in the Proximal Box

Avoid sharps corners, flared, and beveled walls- maintain proximal box at 1.0 mm axial depth

with 90-degree cavosurface margins


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Class II Resistance Form Class II Resistance Form Class II Resistance Form Class II Resistance Form

90-degree to tangent at cavosurface,

“s-curve,” and smooth flowing outline


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Preparing thePreparing thePreparing thePreparing theproximal box proximal box proximal box proximal box

1. Envision box with ideal0.4 mm clearance at proximal

extensions (0.3 - 0.5 mm)

2. Use bur to establish boxform, undermining enamelrods near ideal proximalextensions

0.4 mm

0.4 mm


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Refining the proximal wallsRefining the proximal wallsRefining the proximal wallsRefining the proximal walls

3. Use hatchet or GMT to remove

undermined enamel rods to idealextension to buccoproximal, linguo-proximal, and gingival (0.5 mm) walls

Note that

underminedenamel rods are

subject to failure!

0.5 mm



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Retention Form Retention Form Retention Form Retention Form

Mechanical undercuts and locks

Accessory forms

– Grooves, coves

– Slots, potholes

– Pins



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Retention Form Retention Form Retention Form Retention Form Mechanical undercuts and locks



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Retention Form Retention Form Retention Form Retention Form Accessory forms

– Grooves, coves


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Class II Retention Form Class II Retention Form Class II Retention Form Class II Retention Form

To preventocclusaldisplacement

– Convergence ofbuccal and lingualwalls of occlusal

– Convergence ofbuccoproximal andlinguoproximal walls


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Class II Retention Form Class II Retention Form Class II Retention Form Class II Retention Form

To prevent proximal displacement – Dovetail and buccal and lingual extensions



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Retention Form Retention Form Retention Form Retention Form Accessory forms

– Grooves, coves


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Class II Retention Form Class II Retention Form Class II Retention Form Class II Retention Form To prevent proximal

displacement – Retention grooves at

axiobuccal and axiolingual

line angles


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Retention GroovesRetention GroovesRetention GroovesRetention Grooves

must be in dentin

are extensions of theaxial wall

follow curvature ofaxial wall & DEJ



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Convenience Form Convenience Form Convenience Form Convenience Form

Adequate observation

Accessibility

Ease of operation



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Convenience Form Convenience Form Convenience Form Convenience Form Adequate observation



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Convenience Form Convenience Form Convenience Form Convenience Form Accessibility



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Convenience Form Convenience Form Convenience Form Convenience Form Ease of operation

Class II Convenience FormClass II Convenience FormClass II Convenience FormClass II Convenience Form


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Class II Convenience Form Class II Convenience Form Class II Convenience Form Class II Convenience Form

Axial wall diverges fromproximal surface

Adequate isthmus width for condensation

Cl II I i FCl II I i FCl II I i FCl II I i F


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Class II Inconvenience Form Class II Inconvenience Form Class II Inconvenience Form Class II Inconvenience Form

Axial wall converges with

proximal surfaceDoes not allow for proper

condensationAxiogingival line angleapproaches pulp



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Removing Caries Removing Caries Removing Caries Removing Caries Caries Removal

Removal of decalcified enamel anddentin

Considerations

– Arrest caries process – Solid foundation

– May modify outline, resistance and

retention

StStStSt 5555 R l f C iR l f C iR l f C iR l f C i


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StepStepStepStep 5555: Removal of Caries: Removal of Caries: Removal of Caries: Removal of Caries

Proper outline,

resistance,retention, andconvenience forms

will result inproviding properaccess for

revealing andremoval of allremaining caries

StStStSt 6666


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Finishing Enamel Walls and Margins Finishing Enamel Walls and Margins Finishing Enamel Walls and Margins Finishing Enamel Walls and Margins Create the best marginal seal

Enhance all preparation principles

Finishing the CavityFinishing the CavityFinishing the CavityFinishing the Cavity


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Walls and MarginsWalls and MarginsWalls and MarginsWalls and Margins

Plane proximal and axial walls

Place gingival bevel with gingival margin trimmer


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Perform Toilet of the Cavity Perform Toilet of the Cavity Perform Toilet of the Cavity Perform Toilet of the Cavity

Clean all walls and margins

Remove all debris

Wash and dry, but DO NOT DESICCATE!

Final inspection

amalgam class ii prep

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