Class II amalgam restorations Flashcards by Rachel Sladden

Embrasure

V-shaped valleys between adjacent teeth

-provide spill way for food to escape during chewing which essentially aids in self-cleansing process

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Retention

Use pear-shaped bur

Undercut

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Manipulation and adaptation of amalgam

Good condensation / effective packing to ensure marginal seal

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What needs to be considered

Method of retention for material of choice
Prevention of recurrent caries - elimination of microleakage
Assist remineralisation of tooth tissue
Longevity under occlusal load - fracture and wear resistance
Protect tooth from mechanical failure
Aesthetics

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Class II

Lesions occurring between posterior teeth only

Size can vary from moderate involvement to bulk loss of tooth structure

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Direct restorative materials

Classified as plastic i.e. readily deformable when first mixed
Placed into prepared cavity whilst still in that condition
Modelled/ moulded into appropriate shape e.g. amalgam

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Class II cavity preps if interproximal

Have to drill all the way down through marginal ridge

Try to keep thin enamel at base

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Define D1, D2, D3, D4

D1: initial caries
D2: enamel caries
D3: caries of dentine
D4: pulpal involvement

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Isthmus

Central portion of cavity prep on the occlusal surface of a bicuspid or molar
You have cut it too wide
Try to keep it as narrow as possible

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Iatrogenic damage

Operator damage e.g. on adjacent tooth
Would fail exam
Must inform patient - candour
Avoid by using matrix band

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Axial grooves or locks

For added retention

Locks in dentine not enamel (enamel will shatter)

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Axial wall

Wall closest to pulp
Don’t cut too deep
Maybe put liner there to protect it

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Principles of cavity prep

Do not damage adjacent tooth
Access should be sufficient to allow adequate visualisation of caries and to allow complete removal
Prepare below contact point
Prepare just into embrasures so that margins are visible and can be finished well
Do not leave unsupported enamel at margins
Removal of caries at ADJ

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Wooden wedge

To separate contact point

-for adapting a matrix band to the proximal part of a cavity

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Ditching

Marginal breakdown

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Marginal ridge

Rounded borders that form the mesial and distal margins of the occlusal surface of a tooth
Meant to deflect food from fossa, stops food from getting trapped in contact area

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Indirect restorative materials

Materials usually formed in lab and finished restoration cemented into placed, e.g. Full Gold Crown

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Slot and box

1 - 1.5mm deep box like grooves prepared in dentine to > SA

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Occlusal lock

Dovetail

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Changing concepts

Improved amalgams
Instruments with v small working points
Amalgam bonding systems
Adhesive restorative materials
'If in doubt prevent' rather than 'if in doubt fill'

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Principles of cavity prep

When to extend or not: if proximal lesion visible

If proximal lesion visible & access good then marginal ridge can be conserved

When to extend or not: if proximal lesion is not visible, access is difficult or there is <2mm tooth structure below marginal ridge (occluso-gingivally)

Access through marginal ridge advised

This will produce a small box form sufficient to eliminate lesion

When to extend or not: if tooth is caries free occlusally

NOT necessary to cut out the fissure

Extension is a balance

Between conservation of tooth structure and need to remove defective tooth structure

When to extend or not: where occlusal caries and/ or removal of an old restoration have required extending occlusally

An occlusal lock/ dovetail can be prepared to retain the approximal part of the restoration

Where is initial cut made in Class II prep? What bur should be used?

Initial cut made through marginal ridge to penetrate caries and then widened bucco-lingually Diamond pear shaped bur or tungsten carbide bur

Proximal plate

Can be fractured off with a hand instrument to avoid damage to adjacent tooth (or can you use a matrix band)

What would you remove the proximal wall with?

Gingival margin trimmer

Most important place for caries to be removed from

ADJ

What is the size of the cavity determined by?

Determined by size of carious lesion, extension beyond this should be minimal

How is retention from occlusal forces derived?

From a 2-5 degree divergence of the walls towards floor in both parts of the prep

Where should the margins of the box extend to

Just outside the contact area unless caries dictates otherwise

Exception to box design

When using adhesive materials e.g. composite

Principles of retention for amalgams

Relies on mechanical interlocks | A degree of adhesion can be developed through use of luting or bonding agents

What type of restorative material is an amalgam classed as?

Direct plastic restorative material

Cavo surface angle

Above 70 degrees, preferably 90 degrees to prevent ditching

Accepted minimal dimensions for amalgam

2mm occlusally and 1mm - 1.5mm elsewhere i.e. proximal box | Sufficient bulk to prevent fracture, max thickness of dentine protecting bulk

Deep preps

May require base or liner

Proximal box area

Fractured margins need to be planed with gingival margin trimmer to remove fragile enamel prisms, which could break off and affect marginal seal

Proximal box design amalgam

Retention grooves places B&L 0.5mm deep to ADJ (dentine) gingivally, fading away occlusally, rounded in cross section Directed laterally not pulpally

Extension onto occlusal surface

Prone to fracture at isthmus therefore sufficient depth must be provided here Width of isthmus should not be over-cut Axio-pulpal line angle should be rounded or bevelled to reduce risk of amalgam fracture

Matrix bond and wedges

Avoid creation of overhang at cervical margin | Ensure good contact point with adjacent tooth

Matrix systems purpose

Substitute for missing walls Create contact point Restrict extrusion of amalgam and formation of overhangs or ledges Provide contour for proximal surface restoration Allow adequate surface texture in areas inaccessible to burnishing

Types of matrices

``` Siqveland Tofflemire Automatrix Omnimatrix and luciwedges 'V' ring/ half band matrices ```

Contour

Conves side of spoon excavator used to impart convex contour to matrix band Achieve good contact area with adjacent tooth Ensure dental floss placed below contact point to assist removal of ledges & excess amalgam

Condensing amalgam

Using amalgam pluggers or condenser Adaptation of amalgam to walls of prep Eliminating voids Incremental placement of 1mm thickness essential to ensure max condensation

Carving

Wards carver e.g. No 2 or excavator | Marginal ridge should be carved, taking care not to over carve or miscarve

Post carve burnishing

Light rubbing over surface of carved amalgam with burnisher | Do not use heavy forces, avoid margins

If amalgam soft after carving

Wipe with cotton roll saturated in water to proved additional smoothing

After burnishing

Check occlusion