l3 - metal ceramic preparations

8/10/2019 L3 - Metal Ceramic Preparations

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The metal ceramic crown preparation


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INDICATIONS

Anterior teeth that require complete coverage.

Typical indications are similar to those for all metal complete crowns.


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CONTRAINDICAIONS

Patients with active caries or untreated periodontal disease.

In young patients with large pulp chambers.

More conservative restorative option such as a composite resin or porcelain

laminate veneer can be used.


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ADVANTAGES

combines, to a large degree, the strength of cast metal with the esthetics of an

all-ceramic crown.


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Preparation

The clinical procedure to prepare a tooth for a complete cast crown consists ofthe following steps:

Occlusal guiding grooves.

Occlusal reduction.

Axial alignment grooves.

Axial reduction.


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Guiding grooves


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Occlusal reduction

The occlusal reduction and functional cusp bevel are planed smoothwith a no.

171L buror

when the bur is used to instrument the seating groove


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Axial preparation

A uniform reduction of approximately 1.2 mm is needed ove

the entire facial surface. To achieve adequate reductiowithout encroaching upon the pulp, the facial surface mus

be prepared in two planes that correspond roughly to the tw

geometric planes present on the facial surface of an uncu

tooth.


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If the facial surface is reduced in one plane that is an extension of the gingivalplane, the incisal edge will protrude, resulting in a bad shade match or an

overcontoured "block." If the facial surface is prepared in one plane that hasadequate facial reduction in the incisal aspect, the facial surface will be

overtapered and too close to the pulp.


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Axial preparation The buccal wall are reduced with a flat end diamond bur, whose sides will produce

the desired axial reduction whileits tip forms a shoulder finish line.


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Over-tapperedUndercut


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FinishingAll of the axial surfaces are smoothed with a round carbide

finishing bur or fin grit diamond bur whose size and shape

enable it to finish the chamfer finish line as well.

Wing type

preparation

Wingless

preparation


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Metal ceramic restorations

DegazingOpaquingDentineEnamelFinishing

and Glazing


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l3 - metal ceramic preparations

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