Full Metal Crown Prep

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FULL VENEER CROWN PREPARATION

“That which is finished today has little inherent value, only over time will it become invaluable as a work of art.”

FULL METAL CROWN OCCLUSAL REDUCTION

Planar reduction is started using a medium coarse tapered round ended diamond (6856-016)

Objective is to achieve reduction of the occlusal contours producing planar surfaces

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Make depth orientation grooves on each triangular ridge and each primary developmental groove on facial and lingual

inclines


Reduction of lingual cusps to 0.8 mm (non-functional cusp)

Depth orientation grooves on facial cusps are initially placed at 1.2 mm (functional cusp)

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Comparing the depth groove to the measured

diameter of the diamond bur as a

gauge

Also a 1.0 mm or 1.5 mm enamel chisel can be used to judge depth of depth orientation grooves


Final refinement of occlusal reduction will be done with

final finish

Occlusal reduction generally establishes the planes while initiating reduction

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Check occlusal clearance with strip of red rope wax and compare translucency of imprints of cusps-look for areas that are too thin - the handle helps orient wax bite

facial

FULL METAL CROWN FUNCTIONAL CUSP BEVEL

Placed with medium coarse round ended tapered diamond (6856-016)

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Place depth reduction grooves at 1.2 mm on functional cusp, tapering gingivally to no reduction at the junction of the upper 1/3 of facial cusp


Chisel can help to determine if the amount of reduction is close to 1.2 mm paralleling the angle of the opposing occlusal cusp incline

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FULL METAL CROWN FACIAL & LINGUAL AXIAL REDUCTION

Use medium coarse tapered torpedo-ended diamond (6877K-014) bur

Produces a distinct crisp chamfer finish line

FULL METAL CROWN AXIAL REDUCTION

Facial reduction maintained vertical without over-tapering

Lingual reduction the bur is kept vertical without over- tapering and still creating a definite chamfer

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FULL METAL CROWN AXIAL REDUCTION

Facial and lingual reductions are carried into the proximal with out damaging adjacent teeth to create an island of tooth structure between each adjacent tooth

FULL METAL CROWN PROXIMAL REDUCTION

Initial prep is started with with medium coarse needle diamond (852-012)

Second part with medium coarse flame diamond (862-010) and fine flame diamond (8862-010)

Last with medium coarse tapered torpedo-ended diamond (6877K-014)

Needle Flame Chamfer

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Initial prep with medium coarse needle diamond (852-012) moved in up and down sawing motion until the contact is opened

Objective is to open the mesial and distal enough to be able move to the medium coarse flame diamond (862-010)


Initial preparation with medium coarse needle diamond (852-012) will partially open the contact, but not allow the medium coarse round ended diamond (6877K-014) to fit

Second step is to open space with tapered medium coarse flame diamond (862-010) and fine flame diamond (8862-010) to begin to form the chamfer line

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Lastly use the medium coarse tapered round ended diamond (6877K-014) to refine the finish line

The chamfer finish line is refined at 0.5 mm above the gingival crest in the proximal on mesial and distal surfaces

FULL METAL CROWN PROXIMAL REDUCTIONS

Common error made is to produce a “scallop” at each line angle where the diamond is not brought completely through at the same level

Using a periodontal probe check the draw path between facial and lingual axial reductions

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FULL METAL CROWN Final Finishing

Use fine round ended tapered diamond (8856-016) to go over the occlusal surfaces

Remember when finish lines that are cut with medium or coarse grit diamonds always need smoothing with fine grit diamond

They retain enough microscopic roughness to help to retain the restoration, yet appear smooth visually


Use fine tapered round ended diamond (8856-016) to go over the occlusal surfaces to refine planar shape

Final depth of reduction should be defined at this point to 1.0 mm on lingual non-functional cusp and 1.5 mm on facial functional cusp

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Use fine tapered round ended diamond (8856-016) to go over the functional cusp to smooth and finalize reduction of incline to 1.5 mm at the cusp tip


Use fine tapered torpedo-ended diamond (8877K-014) to smooth and define final chamfer finish line on facial

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Use fine tapered torpedo-ended diamond (8877K-014) to smooth and refine final chamfer finish line in the proximal surfaces

Use fine tapered torpedo-ended diamond (8877K-014) to smooth and refine final chamfer finish line on lingual

FULL METAL CROWN Final Axial Reductions

Final chamfer finish line is adjusted to the height of gingiva at 0.5 mm from the gingival crest

Final preparation axial reductions should be about 6-8 degrees of total occlusal convergence to allow for proper path of draw of restoration

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FULL METAL CROWN SEATING GROOVE

The initial seating groove is placed using the 169L as a guide

Place groove to full diameter of 169L carbide bur checking the draw against the mesial and distal surfaces


Also can check vertical alignment of seating groove using a periodontal probe placed into groove compared to mesial and distal taper

Hold 169L carbide bur against the mesial and distal taper before placing the groove

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After 169L, groove is enlarged/adjusted following the overall draw to the full depth of 171 carbide bur

Groove should extend to 0.5 mm above chamfer finish line and a definite gingival seat created

FULL METAL CROWN The Final Preparation

All line and point angles should be blunted

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FULL METAL CROWN Features & Functions

Functional cusp bevel

Seating groove

Planar occlusal reduction

Axial Reduction

Structural durability Structural durability

Retention and resistance

Retention and resistance

FULL METAL CROWN Clinical Mandibular Full Veneer Crown

Full Metal Crown Prep

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