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28 Cards in this Set
- Front
- Back
What are the Basic PFM Margin Designs?
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1.Conventional metal facial margin
2. "Collarless" facial margin 3. Shoulder porcelain Labial margin |
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What is the range for the conventional facial metal collar?
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-Facial: 0.2-1.0 mm wide
-Lingual: as wide as you want |
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What margin design is described as "disappearing facial collar"?
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"Collarless" Facial margin
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In collarless facial margin what end at the margin/tooth interface?
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Porcelain, opaque, metal all end at the tooth interface
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List the range of mm for the layers in the PFM Crown/Abutment "Sandwich"?
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-Prepared tooth
-Cement layer: < 25 microns -Metal Substructure: 0.3-0.5mm -Opaque layer: 0.3 mm -Body Porcelain: 1.0mm - more |
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How do you get metal, opaque and body porcelain to all converge at a finite, discrete, sharp margin position?
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It impossible-three materials cannot occupy the same location spatially simultaneously-you either have metal, opaque or porcelain that is exposed at the margin
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What is design flaw of having metal, porcelain, opaque exposed?
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-Metal can be polished
-Porcelain can be polished and glazed -Opaque can't neither occur, so it plaque retentive (causes periodontal and recurrent caries issues) |
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What is the design "flaw" of the margin?
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If the margins do not fit, there's no metal to be able to burnish it closed (it fits, or remake)
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What affect alloy type on the crown?
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Depending on the alloy type, porcelain applicaiton cause cause the margin to distort (porcelain firing contraction) and become open
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What describe Shoulder porcelain margin?
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-360 circumferential porcelain margins, metal substructure
-Difficult to make form lab standpoint |
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What is the advantages and disadvantages of Shoulder porcelain PFM crown?
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Advantage: Improve (maximize) esthetics by 1) eliminate the display and discoloration of metal, 2) Maximize thickness of gingival porcelain
Disadvantage: Agressive preparation: potential pulpal embarrassment, weakens remaining prep. tooth structures Note: Perhaps weaker and more brittle margin |
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What is preparation parameters for Shoulders margin?
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-Occlusal reduction: 2.0 mm
-Labial Shoulder reduction: 1.3-1.5 mm infal shoulder width -Shoulders extend from mid-mesial to mid-distal -Metal chamfer reduction on lingual half of tooth (0.8-1.3 mm) -Transition sonize in mid-proximal areas |
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What instrument is used to do a shoulder margination?
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-TGE 1.4:
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Shoulder facial margin should be in what range of degree?
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90-110
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-If the angle formed between shoulder and the external root surface is < 90m there is unsupported ____ ____ .
-If the angle is > 110, there is unsupported ____ on the crown |
-Unsupported tooth structure
-Unsupported porcelain on the crown when over 100. Note: Margin must be smooth |
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What type of margin is on the lingual margin?
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Chamfer margin
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The end-cutting diamond for shoulder prep can be used for smoothing and lower the prep. ledge (T/F)
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False: Primarily for smoothing not lower the prep. ledge
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What would happen you keep don't keep the diamond moving and use water spray on the shoulder diamond bur?
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You will preare facets on the margins
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Margins should be smooth, "_______" on natural teeth
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Glassy
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What are the marginal configurations?
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-Light chamfer
-Heavy chamfer -Shoulder -Combination (Labial shoulder, lingual chamfer) |
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What restoration uses light chamfer margin?
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-0.3-0.5 mm
-Gold restorations -Wide metal lingual collars of PFMs |
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Why would you ever leave the metal collar exposed on an anterior tooth
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-Porcelain/metal junction still have the same design flaw as collarless margin. Most optimum material to place in contact with tissue is either metal, or porcelain (not opaque)
-Lower lip will over this exposure of metal 99% of all pt. |
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What restorations uses heavy chamfer margin?
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-1.0-1.5 mm dimension
-Narrow collars/collarless PFM restoration -Procera (allceramic) and other all-ceramic restorations |
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How much space would you want vertically in a narrow metal collar PFM crown?
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-0.2-0.3 mm vertical height to facial collar
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Ceramic coping-has same dseign requirements as metal as for margin (T/F)
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True
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What restoration use Shoulder Margin?
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-1.0 -1.5 mm
-Shoulder porcelain PFM restorations: 1.3 - 1.5 mm collar width -All-ceramic restorations: 1.5 - 1.8 mm |
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-Gold Restoration: ___ chamfer
-Procera (Allceram) restoration: must have ___ ___ -All other all-ceramic crowns: can have ____ or ___ ____ -PFM restoration: 1. Wide metal collar: __ __ 2. ____ / ____ : heavy chamfer 3. Procelain margin: ____ ___ |
- Gold: light chamfer
-Procera: Heavy chamfer -Other all ceramic: heavy chamfer or shoulder -PFM restoration: 1. Wide: light chamfer 2. Narrow metal collar / collarless 3. Shoulder margin |
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What is the procedure in crown construction?
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-Impress, pour working cast
-Fabricate metal framework- stop metal at shoulder/axial wall junction, or 1-2 mm short (coronal to shoulder) - Apply opaque porcelain (2 firings) -Apply shoulder porcelains (may take 2-3 applications/firings) -Apply body/incisal porcelain -Adjust, occlude, characterize, glaze and polish |