Metal ceramic crowns Flashcards by Caleb Houghton

how is this possible?

The Morphology Of Metal Ceramic
Single Crowns & Fixed Partial Dentures
Should _______ simulate natural morphology

Closely Simulate Natural Tooth Morphology
possible with adequate tooth prep

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how tall must an anterior crown prep lingual wall be

3mm

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what is an MCC? what is advantage of it?

A metal casting (coping) which fits over the prepared tooth with
ceramic fused to it.
Combines the strength and accuracy of cast metal with esthetics of
porcelain.

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what could this be due to?

Indication for Metal-Ceramic Restorations

Need for full coverage with esthetic demands due to:
Extensive tooth destruction
Large restorations / undermined enamel
Opposing ceramic surfaces

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appearence? R and R? fracture? strength? prep?

Advantages of Metal-Ceramic Restorations

Natural appearance - esthetics
Retention and resistance qualities of full crown
More resistant to fracture than all-ceramic / dependable fabrication of FPD
Greater strength w/ less reduction than all-ceramic
Ability to have metal occluding surfaces
Preparation is less demanding than Partial Veneer Crown

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what finish lines can be used with a MCC

chamfer, shoulder, shoulder bevel

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are shoulder bevels superior for MCC

It is certainly acceptable to use such a finish line but it does not make the crown fit better and it does not work with a porcelain margin

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thickness of porcelin? overcontouring?

shoulder finsih lines provide?

provide greater cervical space for an esthetic thickness of porcelain without overcontouring the crown and can be used with porcelain margins

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why use a shoulder finish line

Need for optimal porcelain thickness near the margin for esthetics and particularly when optimal reduction is not possible

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finish line form and gingival trauma

form can influence trauma to gingiva

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ease? needed for what crowns? compared to sharp?

Why Use A Shoulder With A Rounded
Axiogingival Line Angle?

Easier to prepare than a sharp angle
Required for any crown that will be milled
Produces less tooth weakening than sharp axiogingival line angles for small teeth or RCT, teeth that will be subjected to greater force since they are FPD abutments, and teeth with
substantial secondary dentin where there is very little pulp space remaining (older patients)

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when to use a metal collar at the margin

ease of fabrication in non esthetic zones

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how could a metal collar be used in an esthetic zone

subgingival margin

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Metal-Ceramic Facial Margin Designs and Finish Line Geometry

metal collar would be in non esthetic zones usually
porcelin shoulder should only be used when occlusal forces are low
disappearing margin can allow metal to support the porcelin

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MMC have what finish line on the lingual

light chamfer

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what should not be violated with a metal collar or any margin?

biologic width (2mm)

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minimal reduction helps prevent?

overcontouring= impingment on soft tissue and possible food trap

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esthetics/ improving gingival response?

why use a shoulder finish line

Enhanced cervical esthetics
When there is gingival inflammation due to overcontoured crowns and you want to make slightly undercontoured crowns to improve the gingival
response

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caries?

previous restorations?
tooth fx?
root?
R/R?
Esthetics?

Legitimate Reasons for Extending
Margins Subgingivally…

Existing caries
Extensions of previous restorations
Subgingival tooth fracture
Root sensitivity
Retention/ Resistance
Esthetics

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To hide a ceramic or metal-ceramic margin for esthetics, subgingival margin must:

Should not extend more than ½ way into sulcus.
Well-adapted, smooth, proper axial contour

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preserving perio with axial contours

Emergence Profile: the part of the axial contour that extends from the
base of the gingival sulcus past the free margin to the height of contour.
Straight or slightly concave; not bulky or excessively convex

* fx?

?stresses
thickness?

Problems with Porcelain / Ceramics

Porcelain is subject to brittle fracture if thin
Internal stresses
Excessive thickness (>3mm) with no support

porcelin abrassion

can be abrasive to teeth in occlusion, must adjust occlusion or have procelin antagonist

how to prevent porcelin wear

porcelin antagonist
polish porcelin
occlusal adjustment

Metal-Ceramic Crown vs. Complete Metal Crown

*Advantages: * Esthetics *Disadvantages: * Increased removal of tooth structure

Metal-Ceramic Preparation Requirements are based on:

1. Fundamentals of Tooth Preparation: 2. Material requirements (components): 3. Esthetic requirements

_____ angle of margin / ________ finish line → allow for? accomplished how?

acute; obtuse decreased marginal gap. accomplished with Bevel

MCC cervical finish line depends on

shape and bulk of the margin marginal adaptation degree of seating

ideal bevel angle

Margin angles of less than ___ may produce a metal margin that is too thin and weak. ideal margin angles range?

25 degrees | ideally 35-55

biologic width

* The combined connective tissue-epithelial attachment from the alveolar crest to base of the gingival sulcus (approximately 2 mm). * (+ 1 mm for a healthy gingival sulcus = 3mm free gingival margin to alveolar crest (must be 3mm from prep to gingival sulcus base

MCC F-L prep

* Parallel to the facial cervical 1/3 - 2/3 of prep * Lingual wall height is limited: need “ideal” taper for resistance form in F-L direction which prevents dislodgment in protrusive and lateral

most retention of MCC anterior comes from?

parallel M-D walls

components of MCC crown and deminsions

* Metal coping: 0.3-0.5 mm veneered areas and 0.8-1.0 mm un-veneered areas * Opaque porcelain: ~ 0.1-0.2 mm * (Shoulder porcelain) ~ 0.8 mm * Gingival, body, and incisal porcelain: 0.8 – 1.5 / 2 mm

why do we use a two plane facial reduction? too much or too little?

Allows adequate reduction for uniform color / contours and resistance. Inadequate reduction → bulky contour or opaque “bright spot” Over-reduction → decreased resistance / pulpal insult.

single plane under reduction seen as

bright spots: light reflection from the opaque porcelain

single plane over reduction seen as: how much reduction at cervical is too much? amount removed increases with increased? increased TOC and resistance?

* Pulpal “blush” / pulpal exposure * Axial reduction → approaches pulp quickly * 1.2 – 1.5mm at cervical is often too much * Amount removed ↑ with ↑ TOC preparation * ↑TOC = ↓Resistance form

how to establish facial reduction

depth grooves

Uniform proximal reduction facilitates:

the development of normal appearing proximal color and translucency

proximal porcelin vs proximal wing

Porcelain proximal surface allows light transmission Adequate reduction through interproximal is necessary *Proximal wing of preparation → metal in proximal → blocks light transmission

Elimination of proximal wings with: also allows for?

Elimination of proximal wings with gradual transition from facial to lingual allows more esthetic proximal porcelain surface.

how to eliminate proximal wings

Extension of facial shoulder reduction slightly greater than 1mm lingual to contact; gradual blend to lingual

ant MCC shoulder depth

1.2mm

* Finish Line Geometry of ant MCC

* Modified (Radial) Shoulder or disappearing margin with heavy chamfer

# * facial is often where? why? * supragingival? when? * may depend on? * Margin Placement Anterior Teeth:

* facial is often subgingival for esthetics * supragingival if no significant esthetic contraindication * may depend on the type of ceramic restoration used and framework design

metal collar width/ pros and cons

* Width: 0.3-0.5mm * Marginal integrity * Finish * Compromised esthetics

finish lines used with metal collar

* Shoulder with bevel * Heavy chamfer

why use a metal collar

* Ease of fabrication * Include thin, unsupported tooth structure * Extend margin apically with less tooth reduction

MCC reduction on posterior occlusal surface

1.5 mm thickness – porcelain + 0.5 mm thickness – metal 2.0 mm total

using metal occlusion with MCC allows for?

USE METAL ON FUNCTIONAL CUSPS, MAINLY USED ON MAXILLARY (LINGUAL=FUNCTIONAL) * less tooth reduction * less opposing tooth wear * stronger restoration *1.5mm occlusal reduction

Porcelain Occlusion * where? generally not which teeth? * Opposing _____ surfaces * ___mm occlusal reduction

* Esthetic zone * Generally NOT 2nd Molars * Opposing ceramic surfaces * 2.0mm occlusal reduction

# less than this? minimal lingual wall height on ant preps

2-3mm | without this dislodged in protrusove and lateral movement