Ceramic Restorations Flashcards by sophie rosen

Ceramics: Applications
(5)

-All-ceramic crowns, inlays, onlays,
veneers, FPDs
-Metal-ceramic crowns and FPDs
-Implant abutments (and implants)
-Denture teeth
-Ceramic orthodontic brackets

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Ceramics: Benefits
(3)

Enhanced esthetics due to the absence of metal
and improved light transmission.
-Looks like a tooth!
-Most beneficial for teeth with normally colored
dentin as the dentin color can affect restoration
through the ceramic

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Ceramics: Benefits
Physiologic —
response when properly
contoured and highly
glazed/polished.

gingival

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Why and How does ceramic look so much like a real tooth?
(3)

-Color Replication
-Refraction
-Translucency

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-Color Replication

-Ceramics can be tinted/colored to produce
nearly any tooth shade

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-Refraction

-Ceramics reflect and absorb light rays
simulating enamel

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-Translucency

-Type of porcelain (incisal/dentin/opaque)

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Flexural Strength – ceramics are brittle!

-Defined as the strength of a material in bending
-Stress on the outermost fibers of a bent test specimen, at failure

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Fracture Toughness

-Defined as the resistance to fracture when crack present
-Metals –high FT due to plasticity at tip of crack, absorbs energy, making crack
propagation more difficult
-Ceramics –low FT –little plasticity

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Ceramics — as they are fired

shrink

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Thermal insulator
(2)

–poor conductor of heat
-Coefficient of thermal expansion (CTE) is low. Does not expand and contract
much with heat and cold.

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Ceramics are brittle
Griffith flaws
-A.A. Griffith (1921) suggested that the low fracture strength of glass is
due to the presence of

microscopic flaws in the bulk material. Surface
flaws act as stress initiators and cause widening and propagation of
microcracks through the ceramic material.

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Griffith flaws
-A.A. Griffith (1921) suggested that the low fracture strength of glass is
due to the presence of microscopic flaws in the bulk material. Surface
flaws act as stress initiators and cause widening and propagation of
microcracks through the ceramic material.
-Porosities in the porcelain propagate —
-Damage from
-These porosities can be

cracks
grinding, heat propagate cracks
external or within the material

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Crack propagation

(why ceramics fail at lower than
expected stress)
-Crack will propagate through material, or until a particle
is met which stops the crack growth.

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Stress Corrosion

-Strength is reduced in moist environment.
-Stress-dependent chemical reaction between water
vapor and crack tip, causing crack growth and
fracture with comparatively little occlusal loading
(over long periods).

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Sintering:
(4)

-Ceramic powder/liquid is built up and molded (feldspathic porcelain)
-Process of heating ceramic powder once molded
-Called “Firing” the ceramic
-Sintering is the reduction of porosities between particles as the ceramic
becomes more rubbery.

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Glass Transition Temperature: (Tg)
(4)

-This is a range of temperature where porcelain starts to become molten.
-A transition from solid to rubbery.
-This is typically between 540 and 610 degrees Celcius.
-This is below the ceramic melting point.

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Heat Pressing:
-Relies on
-Restoration is made from
-Also known as

external pressure to sinter and shape the ceramic at high temperature
a Wax pattern (lost wax technique)
High Temperature Injection Molding

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CAD/CAM
(2)

-Computer Aided Design
-Computer Aided Manufacture

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Hard Milling
(2)

-Already densely sintered material
-Silicate, glass ceramics, resin-based
ceramics

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-Soft Milling
(3)

-Partially sintered material
-Zirconia and Lithium Disilicate (e.Max)
-Sintering to be completed in oven AFTER
manufacture

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— are used for the milling process

Blocks

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n the past, there have been limited shade selections. However,

newer multishade blocks have improved esthetics
-Also a stain and glaze done with a furnace can improve
esthetics.

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Types of blocks available:
(3)

Glass Ceramics:
Zirconia:
Resin-ceramics:

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skipped Glass Ceramics:

Vita Mark 2, IPS Emax CAD, Celtra Duo Ultra

skipped Zirconia:

IPS Emax ZirCAD, 3M Chairside Zirconia, CEREC Zirconia

skipped Resin-ceramics:

Cerasmart, Vita Enamic Resin: Telio blocks

skipped CAD/CAM systems:

Itero, E4D, Trios, Planmeca, Carestream. -More systems come on the market each year.

Predominately Glass (veneers) (4)

-Most translucent optical properties -Weakest material -Feldspathic porcelain -Can ETCH

Particle filled Glass Ceramic (eMax) (4)

-Less translucency -increased strength -Lithium Disilicate -Can ETCH

Polycrystalline Ceramic (zirconia) (4)

-Low translucency -Highest strength -Alumina, Zirconia -Cannot ETCH

Resin bonding (3)

-Can bond tooth to ceramic with the etchable ceramics -Use of a “coupling agent” Silane enhances bond strength -Resin cement used – either light cure or dual cure

Reinforcement of the crystalline structure of the ceramic (2)

-Dispersed Crystalline phase – Higher strength and fracture resistance -Lithium Disilicate

Transformation Toughening (3)

-Stress induced transformation -Unique to zirconia -Compressive forces at crack tip retard crack propagation

How again does porcelain break? (2)

-Flexure -Improper loading (askew occlusion)

Resin bonding is a high strength cementation procedure, so bonding ceramics will --- the ability of the ceramic to flex. Therefore, --- strength.

decrease adds

Resin Bonding -Resin bonding–etchable glass ceramics ----% increase in glass ceramic crown strength (4) components

50 HF Etched ceramic surface (retention) Silane coupling agent (bifunctional monomers form a chemical bond) Resin Composite Cement Etched enamel / dentin –adhesive layer

How the resin cement have so much strength: (2)

-The movement of the cement into the dentin tubules forming microtags and into the porcelain spaces (above). This forms a matrix that has great retention.

Veneers -Very thin “sheet” of porcelain as thin as --- mm (minimal thickness) -Tooth preparation is specific and is aimed at providing -Veneers are not under -These are --- bonded to enamel -Can be the most --- dental restoration possible -Can be so thin, underlying tooth color can affect --- properties. -Most technically --- to fabricate

0.3 to 0.5 aesthetics and physical support for the veneer. heavy occlusal loads. resin esthetic optical difficult

Crystalline Reinforcement -By adding crystalline aspects to the ceramic, crack propagation is much more difficult.

Small cracks begin, but then have a harder time causing catastrophic failure.

-Enamel flexural strength is around --- MPa -Feldspathic Porcelain flexural strength is much lower at --- MPa

300 60-70

We discussed how to strengthen the porcelain material previously. One additional method to strengthen this porcelain is to add

a metal substructure. -Yes! The PFM (porcelain fused to Metal crowns)!

Material only used for Veneers

Feldspathic Porcelain

-Enamel flexural strength is around 300 Mpa -Leucite reinforced ceramic flexural strength is --- MPa

120-160

Leucite reinforced Ceramic (Empress) Would you use this material on a posterior tooth? -Crown – -Onlay/Inlay –

No maybe (only where occlusal force is low)

Leucite reinforced Ceramic (Empress) -Would Resin bonding help strengthen this material?

-Yes. It can be etched and therefore retention and strength is increased with resin bonding

Leucite reinforced Ceramic (Empress) -Indications –

anterior crowns, veneers

Flexural strength for e.Max is

360-500 Mpa -Finally stronger than enamel alone!

Due to its increased strength, Lithium Disilicate is used for: (4)

Veneers Anterior and Posterior crowns Anterior bridges (particular cases) Inlays/Onlays with low occlusal forces

Can use resin bonding AND other cements like Resin Modified Glass Ionomer (RMGI)

-Should you use e.Max for a posterior three unit bridge?

-Not Indicated -Increased fracture of material

Zirconia has a --- structure -This provides --- strength -This provides a surface that is not abrasive like porcelain, but instead is

Polycrystalline increased gentle on opposing dentition

Resin Bonding will not increase the --- of Zirconia -Resin bonding will do what for zirconia? ----!

strength Retention

-Zirconia needs the internal restoration surface to be

roughened since it cannot be etched. (Zirconia contains no glass to etch) -Air abrasion -diamond bur

A --- is needed for increased bonding of Zirconia with resin cement

bonding primer

Original Zirconia crown was from Glidewell Lab 10 years ago. -3Y zirconia crown called --- -Horrible -- aesthetic early on -Poorly defined -- anatomy

Bruxir translucency occlusal

3Y Bruxir flexural strength around --- Mpa

1200

Ceramics: Zirconia -Because of its ---, any cement can be used. -Crown has to be

toughness ”fired” and will shrink to fit. Shrinks about 25% during firing.

-How are zirconia crowns so strong: -Transformational Toughening (4)

-Stress induced transformation -Unique to zirconia -Compressive forces at crack tip retard crack propogation

Crack initiated; tensile stress at crack tip causes tetragonal→--- shape change

monoclinic

Volume increase with associated compressive stresses in vicinity of crack tip leading to

crack closure

Phase transformation from tetragonal (T) to monoclinic (M) has associated volume increase (3-5%) →

high internal stresses.

Making Zirconia more translucent: (4)

-Adding more Yttria increases translucency -This results in decreased strength -ITS IMPORTANT TO ASK YOUR LAB WHAT KIND OF ZIRCONIA YOU ARE USING!!!

Ceramics: Zirconia-Improving on original zirconia -To improve esthetics,

a zirconia core is used and then porcelain is fused to create the tooth shape and color.

A --- is a porcelain fused to Zirconia.

PFZ crown

Early candidates in this market were not very successful. Lots of porcelain fractures. However, newer formulations are finding greater success and ethetics! -Monolithic options were/are not very esthetic but are

much stronger and do not fracture easily. If they were esthetic, they were not likely to be strong

Ceramics: Zirconia -Failures? PFZ crowns initially had failures Mostly in the

posterior

Zirconia would not fail (very rare), it would be the --- that would fracture.

porcelain

Zirconia would not fail (very rare), it would be the porcelain that would fracture. (3)

-Lack of porcelain support in zirconia substructure -Occlusion, Occlusion, Occlusion -The bond between the Zirconia and the porcelain would not be able to overcome the difference in Coefficient of Thermal Expansion between the Zirconia core and the veneering porcelain

Ceramics: Zirconia -Additional benefits With some dark teeth, a zirconia core PFZ crown can be used to

mask dark dentin

Ceramics: Zirconia -Additional benefits -Because Zirconia is not brittle, any --- technique can be used. -Zirconia copings can be as thin as --- because Zirconia is strong -A monolithic zirconia crown preparation can be very --- similar to gold or pfm crown preparations -Zirconia is friendly to opposing teeth. It is considered --- -Can use --- finish lines for preparations -Zirconia masks dark --- and is beginning to balance that masking with translucency

cement 0.4mm conservative “Wear Friendly”. chamfer or shoulder dentin

-If Zirconia is the Superman of crown material, what’s Zirconia’s kryptonite? -Zirconia’s use is now very ---. Its only really 10 years old in the market. While its strength is high, that strength is compromised to make it aesthetic. What’s the sweet spot for this balance?

heavy

If you want the most esthetic anterior restoration, what material would you choose? - Veneer – -Crown –

Feldspathic Porcelain e.Max or Empress

If you want the most esthetic posterior restoration, what material would you choose? -Crown – -Crown -

e.Max 5Y Zirconia

If you have a bruxing patient, what posterior restoration material would you use? -Crown – -Crown –

3Y Zirconia Gold

Ceramics: Comparison: Occlusion Anterior Teeth (2)

-Lower occlusal forces – Less strength requirement – higher esthetic requirement -Feldpathic Porcelain veneer resin bonded are still the most realistic tooth restoration

Ceramics: Comparison: Occlusion Posterior teeth (2)

-Higher occlusal forces – higher strength requirement – less esthetic requirement -What does the patient present with? Not a grinder – e.Max or Zirconia

Ceramics: Comparison: Occlusion Bruxer/Clencher and needs a bridge? (3)

-fully veneered porcelain not a great option -Recommend monolithic zirconia or PFM. -Possible monolithic material with buccal porcelain.

Ceramics: Comparison: Occlusion Ceramic wear on opposing teeth (4)

-Be aware of this side affect of ceramics!! -Ceramics with glass wear opposing teeth. -Zirconia less so -Gold and metal occlusal least amount of wear.

Glass Ceramic Veneers -Only adjust after -Use -Polish with - --- surface should not be adjusted if at all possible

seated and bonded with resin cement (too fragile to adjust outside the mouth predictably. fine diamonds with a little water diamond impregnated polishing paste Internal

e.Max (Lithium Disilicate) (4)

-Adjustment outside the mouth is acceptable -Fine diamond with a little water -Polish with diamond impregnated polishing paste -Internal surface should not be adjusted if at all possible

Zirconia (4)

-Adjustment outside the mouth is acceptable -Fine diamond with a little water -Polish with diamond impregnated polishing paste -Internal surface needs either air abrasion or diamond bur roughing prior to cementing!

Ceramics: Adjusting -After adjustment with bur is done: (3)

-Course polisher -Fine polisher -Felt wheel or brush with fine diamond polishing paste

Resin Cements -Requires --- free environment -Required for -Requires --- for etched ceramics

moisture low strength ceramics silane coupling agent

Primer containing MDP (methacryloyloxydecyl dihydrogen phosphate) placed on zirconia can enhance the

chemical bond to cements containing resin.

Resin Modified Glass Ionomer -Contraindicated in -Acceptable for ---

low strength ceramics -Water absorption with setting of cement leading to slight expansion and possible fracture of ceramic at thin margin area Zirconia

Ceramic Restorations Flashcards

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