Dental Zirconia explained from porcelain covered to monolithic-multilayerd restorations

Man made solid objects formed by baking non-metallic inorganic minerals at high temperatures.

Ceramics

What is Transformaiton toughness?

Tetragonal —> monoclinic

Increase in size 3-4%

Tensile —> compressive

Transformation toughening

The ability of zirconia to arrest _______ ______ by changing its phase at the cracks edges from tetrgaonal to _______. Thus, the size of the molecules ______, and tesile stresses are replaced by _______ stresses.

crack propagation

monoclinic, increases

compresive

Why zirconia? (2)

The widespread use of CAD/CAM technology

Less expensive and less time consuming option when compared to porcelain fused to metal restorations

What are the 2 ways to classify zirconia?

Monlitihic vs layered

Single vs multi layered

The amount of yttria

Monolithic

The key factor in classifying dental zirconia is what?

yttria content

What form is 3 mol% yttrium oxie in?

tetragonal

What form is 5 mol% yttrium oxide in?

cubic

What form is 4 mol% yttrium oxide in?

tetragonal or cubic

Monolithic Zirconia 3y:

• _____mol% ytrria

• Greater than ____% tetragonal

• Less than _____% cubic

• High ___________

• Low ___________

3

85%

15%

strength

translucency

What are the 2 uses of monolithic zirconia 3y?

1. Posterior singlu unit crowns

2. Fixed prosthetic devices such as birdges

Monolithic Zirconia 3Y: preperation

• Margin?

• Occlusal manufacutre?

• Occlusal studies?

0.5-0.8mm margin, rounded shoulder or heavy chamfer

0.6mm

0.7-1.0mm

Monolithic Zirconia 4Y:

• _____% tetragonal

• ______% cubic

• _______ strength compared to 3Y

• Acceptable _________

75%

25%

Lower

translucency

What is monolithic zirconia 4Y used for?

Single unit restorations (premolar area)

Monolithic Zirconia 4y: preparation

• Margin?

• Oclussal manfuacture?

• Occlusal studies?

0.8-1mm rounded shoulder or heavy chamfer

1mm

1.2mm

Monolithic Zirconia 5y:

• ______% tetraonal

• _______% cubic

• Enhanced _________

• Low _________

• ________ toughness

Less than 50%

More than 50%

translucency

strength

transformation

What are the 2 uses of monolithic zirconia 5y?

1. Anterior crowns

2. Alternative lithium disilicate (emax)

Monlithic Zirconia 5y prep:

• Margin?

• Occlusal manufacture?

• Occlusal studies?

1mm, rounded shoulder or heavy chamfer

1mm

1.5mm

Layers Zirconia:

• What does PFZ mean?

• Core material?

• Core?

• High _________

• Low __________

Porcelain fused to zirconia

Porcelain covered

3 mol% yttria

strength

translucency

Layered Zirconia:

• Porcelain —> _________ zone

• Reduction _____ and _______

• Core mm?

• Porcelain mm?

estheic

core and porcelain

0.6mm

1.2mm but less than 2mm

What happens when you have more than 2mm of unsupported porcelain on layered zirconia?

Porcelain chipping

Multi shade layered zirconia:

• The yttria content is the _______ thoughout the whole restoration

• The whole restoration is made of what?

• The restoation has different ______ in it.

same

3Y,4Y, and 5Y

shades

% of part of multi layered zirconia block:

• Dentin?

• Transition layer 1?

• Transistion layer 2?

• Enamel layer?

35%

15%

15%

35%

Multi shade layered zirconia:

• Preperation guidlines and indication follow what?

yttria content

Multi yttria layered zirconia:

• The yttria content is ________ thought the restoration

• The restoration is made of the same ______

• The restoation has different _______ in it

different

shade

translucencies

Multi-yttria-layered:

• _____ or _____ at the cervical

• _____ at the incisal

• Variable _________ and ________

3y or 4y

5y

strength and translucency

Multi yttria layered:

• Dentin zone?

• Incisal zone?

Very strong conditioned zirconium oxide in the dentin zone 1200 mpa

Highly translucent conditioned zirconium oxide in the incisal zone 650 mpa

When positioning a full contour crown, the ______ positioning in the disc determines the amount of _____ area in the restoration.

height

incisal

Multi-yttria-layered:

• In theory the stronger phase of zirconia at the cervical part of the restoration does what?

• Whats the reality?

increaes its fracture resistance

the weaker zirconia phase at the occlusal part of the restoation decreases its fracture resistance

Multi yttria layered:

• Very ______ is known about preps and indications

• Treat as what?

little

monlithic 5Y

Zirconia generations:

• _________ classification

• Based on ________ order

outdated

chronlogical

Generations: whats the material?

• First?

• Second?

• Third?

• Fourth?

• Fifth?

3Y layered PFZ

3Y monolithic

5Y

4Y

Multi Y

Cementaiton:

• Like _____ crown

• However, use ________ after trying in zirconia, immediately before cementation

• Because zirconia has a high affinity to ______ ______ so cleaning it with sodium hydroxide after the try in is neccessary.

PFM

Sodium hydroxide

salivary proteins

Can you bond Zirconia?

yes, but it has a different protocol compared to other ceramics and depends on the yttria content

What are the 3 steps of bonding zirconia?

1. Air particle abraion 50 micron aluminum oxide, under 2.5 bar pressure for 15 seconds

2. Adhesive phosphate monomer

3. Resin cement (dual or self cure)

Evidence based on 3Y zirconia:

• Studies showed a decrease in the mechanical properties of ______ contatining zirconia after air particle abrasion.

cubic

When in doubt about a zirconia look at what? and not what?

mol% of yttria and not % by weight