6. Intro to ceramics Flashcards
LOs
Main applications of ceramics
•Inlays
•Onlays
•Veneers
•Crowns
•Implant components
•Fixed partial prostheses
•Denture Teeth
Why are ceramics used widely / popular?
Used widely because of their optical similarities to teeth
can mimic shade, translucency and lustre of tooth structure better than other materials
Disadvantages of ceramics
•Brittle in nature (undergo very little deformation before they fail)
microstructure and defects/flaws play a major role in determining strength
Ceramics definition
Examples of ceramic materials
Ceramics can be either :
Type of bonding involved in ceramics
- ionic
- covalent
Are porcelain and ceramics the same
Porcelain is a ceramic but not all ceramics are porcelains
Main types of ceramics used in dent?
Key properties of dental ceramics?
(Chemically unreactive - don’t react with anything in oral environment , no rapid reactions)
Recap differences between glassy and crystalline states
Writing on top left I added
1
What does it mean by the fact that ceramics are brittle?
2
What factors are do ceramics mechanical strength depend on?
2nd q right?
1
What is fracture toughness
2
What is ceramics relative fracture toughness
3
Why is the theoretical tensile strength so high for ceramic compared to the actual tensile strength?
4
Tensile strength varies depending on?
Feldspathic Ceramics (Porcelain)
1
Overall structure
2
Main component in it?
1
- type of ceramic
-mainly glassy
–minor crystalline component
2
Feldspar is main component, KAlSi3O8
first ceramics used in dent
Feldspathic Ceramics (Porcelain)
1
When melted it forms
2
What happens when it cools
Feldspathic Ceramics (Porcelain)
1
Relative flexural strength?
2
Why is it used in aesthetics?
3
Is it mechanically strong?
1
typically 60-80MPa
- relatively weak
2
- Translucent in nature
- Can closely match the shade, translucency and luster of natural dentition
3
- But is low strength and prone to mechanical failures
- Addition of other crystal phases (e.g. fluorapatite) in contemporary materials increases mechanical performance
1
How may mechanical toughening of glassy cements be done
2
What condition must be met for this to be effective
3
EG
- subtle changes to crystalline component of ceramics is used to produce materials with different properties
Eg of different ceramic microstructures
- ceramic manufacturing methods
- can classify diff ceramic materials not only by their structure but also by their manufacturing methods
1
What is sintering of dental ceramics?
2
What are the 2 main types of crystalline reinforced sintered dental ceramics?
SINTERED ALL-CERAMIC RESTORATION:
ALUMINA-BASED MATERIALS
1
Is it still used?
2
Alumina formula and % added?
1
Rarely used system now – but many functioning crowns out there
2
•Alumina is an aluminum oxide, Al2O3
•Typically added in levels of up to 40-50% by weight
SINTERED ALL-CERAMIC RESTORATION:
ALUMINA-BASED MATERIALS
Key problems with it?
- shrinkage during sintering leading to dimensional inaccuracies
- During sintering procedure shrinkage between 10-20% can occur
- opacity of core necessitates veneering with glassy material to achieve esthetics
SINTERED ALL-CERAMIC RESTORATION:
ALUMINA-BASED MATERIALS
1
Good bond with glass phase?
2
How is it formed? Temp?
3
Flexural strength? What does this depend on?
SINTERED ALL-CERAMIC RESTORATION:
ALUMINA-BASED MATERIALS
1
Good bond with glass phase?
2
How is it formed? Temp?
3
Flexural strength? What does this depend on?
SINTERED ALL-CERAMIC RESTORATION:
LEUCITE-REINFORCED MATERIALS
1
Compound made of?
2
Flexural strength?
3
4
What happens during cooling
5
Positives
HEAT-PRESSED ALL-CERAMIC RESTORATIONS
1
What is it?
2
What happens during the process? Pressure? Temp?
3
Why was it introduced?
HEAT-PRESSED ALL-CERAMIC RESTORATIONS?
1
Why is Heat pressing is typically used over classical sintering?
2
What is the final step for final-heat pressed ceramics?
3
Ceramic materials used in heat pressing?
HEAT-PRESSED ALL-CERAMIC RESTORATIONS:
LEUCITE-REINFORCED MATERIALS
1
Properties?
2
Final porosity % vol?
3
Final flexural strength
4
HEAT PRESSED CERAMICS:
LITHIUM DISILICATE MATERIALS
1
Properties
2
final porosity by % vol?
3
Flexural strength
SLIP-CAST ALL-CERAMIC RESTORATIONS
1
What is it
2
How is it formed
3
Types of materials used
4
Commonly used today?
CAD-CAM All-Ceramic Restorations
1
What does it stand for?
2
What happens
3
Disadvantages
4
Common method?
CAD-CAM All-Ceramic Restorations
1
Bulk ceramics are either (make q)
2
2 main types of machining?
3
What is hard machining
4
Advantages of hard machining
5
Limits of hard machining
6
What is soft maching
CAD-CAM All-Ceramic Restorations:
Fully Sintered Materials
1
Three types of materials are currently used in the fully sintered state in CAD-CAM restorations?
CAD-CAM All-Ceramic Restorations:
Fully Sintered Materials
1
Feldspar
2
Leucite-reinforced (K[AlSi2O6]):
3
Lithium disilicates:
MAKE Qs
CAD-CAM All-Ceramic Restorations:
Partially Sintered Materials
1
Partially sintered materials used in CAD-CAM restorations include:
•Alumina
•Spinel (see slip-cast)
•Zirconia
CAD-CAM All-Ceramic Restorations:
Partially Sintered Materials
Make Qs
Mechanical Toughening of Zirconia
Make Qs
CERAMIC-METAL RESTORATION
1
What is it?
2
What are the layers?
CERAMIC-METAL RESTORATION
1
What happens after the additional layers are added?
Ceramic-Metal Restoration: Ceramic-Driven Requirements
Not in lecture but in ppt doc
Qs in lecture
