6. Intro to ceramics Flashcards
LOs
Main applications of ceramics
•Inlays
•Onlays
•Veneers
•Crowns
•Implant components
•Fixed partial prostheses
•Denture Teeth
Why’re ceramics so 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 (can undergo very little deformation before they fail)
microstructure and defects/flaws play a major role in determining strength
1
Ceramics definition
2
Eg of ceramic materials
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?
Recap differences between glassy and crystalline states
1
What does it mean by the fact that ceramics are brittle?
2
What factors are do ceramics mechanical strength depend on?
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
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:
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
