Ceramics Flashcards
(33 cards)
What is a ceramic?
Compound of metallic and non-metallic elements
Elements: oxides, nitrides and carbides
Traditional: china, porcelain, bricks, tiles, glass
What is the building block of ceramic?
Silica - SiO2
Gives rise to crystalline or amorphous structure
Give examples of crystalline and amorphous structures?
Crystalline - quartz, cristoballite
Amorphous - alumina-silicate glass
What type of structure of porcelain is used in restorative dentistry?
Use mix of amorphous and crystallaine for end-product = glass-ceramic
Amorphous structure w/ crystalline particles
What are core material ceramics?
Feldspar, quartz, kaolin (opaque)
What are the 4 different ways of processing dental ceramic?
- Sintering
- Casting
- Hot pressing
- CAD-CAM
CCsH
What are the features/ properties of feldspathic ceramic?
Weak
Only used in thickness up to 1mm
Must be supported
When is feldspathic ceramic used?
Can be supported
- Metal substructure - PFM
- High strength ceramic (zirconia/ alumina)
- Resin bonded crown - bonded to tooth (tooth support)
How can metal-ceramic restorations be produced?
Metal substructure - lost wax casting
Ceramic sintering - ceramic veneer
What are the 3 problems when producing metal-ceramic restoration?
- Space
- Aesthetic
- Technical
Why is space an issue when producing metal-ceramic restoration? (clinical/ technical)
Need 0.5mm for metal substructure and 1.0mm for ceramic
Not very conservation
Why is aesthetic an issue when producing metal-ceramic restoration?
Metal substructure prevent light transmittance
Can appear opaque - tooth more transparent
Metal margins can be seen
Why are the technical issues when producing metal-ceramic restoration?
Metal ceramic bond - unreliable (has weak point)
Metal ceramic junction - vulnerable - susceptible to chip
All ceramic must be supported
Metal/ceramic not compatible
Why are metal-ceramic not compatible?
Different thermal coefficient
TECc > TECm - therefore ceramic shrink more
Issue w/ bonding - cause stress as ceramic placed under tension and metal under compression
Ceramic poor under tension = break (but good under compression)
What would be ideal TEC for metal-ceramic restorations?
TECc < TECm - metal would shrink more
Allow ceramic to be under compression and metal under tension
Therefore TECc must be equal or slightly less than metal
How does 3D structure affect function of ceramic?
Ideal is for materials to be flat
3D structure - if mismatched expansion coefficient - lead to radial tensile stress = cracked enamel
What is the different TEC of metal and ceramic and how overcome?
TEC metal =13-14ppm/c
TEC ceramic = 8ppm/c w/ added leucite
What are the indications for PFM?
Single unit restoration
Multiple unit bridge
Support RPDs
What is a PJC and its adv/disadv?
Porcelain jacket crown - type high strength ceramic substructure (NOT MADE ANYMORE)
- Good aesthetic - opaque core (alumina reinforced core)
- Strength - 80Mpa - only anteriors
- Need significant tooth reduction
- Non-adhesive
- Foil technique = poor marginal fit
What materials are used for high strength ceramic restorations?
- Glass infiltrated materials - not made anymore
- Alumina (rely CAD-CAM) - not made anymore
- Zirconia - available
How can zirconia high strength ceramic restorations be made?
Methods: CAD-CAM, milling, sintering
In-house milling available (need sintering after)
Stained prior to sintering
Used as monolithic materials or substructure
What shades/ translucencies does zirconia come in?
Various translucencies available
Higher translucency - lower strength
Shades A1-D4
What are the problems w/ zirconia?
Too tough/ hard
Initial sintering time long (large units have longer)
Bond between veneering ceramic and zirconia
Adjusting/ removing/ endo = difficult to cut through
Can be abrasive on teeth
How to overcome problem of endo tx teeth w/ zirconia crowns?
Can place access cavity in softer material
