L3- Ceramics and Zirconia Flashcards
Ceramic applications include:
- All ceramic crowns, inlays, onlays, veneers and FPDs
- Metal-ceramic crowns and FPDs
- Implant abutments (and implants)
- Denture teeth
- Ceramic orthodontic brackets
List the benefits of ceramics:
- enhanced esthetics (due to absence of metal and improved light transmission)
- physiologic gingival response
Why are ceramics most beneficial for teeth with normally colored dentin?
dentin coli can affect restoration through the ceramic
We see a physiologic gingival response with ceramics when properly:
contoured and highly glazed/polished
____ is the most realistic restoration that looks like a tooth
ceramics
Why and how does ceramic look so much like a real tooth?
- color replcation
- refraction
- translucency
Describe the color replication of ceramics that makes it look so much like a real tooth:
ceramics can be tinted/colored to produce nearly any tooth shade
Describe the refraction of ceramics that makes it look so much like a real tooth:
ceramics reflect and absorb light rays simulating enamel
Describe the translucency of ceramics that makes it look so much like a real tooth:
type of porcelain (incisal/dentin/opaque)
Important properties of ceramics includes:
- flexural strength
2 fracture toughness - shrinkage
- thermal insulator
Defined as the strength of a material in bending:
flexural strength
Stress on the outermost fibers of a ben test specimen, at failure:
flexural strength
Describe the flexural strength of ceramic:
brittle!
Defined as the resistance to fracture when a crack is present:
fracture toughness
_____ have high fracture toughness due to plasticity at tip of crack, absorbs energy, making crack propagation more difficult
Metals
Describe the fracture toughness of ceramics:
low fracture toughness - little plasticity
What happens to ceramics as they are fired?
they shrink!
Meaning a poor conductor of heat:
thermal insulator
Ceramic is a thermal insulator meaning it is:
a poor conductor of heat
The coefficient of thermal expansion in ceramic is ___. This means that:
low; ceramics do not expand and contract much with heat and cold
CTE:
Coefficient of thermal expansion
What is a major limitation of ceramics?
They are brittle
A.A. Griffith (1921) suggested that the ___ of glass is due to the presence of microscopic flaws in the bulk of material.
low fracture strength
Surface flaws act as ___ and cause widening and propagation of micro cracks through the ceramic material.
Stress initiators
Ceramic limitations:
- ____ in porcelain propgate cracks
- damage from ____ & ____ propagate cracks
- these porosities can be ___ or ___
- porosities
- grinding & heat
- external or within the material
Why do ceramics fail at lower than expected stress?
crack propagation
Crack will propagate through material, or until a particle is met which stops the crack growth:
crack propagation
Crack propagation and stress corrosion are both limitations of:
ceramic
____ describes how strength is reduced in a moist environment
stress corrosion
_____ is reduced in a moist environment
strength
A stress-dependent chemical reaction between water vapor and crack tip, causing crack growth and fracture with comparatively little occlusal loading (over long periods)
Stress corrosion
Stress corrosion is a ____ reaction between ___ & ___, causing crack growth and fracture with relatively little ____ (over long periods)
stress-dependent chemical reaction; water vapor & crack tip; occlusal loading
Ceramic powder/liquid is built up and molded (feldspathic porcelain)
sintering
What type of ceramic is produced through sintering?
Feldspathic porcelain
Process of heating ceramic powder once molded, (also called firing the ceramic)
sintering
The reduction of porosities between particles as the ceramic becomes more rubbery:
sintering
Tg:
Glass transition temperature
A range of temperatures where porcelain starts to become molten:
Glass transition temperature (Tg)
Glass transition temperature describes a transition from:
sold to rubbery
What is the typical glass transition temperature range of ceramics?
540-610 degrees Celsius
It is important to note that the glass transition temperatures of ceramics is:
BELOW the ceramic melting point
The glass transition temperature of ceramic is a range of temperature where porcelain started to become:
molten
During firing (sintering), the space between the particles shrinks until the particles:
fuse together, resulting in dense/hard ceramic
Relies on external pressure to sinter and shape the ceramic at high temperature:
heat pressing
Heat pressing relates on ____ to sinter and shape the ceramic at high temperature
external pressure
During heat pressing, the restoration is made from a ____ (____)
wax pattern (lost wax technique)
Heat pressing is also known as:
high temperature injection molding
CAD:
computer aided design
CAM:
Computer aided manufacture
Involves an already densely sintered material such as silicate, glass ceramics, & resin-based ceramics:
hard milling (CAD/CAM)
Involves partially sintered material such as zirconia, lithium discilicate (e. max) & the sintering is to be completed in oven AFTER manufacture:
soft milling (CAD/CAM)
What type of milling involves sintering AFTER the manufacture?
soft milling
What materials are used with hard milling?
- silicate
- glass ceramics
- resin-based ceramics
(already densely sintered material)
What materials are used with soft milling?
- zirconia
- lithium distillate (e. max)
(partially sintered material)
For CAD/CAM, ___ are used for the milling process
blocks
What has improved esthetics with CAD/CAM?
- newer multi-shade blocks
- a stain and glaze via furnace
List the types of blocks available for CAD/CAM
- glass ceramics
- zirconia
- resin-ceramics
- resin
Classify the following blocks:
- Vita Mark 2
- IPS Emax CAD
- Celtra Duo Ultra
Glass ceramics
Classify the following blocks:
- IPS Emax ZirCAD
- 3M Chairside Zirconia
- CEREC Zirconia
Zirconia
Classify the following blocks:
- Cerasmart
- Vita Enamic
Resin-ceramics
Classify the following blocks:
- Tell blocks
Resin
CAD/CAM systems include:
- Itero
- E4D
- Trios
- Planmeca
- Carestream
T/F: More CAD/CAM systems come to the market every year
True
Ceramics that are predominately glass are considered:
veneers
Ceramics that are particle filled glass ceramics are considered:
Emax
Type of ceramics that have the most translucent optical properties:
Veneers (predominately glass)
What is considered the weakest material?
Veneers (predominately glass)
Feldspathic porcelain is an example of:
Veneers (predominately glass)
Can you etch with Veneers (predominately glass)?
Yes!
Type of ceramics that have less translucency than veneers but not the leas amount of translucency
Particle filled glass ceramic (eMax)
Particle filled glass ceramic (eMax) has a ____ strength
increased (compared to veneers but less than polycrystalline ceramic zirconia)
Can you etch Particle filled glass ceramic (eMax)?
Yes!
Lithium disilicate is an example of:
Particle filled glass ceramic (eMax)
Type of ceramic with the LOWEST translucency:
Polycrystalline ceramic (zirconia)