Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
77 Cards in this Set
- Front
- Back
|
Name the two categories of all ceramic crown material
|
1. Silica or glass based
2. Nonsilica based or high strength |
|
|
Name two categories of silica based ceramics
|
1. Trational Feldspathic Porcelain
2. Reinforced Feldspathic Porcelain |
|
|
________ is one of the most common materials in daily practice
|
Feldspathic porcelain
|
|
|
Name the three main ingredients of feldspathic porcelain
|
1. feldspar
2. silica 3. kaolin |
|
|
What is the chemical formula for feldspar?
|
K2O ·Al2O3·6SiO2
Potassium oxide-Alumina-6Quartz |
|
|
Where is feldspar naturally found?
|
On the banks of rivers
|
|
|
Silica is in what form in feldspathic porcelain?
|
Pure quartz: SiO2
|
|
|
What is the function of silica in feldspathic porcelain?
|
Silica gives feldspathic porcelain stability
|
|
|
What would happen to feldspathic porcelain if silica were not included?
|
Without silica, the material would slump
|
|
|
What is the chemical formula of kaolin?
|
Al2O3·2SiO2·2H2O
Alumina-2Quartz-2Water |
|
|
What is the function of kaolin in feldspathic porcelain?
|
Kaolin, or clay, makes the porcelain opacity
|
|
|
In modern porcelain, what is used to change opacity?
|
Metal oxides - i.e. SnO2, TiO2, ZrO2
|
|
|
How are the ingredients of feldspathic porcelain converted to porcelain?
|
The ingredients of feldspathic porcelain are placed into a furnace where the temperature is increased beyond their melting points. They then combine and lose their individual properties, forming 1 INDIVIDUAL MATRIX AND 1 CONTINUOUS LATTICE.
|
|
|
What are glasses?
|
Super cooled liquids solidify w/o an organized crystalline structure
|
|
|
Give an example of a type of glass
|
Feldspathic porcelain
|
|
|
What makes glass translucent?
|
When light is shined into the material there is nothing to scatter the light
|
|
|
What is the strength of feldspathic porcelain?
|
60-90 MPa- the lowest
|
|
|
T/F Porcelain will effectively mask discolored teeth
|
False- porcelain is very translucent. It is only good to use on teeth that are not discolored
|
|
|
What are the main drawbacks of porcelain?
|
Low flexural strength -> increased brittleness
|
|
|
Why can a crack easily advance all the way through porcelain?
|
When the crack starts on one side, there is nothing within the material to stop it, so little force is required for the crack to continue through to the other side.
|
|
|
Traditional feldspathic porcelain is mainly used to produce _________.
|
Porcelain laminate veneers - single units
|
|
|
Who was the first to introduce reinforced feldspathic porcelain?
|
John McClain (not important)
|
|
|
How is reinforced feldspathic porcelain created?
|
Feldspathic porcelain and aluminum oxide are placed together in an oven and fired up to the lesser melting point, which is that of porcelain. The porcelain melts and the aluminum oxide particles become trapped within the matrix as a filler
|
|
|
What is the melting point of feldspathic porcelain?
|
1,000 deg C
|
|
|
What is the melting point of aluminum oxide?
|
2,000 deg C
|
|
|
The inert presence of aluminum oxide in feldspathic porcelain increases its strength to __________.
|
160 MPa
|
|
|
Why does the presence of aluminum oxide increase the strength of porcelain?
|
When a crack is introduced on one side of the reinforced porcelain, it will at some point run into an aluminum oxide particle, at which point more force is required for the crack to continue around the particle.
|
|
|
T/F Reinforced feldspathic porcelain is an alumina based material.
|
False it is a glass based material
|
|
|
What dictates the properties of a material?
|
The matrix, which in the case of reinforced porcelain, is glass
|
|
|
Name 3 categories of reinforced feldspathic porcelain
|
1. alumina reinforced feldspathic porcelain
2. leucite reinforced feldspathic porcelain 3. lithium silicate reinforced feldspathic porcelain |
|
|
What is the commercial name of alumina reinforced feldspathic porcelain?
|
It does not exist in the market in any form
|
|
|
What is the commercial name of leucite reinforced feldspathic porcelain?
|
Empress 1 (empress has now been changed to Eris)
|
|
|
What is the most popular type of reinforced feldspathic porcelain?
|
Leucite reinforced feldspathic porcelain
|
|
|
Leucite reinforced feldspathic porcelain is a ________ ceramic.
|
Pressable
|
|
|
What is the strength of leucite reinforced feldspathic porcelain?
|
220 megapascals
|
|
|
What are the indications for leucite reinforced feldspathic porcelain?
|
Indications:
1. Onlays- up to the first molar 2. Single units - up to the first molar 3. Veneers 4. Inlays |
|
|
What are the limitations of leucite reinforced feldspathic porcelain?
|
It is still glass based, requires bonding for longevity. Very translucent, does not mask severely discolored teeth very well.
|
|
|
What is most commonly used for bonding leucite reinforced feldspathic porcelain?
|
Bis GMA
|
|
|
What is a commercial name for lithium silicate reinforced feldspathic porcelain?
|
Empress 2 (Eris)
|
|
|
Name the strongest silica based material
|
Lithium silicate reinforced feldspathic porcelain
|
|
|
What is the strength of lithium disilicate reinforced feldspathic porcelain?
|
360 MPa
|
|
|
What are the indications for lithium silicate reinforced feldspathic porcelain?
|
Indications same as those of leucite reinforced feldspathic porcelain - they are both pressable ceramics.
|
|
|
Lithium silicate reinforced feldspathic porcelain was originally developed with what type of device in mind? Why are they not good for this device?
|
Bridges and dentures. Bridges hold together 2 mobile components. Since the porcelain has limited ability to flex, the materials are prone to break.
|
|
|
Another name for non-silica based materials?
|
High strength ceramics
|
|
|
What is the uniqueness of non-silica based materials?
|
Their strength
|
|
|
Why is it difficult to use aluminum for coping in dentistry?
|
Because when it is fired, it shrinks
|
|
|
What are the categories of non-silica based materials?
|
1. Alumina based
2. Zirconia based |
|
|
Give a commercial name of an alumina based material
|
In-ceram Alumina
|
|
|
Name the types of alumina based materials
|
1. Glass infiltrated aluminous porcelain
2. Densely sintered alumina |
|
|
What is the presintering temperature?
|
A very high temperature (lower than the melting point) at which the particles of metal are caused to move towards each other and prevent shrinkage. The particles fuse slightly to one another, causing the metal to be porous.
|
|
|
After alumina powder is fired in the oven at the presintering temperature, what is the next step to make glass infiltrated aluminous porcelain?
|
To cover the porosity of the coping, it is painted with liquid glass then fired again, causing the glass to infiltrate the pores.
|
|
|
What is the matrix of glass infiltrated aluminous porcelain?
|
Alumina, so it is an alumina based material
|
|
|
What is the flexural strength of glass infiltrated aluminous porcelain?
|
450 MPa
|
|
|
The first true cementable all ceramic crown was made of what material?
|
Glass infiltrated aluminous porcelain
|
|
|
T/F You still have to apply feldspathic porcelain on top of glass infiltrated aluminous porcelain
|
True, the glass infiltrated aluminous porcelain is just the coping
|
|
|
What are the indications for glass infiltrated aluminous porcelain?
|
Single units up to the 1st molars
|
|
|
Name a commercial name of densely sintered alumina and glass infiltrated aluminous porcelain?
|
Procera Allceram
|
|
|
What is the flexural strength of densely sintered alumina?
|
700 MPa
|
|
|
Where in the dental arch can densely sintered alumina be cemented?
|
Anywhere
|
|
|
Name one of the biggest obstacles of coping
|
shrinkage
|
|
|
What is the difference between densely sintered alumina and glass infiltrated aluminous porcelain?
|
Densely sintered alumina is fired all the way -densely sintered- so there is no porosity and shrinkage occurs
|
|
|
How is shrinkage overcome in densely sintered alumina?
|
Computers are used to determine the amount of shrinkage, so that it can be compensated for
|
|
|
T/F Densely sintered alumina can effectively cover internal tooth discolorations
|
True
|
|
|
T/F Radiopacity of densely sintered alumina is very similar to that of tooth dentin
|
True
|
|
|
What type of ceramic material has maximum translucency?
|
Silica based
|
|
|
What type of ceramic material can mask discolorations and be cemented?
|
Non-silica based
|
|
|
What is the flexural strength of zirconia based ceramics?
|
1000 MPa
|
|
|
What is the strongest coping of all ceramic materials?
|
Zirconia based
|
|
|
What material is usually used for all ceramic bridges?
|
Zirconia based
|
|
|
Name the typical shapes of zirconia crystals and their corresponding temperature ranges
|
1. Cuboidal- high temp
2. Tetragonal- med temp 3. Monoclinic- room temp |
|
|
Zirconia crystals in zirconia based ceramic are forced into what shape?
|
Tetragonal
|
|
|
What happens if the zirconia crystals sense something trying to force them apart?
|
If the crystals sense something trying to force them apart, they change configuration to monoclinic shape and expand, which doesn't allow the crack to propagate.
|
|
|
Monoclinic crystals are _____ than tetragonal crystals. (compare size)
|
4% larger
|
|
|
What is transformational toughening?
|
Rearrangement of crystals to try to stop the crack from propagating
|
|
|
What are the indications for densely sintered zirconia?
|
Indications:
1. single units 2. teeth supported FPD 3. Implant FPD- screw/cement 4. Implant abutments 5. Adhesively retained FPD |
|
|
Silica based restorations are:
a. Translucent b. Brittle c. Opaque d. Strong |
A&B
Translucent & Brittle |
|
|
Alumina and zirconia are:
a. Weak ceramic materials used to laminate (place on top of) feldspathic restorations b. Strong ceramic materials that are used to fabricate strong cores for all ceramic restorations c. Fruit extracts d. Acrylic derivatives for the enhancement of ceramic crowns |
B
Strong ceramic materials that are used to fabricate strong cores for all ceramic restorations |
