Restorative > Porcelain > Flashcards

Porcelain Flashcards

(65 cards)

Study These Flashcards
0
Q

What is in kaolin?

A

Al2o3. 2sio2. 2H2O

Hydrated aluminosilicate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What are the components of porcelain?

A

Kaolinite
Quartz
Feldspar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is quartz made from?

A

SiO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the most common element in the earth?

A

Silica

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is feldspar?

A

Mixture of potassium and sodium aluminosilicates

K20 Al2O3 6SiO2
N20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are dental porcelains mainly composed of?

A

mainly Felspar some quart hardly any qaolin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the differnce in compostition of high fusing and low fusin porcelain?

A

percetntage: Kaolin, Silica, Feldpar, Glasses
High fusing: 4, 15, 80, 0
Low fusing:, 25, 60, 15

Metal oxides less than 10%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Wen are high fuse porcelains used?

A

they are used mainly for PJC

they fuse at around 2400 degress

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When are low fuse porcelains used?

A

these are used to provide the glaze

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the other componenents added to porcelain?

A

Borax: sodium borate

Metal oxides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the purpse of adding sodium borate, and to what component is it added to?

A

this is added to feldspar

added to reduce melting temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two types of metal oxides added for?

A

pigments and opalscence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which metal oxides are added for pigmentation?

A

iron: brown
copper: green
coablt: blue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which metal oxides are added for opalscence *transparity?

A

Zno

Titanium oxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the physical properties of porcelain?

A

Low thermal conductivity: good since does conduct heat to pulp, bad since thermal stresses can lead to fracture
Excellent aesthetcs
wide range of shades so can mimic dentine and enamel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What determines the opacity or trasparency of porcelains composte and ceramic materials?

A

partcle size and index of refraction of the differnt components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

WHat was the issue with having kaolin in porcelain?

A

it was initally added to increase the abilty to mould and shape the porcelain however, since it was opaque it made it difficlt to achieve a high transluceny of porcelain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the chemical and biological properties of porcelain?

A

bicompatoble
stable
need to ensure that porcelain is glazed since only polishing makes the surface quite rough and promotes plaque accumulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

t/f porcelain is harder than enamel?

A

t

vickers hardness is 450 vs 350 for enamel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the mechanical properties of procelain?

A

brittle
lacks fracture toughness
fails via catostrophic failure and static fatigue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are is static fatigue?

A

decrease in strength over time even in the abscence of load but is accelrated by dynamic loading

SiO bonds slowly hydrolysed and this genreats a rise in OH which elevates pH. this then dissolves oout the Na2O and the K2O (feldpsathic components)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

WHat is catostrphoc failure?

A

this is when the porcelain actually chips away and due to its brittle nature and is rapid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How is the stength of the porcelain reduced?

A

surface roughness
internal voids
porosity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How can the mechaical properties of porcelains be improved?

A
  1. Alter processing: optimising the fabrication condition
  2. produce stronger procelains: optimising the compostions and microstructure
  3. Reinforce porcelain by providing a solid core : structure optimisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
What are the 5 processing imprvments?
Careful tooth prep: redices stresses inside the crown Use finer grain powder: gives a more unifrom microstructure and surface Fire at vacuum or under pressure: reduces porosity Cool slowly from furncae: reudces thermal stresses which can cause cracks Smooth or further fusing: reduces surface roughness and imprefections
25
WHat are the three ways of priducing stronger porcelains?
most common method of failure is via crack propagation from the surface irregularties so need a compressive strenght to combat the froces created at surface imperfections 1. Ion exchange: xreates compressive forces all over surface by soacking the fired porcelain in molten potassium salt 2. thermal stengthening: careful applicaton of heat during inital firing or later heat tempering. 3. adding strengthening particles:alumina added will act as crack stoppers. plate like mica or needle like crystals eg lithium disiclicate are added
26
What are the names of the various stengthening cores that can be added?
``` alumina alumina reinforces feldspathic porcelain glass infiltrated alumina spinel zirconia ```
27
WHat are the advnatages of porcelain?
aestehtics | chemically inert
28
Wgat are the disadvntages of porcelain?
brittle (low fracture toughness) High elastic modulus high vicker hardness so wear to enamel
29
How do you prepare porcelains?
Powder mixed with water and a binder moulded and carved and the compacted and dried fired and cooled glazed or poloshed
30
WHat is the name of the porcelain powder?
a frit
31
How is rhe frit made?
feldspar kaolin silica ground up, mixed and fused *fedpar acts as the flux. rapidly cooled and then ground again
32
What is the binder?
this is made from sugar and starch so improves the working time of the porcelain
33
What do we place the porcelain on when firing?
placed on to foil mould and the porcelain shrinls towards this and assures a god fit of the crown to the tooth
34
what is the purpose of compating?
light vibrations and patting whichsettles the partciles and reduces shirnkage. this gives a uniform contraction over the whjole surface and brings any excess water to the surface.
35
What do modern mnufactures use to make green dense ceramics?
cold isotatic pressing
36
How are drying and sintering carried out>
plced in warm atmosphere less than 100 degrees since if wet procelain placed straight into hot oven it will bloat. once dried at lower temperature, it is then fired at a high temperature by placing in a firnace of more than 1000 degrees sometimes under vaccuum
37
How is glazing performed?
Low fusing transparent glass is used to coat the porcelain and improves the appearance provding greater translucency this proves a smooth impervous finsih protecting agaisnt chemica attack and lowering hardness to reduce wear
38
Which component to porcelain has the lowest melting point?
Feldspar Acts as a flux
39
T/Fporcelaim is strong in compression?
T
40
T/f porcelain is week I tension?
T | This is why cannot be used in thin section
41
What is the name for the feldpathic components?
Soda Na2Oand potash K2O
42
T/F porcelain is a thermal insulator?
T
43
What is a glaze?
Glass put on the surface
44
What is the purpose of the porcelain glaze?
Smooths the surface | Protects against chemical attack
45
What temp are core porcelains fired at?
850-1050 for 5 mins
46
What temp are the enamel and dentine porcelains fired at?
750-900 for 5 mins
47
By how much does porcelain shrink after firing?
40%
48
What are the options for sintered porcelains?
Aluminous porcelain: this is strong and used for cores but not great aesthetics since more opaque Feldpathic reinforces with zirconia or leucite
49
How do you prepare for a PJC?
Incisal reduction by 1/4 or 1/3 Labial reduction in two planes 5% taper Even Palatal reduction 1mm shoulder
50
What are resin bonded crowns?
Made in feldpathic porcelains Minimally intervention Thin section Strength derived from underlying bond to tooth
51
What are the ad and dis of PJVC?
AD: good aesthetics and easy to manufacture Dis: abrasive, brittle, irreversible ,damaging to tooth
52
What is good about PFM?
Strength of metal restoration and Appearance of porcelain
53
When are PFM indicated?
Heavy masticatory load Limited Palatal space Incorpated rest seat
54
What are the dis of PFM?
Destructive Difficult to remove Cost Technqie sensitve
55
How does metal bond to porcelain?
Early theory: van der waals, setting Now: mechanical interlocking, chemical bond to oxide layer, compressive force
56
What are the causes of failure for PFM?
Insufficient metal support Unequal thickness of porcelain Faulty design Fault occlusion
57
What should you avoid with PFM?
Unsupported porcelain | Interfaced of porcelain and metsl under heavy occlusal load
58
What is the function of a Pontic?
Appearance Stabilise occlusion Masticatory Phonetics
59
What are the options for a bridge replacing anterior tooth?
Conventional fixed fixed Cantilever bridge Spring cantilever RRB
60
When preparing the labial preparation phases?
2 stages First cut is incisal third Second cut: gingival third
61
What type of preps are there for PFM?
Winged prep : more resistance and more conservative | Wingless Prep : easier to prepare, less chance of leaving undercut
62
What is the depth of the PFM shoulder?
1.3mm
63
How deep is the Palatal chamfer?
0.7mm
64
What are the stages of bridge prep for anterior teeth?
``` Incisal reduction by 2mm Paired mesial and sitar prep Paired axial prep Cingulam reduction of 1mm Shoulder Finnish ```
Restorative
flashcards
Decks in class (45)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions