7. Dental Ceramics

Question 1

Dental Ceramics

Ceramics
• Solid materials composed of ____ compounds
– ____, clay products, cements, ____ etc.

• Dental Ceramic Materials
– \_\_\_\_ products
– \_\_\_\_ powders with ZnO or MgO 
– \_\_\_\_ brackets
– \_\_\_\_
– Fixed \_\_\_\_

Answer 1

inorganic nonmetallic
pottery
glass

gypsum
cement
orthodontic
crowns
partial

Question 2

Examples of Dental Ceramic Materials

Ceramic materials: ____ cement, gypsum, crowns, ceramic brackets (better ____)

Answer 2

ZNPO4

aesthetics

Question 3

Dental Ceramic Materials
• Silica and other fillers in composites
• Silica as a ____ in casting investments
• Crystalline Silica as a ____ in investments

Silica used as a refractory in an investment > provides for ____ upon heating

Answer 3

binder
refractory
expansion

Question 4

Dental Ceramic Materials

• Silica and aluminum oxide in the ____ in glass ionomer materials

Answer 4

fluoraluminosilicate glass

Question 5

Dental Ceramics General Characteristics

Crystalline – Ionic bonds eg. ____
- Covalent bonds eg. ____

Non Crystalline – ____ Bonds
Silica Glass, dental porcelain

Brittle – Stress Concentrations at surface imperfections lead to crack initiation, propagation and ____ (fracture)

Brittle > no mechanism for ____ > stress applied > the only way that stress is relieved is via fracture/cracking

Answer 5

NaCl
quartz
covalent
failure

plastic deformation

Question 6

Silica in Dental Ceramics

• Non Crystalline
– ____, Vitreous, Fused silica

• Crystalline Silica
– ____
– Cristobalite
– ____

Left example is an example of glass; right is of crystalline silica: these examples are all ____ forms of silica

Answer 6

amorphous glass SiO2

quartz
tridymite

allotropic

Question 7

Dental Ceramics

• Porcelain crowns
– ____

– K2O, Al2O3, SiO2,
– Na2O , Al2O3, SiO2

– Pigment oxides
• ____ (4)
• Opacifiers
• ____

Porcelain is made up of these two groups of materials (combined together in different ratios); the main component is ____; sodium oxide > soda feldspar

Opacifier > helps hide the color behind the material (this is the ____ that is applied when creating a crown); this and the other pigment oxides are already added upon receiving the powder

Feldspathic > highly ____

Answer 7

feldspathic
Fe, Ni, Cu, Ti
Ti, Ce, Sn, Zr

SiO2

first layer

translucent

Question 8

Structure of Porcelains

• Structure of SiO2 glass
• Effect of adding Na2O

Na2O breaks up the structure of the porcelain thereby ____ the material (makes it easier to ____)

Answer 8

weakening

fire

Question 9

Characteristics of Feldspathic porcelains

• ____
• Highly ____
• Easy to make ____
• ____

Answer 9

amorphous-non crystalline
translucent
tooth shades
brittle

Question 10

Fracture of Glassy Ceramic (Porcelain) Crowns

• Feldspathic Porcelain Crowns

• Core Ceramics
– Porcelain with reinforcing crystals, ____, ____

Feldspathic porcelain is used for ____; thin shell that is bonded to the front of the tooth

A polymer cement is used to the bond the veneer, which makes the porcelain even ____ than it is individually

Introduce the crystal > formation of a ____ (alumina and leucite are ____)

Answer 10

alumina
leucite

veneer
stronger

reinforced core
crystalline

Question 11

Crack Propagation In Core Ceramic

• Partially crystalline Ceramics

This diagram is supposed to show what the reinforcing crystalline materials
how they accomplish the goal of strengthening the ceramics. We said
ceramics do not have any mechanisms for ____. So if it
crack starts it is going to go through and cause a fracture.

If you have
these reinforcing ceramics, and if the coefficient of ____ of
the ____ matches that of the ____, the crack
has to go through reinforcing materials which delays crack growth. That in
essence makes the ceramic a ____ material

Answer 11

plastic deformation

thermal expansions
reinforcing ceramic
feldspathic porcelain
stronger

Question 12

Methods of Strengthening Ceramic Restorations

• Fuse to ____
• Incorporate Strong 2nd phase crystals
eg. ____ in substructure
• High strength ceramic Cores eg. ____

Initially, zirconia was only used to form the core because of its opacity; translucency has improved, and now there are zirconia ____ that are translucent and shade matched for patients

____ is important for matching ceramics to teeth; the more translucent, the more ____ it is to add colors and oxides to obtain the right shades that you desire

Answer 12

metal substrate
alumina
zirconia

crowns

translucency
easier

Question 13

Crack Resistance in Ceramics

• Metal Ceramic Crowns

Dentin > Metal > Porcelain (bonded to metal)

Bonding to metal > not a trivial feat > extremely ____ connection

There is a minimum ____ for the porcelain in order to form the right bond

Answer 13

strong

thickness requirement

Question 14

Dental Ceramics Failure of Ceramics

Crown can easily become ____ if the porcelain-metal bond is faulty

Answer 14

cracked

Question 15

Fabrication of Dental Ceramic Restorations

• Porcelain – Jacket Crowns
– Stacking of porcelain powder onto Platinum foil

• Cast Glass ceramic core
• Injection molded ceramic
• CAD-CAM
– Computer aided design and machining of ceramics

Ceramics that are cast like ____ (cast glass ceramic core) where porcelain is stacked on either side for appearance

Injection molded ceramic > similar to ____ (replacing wax pattern with ceramic material)

Porcelain ____ considerably when you fire them; initially, must make it ____ in order to compensate for the shrinking

CAD-CAM > combined with ____ have revolutionized the practice of dentistry

Answer 15

metals

cast glass
shrinks
oversized

digital impressions

Question 16

All Ceramic Fixed Bridge

• All Crystalline Ceramic Core Crowns
– ____
– ____
– ____

• Inlays and onlays

Lithium disilicate > mixture of crystalline and ____ materials

Lithium disilicate and zirconia used much more often than ____; ____ not as strong as zirconia, used for ____ bridges that do not see a large amount of biting forces

Answer 16

alumina
lithium dislicate
zirconia

amorphous

alumina
LID
short-span

Question 17

All Ceramic Fixed Bridge

Top left: porcelain-fused to metal restoration; with ____ you see the metal margin as a dark line

All ceramic restoration is a significant improvement in ____

Answer 17

gingival recession

aesthetics

Question 18

Summary of All-ceramic crown types

Leucite > ____ material
Alumina can be ____

Glass-free ceramics, polycrystallic: no amorphous material, only ____

Glass ceramic (feld) > ____

Glass ceramics with fillers > ____ material present in matrix of ____ material

Answer 18

crystalline
glass-infiltrated

crystalline
amorphous, noncrystalline

crystalline
amorphous

Question 19

Advantages of Ceramics in Dentistry
• \_\_\_\_
• Biocompatibility 
• \_\_\_\_
• Wear Resistance

Metallic materials > ____, release of ions into mouth > mercury within amalgam, allergies, etc.

High ____ and high ____; they are also very ____ (low ____)

Answer 19

esthetics
strength
corrosion

strength
hardness
brittle
ductility

Question 20

Disadvantages of Ceramics 
• \_\_\_\_
• Tensile stresses cause crack propagation and fracture
– Low \_\_\_\_
• \_\_\_\_ fabrication methods

No ____ whatsoever

Resilience is equal to the ____ because no plastic deformation (only the linear portion of the graph exists)

Answer 20

brittle
fracture toughness
difficult
toughness