Dental Materials Lecture 2

Front 1

Ceramics: compounds

Back 1

compounds between metallic and non metallic elements

Ex. Oxides, nitrides, silicates

Front 2

Ceramics: Bonding

Back 2

ionic and covalent

Front 3

Ceramics: Structure

Back 3

Crystalline
Amorphus(glass)

Front 4

Ionic Bonding

Back 4

Metal(+) and non metal(negative)

Front 5

Properties of Ionic Bonding:
MP/BP
Electrical conductivity

Back 5

high MP/BP-->high thermal energy to separate ions

low electrical conductivity
(no free electrons)

* strong bonds = hard to disassociate = high MP/BP

Front 6

Properties of Ionic Compounds
Hardness
Compressive Strength
Brittleness

Back 6

High for all! Not strong tensile, not ductile-->easy to fracture

Front 7

Covalent Bonding:

Electrical conductivity?

Back 7

Sharing a pair of valence elctrons

low

Front 8

Biocompatibility of Ceramics:
Biointerness
Examples:

Back 8

Bioinertness: non reactive to minimize toxic effects and inflammatory responses

Dental Crowns/Bridges:
Alumina: Al2O3
Silica: SiO2
Zirconia: ZrO2
Titania: TiO2(implants! anticorrosive not novel but high resistance to corrosion)

Front 9

Ceramics:
Basic units?
Allotropic forms?
Dental Applications?

Back 9

SiO2 in differ forms

Fused Silica(non crystalline, glass)
Cristobalie(crystalline)
Tridymite(Crystalline)
Quartz(Crystalline

Dental Applications

Front 10

Structure of Ceramics

Back 10

Crystalline: long range order
Non-crystalline: amorphous

Front 11

Crystal Melting Transition:

properties

Back 11

Sharp change at a definite melting point

Discontinuity in specific volume
specific volume = density
Ordered crystall structure= high packing density
Disordered liquid= low packing density

*see solid-solid transitions for SiO2

Front 12

Amorphous Properties
structure?
How to make
phase change?

Back 12

No long range periodicty
Rapid cooling of metled sand to avoid crystallization

NO SHARP PHASE CHANGE from solid to liquid at definite MP, gradual softening

Front 13

Solid-Solid Transition

Back 13

Sharpe changes in specific volume at definite temperatures

Front 14

Glass Transition

Back 14

No sudden increase in volume

gradual increase becomes more rapid above transition temp

Front 15

Formation of Crystalline Solid

Back 15

Crystalline solid: slow cooling of molten cilica

Front 16

Glass formation:Glass

Back 16

Rapid cooling of molten silica(vitrification)-->doesn't allow time for rearrangement and growth of crystal nucllei

Front 17

Glass formation:Devertrification

Back 17

small amount of crystalization of glass
Reorganization of molecules at elevated temp for a long time(annealing)-->translucent

Front 18

Polymers: Synthetic EX

Back 18

Polyethylene
PCV(polyvinyl chloride)

Front 19

Acrylic Resins: what are they
EX?

Back 19

Derivative of ethylene

Acrylic Acid: COOH
Methaccrylic Acid: COOH + CH3 on same carbon

Front 20

Polymer Bonding

Back 20

1. hydrogen
2. van der walls

Front 21

Glass formation:Glass

Back 21

Rapid cooling of molten silica(vitrification)-->doesn't allow time for rearrangement and growth of crystal nucllei

Front 22

Glass formation:Devertrification

Back 22

small amount of crystalization of glass
Reorganization of molecules at elevated temp for a long time(annealing)-->translucent

Front 23

Polymers: Synthetic EX

Back 23

Polyethylene
PCV(polyvinyl chloride)

Front 24

Acrylic Resins: what are they
EX?

Back 24

Derivative of ethylene

Acrylic Acid: COOH
Methaccrylic Acid: COOH + CH3 on same carbon

Front 25

Polymer Bonding:

Back 25

Primary: Covalent monomer-monomer
Secondary
1. hydrogen
2. van der walls

Front 26

Hydrogen bonding

Back 26

weak
NH, OH, FH in polymers

Front 27

Van Der Waals

Back 27

weak,
Iner Gasses: He, Ne, Ar

Front 28

Molecular Weight Definition

Back 28

# of repeating unit x molecular weight of repeating unit

Front 29

Average Molecular Weight
why?
types?

Back 29

many different chains, only average can be defined

Number Average mol. weight
Weight Average molecular weight

Front 30

Number Average Molecular Weight

Back 30

# molecules in a given weight
Mx=Der xi/Mi

Front 31

Number Average Molecular Weight

Back 31

Sum of:
Mean Molecular Weight Range x Xi(occurence)

essentially mean/average of molecular weights of individual macromolecules

Front 32

Weight average molecular weight

Back 32

Sum of:
Mean wt range x Wi(occurence)

Front 33

Degree of Polymerization:

Number Average dgree of polymerization

Weight Average degree of polymerization

Back 33

# of repeating unit
Number: Mn/molecular weight

Weight: Mw/molecular weight

Front 34

Degree of Poly Generalizations:
High:
Lower:

Back 34

High: fewer, longer chains, more rigid less soluble

Low: More, shorter chains, less rigid, more soluble

Front 35

Molecular Weight

<100g/mol
=1000g/mol
>10,00g/mol

Back 35

liquid
waxy solid
solid

Front 36

Polymer Structure of 1 vs. 2 compounds

Back 36

See notebook
Homo-->linear, branched
Copolymer-->linear(blk/random), Branched(random, graft)

Front 37

Spatial Structure of Polymers

Back 37

Linear-vanderwals
Branched-inefficient packing
Crosslinked-covalent
Network

Front 38

Thermoplastic Polyers

Back 38

reversible
softens upon heating, harden cooling

flexible linear w/ some branches

most dental resin

Front 39

Thermoset

Back 39

Irreversible crosslinks
hardens heated
crosslinked-networked
harder, stronger, more brittle than thermoplastics