6. Introduction to Dental Polymers and Ceramics Flashcards Preview

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1

Polymer Materials in Dentistry

-____ materials
- Denture base materials
____

- Composite resin restorative materials
____
____

Composite resin restorative materials (proper name should be polymer composite or resin composites because its a mixture of a ____ and ____ particles).

Bis-GMA and urethane dimethacrylate are mixed together to provide the right ____ for composite resin.

Impression
polymetyl methacrylate (PMMA)

bis-phenol A glycidyl methacrylate (Bis-GMA)
urethane dimethacrylate

polymer
inorganic filler
composition

2

Impression Materials

This is a rubber material that is syringed onto the tooth that comes as a toothpaste system. It comes out as a ____ material. Syringe it onto a tray that goes into the mouth. The material is very ____ and the final product is very rubbery and provides an impression.

mixed
viscous

3

Denture Base Resins

We have an acrylic denture incorporating a metal clip. Commonly the powder and liquid (both are ____) are ____ to make the mixture for acrylic dentures.

pre-polymerized
mixed

4

Complete Resins

Composites have a matrix of ____. This shows an application of composite resins to repair ____.

polymer
fractured incisors

5

-Resins
____ materials synthesized from ____ compounds that can be molded when soft and hardened for use.

____: Long chain molecules consisting of many repeating units

Resins can be found either as a ____ fluid or a ____. They may occur ____ or be synthesized ____.

Have to remember that a polymer is a long chain molecule consisting of many ____.

non metallic
organic

polymer

viscous
solid
naturally
artificially

repeating units

6

Classification of polymers based on origin

- Natural :
Proteins and Nucleic Acids
____ eg. rubber and gutta percha
(____ rubber)
Polysaccharides eg. ____, agar and ____

____:
PMMA
Nylon
Teflon

polyisoprenes
percha
starch
alginates

synthetic

7

Classification of polymers based on thermal behavior

Thermoplastic resins:
____ under heat and pressure and
harden when ____
No ____
Generally ____ in organic solvents

Thermoset resins:
____ by a chemical reaction
Generally ____ in organic solvents

Note that there is no ____ taking place when molded for thermoplastic resins.

Thermoset resins: If you try to heat a thermoset resin they often will not heat and rather will ____. A good example is ____ material that sets by a chemical reaction.

soften
cooled
chemical reaction
soluble

harden
insoluble

thermal reaction
decompose/degrade
alginate impression

8

POLYMERIZATION
Series of chemical reactions by which a macromolecule (____) is formed from single molecules (____)

Monomer : one molecule or mer

polymer
monomer

9

Types of Polymerization
Condensation (Step Growth) Polymerization

Repeating units are joined by ____
Reaction is ____ and giant molecules are difficult to form.

eg:
____ impression
____ impression

Two types of polymerization:
It takes ____ to get a Step Growth (Condensation Polymerization reaction) to continue since giant molecules are difficult to form

functional groups
slow
condensation silicone
polysulfide

coaxing

10

Condensation (Step Growth) - Polymerization

Reaction between two molecules to form a larger molecule with the elimination of a ____ molecule

There are functional groups that react. In this figure this shows ____ (also known as polysulfide). Mercaptan is a viscous, pre-polymerized material. The distinctive feature about the polysulfide molecule is that it is a ____ molecule and it has terminal ____ at the ends of the branches.

In the presence of ____, the hydrogen’s at the ends of 2 chains will condense with an oxygen molecule from ____ which will result in the release of ____ and we’ll have an elongation of the chain. This process will repeat on and on until there is a long chain. Since we’re starting with a polymer the product will be ____.

Mercaptan is present as a ____; lead dioxide is a ____ and when they’re reacted together this results in formation of lead oxide (____) and water. It’s important to notice that whenever we have a condensation polymerization reaction, we’re going to have a ____: Usually a low molecular weight often volatile byproduct of the reaction. Water may be released as ____ due to the reaction. The release of water occurs multiple times as the reaction proceeds which leads to ____ of the impression material. This is a major disadvantage of impression materials that form via condensation polymerization reactions.

*Sulfhydryl groups react with lead oxide and lead to the release of water and subsequent linking of sulfur groups at the ends of the chains. The reaction as a whole takes place one step at a time which leads to formation of the macromolecule (polymer).

smaller

mercaptan
branched
sulfhydryl (SH groups)

lead dioxide
lead dioxide
water
cross-linked

base paste
catalyst
impression material
condensate
shrinkage

11

Addition Polymerization

Successive reactions between monomer molecules to form a polymer without formation of ____ by-products.

Features:
The presence of an ____ group
Readily form ____ molecules
Chain growth can continue ____
____ reactions

This reaction is more commonly exothermic but it can be ____ as well. Step- growth reaction is also ____

Important to note that there is no formation of volatile byproducts or water. This makes them more ____ for use than step growth (condensation) materials

volatile
unsaturated
giant
indefinitely
exothermic

endothermic
exothermic

accurate

12

Addition Polymerization of Methyl Methacryate (Acrylic)

Figure on the left represents a monomer of methyl methacrylate.
Figure on the right represents what occurs when the chain is formed and several molecules attach to both of the ends.

This is an ____ polymer
R groups are side chains

acrylic

13

Addition Polymerization
Stages

Initiation
- Activation of initiator (____ formation)
- Activated ____

____ is the initiator of the addition polymerization reaction of acrylic. When it’s heated it breaks down into 2 ____ and ____. The free radical will react wit a monomer to form an activated monomer and this is the beginning of the addition polymerization process.

free radical
monomer

benzoyl peroxide
free radicals
carbon dioxide

14

Addition Polymerization
Propagation

The next step is for the activated monomer to react with another ____ and the chain continues during

Propagation.
R*-M = Activated ____
M = Additional ____

R* + M --------> R-M*
R-M* + M ------> R-M-M*

monomer
monomer
monomer

15

Addition Polymerization
Termination

The reaction of an activated monomer reacting with a ____, or 2 activated monomers reacting ____, will ____ the addition polymerization reaction.

The three steps are: ____, ____, and ____

R-Mn-M* + R* ----> R-Mn+1-R

R-Mn* + RMm* ----> R-Mn + R-Mm

free radical
together
terminate

initiation
propagation
termination

16

Activators of Addition polymerization

____
____ amine
____ (UV, Visible) ____ energy

Other ways of breaking down initiators:
1. Reacting ____ with tertiary amine.
2. Use of UV light (more commonly today ____ is used) to initiate polymerization reaction. Example is use of blue light with application of composite filling to get that to polymerize in the process of making a restoration.

heat
tertiary
light
microwave

visible light

17

Inhibitors of Polymerization
____
____
____

These 3 components are inhibitors of polymerization.
1. Impurities (occur when the monomer has been exposed to ____ for too long).
2. Hydroquinone is deliberately added to acrylic to prevent spontaneous polymerization during ____ (it provides ____- how long you can store it before use).
3. Oxygen will attack the ____. If you are polymerizing composite resin, there is oxygen in the ____ and this can inhibit the polymerization especially on the top layer of the composite material. To prevent this, ____ then polymerize then take off the top layer that is poorly polymerized. This is called the ____. As long as you keep adding new material the material inside the filling will be well polymerized. The top most layer will be soft and needs to be removed. In adjusting the occlusion, a lot of this top most layer will be removed.

Inhibitors of polymerization will result in a still ____ material after you’ve attempted to get it to polymerize.

impurities
hydroquinone
oxygen

environment
storage
"shelf-life"

free radicals
oral cavity
overfill
air-inhibited layer

soft

18

Structure Of Polymers

Linear
Branched

____: Polymerization of two or more monomer molecules to form a polymer

Effects: Tailor made polymers

Branched: Have formation of side chains.

When two chains are linked they are called ____ polymers.

____ - The ability to copolymerization different monomers together, we can decide which properties we want in a polymer and select the appropriate monomers to polymerize together.

copolymerization
cross-linked
tailor made polymers

19

Crosslinking
Formation of bridges between chains of polymers to form a ____ network

Effects
Increased ____ Increased ____
Decreased ____
Decreased ____
Increased ____

In general cross linking improves the ____ properties of our polymer. However it make the polymer more ____

3D

glass-transition temperature
strength
solubility
water-sorption
brittleness

mechanical
brittle

20

Plasticizers

Added to monomers to increase ____ and decrease ____ of a polymer
It facilitates ____ of polymer chains along each other

Effects
Reduced: ____, ___, ____

____ for the particular polymer (maybe the solvent is diluted heavily so it doesn’t dissolve completely but softens the monomer).

Cross linking increases brittleness and strength, plasticizers do the ____. They soften the material on a ____ level, which makes it easier for polymer chains to slip past one another.

solubility
brittleness
slipping
strength
hardness
glass-transition temp

solvents
opposite
molecular

21

Plasticizer

Effect of solvent/plasticizer on polymer molecule in solution

A plasticizer ____ up the chain once the chain is exposed to it leading to ____ of the material.

open
softening

22

Soft Reline Materials

This shows an edentulous patient and a full denture made for that patient. Very often, after a long time of wearing the denture there may be a ____ area due to irritation. Removing the denture for a few days typically does not resolve this.

An alternative way to treat the inflamed gums is to use a ____ to allow the tissues below the denture to heal. This material is used on the ____ of the denture.

reddish
soft reline
fitting surface

23

Physical Properties Of Polymers

Average degree of polymerization:
Average number of ____ in a polymer molecule

Degree of conversion:
Fraction of ____ converted to ____ after polymerization

Recall that for an addition polymerization reaction to take place, it requires an ____ (a double bond or triple bond). During the polymerization these bonds are opening up and becoming ____. The conversion is rarely ____ from double bonds to single bonds. The graph shows the degree of polymerization (the number of repeating monomers in the polymer) and it shows as a rather sharp increase in ____ corresponding with increase in degree of polymerization.

The higher the degree of polymerization; the higher the ____ of the polymer

Degree of conversion closely relates to the ____ of material, resistance to ____, and ____ (which is higher if there’s a higher degree of conversion).

repeating units
double bonds
single bonds

unsaturated bond
single bond
100%
strength

strength

strength
solubility
chemical stability

24

Strength Properties

Strong influence of ____ on strength

Other influences:
____
Molecular weight
____
Residual monomer

As the temperature increased, the polymer reflects a smaller ____ (???). At low temperatures the polymer is ____ and as the temperature increases it becomes more and more ____.

There will always be unpolymerized monomer after a polymerization reaction. We want 100% polymerized but this does not occur. The lower the amount of residual monomer, the ____ for the properties of the material. Residual monomers can cause problems with water absorption, which can lead to ____

temperature
composition
structure

modulus of elasticity
brittle
ductile

better
halitosis

25

Physical Properties Of Polymers

Glass transition temperature
Temperature at which a polymer changes from a ____ to a ____ structure

Top box: Shows the polymer chain and what happens when it is heated - it opens up and ____ is improved; becomes more rubbery in nature and appearance.

rigid
rubbery

flow

26

Polymerization Shrinkage

(Look at the table)

Another important property for dentistry is polymerization shrinkage.

Unfilled Resin - What is supplied by the manufacture. Has the highest ____ value.

If you add inorganic filler particles into unfilled resin, this begins to decrease amount of ____. Shrinkage value vs Filler values are not linear because there are different ways of adding inorganic filler particles but the general trend is a strong decrease in polymerization ____ as filler particles are added into resin.

If you have a composite in a tooth, and you polymerize it and it shrinks, it is pulling away from the walls of the cavity which results in ____. This also occurred with thermal expansion. Polymerization shrinkage is a bigger culprit for leakage around composites. This can result in sensitivity and caries.

shrinkage

shrinkage
shrinkage

marginal/microleakage

27

Biological Properties

Taste, smell, toxicity, soft tissue irritation influenced by:

____ uptake
____
____ monomer
Bond to ____

Want to avoid water uptake because it results in bad smell in the mouth

water
solubility
residual
tooth structure

28

Composite Resins

A combination of materials in which each component retains its ____

Polymer Composite:
Matrix (____)
Filler (____ or ____)

Dental Examples:
____ materials
____ restorative
materials

identity

polymer
particulate fibers
whiskers

impression
composite

29

Composition of Dental Composite Resin

Polymer matrix
An ____ or ____ (Bisphenol A Glycidyl Methacrylate - Bis-GMA)

Diluents
____

Bis-GMA and Urethane dimethacrylate are very viscous materials and commonly TEGDMA is mixed with them to make them less ____. Diluents make it easier to mix in the ____ during the manufacturing process.

aromatic
urethane dimethacrylate

triethylene glycol dimethacrylate - TEGDMA

viscous
filler particles

30

Fillers- Dispersed inorganic phase

____
Borosilicate glass
____
Barium aluminum silicate – ____
____ – radio-opacity
Colloidal silica

Both types of silicate and strontium glass provide ____ in the composite. Provides ability to ____ new decay.

quartz
lithium aluminum silicate
radio-opacity
strontium glass

radio-opacity
diagnose