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Dental Materials > Polymerization > Flashcards

Polymerization Flashcards

1
Q

Polymers are the _________ because their __________ is the ______ rather than a ________.

It is held together by _________.

A

most diverse class of materials

unit structure is the molecule rather than a crystal lattie

Covalent Bonds

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2
Q

Not all monomer reacts. What happens ?

A

Residual monomer is trapped in the polymer

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3
Q

What are the 3 ways to trigger polymerization?

A

Heat Cure
Chemical Cure
Light Cure

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4
Q

High degrees of polymerization leads to ________ and less ___________.

Is this good or bad?

A

more rigid, less soluble

GOOD

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5
Q

High degree of polymerization have ______ long polymer chains.

A

FEWER

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6
Q

What are the three chemical stages of bonding?

A
  1. Initiation by activation of monomer
  2. Propogation by chain growth
  3. Termination by reaction completion
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7
Q

What is addition polymerization?

Are there by-products?

A

Free radical (highly reactive molecule with FREE electron) is formed.

These are initiators.

NO co-generation of by-products.

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8
Q

What are advantages of addition polymerization?

A

Preferred Clinically

No risk of leaching of by-product intraorally

Prevents increase shrinkage

Toxic Reactions to the patient

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9
Q

What is crosslinking?

A

Link between polymer chains by adding cross-linking agent.

Amount of agent controls final properties.

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10
Q

What can the amount of cross-linking agents control?

A

Melting temp
Strength
Flexibility
Increased wear resistance
Degradation from Solvents such as alcohol

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11
Q

What are copolymers?

A

Two or more different types of monomers in polymer network

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12
Q

What are homopolymers?

A

Polymer is made of one monomer.

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13
Q

What are fillers?

A

Solid particles that change their optical or physical properties.

Ex. Adding substance to increase resistance

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14
Q

What are plasticizers?

A

Modify interactions between polymer strands.

Liquid becomes rubber

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15
Q

Fillers and plasticizers are _____________ to the polymer network. They can two do things. What are they?

A

Chemically linked

Increase Wear Resistance
Decrease Shrinkage

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16
Q

Dentures and fake teeth are made of _______.

A

PMMA

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17
Q

What is the Glass Transition Temperature?

What two thinks are decreased at this temperature?

A

Temperature at which a significant loss of modulus or STIFFNESS occurs.

A significant loss of volume occurs.

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18
Q

What property changes at the Glass Transition Temperature?

Chemical or Mechanical?

A

Mechanical

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19
Q

Thermoplastic polymers have ______ and _____ structures made of ___________ bonded together ___________ which makes them easy to _______.

They ______ when heated and ____ when cooled. This process is ________ and can be ______.

The heating and cooling process __________ a significant change on the polymer properties.

A

linear and branched , long main chain of carbon atoms bonded together COVALENTLY.

Easy to fabricate

soften/harden - reversible and can be repeated

does NOT HAVE

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20
Q

What are 3 examples of thermoplastics?

A

Polystyrene

PMMAcrylate

PVAcryilic

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21
Q

Thermoplastics can always be remelted back to ________ unlike ________ which remains in a ______.

A

liquid

thermoset; permanent solid state

22
Q

Thermoset polymers require _______ to permanently set the ________.

They are formed into shape by ______________.

Once hardened, the structure will _________ upon heating

If heated at a high temperature, _______

A

heat, plastic

temporarily disabling the cross linking

not soften

degraded or decomposed

23
Q

Thermoset polymers are _____ and _____ than thermoplastics.

A

Harder and stronger

24
Q

What are 3 examples of thermosets?

A

Silicones

X-linked PMMA

Polyisoprene

25
Q

Thermoset polymers are one ___________ while thermoplastics are _________.

A

big macromolecule

Linear/branched polymers

26
Q

What are the 4 elements of a polymer?

A
  1. Monomer Matrix
  2. Initiator- Sometimes
  3. Accelerator
  4. Others such as pigments
27
Q

Polymerization is initiated by the interaction of a __________ with _______.

A

Free Radical (Element with free electron)

Chemical Curing - Benzoyl Peroxide

Heath Curing - Benzoyl Peroxide

Light Curing- Camphorquinone

28
Q

The curing of resins by light is triggered by ______ at wavelength _______.

The initiator is _________.

The accelerator is __________.

A

blue light, 465 nm

camphorquinone

organic amines; DAEMA

29
Q

Chemical curing methods use _________ and ________ to activate and are initiated by ___________.

A

Organic Amine Catalyst Paste
Iodonium Salts

Organic Peroxide; Benzoyl Peroxide

30
Q

Some resins need to be dual cured by ________ and ______.

A

Light and chemical

31
Q

What is the degree of ______ to ______ conversion for the following?

Light Curing
Chemical Curing
Dual Curing

A

monomer to polymer

40-75%
40 to 70% ——> usually 40 to high 50%
70-80%

32
Q

What is the result of inadequate polymerization?

A

Poor resistance to wer
Poor color stability
Secondary caries
Adverse soft tissue/pulp reactions

33
Q

Composites are provided in ______ or more shades ranging from ______ to ______.

A

10

yellow to gray

34
Q

_________ pigments (______) are added in small amounts to ___________.

A

Inorganic

oxides of iron

match tooth color

35
Q

_________ are added to enhance optical vitality.

They offer enhanced __________.

A

Fluorescent agents; whitening effect

36
Q

Volumetric shrinkage of dental composites is around __________. It is dependent on several factors such as _________ as well as the quality of ________.

What do we do to compensate?

A

1-6%

amount (depth height), type, size of filler

Quality of lamp

Layering techniques!

37
Q

What is PMMA and what is it produced by?

Does it have byproducts?

Is it exothermic or endothermic?

A

Poly (Methyl Methacrylate)

Produced by free radical polymerization

NO by-products, exothermic process

38
Q

What is the first polymer of dentistry?

A

PMMA

39
Q

The monomer of PMMA is ________ which is formed by __________.

A

Methyl Methyacrylate which is formed by free radical polymerization.

40
Q

MMA is _________, ________ and allergenic.

A

Liquid, high flammable

41
Q

PMMA production has byproducts.

True or false?

A

FALSE

42
Q

MMA is intiated by _______.

A

Benzoyl Peroxide

43
Q

What are the 3 different PMMA polymerization systems?

A
  1. Heat-cure
  2. Chemical-cure
  3. Light cure
44
Q

PMMA is

Transparent/Opaque
High Clarity/Low Clarity
Rigid/ Elastic

Tg?

A

Transparent

High Clarity

Rigid

125 C

45
Q

Prior to using PMMA, surfaces must be disinfected with _______ since bacteria accumulate and grow in pores and recess on ________.

A

Clorox or Calgon

polymer surface

46
Q

What will dissolve or swell PMMA?

A

Alcohol or Acetone

47
Q

Cross-linking makes materials _____ soluble.

A

LESS

48
Q

PEMA is ________ in molecular weight than PMMA.

It is _____ at oral environment.

What improves its properties? What is the con of this?

A

Poly (ethyl methyacrylate)

higher

soft

Addition of plasticizers to increase stiffness

LEACHING

49
Q

Bis-Acrylic Composite consists of ________ to provide _______ that make it ________

It contains __________ monomers and _______ fillers.

A

bi-functional substrates ; cross linkage

strong and tough

divinyl methacrylate and inorganic

50
Q

Compared to PMMA, Bis-Acrylic Composite has

______ polymerization shrinkage
________exothermic reaction
________ tissue toxicity
_________wear resistance and strength

A

low
low
low

GOOD

51
Q

Compared to PMMA what are the disadvantages of Bis-Acrylic Composite ?

A

More brittle

Less stain resistant

More expensive

Lower hardness

Limited Shades

Dental Materials (6 decks)

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