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AU13 - Operative Biomaterials > Biomaterials Exam - Introduction to Biomaterials > Flashcards

Biomaterials Exam - Introduction to Biomaterials Flashcards

questions taken from lecture slides with guidance from Schricker's study guide

1
Q

What are the three main classes of materials?

A

metals, ceramics, and polymers

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2
Q

Give the characteristics of metals (hard/soft, ductile/brittle, strong/weak).

A

hard, ductile (tough), strong

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3
Q

Give the characteristics of ceramics (hard/soft, ductile/brittle, strong/weak).

A

hard, brittle, strong

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4
Q

Give the characteristics of polymers (hard/soft, ductile/brittle, strong/weak).

A

soft, ductile (tough), weak

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5
Q

Do metals have high or low processing temperatures?

A

high

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6
Q

Do ceramics have high or low processing temperatures?

A

high

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7
Q

Do polymers have high or low processing temperatures?

A

low

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8
Q

True or false: Polymers tend to be used as direct processing materials.

A

true

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9
Q

What factors contribute to each materials mechanical properties?

A
  • Atomic arrangement (crystalline vs. non-crystalline)
  • Bonding
    • primary (metallic, ionic, covalent)
    • secondary (hydrogen, van der Waals)
  • Composition (elements and phases)
  • Defects
    • macroscopic (pores)
    • atomic scale (microflaws)
  • Remember: ABCD!
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10
Q

What is key to metallic bonds?

A

Electrons!

-metallic elements have 1, 2, or 3 electrons in their outer shell and electrons are loosely bound to nucleus

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11
Q

What two characteristics do metallic bonds possess due to the mobility of electrons?

A
  • thermal and electrical conductivity

- ductility (can bend without breaking)

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12
Q

When a metal alloy is created (mixture of 2 or more metals), how does the characteristics of the material change?

A

A pure metal is ductile since the atoms are all the same size and are able to slide.
An alloy is stronger, but less ductile since there are different sized atoms.

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13
Q

What types of bonds are associated with ceramic bonds? Are they stronger or weaker than metallic bonds?

A
  • ionic and covalent bonds (covalent > ionic)

- both are stronger than metallic bonds

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14
Q

What makes up the microstructure of ceramics?

A

mixture of metallic and non-metallic elements

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15
Q

What are the most common compounds in ceramics for dentistry? What is the building block of ceramics?

A
  • 3 metallic oxides: SiO2, Al2O3, and K2O are most common

- SiO4 tetrahedron is the building block

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16
Q

What makes up the microstructure of dental porcelain?

A
  • SiO4 is the building block

- primarily a glass with some crystalline residuals (quartz and leucite)

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17
Q

What type of bond is found in polymer bonds?

A

covalent bonds

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18
Q

What elements primarily make-up polymers?

A

nonmetallic elements (C, O, N, and H)

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19
Q

How may polymerization be initiated?

A

by light, heat, and chemical mixing

20
Q

Name and describe the 4 stages of chain reaction polymerization.

A
  1. Activation - free radical initiation (with light, heat, or chemical mixing)
  2. Initiation - free radical combination with monomer unit; double-bond opening
  3. Propagation - chain growth, volume decrease, shrinkage
  4. Termination
21
Q

Name the monomer functional group needed to make a linear polymer.

A

monomethacrylates - each only has one polymerizable unit so it makes linear chains

22
Q

Name the monomer functional group needed to make a branched and cross-linked polymer.

A

dimethacrylates - has two polymerizable units so it may make branched and cross-linked polymers

23
Q

What is needed in a direct placement material?

A
  • flowable material
  • stable material
  • trigger for setting
  • rapid setting
  • room temperature setting reaction
24
Q

What are the pros and cons of a direct placement material?

A

Pros: less preparation needed, one visit
Cons: material often does not last as long

25
Q

What are the pros and cons of an indirect placement material?

A

Pros: longevity of restoration
Cons: multiple visits needed, expensive

26
Q

Metals are typically used for indirect placement with one exception. What is that exception?

A

amalgam

27
Q

Ceramics are typically used for indirect placement with one exception. What is that exception?

A

cements

28
Q

Are polymers generally used for direct or indirect placement?

A

direct placement

29
Q

What is a composite?

A

a physical mixture of metals, ceramics, and/or polymers in order to achieve some intermediate properties between the two material types

30
Q

What is the rule of mixtures?

A

by knowing the phases present in the structure of any material and the interfacial interactions, it is possible to predict the overall properties fairly well

31
Q

When the volume of filler increases, does the strength of the material increase or decrease?

A

increase

32
Q

When the volume of filler increases, does the modulus (stiffness) increase or decrease?

A

increase

33
Q

When the volume of filler increases, does the viscosity increase or decrease?

A

increase

34
Q

When the volume of filler increases, does the shrinkage increase or decrease?

A

decreases

35
Q

When the filler size increases, does the surface roughness increase or decrease?

A

increase

36
Q

Rank the thermal expansion coefficient from smallest to largest for polymers, ceramics, and metals.

A

smallest: ceramics (1-15 ppm/*C)
metals (10-30)
largest: polymers (30-600)

37
Q

Rank the thermal expansion coefficient from smallest to largest for amalgam, tooth, and composite.

A

smallest: tooth (9-11)
amalgam (25)
largest: composite (28-35)

38
Q

When a material is heated, does it expand or contract?

A

expand

39
Q

Explain heat flow in a tooth. What are the clinical consequences of heat flow in dentistry?

A
  • teeth are insulators due to high mineral content
  • pulp can only withstand small temperature changes for a short time due to the restricted circulation of pulp which cannot dissipate heat and carry it away
40
Q

Do metals have a high or low thermal conductivity?

A

high thermal conductivity so they need a thermal insulator-like base

41
Q

Do composites have a high or low thermal conductivity?

A

low thermal conductivity so they do not need a thermal insulator-like base

42
Q

How many dimensions define color? What are those dimensions?

A

3 dimensions (3D); hue, value, and chroma

43
Q

What is hue?

A

wavelength and color (ROYGBIV)

44
Q

What is value?

A

intensity and brightness

45
Q

What is chroma?

A

purity and density/concentration

46
Q

What is metamerism?

A

two objects that appear the same color under one light source and different under another light source; they have different spectral characteristics

AU13 - Operative Biomaterials (6 decks)

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