Dental Materials I

Front 1

1. What the illuminant?

What happens when the illuminant hits the object?

Back 1

Lighting that is affected by surroundings (natural, fluorescent)

Reflection and transmission reach observer

Front 2

2. What is does transmission mean?

Is the reflection the same for every observer?

Back 2

Goes through dental material

Reflection seen by observer varies for each person (i.e. some people might be color blind)

Front 3

3. What is the chameleon effect?

How do wavelengths go through clearer materials (transparent)?

How do wavelengths go through translucent materials?

Opaque?

Back 3

Restoration blends in w/ surrounding tooth structure and picks up some of it

In an organized manner

Scattered

Don't go through (lost)

Front 4

4. In a restoration, is any light reflected off the restoration?

Where is the basic shade of a restoration?

How is the color around the gingiva?

The edge?

Incisal edge?

Back 4

Some light is reflected off

Basic shade is in center of tooth

More intense color

Orange hue (where enamel plates come together)

Blue hue

Front 5

5. If a restoration is too dark what does it have too much of?

If it's too translucent what happens?

Back 5

Too much chroma

Can be lost inside oral cavity

Front 6

6. What is the Munsell color system?

Back 6

1. Hue
-refers to wavelengths of visible spectrum
-basic color (i.e. red, orange)

2. Chroma
-how much of hue is present
-intensity

3. Value
-brightness

**brighter area has higher value regardless of hue or chroma

Front 7

7. Where is value on the wheel diagram?

Where is hue on the wheel diagram?

Where is chroma on the wheel diagram?

Back 7

Vertical dimension
(amount of whiteness)

Around the wheel
(each space = hue)

Horizontal dimension
(further out on the spoke, the more intense the color)

Front 8

8. What is the L a-b color system?

Back 8

Mathematical system to give color

**Use value and chroma

Value: vertical
Chroma: horizontal

Front 9

9. How is a shade guide ordered?

How do you pick a shade

Back 9

Along value lines

1. Pick hue

2. Best value match

Front 10

10. What is the grayscale based upon?

Back 10

Just value (brightness)

Brightness in each family is not equal

Front 11

11. How does the new value system work?

Back 11

1. Focus on brightness (value)
-5 families of brightness

2. Go down value and determine intensity (chroma)

3. Determine hue
-goes from yellowish to reddish

Front 12

12. What is the vita bleach guide?

How is a shade ordered tab?

Back 12

Pure value based

Use neutral shading w/ evenly spaced value

Decreasing in brightness

Front 13

13. What is infinite optimal thickness?

How does it vary?

Back 13

Point at which doesn't matter what's behind material

Varies w/ wavelength and w/ composite shade used

Front 14

14. What does the scattering coefficient do?

What does it depend on?

Back 14

Good, it adds opacity and allows for chameleon effect

Depends on wavelength (light source) and composite

Front 15

15. What is metamerism?

What is isomerism?

What color gives the best shade matching?

Back 15

Two objects match under one light source but not under another light source are a metameric pair

Matching under all light sources

Light blue

Front 16

16. What is fluorescence?

How do crowns and teeth fluoresce?

Back 16

Emission of light from a material at wavelengths different than the illuminant

Teeth fluoresce blue under UV light

Crowns don't fluoresce

Front 17

17. What are some clinical consideration in optical properties and color?

Five things...

Back 17

1. Hue, chroma, and value

2. Opacity and translucency

3. Gloss and reflectance

4. Reflected and transmitted color

5. Light source or illuminant

Front 18

18. What 3 things does perceived color depend upon?

Back 18

1. Materials properties (what's absorbed, reflected)

2. Illuminant properties (histogram)

3. Receptor or sensor

Front 19

19. Why do you polish restorations?

Four things...

Back 19

1. Reduce adhesions
-reduce adhesive plaque

2. Produce a smooth feel
-feel natural so patient doesn't notice

3. Enhance esthetics: reflection

4. Reduce corrosion
**smooth area has less surface energy than rough surface

Front 20

20. How are reflections affected by polishing?

Back 20

Reduce scratches so increase amount of ordered reflections

Decrease diffused reflections and specular reflections

Front 21

21. How are smooth and glossy different?

When polishing what do you remove?

What is considered dull?

What is considered rough?

Back 21

Smooth is tactile
Glossy is visual

Progressive abrasion
Removal of scratches

Dull: > 0.5 um scratches

Rough:
> 20um gives rough "feel"
< 2um gives smooth "feel"

Front 22

22. How are optical properties and color related to x-ray irradiation?

Back 22

Want it to be opaque to x-ray

Radiopacity: appears white

Radiolucency
-composites containing lithium, barium, and strontium

Front 23

23. What is specific heat?

Back 23

Amount of heat needed to raise one gram of substance one degree
-equal calories

For 1g of water, specific heat = 1 calorie

Front 24

24. What is the heat of fusion?

What is thermal conductivity?

What does it equal?

What does it not consider?

Back 24

Change in physical state (solid to liquid)

Speed of heat flow through material
-how fast does heat go through a material

Calories / second x cm x degree

Does not consider calories needed to raise the material itself by a given degree of heat

Front 25

25. What is thermal diffusivity?

What does it equal?

What is it a measure of?

What does it depend on?

Back 25

Rate at which a body w/ non-uniform temperature approached equilibrium

Conductivity / specific heat x density

Measure of transient heat flow

Depends on properties of material

Front 26

26. What is a thermal shock to the tooth?

Back 26

High thermal diffusivity material w/....

1. Low specific heat

and/or

2. High thermal conductivity

**Metallic metals have high potential for thermal shock to tooth

Front 27

27. What are the thermal diffusivity for material such as dentin, enamel, amalgam, resin composite, pure gold?

Back 27

Dentin and enamel are about same (.183 or .258 and .469 respectively)

Amalgam ~ 9.6

Resin comp. ~ .238 (good)

Pure gold ~ 118

Front 28

28. What is the linear coefficient of thermal expansion?

What are examples of linear coefficient of thermal expansion for tooth, amalgam, wax, acrylic, resin composite?

Back 28

Linear expansion per degree Celsius

Tooth ~ 11.4
Amalgam ~ 22-28 (little higher)
Resin comp ~ 14-15
Acrylic ~ 76
Inlay wax ~ 350-450

Front 29

29. What are the clinical implications of thermal expansion?

Back 29

1. Percolation at restoration margins

2. Porcelain addition to PFM crowns

3. Casting of indirect metal restorations

4. Wax pattern production and handling

Front 30

30. What is percolation?

Back 30

Pumping action that allows fluid to get along a restoration and allows fluid access to cut down dentin tubules

**Bad

Can cause composite restoration to fail

Front 31

31. What happens in metal undercasting?

Back 31

Opaquing layer fused to metal

2nd layer of porcelain powder being added

**expansion and shrinkage is matched to metal

Front 32

32. What are 4 electrical and electrochemical properties of materials?

Back 32

1. Electrode potentials

2. Resistivity / Conductivity

3. Galvanism

4. Electrochemical corrosion

Front 33

33. What is the electrode potential of an element?

What is the reference?

What is oxidation potential?

What is reduction potential?

Which metals have large positive reduction potential and resist corrosion?

Back 33

Ability to gain or loose electrons in solution

Hydrogen = 0 volts

Electron loss potential

Electron gain potential

Gold and platinum

Front 34

34. What is resistivity / conductivity?

What does resistance equal?

Back 34

Ability of a material to support flow of an electrical current

Resistivity x length / c.s. area

Front 35

35. What are some examples of resistivity?

Back 35

Enamel 2.9-3.6 x 10^6

Dentin .7-.6 x 10^4

ZOE cement 1 x10^9 - 10^10

Front 36

36. How doe electrical caries monitor work?

Back 36

Porosities develop in enamel

Fill w/ electrolytic saliva
(when filled w/ saliva conducts electricity better)

Decreased resistivity measured

**measure current flow through caries area (conduct current better than healthy areas)

Front 37

37. What is galvanism?

Back 37

Presence of an electric cell in the oral environment resulting in clinical sensation

1. Restorations w/ dissimilar electrical potentials, saliva, bone fluids: short-circuit thru dental pulp

OR

2. Single restoration, saliva, bone fluids

Front 38

38. What is electrochemical corrosion?

Back 38

Surface/subsurface electrical/chemical action

1. Loss of material
2. Roughness and pitting

Front 39

39. What is tarnish?

Back 39

Surface dulling and discoloration by chemical reaction

1. No loss of material, roughness, or pitting

2. Common reactions: chlorides and sulfides