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Dental Materials > 2. Physical Properties of Dental Materials > Flashcards

2. Physical Properties of Dental Materials Flashcards

1
Q

Physical Properties of Dental Materials

____ Properties
____ Properties
____ Properties

A

Thermal
Rheologic
Optical

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2
Q

Physical Properties

Properties of a material based on ____ laws

How materials respond to changes in their ____

Laws of mechanics, optics, thermodynamics, electricity, magnetism, radiation etc.

A

physical

environments

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3
Q

Thermal Properties

thermal ____
thermal ____
thermal ____

A

conductivity
diffusivity
expansions

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4
Q

Thermal Conductivity

The ease with which heat is ____ through a material
— ____ Vibrations, Motion of electrons

Heat passing through a body, 1cm thick and 1cm2 cross-section per second when the temp. diff. is 1oC

Units: ____ (W.m-1.K-1)

A

transferred
lattice
cal/cm.sec.celsius

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5
Q

Thermal Conductivity

____ are better heat conductors than ____

Large metallic restorations require an ____ to protect the pulp

Heat flows from ____ temp points to ____ temp points

A 
metals
non-metals
insulating cement base
high
low
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6
Q

Relative Values of Thermal Conductivity

Metallic materials have higher ____ than non-metallic materials

Cover the base of preparations with non-metallic materials (____) before you place the metallic restoration above it

A

thermal conductivities

zinc oxide

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7
Q

Thermal Diffusivity (h)

The ____ at which the temp. of a body changes as heat passes through it

The transfer of heat from a hot to a cold source depends on both ____ and ____ and ____.

kappa = Conductivity (cm2/s) ; Cp= Heat capacity (cal/g.C); p = Density (g/cm3)

____ doesn’t take into account the specific heat and density; thermal diffusivity does take it into account

A 
rate
thermal conductivity
density
specific heat
thermal conductivity
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8
Q

Specific heat (Cp)

- Quantity of heat to raise the temp of a unit volume of a material by \_\_\_\_ degree C - Units: \_\_\_\_
A

1

cal/gm^-1 oC

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9
Q

Relative Values of Diffusivity

Metallic materials are highly ____; and non-metallic materials are ____ (low conducting)

A

conducting

insulating

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10
Q

Considerations for Insulation

Lining efficiency is proportional to the ____, divided by the square root of the ____

____ based is desired when placing restorations

A

thickness of insulating material
thermal diffusivity

highly thick

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11
Q

Coefficient of Thermal Expansion

Change in ____ per unit of the original length (of an object) when its temperature is raised 1 oC.

The coefficient (alpha) increases with ____

A

length

temperature

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12
Q

Thermal Expansion

Clinical Consequences

  • ____ around restorations
  • Shrinkage of ____
  • Differential shrinkage of ____

Filling material with high thermal expansion; if patients eats cold ice, the filling will ____ and the margins will be eliminated resulting in leakage

Two materials of PFM crowns expand and contract to ____, must be wary of fractures

A 
leakage
wax patterns
PFM crowns
shrink
different degrees
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13
Q

Relative Values of Coefficient of Thermal Expansion

Heat all to same degree; the dotted line is the amount of expansion you will observe (____ expands the highest)

Amalgam is ____ tooth, composite is ____ tooth, and acrylic is ____ tooth structure

A

acrylic
2x
3x
8x

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14
Q

Biological Consequences

____ along tooth/restoration interface

Corrosion products from ____ reduce microleakage

A

microleakage

amalgam

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15
Q

Rheology (Flow Properties)

Study of ____ of materials

Viscosity is the ____ to flow of a material under an applied stress

High viscosity implies ____ flow

A

flow
resistance
slow

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16
Q

Viscosity

Two plates with liquid in between them; apply force resulting in velocity (v)

Based on force applied you can determine the ____ (____)

____ > velocity of the top plate divided by the distance between

Based on the two > determine the ____ (____)

A

shear stress
MPa

shear strain rate

viscosity
centipoise

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17
Q

Some Typical Values of Viscosity

Pure water at 20oC = ____ cp

Light body polysulfide = ____ cp at 45oC

Heavy body polysulfide = ____ cp at 36oC

A

1.0
281,000
1,360,000

18
Q

Rheologic Behavior Fluids

Moving the top plate, moves at a velocity (v); distance and area are fixed > the only things change are the force and velocity

If you apply a force on top plate, and the movement is proportional (velocity) > you can plot shear stress (F) and strain rate (velocity) > if force and velocity are ____, you get a straight line between > force is occurring in a ____

If plate is moving rapidly (little force, lots of velocity) > fluid is behaving as ____ (shear thinning > as you increase the shear the material acts as if it was very thin)

____ (velocity decreases as you increase the force) is opposite to pseudoplastic > plate begins to move, you need much higher forces to continue to get it to move

Plastic > when you apply a force it doesn’t move until you hit a ____ of force

A 
propertional
newtonion fluid
pseudoplastic fluid
dilatant
threshold
19
Q

Rheologic Behavior Fluids

Newtonian Fluid
eg. ____

Pseudoplastic Fluid
(Shear thinning)
eg.
____

A

ZnPO4 cement

Znpolycarboxylate

20
Q

Viscosity (Other flow behavior)

Thixotropic Behavior

Viscosity that is dependent on ____

Molecular ____ during mixing

Thixotropic manner > viscosity changes upon previous deformation (mixing paint, for example); you break up the ____ as you deform the material, thereby making it less ____

A

previous deformation
rearrangement
secondary molecular bonds
viscous

21
Q

Flow and Cementation of Crowns

Flow behavior of cement determines pressure needed for ____

If cement is pseudoplastic > little force on crown and it goes easily and becomes ____ (you probably want a pseudoplastic cement in your practice)

If newtonian > force and pressure and ____

A

complete eating
well seated
proportional

22
Q

Color and Esthetics in Dentistry

Electromagnetic radiation from the sun

Light is electromagnetic radiation of wavelength ____ nm

Primary colors : ____

A

400-700

red, blue, green

23
Q

Visible light

Spectrum of white (visible) light

Wavelength range
____ nm

Wavelength of maximum visual perception -____nm

Range is ____nm for wavelength of maximum visual perception

A

400-700
555
540-570

24
Q

Spectral Distribution of Light

Different light
sources have
different
wavelength
distribution

Combine both ____ and ____, you form daylight

Tungsten lamp > strong ____ component

A

typical direct sunlight
blue sky light
red

25
Q

Spectral Distribution of Light

Fluorescent Light

Neylite

Vitalight

Neylite and Vitalight > made to simulate ____

A

natural daylight

26
Q

The Color Wheel

Primary colors: ____

Complementary colors: Colors ____ each other on color wheel.

A

red, blue, green

opposite

27
Q

The Color Wheels

Light mixture (Additive) color system
Pigment mixture system
Primary colors - blue, green, red
Complementary to blue: ____; red: ____; green: ____

We are using the ____ system (the square on top)

A

additive

yellow
cyan
magenta

Additive

28
Q

Color Measurement Systems

____ System
Hue (circumferential)
Chroma (diameter)
Value (horizontal)

A

Munsell

29
Q

The Color Solid

The three dimensions of color

Value = ____ from top to bottom

Chroma increases from ____ to ____

Hue changes ____

A

decreases
center
outward
circumferentially

30
Q

Color Measurement Systems

In addition to the hue-value-chroma system, there exists another system (____)

Value = central axis; chroma = diameter axis; hue = circumfertial

A

Lab color system

31
Q

Definitions (color perception)

Metamerism

Change in color matching of two objects
under different light sources

The first property is metamerism. Metamerism occurs when we have 2 objects that when we expose them to ____ light source they appear to be ____.
Object 1 and object 2 with light source A seems to have the same color. But when you
expose the same 2 objects to a different light source. They appear mis matched. We say
that we have ____.

A

one
matched
metamerism

32
Q

Definitions (Color perception)

Translucency/
Opacity

Amount of ____
light transmitted
by an object that
____ part of the light

Transparent material = ____; completely opaque = ____; and in between you have several degrees of translucencies

Enamel is more ____ (____) than dentin

A 
incident
scatters
0
1
translucent
transparent
33
Q

Definitions (Color perception)

Gloss:
Proportion of ____ reflection to ____ reflection of light

Specular reflection is high if you have a highly ____ surface; and vice-versa

A

specular
diffuse
glossed

34
Q

Definitions (Color perception)

Fluorescence
____ nm absorbed
(near ____ radiation)

____nm emitted (____)

When in your teens, you have more ____ and light can be absorbed making that part of the tooth look blue (fluorescence)

A

300-400
uv

400-450
blueish

enamel

35
Q

Color Rendering Index

Degree to which a light source can ____ the color of an object compared to a reference source

A

impart

36
Q

The Tooth Shade Guide

Viewed with different light sources

Tungsten light > all the teeth look ____
Blue sky light > ____

Light source ____ which color shade you end up selecting (you want ____ sunlight)

A

yellow
blueish
influences
directing

37
Q

Lights for Shade Matching

Artificial light sources that mimic ____ (____)
For accurate consistent shade matching

A

sunlight

wavelength distribution

38
Q

Shade Selection for Restorative Dentistry

Shade guide tabs arranged in ____ order of value (From ____ to ____)

Main issue with shade matching is obtaining the right ____ (hue varies minimally)

A

decreasing
light
dark
value

39
Q

Shade Matching in Dentistry

Light sources (at least 2)
Background color
Color blindness

Tooth color is not completely uniform; ____ is usually darker than the rest of the tooth; sometimes you have to take different shades for different parts of your teeth

Must be aware of the ____ on shade matching (bright color background will affect the shade)

A

gingival margin

background color

40
Q

Other Properties

Tarnish

- \_\_\_\_ discoloration of a metal
- Saliva, \_\_\_\_, chemicals
- Thin films of \_\_\_\_, sulfides and chlorides

Corrosion

- Reaction of \_\_\_\_ material with environment
- Progressive and \_\_\_\_
- Aggravated by \_\_\_\_, acidity, and corrosive compounds (oxygen, chlorine, sulfur and other chemicals)
A

surface
bacteria
oxides

metallic
destructive
water

41
Q

Other Properties

Electrical - Galvanism

Opposing ____ restorations

Saliva as ____
Current Flow

A

metallic

electrolyte

Dental Materials (7 decks)

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