Material Properties restorative

8/13/2019 Material Properties restorative

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Material Properties


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Material Properties

Physical Properties

Mechanical Properties

Chemical Properties Biologic Properties


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Physical Properties

Thermal Properties

Temperature = Expansion

Temperature = Contraction


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Physical Properties

Thermal Properties Coefficient of Thermal Expansion- rate of change in

relation to temperature

Linear Coefficient of Thermal Expansion- if it is referring to

a single dimension

Average LCTE

Ceramics 1 to 15 ppm/ C

Metals 10 to 30 ppm/ C

Polymers 30 to 300 ppm/ C

Tooth Structure 9 to 11 ppm/ C


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Physical Properties

Thermal Properties

Percolation- cyclic ingress and egress of fluids at the

restoration margin


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Physical Properties

Heat Flow

Insulators- materials that does not permits an

electric current to flow

Conductors- materials that permits an electric

current to flow

Thermal Conductivity- rate of heat conduction

Thermal diffusivity- amount of heat conductionper unit time


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Physical Properties

Heat Flow

Dental pulp can withstand

37-42 C for 30-60 sec without any

permanent damage


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Physical Properties

Electrical Conductivity

Is a measure of relative rate of electron transport

through metal


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Physical Properties

Mass

Involves density and specific gravity

Density = materials weight / mass per unit volume

Metal- 6 to 9g/ cm3

Ceramic- 2 to 6 g/cm3

Polymer- 0.8 to 1.2 g/cm3

Specific Gravity density of material / density of water

1g/cm3


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Physical Properties

Optical Properties

Interactions with electromagnetic radiation

Propagation of light:

1) Reflection :

light is reflected in all directions, this is called diffuse

reflection

light in one direction only, this is called specularreflection


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Propagation of light:

2) Refraction : is a change in the direction of light as it enters the other

medium

3) Scattering :

this occurs when light passing through an opticalmedium redirects some of the radiation into directionother than that of the beam.

4) transmission:

light passing through an optical medium withoutattenuation is said to be completely transmitted. Totaltransmission is undergone by perfectly transparentmaterial


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Transparency, Translucency, Opacity

and Metamerism

Transparency: is the property of materials that

allow the passage of light in such a manner thatobjects can be clearly seen through them. e,.g.

glass and clear acrylic resin.


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and Metamerism

Translucency: is the property of materials that

allow the passage of some light but disperses

( scatters or reflects) the rest so that objectscannot be clearly seen through them e.g. dental

porcelain, composite resin and pigmented

acrylic resin .


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and Metamerism

Opacity: is the property of materials that

prevents the passage of light. An opaque

material either absorbs or reflects all of the

light. When all light is absorbed the materialappears black.

Examples of opaque materials are metals.


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and Metamerism

Metamerism : the color of objects under one

type of light may appear different under

another light source.


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Physical Properties

Color parameters:a) Hue: this represents the color of the material .

E.g. blue, green, yellow , orange,

b) Chroma: it is strength of color, or it is a measurementof color intensity. A beaker of water containing one dropof colorant is lower in chroma than a beaker of watercontaining ten drops of the same colorant.

c)Value : it represents the lightness or darkness of a

color. A black standard is assigned a value of 0, where as awhite standard is assigned 100. A tooth of low valueappears gray and non-vital therefore it is the mostimportant parameter.


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Physical Properties

Munsells

Chart


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Physical Properties

Surface properties

interaction with other materials

How the surface interacts with saliva, cells and other

materials

Clinical consequence:

Bonding and adhesives

Wetting can be anticipated on the basis of the

Hydrophobicity (water-hating) and hydrophilicity (water

loving) of materials


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Physical Properties

Measure: contact angle used to measure how liquid interacts

with solid

Good wettinglow contact angle (approach 0)

Poor wetting- high contact angle (approach 180)


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interaction of materials with loading

EXTERNAL LOAD

Compression

Tension

Shear

TorsionFlexion


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LOAD Deformation


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Stress and Strain

Stress = Load per unit of cross sectional area

= Load / Area

Stain = Deformation / unit length


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Plastic Deformation

Ductile (Tension)

Malleable (Compression)

Brittle


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Studying Stress-Strain Curves

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Material Properties restorative