Dental Materials: Chapter 3

based on the laws of physics that describe mass, energy, force, light, heat, electricity and other physical phenomena

physical properties

subgroup of physical properties. Describes the material's ability to resist forces

mechanical properties

describe the setting reactions as well as the decay or degradation of materials

chemical properties

effects the materials having on a living tissue

biologic properties

amount or mass of a material in a given volume

density

two physical properties of materials

boiling and melting points

measure of a liquid's tendency to evaporate and become a gas

vapor pressure

rate of heat flow through a material

thermal conductivity

measure of amount of thermal energy that a material can hoard

heat capacity

amount of energy needed to raise the temperature of one unit of mass of that material by 1 degree C

specific heat capacity

amount of energy required to melt a material

heat of fusion

amount of energy required to boil a material

heat of vaporation

measure of this change in volume in relation to the change in temperature; shrink or contract

coefficient of thermal expansion

process of heating and cooling, and the accompanying oening and closing of the gap

percolation

new amalgam filling will hurt when it is touched with a metal form. result of electricity flowing from the fork to the amalgam and through the pulp

galvanic shock

material's ability to flow

viscosity

doing this brings material into intimate association with the surface so that chemical and micromechanical bonding can occur

wetting

measured by scientific instruments that press a special tip into the surface of the test material

hardness

measures how deep a steel ball will sink in a soft material

durometer measurements

wear resistance

abrasion resistance

not too hard and not too soft.. just right

Goldilocks principle

amount of a material that dissolves in a liquid such as water

solubility, like sugar

materials absorbing water

water sorption

weight or load applied to an object

force

force divided by the area on which the force has been applied

stress

a measure of push or pull that changes the shape of an object

elasticity

change in length divided by the original length

strain

slope of a graph of stress versus strain

modulus of elesticity

when a stress is removed and the object returns to its original length, the initial change in length is called

elastic deformation

permanently stretched out

plastic deformation or permanent deformation

The point on the stress-strain plot at which the line starts to curve and plastic deformation begins is called

elastic limit, proportional limit, or yield point

exceeding the strength of the spring

ultimate strength

test is a tensile test

ultimate tensile strength

test is a compressive test

ultimate compressive strength

Types of stress

compression
tension
shear
torsion
bending

mechanical property that is the ratio of the strain in the direction of stress to the strain in a direction perpendicular to the stress

poisson's ratio

ability to absorb energy and not become deformed

resilience

the energy absorbed up to the failure point on the stress-strain diagram is the

toughness of materials

measure of the enrgy required to fracture a material when a crack is present

fracture toughness

many things fail after being stressed repetitively for a long time

fatigue

small change in shape that results when an object is under continuous compression

creep

slow decrease in force over time

stress relaxation

stress increases around defects

stress concentration

a drop of water on a popsicle is an example of
a. poor wetting (low contact angle)
b. good wetting (high contact angle)
c. good wetting (low contact angle)
d. poor wetting (high contact angle)

c. good wetting (low contact angle)

the tightening of a guitar string is an example of which of the following stresses?
a. compression
b. torsion
c. shear
d. tension

d. tension

The modulus of elasticity is an indication of what property of a material?
a. resilience
b. strength
c. stiffness
d. tension

c. stiffness

T/F
Cooled materials will contract, and heated materials will expand. A measurement of this change in volume in relation to change in temperature is called the coefficient of thermal expansion.

Both statements are true

When a stress is induced in a material that is greater than the material's yield strength, the stress is _______ proportional to the strain, and the material does not return to its original shape
a. always
b. no longer
c. equally
d. none of the above

b. no longer

Which formula defines the modulus of elasticity?
a. stress/strain
b. stress^2/strain
c. strain/stress
d/ 2 x stress/strain

a. stress/ strain

An example of a physical property is
a. density
b. strength
c. stiffness
d. setting reaction

a. density

A twisting force is termed
a. compression
b. shear
c. tension
d. torsion
e. bending

d. torsion

The ability of a material to dissolve in liquid is termed
a. viscosity
b. water sorption
c. solubility
d. wetting

c. solubility

Elasticity is an example of which of the following properties?
a. physical
b. mechanical
c. chemical
d. biologic

b. mechanical

The rate of heat flow through a material is referred to as
a. heat of fusion
b. coefficient of thermal expansion
c. heat capacity
d. thermal conductivity

d. thermal conductivity

Jennifer is a practicing hygienist who goes to a nearby restaurant each day for lunch. She often orders a cola with ice and a bowl of homemade soup. As she eats and drinks her composite restoration and tooth structure are expanding and contracting at diff

b. coefficient of thermal expansion

Fingernail polish remover has "solvent' properties, as it will remove the polish from our fingernails. Another property polish remover has is its tendency to evaporate. Fingernail polish remover can be said to have.
a. high vapor pressure
b. low vapor pre

a. high vapor pressure

_______ is the force used to condense an amalgam in a preparation

compression

A hardened cement having "low" ______________ can firmly hold a patient's gold crown in place for years in a wet environment

solubility

_____ is the term given to the increase of stress around defects within an object

stress concentration