Dental Materials - Chapter 3 Terms

Front 1

Physical properties

Back 1

based on law of physics; describe mass, energy, force, light, heat, electricity, and other physical phenomena

example: color, density, thermal conductivity

Front 2

Mechanical properties

Back 2

subgroup of physical properties; describe material's ability to resist forces, dependent on amount of material and on size and shape of object

-example: stiffness, strength

Front 3

Chemical properties

Back 3

describe setting reactions, decay or degredation of materials

-example: gypsum products set by precipitation process; dental composites polymerize

Front 4

Biological properties

Back 4

effects material has on living tissues

Front 5

Density

Back 5

amount of mass in a given volume

unit: grams/centimeters^3

density depends on type of atom present, packing of atoms together, and voids in the material

Front 6

Vapor pressure

Back 6

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

-temperature increases, vapor pressure also increases

high vapor pressure- evaporates quickly (useful as solvents in application of viscous fluid)

low vapor pressure- does not evaporate quickly

Front 7

Thermal conductivity

Back 7

rate of heat flow through a material; measurement of conductivity depends on distance traveled, area that is traveled and difference in temperature between source and destination

measures heat flow over time

unit: calories/second x meter x degree

Front 8

heat capacity

Back 8

measure of amount of thermal energy that a material can hoard

Front 9

specific heat capacity

Back 9

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

unit: cal/gram x degree

Front 10

heat of fusion

Back 10

amount of energy required to melt a material

Front 11

heat of vaporization

Back 11

amount of energy required to boil material

Front 12

Coefficient of thermal expansion

Back 12

measure of this change in volume in relation to change in temperature

-measures expansion, or shrinking/contracting of material when heat is applied

fractional change in volume or length

Front 13

percolation

Back 13

the opening and closing of a gap between material and tooth structure when heating and cooling of area occurs

results in microleakage, tooth sensitivity, and recurrent decay

Front 14

Hardness

Back 14

property that is measured by scientific instruments

-instrument presses a special tip into surface of material, size of indentation is measured and used to calculate hardness

-different methods: Brinell and Knoop method as well as Rockwell and Vickers hardness test

Front 15

abrasion resistance

Back 15

ability of a material to resist wear and tear done by food, opposing teeth and other dental materials

-important in dentistry for proper use of dental materials to increase longevity

Front 16

Goldilocks Principle

Back 16

not to hard, not too soft, just right principle when choosing restorative material in dentistry

-concept that material must be hard enough to avoid wearing away, but not too hard that it wears the opposing tooth structure

Front 17

Solubility

Back 17

amount of material that dissolves in a liquid

important in dentistry because high solubility of restorative material will result in dissolving of restoration and risk of recurrent decay

Front 18

Water Sorption

Back 18

ability of material to absorb water

Front 19

Color

Back 19

complex phenomena; psychological response to physical stimulus

light hits rods and cones of eye and projects as different colors

perception varies by individual

Front 20

Shade Guide

Back 20

set of color tabs or shades that each esthetic material has

Front 21

Force

Back 21

weight or load applied to an object

Front 22

Load

Back 22

weight that is applied to another object

Front 23

Stress

Back 23

force divided by area on which force has been applied; response to a force

stress=load/area

measured in psi or pascals

Front 24

Elasticity

Back 24

phenomena in which an object can be stretched or bent, and returns to original position, because atomic bonds of object allow flexibility and return to original position

Front 25

Strain

Back 25

change in length divided by original length

-measured as a fraction or percentage

Front 26

modulus of elasticity

Back 26

slope of graph of stress and strain, Young's modulus

-modulus=stress/strain

characteristic of atoms and atomic bonds of an object

scientific term for stiffness of material

measured in psi pascals

Front 27

Elastic deformation

Back 27

when stress is removed and object returns to original length, initial change in length is referred to as elastic deformation

Front 28

plastic deformation

Back 28

also known as permanent deformation; point in which object is stressed enough where it does not return to original shape and becomes permanently stretched out

Front 29

permanent deformation

Back 29

also known as plastic deformation; when object is stressed to the point where it does not return to original shape

Front 30

elastic limit

Back 30

interchangeable with proportional limit, and yield point; point on the stress-strain plot at which a line starts to curve and plastic deformation begins

Front 31

Proportional limit

Back 31

interchangeable with yield point or elastic limit, point on a stress-strain plot

Front 32

yield point

Back 32

interchangeable with proportional limit or elastic limit, point on stress-strain graph

Front 33

ultimate strength

Back 33

stress applied that exceeds the strength of object; point at which object breaks from too much stress

Front 34

ultimate tensile test

Back 34

if tensile test is being done on object, point at which object breaks

Front 35

ultimate compressive strength

Back 35

when performing compressive test, point at which load causes enough stress to break atomic bonds and break object

Front 36

Compression

Back 36

type of stress; pushing or crushing stress

Front 37

Tension

Back 37

pulling stress

Front 38

shear

Back 38

stress that occurs when parts of object slide by one another

Front 39

torsion

Back 39

stress when twisting force is applied

Front 40

Bending

Back 40

combination of several types of stress, one side is compressed, and opposite side is stretched, shear forces also occur inside the object

Front 41

Poisson's ratios

Back 41

mechanical property; ratio: (strain in direction of stress) to (strain perpendicular to stress)

-example: when one bites down on filling and compressive force is applied in occlusal/apical directions, mesial/distal and buccal/lingual filling areas become wider (microscopic degree)

Front 42

resilience

Back 42

ability of object to absorb energy and not become deformed

-measured as area under the stress-strain curve up to the yield point

Front 43

toughness

Back 43

energy absorbed up to the failure point of an object on the stress-strain diagram

Front 44

Fracture toughness

Back 44

measure of energy required to fracture a material when a crack is present

-measured in megapascals times square root of meters

-glass and dental porcelain have low fracture toughness, where as metals have high fracture toughness

Front 45

Fatigue

Back 45

failure of object after being stressed repetitively for long time

test requires the object be repetitively stressed and number of cycles recorded until object breaks

Front 46

Creep

Back 46

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

increases as temperature increases

Front 47

Stress relaxation

Back 47

similar to creep, occur slowly, over time

slow decrease in force over time

increase as temperature increases

Front 48

stress concentration

Back 48

phenomena in which stress increases around the defects