Intro to Dental materials slides

Question 1

Is the stress on the stress-strain curve when it ceases to be linear

Answer 1

Proportional Limit

Question 2

Yield Strength is…

Answer 2

Is the stress at some arbitrarily selected value of permanent strain

Question 3

The Elastic Modulus is…

Answer 3

a measure of
the stiffness of a material The Elastic Modulus is the slope of the stress-strain curve in the initial
straight-line portion

Question 4

Ultimate Strength is…

Answer 4

the stress at which the fracture occurs.

Question 5

Denture base should be constructed from a rigid material for two reasons:

Answer 5

1. Load distribution

2. To be used in thin sections without bending

Question 6

The Yield strength of human enamel is…

Answer 6

344 Mpa

Question 7

The Yield Strength of composite are…

Answer 7

138-172 Mpa

Question 8

Average of biting forces: For molars***

Answer 8

580 N

Question 9

Average of biting forces: Bicuspids ***

Answer 9

310 N

Question 10

Average of biting forces: Cuspids***

Answer 10

220 N

Question 11

Average of biting forces: Incisors***

Answer 11

180 N

Question 12

Patients with restorations and prosthesis decreases the biting forces by**

Answer 12

50-80%

Question 13

Stress is…

Answer 13

is the internal action to the external applied force

Question 14

Stress =

Answer 14

=Force/Area

Question 15

For a given force, the_______ the area over which is applied, the______ the value of the stress

Answer 15

smaller

larger

Question 16

Strain is…

Answer 16

Is the change in length per unit length of a material produced by stress.

Strain = Deformation/Length

Question 17

elastic strain is…

Answer 17

Temporary

Question 18

Plastic strain is…

Answer 18

Permanent

Question 19

Ultimate compressive strength for human enamel?

Answer 19

400 MPa

Question 20

Ultimate Tensile strength for gold alloys?

Answer 20

414-828 MPa

Question 21

Ultimate tensile strength for nickel-chromium alloy?

Answer 21

421 MPa

Question 22

Elongation and Compression is?

Answer 22

The amount of deformation that a
material can resist before rupture
and is reported as the percent of
elongation when the material is
under tensile stress or the percent
of compression when it is under
compressive stress.

Question 23

The percent of elongation and compression are measures of

Answer 23

ductility and malleability, respectively.

Question 24

Percent of Elongation—>

Answer 24

Ductility

Question 25

Percent of Compression--->

Answer 25

Malleability

Question 26

indicate the brittleness of the material.

Answer 26

Ductility, and Malleability

Question 27

In general, alloys with elongation less than 5% are considered

Answer 27

brittle

Question 28

Alloys with elongation higher than 5% are considered

Answer 28

ductile

Question 29

 Toughness:*****

Answer 29

Energy necessary to fracture a material

Question 30

 Resilience:*****

Answer 30

Energy required to deform a material permanently

Question 31

The resilience has a particular importance in the evaluation of:

Answer 31

1. Orthodontic wires, for the expected amount of work from a spring to move a tooth. 2. Acrylic denture teeth: they are more resilient than porcelain so, they absorb most of the masticatory forces & transmit less force to the ridge

Question 32

The hardness of dental materials is | reported in...

Answer 32

Knoop hardness

Question 33

A material is considered hard if it

Answer 33

strongly resists indentation by a | hard material such as diamond.

Question 34

Galvanism Results from the

Answer 34

presence of dissimilar metals in the mouth

Question 35

is a measure of the body’s response to an | specific material.

Answer 35

Biocompatibility

Question 36

The linear thermal expansion is expressed as a

Answer 36

coefficient of | thermal expansion

Question 37

coefficient of thermal expansion for Wax

Answer 37

300-1000

Question 38

coefficient of thermal expansion for Human teeth

Answer 38

10-15

Question 39

coefficient of thermal expansion for Composites

Answer 39

25-68

Question 40

coefficient of thermal expansion for Gold alloy

Answer 40

12-15

Question 41

coefficient of thermal expansion for Amalgam

Answer 41

22-28

Question 42

coefficient of thermal expansion for Porcelain

Answer 42

8

Question 43

Thermal conductivity of Dental amalgam

Answer 43

0.055

Question 44

Thermal conductivity of Gold alloys

Answer 44

0.710

Question 45

is a measure of the affinity of a liquid for a solid as indicated by spreading of a drop.

Answer 45

Wettability