Quiz 1: Lecture 1+ 2

Question 1

What is enamel made up of?

Answer 1

Rods and Interrods.

***Rod sheath= narrow space around 3/4 of each rod Keyhole shape

Question 2

What is Intertubular dentin?

Answer 2

Structural component of the hydroxyapatite-embedded collagen matrix- bulk of the dentin

Question 3

What is Peritubular dentin?

Answer 3

Limited to the lining of the tubular walls- little organic matrix densely packed w/ apatite crystals

Question 4

What is the strongest and simplest bond within atoms?

Answer 4

Covalent;

Example 2 H+ bonds overlapping

Question 5

What is the Biological type of properties for materials?

Answer 5

toxicity and sensitivity reactions that occur locally or systemically within associated tissues.

Question 6

What is surface energy ?

Answer 6

A LOW surface energy liquid will readily spread over a HIGH surface energy substance

Question 7

What is Wetability?

Answer 7

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

Question 8

What is Adsorption?

Answer 8

Dissilimar substance in intimate contact with the surface of a solid= adhere
**HIGH energy surfaces will adsorb molecules more readily than LOW energy surfaces

Question 9

What is Absorption?

Answer 9

The uptake of a liquid by a bulk solid. The substance absorbed diffuses into the solid material

Question 10

Describe the Biocompatibility usage test?

Answer 10

Material is placed in a situation identical to its intended clinical use. In animals or humans (clinical trials)

Question 11

What is Microleakage?

Answer 11

Materials may not bond with sufficient strength to resist contraction on polymerization, wear, thermal cycling

Question 12

What does the gap between the tooth and restoration allow?

Answer 12

Allows influx of materials that may irrigate the pulp

Question 13

Acids used to remove smear layer are potential source of irritation.. Depends on:

Answer 13

1) ****Remaining Dental Thickness (RDT) - 0.5mm min
2) Strength of the acid
3) Degree of etching

Question 14

How is stress measured?

Answer 14

The force & the area to which it is applied are measured and stress is calculated from the
RATIO OF FORCE PER AREA* (F/A)

Question 15

What are the types of stress? Specifically Tension?

Answer 15

**Elongation!
Forces are directed away from each other in the same straight line
(Axial- Molecules resist being pulled apart)

Question 16

What is Compression force?

Answer 16

***Shrinkage!
Forces directed toward each other in the same straight line
(Molec. resist being forced more closely together)

Question 17

What is a Shear force?

Answer 17

Forces directed parallel to each other **NOT along the same straight line
(One portion resists sliding past the other)

Question 18

What is a Torsion force?

Answer 18

Twisting forces

Question 19

What is bending forces?

Answer 19

Results from a bending moment

Question 20

What is Strain?

Answer 20

*****Deformation CAUSED by STRESS **

Deformation = deformation/length

Question 21

What is the proportional limit?

Answer 21

The greatest stress sustained without deviation from the linear proportionality of the dress and strain

Question 22

What is Elastic limit?

Answer 22

The greatest stress sustained without permeant deformation

Question 23

Elastic deformation is __________?

Answer 23

***NON-permanent

Question 24

Plastic deformation is __________?

Answer 24

**PERMANENT

Question 25

What is Yield Strength?

Answer 25

The stress at which the material begins to function in a plastic manner. Limited permanent strain has occurred

Question 26

Is Permanent Deformation a good or bad thing?

Answer 26

BOTH*** Destructively: filings, crowns, bridges, can be deformed casing improper occasion Constructively: Ortho appliances adjustment to fix bite..etc

Question 27

What is Ultimate Strength?

Answer 27

-Max stress that a material can withstand in tension or compression. -Greatest stress occurs at the **HIGHEST POINT** (center of graph (C)

Question 28

What is Fracture Strength?

Answer 28

- Stress at which a brittle material fractures | - At the END of graph where it FAILS (BREAKS) (D )

Question 29

What is Elongation?

Answer 29

-Deformation that results from the application of TENSILE FORCE -Takes in the WHOLE CURVE (***Indicates the workability of alloy)

Question 30

What is Elastic Modulus? (Young's Modulus)

Answer 30

* **The measure of elasticity * **The HIGHER the value of E, the MORE STIFF/RIGID the material (Represents the stiffness/rigid/flexible of a material within the elastic region)

Question 31

What is Resilience?

Answer 31

* **Resistance of a material to permeant deformation * The amount of energy needed to deform the material to theproportional limit (Area under the Elastic portion)

Question 32

What is Toughness?

Answer 32

* **The resistance of material to fracture * **Indicates the amount of energy needed to cause fracture * ** Combination of yield strength, ultimate strength, strain INCREASING any of these, INCREASES TOUGHNESS! (-Area under the elastic & plastic area )

Question 33

What is Fracture Toughness?

Answer 33

Fracture Mechanics- Characterizes the behavior of materials with cracks or flaws

Question 34

What do Defects generally do to material ?

Answer 34

**Weaken material and may result in fractures at stresses well below the yield stress. (larger the flaw, less stress need to create flaw)

Question 35

What is Tensile properties of Brittle Materials ?

Answer 35

Tensile properties of brittle materials, hard to measure so ****Diametral Compression Test

Question 36

When creating "Compression strength" of brittle material, what is the pastil response like?

Answer 36

The plastic response is small

Question 37

What is Fatigue strength?

Answer 37

The stress at which a material fails under repeated loading | ***DEPENDS OF MAGNITUDE of the LOAD & the # of LOADINGS

Question 38

What is Endurance Limit?

Answer 38

Stress at which the material can be loaded an infinite number of times WITHOUT FAILING

Question 39

What is Viscoelasticity?

Answer 39

***RATE of LOADING is important for many materials. (alginate, elastomeric immersion materials, waxes, amalgam, polymers)

Question 40

Materials with mechanical properties dependent on loading rate are termed?

Answer 40

***Viscoelastic

Question 41

What is Viscosity?

Answer 41

-The resistance of a fluid to flow ***time and temp DEPENDENT

Question 42

What is CREEP?

Answer 42

Increase in strain in material under constance stress (amalgam)

Question 43

What is Tear Strength?

Answer 43

Resistance to tearing forces | rapid loading = higher value (less likely to tear

Question 44

What kind of bonds to Ceramics have?

Answer 44

-Ionic bonds - crystalline (leucite) and amorphous (glass)

Question 45

What kind of bonds do Metals have?

Answer 45

Metallic bonds- crystalline

Question 46

What kind of bonds do Polmers have?

Answer 46

Molecular solids -covalent and secondary bonds