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Flashcards in Test One Deck (107):
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Dental impression compound

Tray compound - rigid

Impression compound

1

Impression plaster

Rigid

2

Zinc oxide- eugenol impression material

Rigid

3

Alginate impression material

Flexible

4

Agar hydocolloid impression material

Flexible

5

Agar- alignate impression material

Flexible

6

Elastomeric impression materials

Flexible

Polysulfide rubber impression material, silicone rubber impression material (condensation type & addition type), polyether rubber impression material

7

Gypsum dental plaster and stone

To produce a positive reproduction of the oral structures

*** remember that the patients impression needed to be in a bag with birex for at least 10 minutes to disinfect prior to pouring ***

8

Uses for plaster

- to fabricate study models for tx planning

- diagnostic aid- view mouth from all angles

- serves as a permanent record of the patients occlusion & alignment of their teeth prior to treatment

- visual aid during case presentation for patient education

9

What does mounting casts to the articulator do?

Reproduces the "hinge" motion of the jaw

10

Gypsum in rock form, ground and heated to remove water- powder particles porous & rough- betshemihydrate

Plaster

11

Gypsum in rock form, ground & heated under steam pressure to remove water. Powder particles smooth and dense - alpha- hemihydrate

Stone

12

Modifiers added to gypsum

Potassium sulfate- accelerator
Borax- retarder and reduce setting expansion
Pigments- buffs and pastels added to distinguish between plaster (white) and stone (yellow)

13

Ada classification system

5 gypsums- two plasters and three stones

14

Five types of gypsum

Type 1- impression plaster - rigid, edentulous pts only

Type 2- model plaster- construct study models (tx plan)

Type 3- dental stone- casts for denture fabrication (rpd, rfd)

Type 4- die stone- cats for in/onlays, crowns, bridge fabrication (high strength, hardness and low expansion)

Type 5- high strength, expansion stone- newest edition; accommodates the greater shrinkage of newer alloys

15

Rigid, edentulous pts only

Impression plaster

16

Construct study models (tx plan)

Model plaster

17

Casts for denture fabrication (rpd, rfd)

Dental stone

18

Casts for in/onlays, crowns, bridge fabrication- high strength, hardness and low expansion

Die stone

19

newest edition; accommodates the greater brink age of newer alloys

High strength, high expansion stone

20

Strength and hardness is directly related to...

The amount of water added to powder

21

More water =

Weaker mix

22

Exothermic reaction

Water controls strength, rigidity & hardness
Formation of "crystals"- these crystals gives final strength & rigidity

23

Too much water added to powder...

Increase in setting time, fewer crystals - reduced strength

24

Not enough water mixed with powder

Reduces setting time, less working time, crumbly mixture of reduced strength

25

Ideal water temp for impression setting

68-72 degrees

26

High water temperature

Accelerates set time

27

Lower temperature...

Prolongs set time

28

What does a mechanical vibrator do?

Removes air bubbles

29

Approximate working time for pouring

5 minutes

30

Initial set takes about...

7-15 minutes

31

Final set takes about

45-60 minutes

32

Dry set takes about

24 hours

33

What is the function of the impression material?

To accurately record the dimensions I oral tissues and their spatial relationship to make a replica of the oral tissues

34

Properties for an ideal impression

- ease of manipulation and reasonable cost

- appropriate setting time

- safe (non toxic)

- good keeping qualities

35

Is used to prepare a custom made preliminary impression or tray that will record the final impression

Tray compound

36

Commonly used to take a final impression of a tooth prep and help check the accuracy of the prep

Impression compound

37

Composition of a dental impression

-40% resin
- 7% waxes
- 3% organic acids
- 50% fillers (chalk, talic... Ect.)
- coloring

38

Must soften and then place in mouth the form it or it can be in a shape of an arch already, then make a tray. Then a rubber impression material will go in "that tray" to take an impression

Tray compound

39

The principle indication for this material is for a "check impression" l. A stick of the material is heated and then is allowed to flow into impression and held until it cools and sets

Impression compound

40

Is rarely used to take impressions because it is so rigid and fractures so easily. This materials primary use is to mount cats of an articulator. Setting time 3-5 minutes

Impression plaster

41

Is early used. Has been replaced by rubber impression materials

Zinc oxide- euginal impression material

42

Irreversible- can not be turned back to a liquid state. Originates from seaweed and kelp. Most widely used dental impression materials because it is easy to mix and manipulate, low cost, flexible.

Alignate impression materials

43

They are global and they have standards in place for nuclear, electrical, construction, Ect.

American national standards institute (ANSI)

44

Different types of alignate

Type 1- fast set, 1-2 minutes

Type 2- normal set, 2-5.4 minutes

45

Powder is added to the...

Water

46

Cooling water decreases temperature and increases....

Setting time

47

Warmer water, increases temperature and decreases...

Setting time

48

Lo lectures for taking an an alignate impression

- all teeth are included
- entire alveolar process
- retromolar area must be present
-maxillary tuberosity present
- detailed, undistorted and bubble free reproduction of the oral tissue

49

Fill the tray in the ______ area first and then move anteriorly

Posterior

50

The impression must be poured within...

One hour

51

Four classes of materials

Metals, ceramics, polymers, and composites

52

- have high thermal and electrical conductivity
- can bend without breaking conducive to restore teeth (ductility)
- do not transmits light (opacity)
- they have a surface that reflects light and appears bright and shiny (luster)

Metals

53

Solidify with their aromas in a regular or crystalline arrangement, often form a cube. The high strength "metallic bond" causes ______ to have high melting temperatures

Metals

54

Superb esthetic result can be achieved
-formed by the union of metallic and nonmetallic element
- porcelain is a type
- very brittle, cannot bend
- high melting point (good insulator)
- not chemical active, natural

Ceramics

55

Used for reinforcing agents or fillers for composites (tooth colored filling)

- veneers, onlays, inlays, crowns, bridges, implants

Glass ceramics

56

Newest addition
- giant long chain organic molecules
-poor conductors of heat and electricity
- tremendous strength
- diverse applications ex. Bathroom caulk

Polymers

57

Used to make dentures, temporary bridges and crowns. If mixed with glass particles ____ are formed into a dental composite an can be used as a posterior restoration

Polymers

58

Holds two solids together

Primary bonding

59

Holds liquids together

Secondary bonding

60

Strong and stable sharing I electrons between two atoms (materials used in dentures)

Covalent bond

61

A bond from a positive and negative charge- cements and table salt

Ionic bond

62

Many atoms share outer electrons with their neighbors- all metals use in bond

Metallic

63

Irregular material solidified

Amorphous

64

Are used as loners and bases close to the pulp under almalgam

Materials that so not conduct either thermal and electrical stimuli

65

The ________ have fluid in them and they may also react (expand or contract) with temperature changes, a base, sealer, liner may be necessary

Dentinal tubules

66

All materials are soluble to some extent, they dissolve in water, the least soluble are _______ and ________

Porcelains and ceramics

67

The loss of small organic molecules in the oral cavity

Solubility

68

The uptake of fluids
- May cause discoloration to materials
- may even cause expansion to the material and even enhance to deal at the margin
- can cause washout (failure of the restoration)

Sorption

69

The force of attraction between the molecules or atoms on two different surfaces as they are brought into contact

Adhesion

70

The force of attraction between the molecules or atoms within a given material (not on the surface)

Cohesion

71

The extent which the adhesive will spread on the surface.

Wetting

72

The angle between the adhesive and the surface is called

Contact angle

73

Good ____ is necessary for two surfaces within the atomic and molecular distances required to achieve chemical interactions

Wetting

74

Poor wetting is due to

-contamination
-plaque in the mouth
- pellicle (thin layer of organic mix in the tooth deposited from salvia)

75

The attraction that the atoms and molecules have for one another

Surface tension

76

A measure of the liquids resistance to forces that tend to cause it to flow

Viscosity

77

High resistance to flow, less likely to flow

High viscosity

78

Refers to the dominant color of the object

Hue

79

Refers to the lightness of the color.
Scale 1-10
1= black
10= white
Natural teeth 6-8

Value

80

Refers to the intensity of the color
Scale 1-10
10= saturated is it rich or is it pale?
Natural teeth are relatively low, in the range of 1-3

Chroma

81

Refers to the fact that light is entering the tooth

- light can be transmitted (light through), reflected (not penetrated at all), scattered (then absorbed)

Translucency

82

Discoloration, it is reversible

Tarnish *

83

The deterioration of metal by a chemical or electrochemical reaction, NOT reversible. Eats away material

Corrosion

84

The more active metal

Anode

85

The site which reduction occurs

Cathode

86

Similar to a battery
- the anode and cathode
- two dissimilar metals reacting and many times seen as a metallic taste
- May be also seen as possible pain

Galvanic cell

87

A gap, groove or slot exists next to or on a metal
- ex. The margin around an amalgam
- is an issue because of secondary decay/recurrent decay forming around the margin

Crevice corrosion

88

What are the three force seen in the oral cavity?

Tensile, compressive, shear

89

The force that pull the objects apart

Tensile

90

An object subjected to force, application of force on an object, squeezing together

Compressive

91

Sliding the too of an object over another

Shear

92

Force per area, when the stress exceeds the cohesive strength of the object, the object breaks

Stress

93

When force is applied and the object experiences some deformation (change)

Strain

94

Young modulus- the stiffness of a material

Elastic modulus

95

Maximum stress limit

Elastic limit

96

Stress/ strain may be caused from

Saliva, chlorine and oxygen

97

A measure of elastic limit ***

Maximum flexibility

98

Permanent strain ***

Plastic Deformation

99

The maximum stress that can be withstood before breaking ***

Ultimate strength

100

The measure of dimensional change that a wire can undergo before breaking ****

Percent elongation or ductility

101

Low ductility ****

Brittle

102

Refers to the ability of a material to resist orcas indentation ***

Hardness

103

A reappeared application of stress to an object, may cause tiny cracks and cause failure ***

Fatigue

104

Gradual but permanent change that occurs because of a constant load ***

Creep

105

Ability to resist further movement of an existing crack

Fracture toughness

106

Is complex, two surfaces brought in direct contact or indirect contact and or with a third body acting between them ***

Wear