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Flashcards in Fixed Q2 Deck (162):
1

Once the impression is in stone what is it placed on

articultor

2

what material should the impression be poured up in

gypsum

3

Gypsum. when the semi hydrate is mixed with water, a suspension is formed that is ____ and ____

fluid and workable

4

the hemihydrate dissolves until what point

forms saturated solution

5

what does the hemihydrate solution precipitate out

dihydrate

6

Polymers...

Stone....

Wax...

shrink

expand

temp dependent

7

PIMWIC, what 2 stages shrink, what 2 expand?

Impression and Cast shrink

Mount and Investment Expand

8

Gypsum rxn: powder + water = stone + heat

or...

hemihydrate + water = dihydrate + unreacted hemihydrate + heat

9

In the gypsum rxn, there is dissolution of...

precipitation of....

as long as...

hemihydrate

dihydrate

new crystals form/current crystals grow

10

what is the use for slurry water

to make the stone set quicker

11

how is gypsum classified

1-5 for compressive strength

12

classify the following: mounting plaster, dental stone, model plaster, dental stone-high strength low expansion, dental stone-high strength high expansion

1,3,2,4,5

13

what is the difference between types 4 and 5

4 low expansion

5 high expansion

14

What does the slurry water add that makes the gypsum precipitate more quickly?

More sites of nucleation

15

Gypsum classificaiton, Type I

Type II

Type III

Type IV

Type V

mounting plaster

model plaster

dental stone

dental stone - high strength, low expansion

dental stone - high strength, high expansion

16

Describe the particles of Plaster (gypsum) Type I/II:

This is a _____ hemihydrate:

large, irregular particles

Beta

17

Describe the particles of Stone type III-V:

This is a ____ hemihydrate:

small, greater strength

alpha

18

3 effects of adding water to the gypsum powder:

Increases Setting time

Weaker

Less expansion

19

why is type 3 used for making dentures

the final step of denture making involves breaking the stone. type 3 is easier to break

20

what class of gypsum is used for making impressions on a pt and why

*diagnostic

III

cheaper

21

what class is used for crowns and bridges

4 or 5

22

what type of gypsum should be used for high shrinking base metals

type 5 because it can compensate because it has higher expansion

23

what type of gypsum does Ahwatukee lab use.

Excalibur - type IV

24

Why should a cast be soaked in water before trimming?

Easier to trim, clean up, rid of particles

25

what are the advantages/disadvantages of the removable die system

advantages: it can get to all areas when doing a wax up. easier to fabricate.

Disadvantages: we have moving parts and movement can make contacts stronger or weaker

26

why does the lab send back a solid metal

Verify seating/interproximal contacts

allows for better testing of inter proximal contacts

27

3 ways we mount the 2 arches against each other

maxillo-mandibular jaw relation record

jaw relation record (JRR)

Bite registration

28

In mounting the arches against each other, it is possible to hand articulate when?

What verifies the mounting?

If max intercuspation is stable

bite registration

29

if MIP is not stable what is required to mount the cast accurately

bite registration

30

2 types of Bite Registration matl:

Take 1

Regisil

31

Take 1 (bite reg. matl) Working Time:

Setting time:

Rigidity:

color:

15 secs

1 min.

extremely rigid

green

32

Regisil (bite reg. matl) Working Time:

Setting time:

Rigidity:

color:

45 secs

1 min. 30 secs

less rigid than Take1

purple

33

Working time PVS:

Setting time PVS:

1 min 10 secs

5 min

34

Wax up: why do we mark the margin

to make sure we place it properly

35

What is the purpose of a die spacer?

To make room for cemet

36

Recommended space of die spacer:

comes in various thickness - but factors that influence amount of relief are the type of cement and _____

25-40 micrometers

TOC

37

type 1 wax is ____ hardness and used for _____ technique for making patterns


medium

direct

38

type 2 wax is ______ wax and used for _____ fabrication of castings

softer

indirect

39

Wax expands when heated, contracts when cooled and needs to be burned out cleanly leaving less than ___ % residue.

0.1%

40

T/F
The wax up should look like a tooth

True

41

What is the function of the sprue?

Allows molten wax to escape from mold

42

The design of the sprue must enable the molten metal to do what?

Flow in with little turbulence

43

where should the sprue be attached and what is a common placement

the bulkiest noncritical part and the non functional cusp is usually used

44

How far is the wax pattern usually placed from the top of the investment?

6 mm

45

What is the sprue attached to?

crucible and casting ring

46

The metal within the sprue remains molten slightly longer than the alloy that has filled the mold, providing a ____ to compensate for the shrinkage that occurs during solidification

reservoir

47

What factors influence the expansion of the investment?

Liner

Ring/Ringless

Setting, hygroscopic, thermal expansion

48

Adding liners allows for more expansion of the ______

investment

49

Ringless design allows for what?

unrestricted expansion

50

Hygroscopic expands the most, and is accomplished by doing what?

submerging ring in 100 degree F water bath for 1 hr immediately after investing

51

T/F
In order of increasing Investment expansion: Normal, 1 liner, 2 liner, Hygroscopic

True

52

3 requirements of Investment matl:

Precisely reproduce wax up

Strong enough for heat and casting

Expand to compensate for alloy shrinkage

53

What 3 binding matls regulate Rigidity of the Investment?

Gypsum

Phosphate

Ethyl Silicate

54

What regulates thermal expansion of the Investment matl?

(refractory)

Silica

55

What Investment matl is generally used only for Gold b/c it can't be heated above 650 C?

*not used much any more

Gypsum

56

What Investment matl can be heated above 650 C but has rough casts and is difficult to remove?

Phosphate

57

What Investment matl is used for high fusing base metal partial denture alloys

Ethyl silicate

58

What type of investment material do we use at ASDOH

GC fujivest II which is a phosphate bonded investment that can withstand high temps.

59

GC fujifest II (Investment matl) working time:

Setting time:

6 mim

20 min

60

How are metal alloys classified?

Noble metal content

61

Why do we use noble metals?

Stable, don't corrode

62

High noble alloy:

40% Au

60% nobles

*by weight

63

Noble alloy:

25% noble

*by weight

64

Predominately Base Metal:

less than 25% noble

65

7 Noble metals:

Au, Pt, Pd, Rh, Ru, Ir, Os

66

Elastic Modulus =

Stress/Strain

(rise/run)

67

The stress at which a matl shows a specific amount of plastic strain:

Yield strength

68

Classify metal ceramic crowns: Argebond 80

Argedent Euro

Noble

High noble

69

Classify Full Gold Crown: Argenco 56

Argenco Y+

High noble

Noble

70

What kind of bur would you use to cut through porcelain, metal?

Porcelain - diamond

Metal - carbide

71

High noble, Melting temp:

Shrinkage:

Castability:

Hardness

Corrosion:

lower

less

better

softer

less

72

PVS shrinks and is hydrophobic

True

73

When doing investments what does gypsum, phosphate, and ethyl silicate determine?

Temperature

74

When doing investment what does quartz cause?

Expansion

75

What are the 3 properties of Excalibur Type IV mounting material that we use at ASDOH?

quick setting

low strength

low expansion

76

PVS differentiated by viscosity

stone (I-IV) by strength

Investment by matl (gypsum, phosphate, ethyl silicate, quarz/cristobiolite)

Cast by Nobility

True

77

Lowest point of the Orbitale to highest point of the external auditory meatus

Frankfort Horizontal Plane

78

How should the Frankfort horizontal plane be aligned with the floor?

Parallel

79

What acts as the 3rd point of reference (1. upper margin ext. aud meatus. 2. lower orbitale)

Nasion

80

The average distance between the Nasion and the Frankfort horizontal plane?

23 mm

81

What is the purpose of the Facebow?

Position Max cast onto articulator relating to pts hinge axis in 3 dimensions

82

The path of the condyle follows what?

Articular Eminence

83

As the condylar inclination increases what also increases?

Space between posterior teeth in disclusion

84

What allows the mandibular movements of the articulator to simulate the movement of the mouth?

Facebow record

85

3 things captured in triple tray:

opposing arch

jaw relation

prep (and adjacent teeth)

86

In group function what teeth contact in laterotrusive movement?

posterior

87

Why are we less concerned if pt has canine guidance?

posterior teeth don't contact each other in laterotrusive movement

88

What is the anatomical average Condylar Guidance Angle?

25-30 degrees

89

What info is lost using a triple tray?

guidance in non-working movement

relationship between teeth and hinge axis

canine guidance

90

What are the advantages to using a triple tray?

Minimize use of impression matl

no need for separate impression of opposing arch

jaw relationship w/ PDL in compression

91

T/F
A fully adjustable articulator can move condyles, ours can't

True

92

In what type of articulator dose the condylar inclination stay the same?

Arcon

*we have arcon

93

An Arcon articulator has the condyle on the ______, while a non-Arcon has the condyle on the ______

Mandible

Maxilla

94

In an Arcon articulator, when you open the pin in a vertical dimension, what happens to Vertical Dimension?

Condylar inclination?

Increases

Stays the same

95

Changing the vertical dimension in an Arcon articulator will not change the angle

True

96

What are 5 contraindications to using a triple tray?

Multiple fixed units

Fixed partial denture

survey crown

Class 2 and 3 occlusion

Implants

97

Which articulator do we currently use?

Arcon

98

What establishes the chemical bond between the Metal and Porcelain?

Controlled Oxide layer

99

How do we create an Oxide layer so porcelain can bond to metal?

Put in oven

100

What type of metal has a controlled oxide layer?

What is uncontrolled?

What is a side effect of uncontrolled oxide layer?

Nobles

Bases

Bad adhesion

101

5 Steps to adding Porcelain onto metal:

*in decreasing temperature

Oxidize

Opaque (blocks out metal color)

Margin

Dentin

Glaze

102

Why do all the steps of adding porcelain decrease in temperature?

Sintering

103

What has a higher CTE (coefficient of thermal expansion) - porcelain or metal?

Metal

104

What are the 2 phases of Feldspar?

Glassy

Crystalline

105

If something is 100% gold, could you stack porcelain?

Would be difficult b/c doesn't readily form oxide layer

106

What 2 factors influence the amount of die spacer we use?

Type of cement

TOC

107

How does TOC affect the space in a die spacer?

Less TOC, more die spacer

*If a lot of TOC (lots of taper), cement will flow and less die spacer needed

108

What 4 elements are often added to Noble metals to ensure an Oxide Layer forms?

Iron

Tin

Indium

Gallium

109

Base metals are principally ______ and _______

_______ oxidation provides chemical bonding for porcelain adherence

Nickel, Cobalt

Chromium oxidation

110

T/F
Base metals used for metal-ceramic restorations go through continuous oxidation

True

111

What can the continuous oxide formation by base metals cause?

Potential failure via a Thick Oxide Layer that can't be controlled

112

The oxide layer close to the surface is mostly made up of what element?

Silica (Si)

113

What is the main raw component of dental porcelains?

Feldspar

114

What does Feldspar look like in its mineral state?

Crystalline and opaque

115

2 Types of Feldspar:

Potassium aluminosiclicate "potash feldspar"

Sodium aluminosilicate "soda feldspar"

116

Most veneering ceramics are derived from what type of feldspar?

Potash


(Potassium aluminosilicate)

117

Feldspathic Porcelain exists in what 2 phases?

Glassy (silica)

Crystalline (leucite)

118

What phase of Feldspathic porcelain provides strength?

Crystalline

119

Describe both phases of Feldspar:

Glassy: high translucency

Crystalline: strength

120

How much of Feldspar is made up of the Crystalline phase?

15-25%

121

T/F

Porcelain is stronger when in compression

True

122

The process of forming a solid mass by heat/pressure without melting to lequefaction

Sintering

123

4 Steps to the Firing Chart:

(High to low temp)

Opaque

Margin

Dentin/Mod/Enamels

Glaze

124

Why would a thick oxide layer cause fracture?

Not as strong, if too thick of a hybrid layer can cause structural problems

125

What is a problem of sintering porcelain?

What is a solution?

Fused mass too viscous to allow air to escape = Trapped air/voids

Vacuum firing

126

What is the purpose of the Opaque Layer?

Block the metal from view

127

What has a higher thermal expansion - porcelain or metal?

Metal

128

Because the metal contracts more during cooling than porcelain, this creates what?

Porcelain in slight residual compression

129

T/F
Porcelain does well under tensile stress and not well under compression

False

*Porcelain does well under compression - flat marginal ridge

130

What makes porcelain less sensitive to the tensile stresses induced by mechanical loading?

Residual compression due to metal shrinking more on cooling

131

Bond failures between 2 materials:

Bond failures within a dental material:

Adhesive failure

Cohesive failure

132

Fractures at the metal to metal/oxide layer is a _______ failure and commonly observed with poor ________

adhesive

bonding

133

Why would a fracture occur through the oxide layer?

If oxide layer too thick

*cohesive failure in METAL

134

If everything is properly bonded, where would a fracture occur in a metal/porcelain crown?

Porcelain

*cohesive

135

Dipping a die into molten wax produces an Even Thickness - doing what to the porcelain layer?

Consequence:

Makes uneven

porcelain fractures due to lack of support

136

For predictable success in creating an even porcelain layer onto the metal, use a _____ technique

Cut-back

(from full contour wax up)

137

2 Aqueous Hydrocolloids:

3 Non-aqueous Elastomers

(these are the Elastic categories)

Agar, Alginate

Polysulfide, Polyether, PolyVinyl Siloxane (Condensation/addition)

138

What non-aqueous elastomer is Hydrophilic and rigid, with a defined working time ("snap set")?

Polyether

139

Bottom cord should be what size?

Top cord?

small - 000 or 00

larger - 0

140

Cords are typically soaked in what?

Hemostatic agent

141

2 techniques for Gingival Retraction other than cord:

Expasyl - paste

Laser

142

Advantages to a Supragingival margin:

Disadvantages:

No cord, verify margins

Not esthetic, tooth structure exposed

143

Advantages to an Equigingival margin:

Disadvantages:

minimal retraction

recession will expose margin

144

Advantages to a Subgingival margin:

Disadvantages:

Esthetics

Retraction difficult

145

7 Requirements for Provisional Restorations:

Pulpal protection

Positional stability

Occlusal function

Ease of cleaning

Nonimpinging margins (overhangs, etc)

Strength/Retention

Esthetic

146

If you haven't reduced the occlusal surface enough, the lab sends you...

Reduction Coping

147

A lab prescription should have what 3 surfaces specified for a restoration?

*and another thing:

Facial

Occlusal

Lingual

*shade of porcelain

148

Facial and Occlusal surfaces can be in what materials?

Lingual?

Porcelain or metal

metal

149

When will the lab send you a 360 metal collar?

When facial/lingual surfaces both in metal

150

T/F
360 metal collar has the best marginal integrity

True

151

4 cases in which the used of metal over porcelain on the occlusal surface:

Bruxism

Large mm.

Hx porcelain fracture

Most posterior tooth

152

Why would the most posterior tooth not get a porcelain occlusal restoration?

Teeth shorter - not enough pulpal room for big reduction

153

The vasoconstrictor for cord is usually:

Viscostat:

Viscostat clear:

Aluminum chloride

Ferric sulfate

Aluminum chloride

154

Pack 2 cords and take the top out after __ minutes. You need a clean, dry, field.

5

155

If making an FMC do the final impression using _______, then look for bubbles/clean margin

Custom tray

156

Why can't you do a bite registration off of a stone cast?

Has expanded

157

What shrinks more - noble or base metals?

What must you use to offset the higher shrinkage?

Base

Type V dental stone

158

Casts (yellow) are in Type ____

Plaster (white) that connects to the Articulator is Type _____

3

1

159

In posterior teeth, porcelain tends to fracture where?

Marginal Ridges

160

Ringless means a _____ ring and allows for expansion of ______

Plastic

Investment

161


Invest, Cast - then break, cut off Sprue. If metal - you're good. If stacked to porcelain, then _______

Coping

162

What do you have to do to the prep before you wax?

Lube

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