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indirect Restoration > Focused Quiz: 9/29 > Flashcards

Focused Quiz: 9/29 Flashcards

1
Q

Gypsum is made of:

A

calcium sulfate dihydrate (CSD - think cast)

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2
Q

We use gypsum for:

A

casts and investment material

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3
Q

how is a dihydrate made to hemi?

A

reduction/ oxidation

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4
Q

Both alpha and beta hemihydrate have this driven off:

A

water

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5
Q

Which is the natural form, di or hemi hydrate?

A

di

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6
Q

How is a-hemihydrate produced?

A

steam and pressure

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7
Q

Shape of crystalline HH:

A

rods, prisms (a-HH can be cuboidal)

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8
Q

How is b-HH produced?

A

heating in air (dessication)

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9
Q

Shape of b-hh:

A

irregular

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10
Q

What is b-hh?

A

fibrous aggregate of fine crystals

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11
Q

How many times more soluble is hh than dh?

A

4 times

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12
Q

What precipitates when water is added to HH?

A

DH

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13
Q

As more DH precipitates:

A

more HH dissolves

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14
Q

What initiates setting expansion?

A

DH formation, molecules bumping into one and other

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15
Q

How to increase nucleation:

A

over spatulation, less water, dirt, slurry water, finer particle size of HH

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16
Q

How to inc reaction rate:

A

inc nucleation, additives (inorganic salts, K2SO4)

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17
Q

How to decrease the rate of reaction:

A

more water, shorter, slower mixing, blood, borax, coarser particle size of HH

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18
Q

How to enhance setting expansion:

A

by nuclei forming close together, less water, over spatulation

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19
Q

surface tension is aka:

A

restriction

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20
Q

How to remove surface tension on gyspum:

A

put setting gypsum under water

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21
Q

Does surface tension restrict or aide movement?

A

restricts

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22
Q

hygroscopic:

A

tending to absorb moisture from the air

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23
Q

Setting expansion of gypsum:

A

0-0.3%, very small

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24
Q

How will increased porosit affect strength?

A

decrease

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25
Q

What affects amt of porosity?

A

w/p ratio, vaccum mixing

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26
Q

How do accelerators and retarders affect compressive stregnht?

A

decrease

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27
Q

Surface area of particles is proportional to:

A

amt of water needed to “float and coat”

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28
Q

“Float and coat”

A

getting particles into suspension, not dissolving, supersaturated solution that can precipitate, denser = stronger

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29
Q

w/p ratio affects

A

set strength, ratio of hemihydrate or dihydrate in the mix

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30
Q

How much dimensional change does gypsum undergo if under running water for 20m?

A

0.1%

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31
Q

What should you soak a gypsum cast in?

A

saturated calcium sulfate, best: a container with gypsum pieces on bottom

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32
Q

Why does snap stone set faster?

A

additives added

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33
Q

Dental stone, high strength:

A

Type 4

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34
Q

Dental plaster:

A

Type 2

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35
Q

Impression plaster:

A

Type 1

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36
Q

Dental stone, high strength, high expansion:

A

Type 5

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37
Q

Dental stone:

A

Type 3

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38
Q

Type I plaster are made of:

A

polysulfides and polyethers

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39
Q

Type I dental stone:

A

impression plaster, rarely used, lowest strenth, porous b-HH, 0.5W/ 0.75P, setting expansion: 0-0.15%

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40
Q

Type II:

A

Dental plaster, usually white, mounting plaster, denture flasking, weak, 0.45W/ 0.5P, setting expansion: 0-0.3%, accuracy not required

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41
Q

Type II, a-hh or b-hh?

A

b-hh

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42
Q

Type III, a-h or b-hh:

A

a-hh

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43
Q

Type III:

A

dental stone, calcination (reduction/ oxidiation) under steam, a-hh, 0.28W/ 0.3P, settting expansion: 0-0.2%

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44
Q

Type III stone has half the w/p ratio as these

A

Type I and almost Type II (0.5 vs. 0.45)

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45
Q

What accounts for the drop in the w/p ratio for Type III stone?

A

a-hh, reduced sa

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46
Q

Type IV dental stone:

A

densite a-hh, cuboidal-shaped particles (reduced sa), 0.22W/ 0.24P, setting expansion: 0.0.1%

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47
Q

Type V dental stone:

A

stronger that IV, 0.18W/ 0.22P, setting expansion: 0.1-0.3%, expansion compensates for base metal shrinkage

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48
Q

What does Type V stone expansion compensate for?

A

base metal shrinkage in casting

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49
Q

Type IV, a-hh or b-hh?

A

a-hh

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50
Q

Which is more accurate, weight or volumetric measurements?

A

weight

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51
Q

Next ppt:

A

investment materials and metal alloys

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52
Q

the sprue is cast onto this (not the tooth):

A

crucible former

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53
Q

What happens after the sprue is attached to the tooth?

A

burnout and sectioned

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54
Q

Steps to lost wax technique:

A

impression, cast, restoration in wax, invest wax pattern, burnout, cast

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55
Q

How should investment be mixed?

A

under vacuum

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56
Q

Big contact angle:

A

Big glob of water (check, this was backwards in my notes)

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57
Q

Function of investment:

A

preservation of the wax pattern after melting

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58
Q

Material that can be used for lost wax tech:

A

alloy or ceramic

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59
Q

Wax, high or low surface energy?

A

low, needs wetting agent

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60
Q

Why do we need wetting agent?

A

lots of water in investment material, doesn’t spread well over wax (lipid), this helps preserve the pattern

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61
Q

Ideal properties of investment:

A

heat resistabt, expands, accurate reproduction, strength, porosity for gas escape, ability to recover casting

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62
Q

What stone to use to compensate for alloy shrinkage:

A

Type 4

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63
Q

What would make recovering the cast difficult?

A

material that is too strong

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64
Q

2 main components of investment:

A

refractory material, binder

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65
Q

refractory material:

A

resistant to high temps, not easily melted or worked

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66
Q

Is investment heat resistant?

A

yes

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67
Q

Refractory used in investment:

A

silica, quartz or cristobalite

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68
Q

How is thermal expansion controlled in investment?

A

inversion: low temp (alpha) and high-temp (beta) phases

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69
Q

Function of refractory:

A

strenght, resistant to heat, and thermal expansion

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70
Q

Greater expansion: cristobalite or quartz?

A

cristobalite

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71
Q

Undergoes thermal expansion at a lower temp, cristobalite or quartz?

A

cristobalite (250C vs 573C)

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72
Q

Cristobalite can get up to __% expansion:

A

2%

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73
Q

Binder:

A

added to form dry ingredients to maintain even consistency

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74
Q

Function of binder:

A

strength for investment

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75
Q

2 types of binder used in investments:

A

gypsum, phosphate

76
Q

How are investment materials classified?

A

binder type

77
Q

What compensates for alloy shrinkage during cooling from liquid ot solid phase?

A

expansion of investment

78
Q

3 types of expansion:

A

setting, hygroscopic, thermal

79
Q

Molecular level change occuring when gypsum udergoes setting expansion:

A

HH to DH

80
Q

What allows for equal expansion in the casting ring?

A

liner

81
Q

When does setting expansion occur?

A

as binder sets

82
Q

How to maximize hygoscopic expanion:

A

get into water bath sooner

83
Q

When will hygroscopic expasion occur in gypsum?

A

if it sets under water

84
Q

When does most hygroscopic setting expansion occur?

A

during initial set

85
Q

How to increase expansion of gypsum setting under water?

A

heat the water

86
Q

Theory of hygroscopic expansion:

A

reduced surface tension means less confinement of growing crystals

87
Q

How many times more expansion can you get, normal vs. hygroscopic?

A

4 times more

88
Q

Normal expansion:

A

none at beginning, 1st 10 minutes very little, most occurs bw 10 and 20 min

89
Q

Hygroscopic expansion:

A

majority of expansion bw 5-10min, up to 1.3% at 10min,

2% max

90
Q

What is thermal expansion dependent upon?

A

the refractory material, which type of silica, quartz or cristobalite?

91
Q

Quartz transition temp:

A

1067F, almost 3 times higher than cristobalite

92
Q

Cristobalite transition temp:

A

About 400F

93
Q

1st investment used in dentistry:

A

gypsum bonded

94
Q

When does the refractory material lose stability?

A

1200F

95
Q

What do we add to refractory material to increase the temperature it which it can remain stable?

A

gold alloys

96
Q

heating gypsum converts:

A

DH to HH

97
Q

What type of refractory does beauty cast have?

A

quartz refractory

98
Q

Is gypsum bonded with cristobalite hygroscopic expansion used?

A

no, the addition of cristobalite would lead to too much expansion

99
Q

Can all alloys be cast in gypsum?

A

no

100
Q

Binder for phosphate bonded:

A

magnesium oxide and phosphate

101
Q

When is phosphate bonded investment necessary?

A

materials that melt over 1200C/ 2200F, most metal ceramic alloys and cast ceramics

102
Q

What refractory is used in phosphate bonded investment?

A

silica, as always

103
Q

What types of expansion occur with phosphate bonded investment?

A

setting and thermal

104
Q

What is thermal expansion controlled by in phosphate bonded investment?

A

amount of silica, amount of special liquid that comes with phoshate bonded investment, mix before use to equally suspend silica

105
Q

What is special liquid:

A

colloidal silica

106
Q

Does setting expansion increase or decrease with the addition of the special liquid?

A

increase

107
Q

Does thermal expansion increase or decrease with the addition of the special liquid?

A

increase

108
Q

Phosphate investment:

A

Stable at higher temps, allows greater thermal expansion, more prone to surface nodules (harder to adapt wax), difficult to breakout casting, stronger, harder

109
Q

Commercial labs typically use this investment:

A

phosphate

110
Q

Recommended max investment thickness:

A

6mm. to allow gas release scratch off top of investment, decrease chance of air bubbles

111
Q

Liners are made of:

A

aluminum silicate ceramic or paper

112
Q

Functions of liner:

A

allow expansion, recovery of casting is easier, can push cast out of ring and break up investment

113
Q

What can lead to rough casting:

A

improper finish of wax pattern, excess surfactant, wrong w/p ratio, excess temperature during burnout

114
Q

Most common casting failure:

A

rough casting/ not good finish

115
Q

Casting failures:

A

rough casting, fins, nodules, incomplete casting, porosity

116
Q

Causes of fins (cracks that get filled w material):

A

increased w/p ratio, bad pattern position, premature heating, rapid heating, dropping ring, investment not fully set, too much moisture,

117
Q

The (investment?) is more prone to cracking if the wax pattern/ outline is less than __ mm from the top:

A

6

118
Q

All nodules are due to:

A

air

119
Q

What better o have on the casting, neg or pos?

A

neg

120
Q

What to do when removing a positive nodule:

A

remove a little extra, neg better than pos

121
Q

Cause of nodules:

A

inadequate vacuum, no surfactant

122
Q

These can lead to incomplete casting:

A

wax pattern too thin, incomplete wax elimination/ burnout, cool mold or melt, inadequate metal

123
Q

Area of crown this is most often too thin:

A

occlusal surface

124
Q

How does the density of the alloy affect the amt of the alloy required for a crown?

A

more dense, less alloy needed

125
Q

These can lead to porosities:

A

improper melting temp, pattern position or sprue location or thickness

126
Q

How is metal bonded to ceramic in PFM?

A

intermediate oxide layer

127
Q

We could start to make PFM restos when:

A

decreasing the coefficient of thermal expansion of metal

128
Q

What would happen if metal and procelain didn’t have similar coefficients of thermal expansion?

A

one would crack

129
Q

Disadvantages to PFM compared to CCC:

A

remove more tooth structure, risk of porcelain fracture

130
Q

These help determine the risk of porcelain fracture:

A

design of framework, how the porcelain was applied

131
Q

Advantages and disadvantages of PFM vs. al ceramic:

A

adv: more conservative prep, stronger, disadv: poor esthetics (usually)

132
Q

Dentistry is going in the direction of using this crown type:

A

all ceramic (check, why? less conservative than PFM)

133
Q

Alloy:

A

mutually soluble in each other in molten state

134
Q

Function of gold in alloy:

A

soft, inc resistance to tarnish and corrosion, increase ductility and malleability

135
Q

Function of copper in alloy:

A

hardener, neccesary for heat tx for conc greater than 12 wt%

136
Q

Function of silver in alloy:

A

dec melting temp, inc ductility and maleability

137
Q

problem with adding silver to alloy:

A

any alloy that has silver must use a compatible ceramic, comes form the oxidation of the silver

138
Q

Platinum:

A

increases melt temp, increases tensile strength, decreases CTH, reduces tarnish and corrosion

139
Q

Palladium:

A

increases melt temp, increases hardness, absorbs H2 gas which can cause porosity, prevents tarnsih and corrosion, strong whitening effect on gold alloys

140
Q

Zinc:

A

scavenger, prevents oxidation, increases fluidity , decreases st, which improves castabilitiy

141
Q

Iridium:

A

grain refiner, increases tensile strength and % elongation (ductility)

142
Q

Tin and indium:

A

allow oxidation, added to high noble alloys to get oxidation, the fusing of porce to metal requires an oxide layer

143
Q

High noble:

A

60% min, at least 40% of that is gold

144
Q

2 metals in all high noble alloys:

A

gold and palladium, just those 2, add silver, or add platinum

145
Q

Metal type most often used:

A

noble

146
Q

Why do you need to choose porcelain based on the oble metal cois>

A

greening problem

147
Q

All noble metals have this metal:

A

pladium, that and silver, or that and galllium, or that and copper and gallium

148
Q

Noble metal requireent for base metals:

A

none

149
Q

Metal found in base metals:

A

chromium, that and cobalt or that and nickel

150
Q

Issue with using some base metals:

A

some have nickel in them, allergies

151
Q

Most difficult base metal to use:

A

Co-Cr

152
Q

What metal causes greening in some porcelain systems?

A

silver

153
Q

How to melt traditional high gold alloys:

A

gas-air torch

154
Q

How to melt metal ceramic alots:

A

gas-oxygen torch, gas-air won’t get hot enough to melt

155
Q

Color of burning gas:

A

blue

156
Q

what type of atmosphere does burning create

A

redeced

157
Q

Hottest, best zone or melting:

A

transition bw blue are and the area just supperior to it (burnt gases, oxidizing atmosphere

158
Q

This forms reducing atmosphere and this is the oxidizing atmosphere:

A

burning gases, burnt gases

159
Q

To minimize oxidation oxidation of the alloy:

A

use the hottest zone, best for melting

160
Q

Relationship bw strength and esthetics:

A

inverse relationship, strength increases, esthrtics decreases

161
Q

% of high noble in base metal:

A

less than 25%

162
Q

Colors of high gold metals:

A

yellow or white (gold or silveer)

163
Q

captek:

A

we will not use, very esthetic metal ceramic crown, copper/gold material, chipping is common

164
Q

Titanium alloy:

A

creates thick oxide layer, not good bonding between ceramic and titanium

165
Q

The working cast is made from:

A

definitive impression (heavy and light body)

166
Q

Indications for complete cast crown:

A

extensive coronal destruction (caries, trauma, resto), max retention and resistnace form is needed, short crown, correction of axial (wall height, too tilted) is needed, to restor teeth w endo

167
Q

Crown type for a bruxer:

A

full coverage crown

168
Q

Crown type for short crownx

A

Zirconia, requires low reduction for posterior teeth, similar to CCC reduction

169
Q

Can angulation of a tilted tooth be corrected with direct restorations?

A

no

170
Q

Greater occlusal reduction leads to decreased:

A

retentive and resistance forms

171
Q

Conctraindications for CCC:

A

active caries, untreated pd, more conservative resto will suffice (intact B or L walls, less need for retention or resistance form), anterior teeth (esthetics)

172
Q

Advantages of CCC:

A

longevity, greater resistnace and retention forms than more conservative restos, stronger, adaptable to proper contours, better control of the occlusion - modifications compared to more conservative restorations, more conservative prep than other crown preps

173
Q

Finish line design or CCC:

A

feather edge

174
Q

Crown type to use when you need good adaptation to a furcation area:

A

CCC

175
Q

Crown type for pts with larger pulp:

A

CCC, less preparation

176
Q

Disadvantages to CCC:

A

more tooth removeal than more conservative preps, inflammation of gingiva, can’t do pulp testing bc of the conductivity of the alloy, allergy to base metals, esthetics

177
Q

How is pulp testing altered with a CCC?

A

amplified, unreliable response

178
Q

Only do CCC’s on these teeth:

A

Max 2nd molar, man molars and premolars

179
Q

More esthetic, all ceramic or metal ceramic?

A

all ceramic

180
Q

Better marginal fit, all ceramic or metal ceramic:

A

metal ceramic

181
Q

more durable, metal ceramic or all ceramic:

A

metal ceramic

182
Q

Indications for metal ceramic crown:

A

same as CCC

183
Q

Contraindication for metal ceramic restoration:

A

active caries, untreated pd, young pts with large pulp chamber, when you can be more conservative

184
Q

more durable, all ceramic FPD or metal ceramic FPD?

A

metal ceramic, connectors can also be soldered or cast

185
Q

Crown type to use for survey crowns:

A

metal ceramic, not all ceramic

indirect Restoration (54 decks)

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