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FixedPros > E2: Lect 8 Investing > Flashcards

E2: Lect 8 Investing Flashcards

(90 cards)

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1
Q

What is the Method to convert wax patterns to cast metal?

A

Lost Wax Technique

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2
Q

What are the 3 requirements of an investment?

A

RHE 1.Reproduce detail 2.withstand Heat 3.Expansion

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3
Q

GOLD alloys SHRINK by approx ___% when casting!

A

1.5%

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4
Q

Nickel-chromium alloys SHRINK by as much as ___% when casting!

A

2.4%

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5
Q

Because the alloy shrinks when casting, the MOLD must be made correspondingly _______ than the original wax pattern.

A

LARGER

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6
Q

As the gypsum investment sets after mixing, it expands and slightly enlarges the mold:

A

Setting Expansion

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7
Q

In Setting Expansion, less water _________ expansion and will yield a _______ casting

A

increases expansion, larger casting

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8
Q

The investment is allowed to set in the presence of water, producing additional expansion. (1000 F or 38oC):

A

HygroScopic Expansion

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9
Q

In a lined, rigid, metal ring, the expansion attributed to hygroscopic expansion is more likely due to expansion of the _________ caused by the elevated temperature of the water

A

wax pattern

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10
Q

Wax patterns _______ while the investment is still fluid and the wax is warmed above the temperature at which it was formed….What 2 reasons??

A

expand…1. chemical reaction of the investment 2.immersion into a warm water bath

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11
Q

As the mold is heated to eliminate the wax, ______ expansion occurs.

A

thermal

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12
Q

**WHAT IS PRINCIPALLY RESPONSIBLE FOR THERMAL EXPANSION OF THE INVESTMENT MOLD?

A

THE SILICA REFRACTORY MATERIAL

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13
Q

What are the 3 types of investment materials?

A

1.Gypsum bonded 2.Phosphate Bonded 3.Silica Bonded

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14
Q

Ideal Investment: Controllable _______ to compensate precisely for shrinkage of the cast alloy during cooling.

A

expansion

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15
Q

Ideal Investment: The ability to produce ______ castings with accurate surface reproduction and without nodules.

A

smooth

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16
Q

Ideal Investment: Chemical ________ at high casting temperatures.

A

stability

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17
Q

Ideal Investment: Adequate _______ to resist casting forces.

A

strength

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18
Q

Ideal Investment: Sufficient ______ to allow for gas escape.

A

porosity

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19
Q

Ideal Investment: Easy _______ of the casting.

A

recovery

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20
Q

Gypsum = ______ = 30-35%

A

BINDER

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21
Q

Cristobalite and Quartz = __________ = 60-65%

A

refractory material

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22
Q

GYPSUM bonding investment is for ______ alloys because it is NOT stable above ____ degrees.

A

gold…650 degrees

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23
Q

What type of restoration/alloy is Gypsum Investment NOT suitable for?

A

PFM alloys! (heat req too high!)

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24
Q

What type of investment do we use for PFM?

A

Phosphate Bonded Investment

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25
What is the BINDER in Phosphate Bonded Investment?
Water soluble Phosphate Ion
26
What is the REFRACTORY material in Phosphate Bonded Investment?
Colloidal Silica in Water
27
Used for high gold or palladium content alloys, because this material is stable at burnout temperatures above 650o C (1200o F).
Phosphate Bonded investment
28
What is more smooth and precise? Phosphate Bonded Investment or Gypsum Investment?
Gypsum
29
DENTAL CASTING ALLOYS: High Nobel-Content??
Noble metal of at least 60% with 40% gold
30
DENTAL CASTING ALLOYS: Nobel-Content??
Noble metal of at least 25% with no gold content | specified
31
DENTAL CASTING ALLOYS: Base Metal- Content??
Noble metal less than 25% with no gold content specified
32
What are the 6 Nobel Metals?
RR-PP-GO..Ruthenium, Rhodium, Palladium,Platinum,Gold,Osmium
33
What are the 9 Base Metals?
NC-ZG-ST-BIT....Nickel, Copper, ZInc, Gallium, SILVER, Tin, Beryllium, Indium, TITANIUM
34
Casting Alloy: Type I =
Soft
35
Casting Alloy: Type II =
Medium
36
Casting Alloy: Type III =
Hard
37
Casting Alloy: Type IV =
Extra Hard
38
Casting Alloy - Type I used for:
simple inlays
39
Casting Alloy - Type II used for:
complex inlays
40
Casting Alloy - Type III used for:
Crowns and Fixed Pros
41
Casting Alloy - Type IV used for:
partial removable dental prostheses
42
Casting Alloy - Porcelain used for
Porcelain: metal-ceramic alloys ? not sure I understand this one
43
CastingAlloy Mechanical Properties...Modulus of ______ Resists deformation
Elasticity
44
CastingAlloy Mechanical Properties...____ strength (proportional limit)...High value indicates difficulty in adjusting
Yield
45
CastingAlloy Mechanical Properties... _______-Affects ability to finish the alloy
Hardness
46
CastingAlloy Mechanical Properties... ______-Dimensional changes during porcelain firing
Creep
47
How much space do you need OVER your wax pattern when set up in the investment ring??
6mm
48
How much space is recommended for distance between wax pattern and the sprue?
6.0mm
49
Connects the wax pattern to the crucible former
sprue
50
Sprue-______ diameter recommended
large
51
Sprue- Location (attached to the bulkiest noncritical area)
Non-Fxn cusp
52
The sprue must enable the molten metal to flow into the mold with as little _______ as possible.
TURBULENCE!
53
Serves as a base for the casting ring during investing.... | Usually made of rubber.... Where the sprue Attaches
Crucible Former
54
Container for the investment....Normally a liner is placed inside the ring to allow for more expansion (sometimes two liners are used)
Casting Ring / Liner
55
investing step 1. Paint pattern with _______ reducer
surface tension
56
investing step 2. Add investment _____ to the ______ in the mixing bowl and quickly incorporate by hand
POWDER to LIQUID
57
Investing step 6. Allow investment to set or for _______ technique place in a water bath for 1 hour
hydroscopic
58
How hot is the burn out oven? (C and F) How long?
Place in furnace at 200o C or 400o F for 30 minutes
59
***WHAT IS THE HOTTEST PART OF A FLAME?
Light blue CENTER/REDUCING area
60
Why do we NEVER want to heat our alloy with the base or end of the flame?
BASE: MOST oxidizing zone....open end: oxidixing zone
61
If newly cast metal is _______ while it is too hot, the gold will be softer and weaker.
quenched
62
Prevents removal of the restoration along the path of insertion of the tooth preparation.
Retention
63
Prevents dislodgments of the restoration by forces directed in an apical or oblique direction.
Resistance
64
Prevents any movement of the restoration under occlusal forces.
Resistance
65
An extracoronal restoration uses opposing ________ surfaces for retention.
opposing external
66
An intracoronal restoration uses opposing ______ surface for retention.
internal
67
A 6 degree preparation would give two opposing surfaces with __ degree inclination each.
3 degree
68
HAHA go figure: Studies Have shown that actual crown preps are much greater than the recommended value: on average the taper is ___ degrees! When do we lose retention?
19 degrees...lose retention @ 22 degrees
69
For adequate Retention and resistance form the height/base ratio should be _______ for all teeth.
GREATER than 0.4
70
Height Base Ratio- INCISORS and PM's..whats the minimum height?
3mm minimum height
71
Height Base Ratio- Molars..whats the minimum height?
4mm minimum height
72
Maximum Retention has _____ path(s) of removal of the crown.
ONE PATH
73
Resistance of a short preparation can be improved by adding ______.
grooves
74
Parker et al found that ____% of anterior preparations had adequate resistance form compared to ___% on molars.
95%...46%
75
Margins: Round internal line angle. Preferred gingival margins for full gold crown.
Chamfer
76
Round bigger radius internal line angle. A 90 degree cavosurface line angle.
Heavy Chamfer
77
A wide ledge ( instead of a radius) design. 90 degree internal line angle....Concentrates stress and induce coronal fracture....Technically impossible to be produced by human hand.
Classic Shoulder
78
What is also called a BUTT MARGIN DESIGN?
RADIAL SHOULDER
79
Round internal line angle but does not have a circular arc like the chamfer...
RADIAL SHOULDER/ BUTT MARGIN
80
A ledge design margin., Round internal line angle, 120 degree cavosurface line angle.
Sloped Shoulder
81
The ultimate finish line that permits an acute margin of metal.
Knife Edge
82
Margin placement must be at least ____ mm away from the J.E.
0.5mm
83
What are the 4 contraindications for a full coverage crown?
1.Active Caries 2.Perio Disease 3.Large Pulp 4.if more conserve prep an option
84
Goal of metal design is to minimize ______ stress
tensile
85
What is the default labial margin?
"disappearing margin"
86
**Minimum Metal Thicknes**
0.3 to 0.5 mm
87
**Minimum Porcelain Thickness**
1.0-1.2mm
88
**Contact Distance from M/P Junction**
1.0-1.5mm
89
****OCCLUSIAL CONTACTS in MIP ___mm from M/P Junciton ON METAL****
1.0mm
90
****OCCLUSIAL CONTACTS in MIP ___mm from M/P Junciton ON PORCELAIN****
1.0mm

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