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FixedPros > E2: Lect 8 Investing > Flashcards

E2: Lect 8 Investing Flashcards

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
Q

What is the BINDER in Phosphate Bonded Investment?

A

Water soluble Phosphate Ion

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26
Q

What is the REFRACTORY material in Phosphate Bonded Investment?

A

Colloidal Silica in Water

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27
Q

Used for high gold or palladium content alloys, because this material is stable at burnout temperatures above 650o C (1200o F).

A

Phosphate Bonded investment

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28
Q

What is more smooth and precise? Phosphate Bonded Investment or Gypsum Investment?

A

Gypsum

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29
Q

DENTAL CASTING ALLOYS: High Nobel-Content??

A

Noble metal of at least 60% with 40% gold

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30
Q

DENTAL CASTING ALLOYS: Nobel-Content??

A

Noble metal of at least 25% with no gold content

specified

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31
Q

DENTAL CASTING ALLOYS: Base Metal- Content??

A

Noble metal less than 25% with no gold content specified

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32
Q

What are the 6 Nobel Metals?

A

RR-PP-GO..Ruthenium, Rhodium, Palladium,Platinum,Gold,Osmium

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33
Q

What are the 9 Base Metals?

A

NC-ZG-ST-BIT….Nickel, Copper, ZInc, Gallium, SILVER, Tin, Beryllium, Indium, TITANIUM

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34
Q

Casting Alloy: Type I =

A

Soft

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35
Q

Casting Alloy: Type II =

A

Medium

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36
Q

Casting Alloy: Type III =

A

Hard

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37
Q

Casting Alloy: Type IV =

A

Extra Hard

38
Q

Casting Alloy - Type I used for:

A

simple inlays

39
Q

Casting Alloy - Type II used for:

A

complex inlays

40
Q

Casting Alloy - Type III used for:

A

Crowns and Fixed Pros

41
Q

Casting Alloy - Type IV used for:

A

partial removable dental prostheses

42
Q

Casting Alloy - Porcelain used for

A

Porcelain: metal-ceramic alloys ? not sure I understand this one

43
Q

CastingAlloy Mechanical Properties…Modulus of ______ Resists deformation

A

Elasticity

44
Q

CastingAlloy Mechanical Properties…____ strength (proportional limit)…High value indicates difficulty in adjusting

A

Yield

45
Q

CastingAlloy Mechanical Properties… _______-Affects ability to finish the alloy

A

Hardness

46
Q

CastingAlloy Mechanical Properties… ______-Dimensional changes during porcelain firing

A

Creep

47
Q

How much space do you need OVER your wax pattern when set up in the investment ring??

A

6mm

48
Q

How much space is recommended for distance between wax pattern and the sprue?

A

6.0mm

49
Q

Connects the wax pattern to the crucible former

A

sprue

50
Q

Sprue-______ diameter recommended

A

large

51
Q

Sprue- Location (attached to the bulkiest noncritical area)

A

Non-Fxn cusp

52
Q

The sprue must enable the molten metal to flow into the mold with as little _______ as possible.

A

TURBULENCE!

53
Q

Serves as a base for the casting ring during investing….

Usually made of rubber…. Where the sprue Attaches

A

Crucible Former

54
Q

Container for the investment….Normally a liner is placed inside the ring to allow for more expansion (sometimes two liners are used)

A

Casting Ring / Liner

55
Q

investing step 1. Paint pattern with _______ reducer

A

surface tension

56
Q

investing step 2. Add investment _____ to the ______ in the mixing bowl and quickly incorporate by hand

A

POWDER to LIQUID

57
Q

Investing step 6. Allow investment to set or for _______ technique place in a water bath for 1 hour

A

hydroscopic

58
Q

How hot is the burn out oven? (C and F) How long?

A

Place in furnace at 200o C or 400o F for 30 minutes

59
Q

***WHAT IS THE HOTTEST PART OF A FLAME?

A

Light blue CENTER/REDUCING area

60
Q

Why do we NEVER want to heat our alloy with the base or end of the flame?

A

BASE: MOST oxidizing zone….open end: oxidixing zone

61
Q

If newly cast metal is _______ while it is too hot, the gold will be softer and weaker.

A

quenched

62
Q

Prevents removal of the restoration along the path of insertion of the tooth preparation.

A

Retention

63
Q

Prevents dislodgments of the restoration by forces directed in an apical or oblique direction.

A

Resistance

64
Q

Prevents any movement of the restoration under occlusal forces.

A

Resistance

65
Q

An extracoronal restoration uses opposing ________ surfaces for retention.

A

opposing external

66
Q

An intracoronal restoration uses opposing ______ surface for retention.

A

internal

67
Q

A 6 degree preparation would give two opposing surfaces with __ degree inclination each.

A

3 degree

68
Q

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?

A

19 degrees…lose retention @ 22 degrees

69
Q

For adequate Retention and resistance form the height/base ratio should be _______ for all teeth.

A

GREATER than 0.4

70
Q

Height Base Ratio- INCISORS and PM’s..whats the minimum height?

A

3mm minimum height

71
Q

Height Base Ratio- Molars..whats the minimum height?

A

4mm minimum height

72
Q

Maximum Retention has _____ path(s) of removal of the crown.

A

ONE PATH

73
Q

Resistance of a short preparation can be improved by adding ______.

A

grooves

74
Q

Parker et al found that ____% of anterior preparations had adequate resistance form compared to ___% on molars.

A

95%…46%

75
Q

Margins: Round internal line angle. Preferred gingival margins for full gold crown.

A

Chamfer

76
Q

Round bigger radius internal line angle. A 90 degree cavosurface line angle.

A

Heavy Chamfer

77
Q

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.

A

Classic Shoulder

78
Q

What is also called a BUTT MARGIN DESIGN?

A

RADIAL SHOULDER

79
Q

Round internal line angle but does not have a circular arc like the chamfer…

A

RADIAL SHOULDER/ BUTT MARGIN

80
Q

A ledge design margin., Round internal line angle, 120 degree cavosurface line angle.

A

Sloped Shoulder

81
Q

The ultimate finish line that permits an acute margin of metal.

A

Knife Edge

82
Q

Margin placement must be at least ____ mm away from the J.E.

A

0.5mm

83
Q

What are the 4 contraindications for a full coverage crown?

A

1.Active Caries 2.Perio Disease 3.Large Pulp 4.if more conserve prep an option

84
Q

Goal of metal design is to minimize ______ stress

A

tensile

85
Q

What is the default labial margin?

A

“disappearing margin”

86
Q

Minimum Metal Thicknes

A

0.3 to 0.5 mm

87
Q

Minimum Porcelain Thickness

A

1.0-1.2mm

88
Q

Contact Distance from M/P Junction

A

1.0-1.5mm

89
Q

OCCLUSIAL CONTACTS in MIP ___mm from M/P Junciton ON METAL

A

1.0mm

90
Q

OCCLUSIAL CONTACTS in MIP ___mm from M/P Junciton ON PORCELAIN

A

1.0mm

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