FIXP 5001 > Midterm > Flashcards

Midterm Flashcards

(67 cards)

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1
Q

Principle of retention: Grooves

A

Opposing divergent vertical walls of the tooth

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2
Q

Principle of retention: Pin

A

LONG vertical walls of tooth with foundation

-2 mm deep, 1-1.5 mm inside DEJ

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3
Q

Principle of retention: Slot

A

SHORT vertical walls of tooth with foundation

  • 1 mm deep, at least 1 mm inside DEJ (maybe 1.5 so crown prep doesn’t hit it)
  • use inverted cone bur (33 1/2)
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4
Q

What is stronger/more retentive, slot or pin?

A

pin

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5
Q

What is the angle of insertion for a pin?

A

Parallel to the external surface closest to the pin

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6
Q

What do you want to avoid the MOST with pin placement?

A

perforation outside the tooth is the most detrimental

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7
Q

Stainless steel pin vs. titanium

A

Titanium is stronger, but you can see stainless steel better radiographically

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8
Q

2-2-2 rule?

A

2 mm into tooth, 2 mm in the amalgam, 2 mm above the top of the pin (3-5 mm to the next pin)

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9
Q

Two different types of pins

A

Minikin: Red for premolars, shorter and has a rounded head
Minim: grey/silver for molars

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10
Q

When are threaded pins used?

A
  • At or apical to CEJ

- on vital teeth ONLY

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11
Q

When do you use amalgapins? (slots or wells)

A
  • occlusal to CEJ
  • stable matrix
  • Endo teeth
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12
Q

blockout vs. foundation

A

Blockout is for undercuts, foundation is for retention

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13
Q

Pros and cons of amalgabond

A

helpful for reducing sensitivity and leakage, but does not replace mechanical retention

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14
Q

How can you see a crack in a cusp?

A

Must be viewed from the inside out–have to remove restoration first b/c they start on inside

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15
Q

Most common reasons for crown prep?

A

Large restoration and existing cracks in teeth

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16
Q

How is outline form determined?

A
  • no decalcified cavosurface margin
  • No chalky prepared enamel
  • No discolored DEJ
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17
Q

Clinical symptoms of fractured cusp

A

Bite down, hurts upon release

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18
Q

Position of bur when dropping box

A

2/3 in dentin, 1/3 in enamel

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19
Q

3 basic classes of elastomeric impression material options

A
  1. poly sulfide: rubber base–pour within 2-6 hrs, smells
  2. poly ether: stable, tears easily and tastes bad
  3. Poly vinyl siloxane: desirable properties of the other two, can be stable for months
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20
Q

Use of light vs. heavy body

A

Light: thin with low viscosity–used to capture margin and occlusal (blue)
Heavy: thick and stackable and durable to fill tray (purple)

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21
Q

To avoid breaking teeth during impression (intraoral)

A

blockout embrasures of mandibular teeth with wax before impression (in dentaform you can cut inteproximals before pouring stone)

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22
Q

Where should gauge be when hose is plugged in but not in the bowl yet?

A

Below 10–otherwise it is clogged (once plugged into bowl it should be in green between 25-30)

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23
Q

Jade stone instructions: water/powder, hand mix, vacuum mix, working time, separation time

A
  • water/powder ratio is 15.5 mL/70 g
  • hand mix 10-15 sec
  • vacuum mix 20 sec
  • working time 4-6 min
  • separation after at least 30 min (1 hr is preferable)
  • stack 6-8 mm
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24
Q

How to avoid slurry?

A

Use separating agent (super sep) before trimming or wet and rinse frequently
-soak cast for 5 min before trimming

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25
Settings for WHIP MIX articulator when mounting maxillary cast?
Condylar guidance: 30 Bennett angle: 15 Everything else at 0 *no notches, roughen top of cast, then wet*
26
How should the dowel pins be oriented when seated in the working cast?
Bucco-lingually
27
After sleeves placed on dowel pins, what are the next steps?
- bevel lingual - die hardener - cap the ends of pins - spray super sep all over - use pindex mold to make the base
28
What is the removable die used for?
Fit and margins; occlusion and contour
29
What is the working cast used for?
proximal contacts and major marginal problems
30
Steps to begin waxing the removable die
- Mark the margins with red wax pencil - Die hardener - Die spacer: 4 coats of Taub, 25 micron spacer, end with silver 1-1.5 mm from margin - Die lubricant--put EVERYWHERE you don't want wax to stick! - Wax pot slightly over margins
31
3 difficulties to overcome with dental casting
1. Solidification shrinking-->causes porosity in casting 2. Thermal contraction-->causes shrinkage (1.5% gold alloys and 2.2% base metal alloys like NiCr or CoCr) 3. Gas entrapment-->incomplete casting/voids
32
Order of casting solidification
Margins-->sprue-->button
33
What happens if debubblizer is left wet on wax?
- changes water/powder ratio of investment - can pool at 'heat center' of ring-->suck-back porosity, gold doesn't freeze there and gets pulled into sprue area when that solidifies
34
Rules governing sprue length
- sprue should be 6-9 mm in length | - wax pattern shouldn't be more than 6 mm from end of ring
35
Investment cracking causes...
fins: excess material on the crown that can be taken off with disc
36
Wax hydrophobicity causes...
nodules and blebs: wax is oily and hydrophobic, so we use the debubblizer to make sure investment will properly wet the surface (but needs to be dry to invest)
37
If sprue isn't joined to wax pattern well..
- pattern can come off during investing | - spines of investment can form at junction
38
How do we compensate for casting shrinkage/thermal contraction?
Burnout: this gets rid of the wax pattern and sprue and expands the mold to compensate (setting, thermal, and hygroscopic expansion) -put ring in 'cold' furnace of 400 degrees F, ring needs to be soaked otherwise it can crack
39
What part of flame is the best area for heating?
Reducing zone
40
Main function of liner in casting ring?
allow uniform and uninhibited setting expansion of the investment
41
Shrinkage porosity in gold casting associated with what?
Sprue diameter
42
Back pressure porosity is often evidenced by what?
rounded margins on casting
43
What happens if you use a thinner mix of gypsum-bonded casting investment?
Decrease setting expansion
44
Base metal alloys compared to high gold content alloy
base metal: higher mp, lower specific gravity, higher yield strength and hardness, less consistent bond to porcelain
45
Most common reason for cast not to seat on patient's tooth?
Excessive proximal contact
46
What technique do we use at the school for casting the crown?
Induction casting
47
Burnout furnace uses air pressure and what gas to reduce oxidation?
Argon
48
Steps for cleaning out the casting before fitting it onto the dye
1. remove bulk of investment with blunt instrument from inside 2. ultrasonic 1-2 min 3. steam clean 4. Sandblaster (AlO3) 5. Inspect inside for blebs or irregularities (remove with small diamond on axial or 1/4 round on occlusal)
49
Where do positives and negatives on casting come from?
Trapped air during investing
50
What are lute lines?
Lines on the inside of the casting that have air trapped in them which prevents proper seating...comes from improper wax additions during coping
51
What do you use to shape the sprue?
Heatless stone or separating disc and green stone
52
How do you adjust proximal and occlusal contacts?
-grey rubber wheel, brownie wheel, green HP/white FG stone, brownie/greenie HP points
53
What do you use for contouring and what should you avoid?
Green stone disc or point---avoid proximal/occlusal contacts and margin
54
Polishing sequence
- Grey rubber wheel, Brownie, Greenie, (for occlusal start with green or white stone or carbide) - BBC on coarse Robinson brush - Rouge on medium Robinson brush
55
Speed and pressure for the Grey rubber wheel?
Slow speed, heavy pressure (same with brownie, but greenie is faster with less pressure) Use gear down
56
Speed and pressure for polishing compounds?
Max speed and light pressure (Without gear down) brush can't contact die! Start with heavy pressure and slow speed but gradually get lighter and faster
57
What else can be used for the application of rouge?
Muslin wheel with high speed and light pressure
58
Indications for a gold crown
- not enough tooth structure for direct restoration - endo treated posterior teeth - can't place direct restoration b/c of tooth contour or access - need for occlusal plane or contour corrections (supra-erupted teeth or short teeth) - longevity/compatability of metal - cracked tooth
59
Reduction requirements for gold crown? occlusal and axial
1.5 mm for occlusal and 1 mm axial (minimum)
60
How far should the margin extend past the foundation?
- amalgam=1 mm apically, composite=2 mm | - without violating gingival attachment
61
Composite as core material
stronger than glass ionomer and more flexible than amalgam, can be used with enough coronal structure left but not without supporting dentin
62
Reasons for composite instead of amalgam for foundation
- matrix band doesn't match tooth anatomy - enough tooth below foundation for 2 mm of prep, easier and quicker with no loss of longevity - thin root that can fracture with condensation - immediate prep of foundation
63
What is used to remove gutta percha?
Gates glidden drill--go 2 mm into canal for amalgam
64
Advantages of ion metal provisional
- good for posterior single crowns - simple and user friendly - minimal occlusal adjustment - easy to avoid adjacent undercuts
65
Disadvantages of ion metal provisional
- need variety of sizes - difficult to correct margins and proximal contacts - limited time use (2-4 weeks) - esthetics
66
How many medicine cups does it take to reline? bead and brush? What's another difference between the two?
One for reline, two for bead and brush | -With bead and brush you let it fully set, with reline you remove it before it sets
67
Stages of PMMA acrylic resin
Runny stringy doughy memory
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