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fixed pros. > def cast and dies > Flashcards

def cast and dies Flashcards

1
Q

Definitive (Master or Working)
Cast

A

Definitive (Master or Working)
Cast: A replica of the tooth surfaces,
residual ridge areas, and/or other
parts of the dental arch and/or facial
structures used to fabricate a dental
restoration or prosthesis.

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2
Q

Die:

A

Die: Positive reproduction of the
individual prepared tooth; used for
wax pattern fabrication.

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3
Q

A good cast must be:

A

Bubble free
Distortion free

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4
Q

cast must reporduce which surfaces?

A

*Reproduce both prepared and unprepared tooth surfaces, and be free
of voids.

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5
Q

occluding surfaces of casts must allow for

A

All occluding surfaces must allow for precise articulation of the opposing casts.

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6
Q

soft tissues of cast

A

*All relevant soft tissues should be reproduced.
*Edentulous spaces and ridge contours involved in FPD

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7
Q

Requirements for the Die:
*Reproduces?
*All surfaces must be?
*bubbles or voids?
*The apical unprepared tooth structure?
*Adequate access for?
*Establish correct?

A

*Reproduces the prepared tooth exactly.
*All surfaces must be accurately duplicated.
*No bubbles or voids especially along the finish line.
*The unprepared tooth structure apical to the finish line should be
easily visible (0.5 – 1mm).
*Adequate access for carving wax pattern margin.
*Establish correct cervical contour of the restoration.

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8
Q

Advantages of the FULL ARCH CAST:
*Guide to?
*Ease of?
*Development of?

A

*Guide to occlusal surfaces and contours
*Ease of articulation
*Development of optimum occlusion
*(Development of optimum pontic adaptation and esthetics)

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9
Q

Classification of gypsum products according
to ADA Specification No-25

A

*ADA Types I -V
*Type I and II: impression plaster / model and
mounting plaster
*Type III: dental stone (general purpose casts)
*Type IV: high strength / lowest expansion (die
stone)
*Type V: high strength / high expansion (die stone)

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10
Q

Desirable Properties of Cast / Die Materials

A

*Accuracy
*Reproduce fine detail (20μ-wide-line)
*Strong and durable
* color

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11
Q

*Strong and durable cast qualities

A

*Strength (wet strength / dry strength)
*Resistance to shearing forces (edge strength)
*Abrasion resistance

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12
Q

*Color of cast

A

*Contrast to wax
*Scanning visibility
(CAD-CAM)

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13
Q

Water : Powder Ratio

A

*Least amount of water necessary to obtain proper manipulation of stone
*Manufacturer’s recommendation
*Add powder to liquid in mixing bowl for proper wetting.

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14
Q

Properties related to water:powder ratio

A

*Directly proportional: setting times / manipulation
*↑water = ↑ setting time; ↑ fluidity

*Inversely related: strength and setting expansion
*↑water = ↓ compressive strength
*↑water = ↓ setting expansion
*(important in gypsum investment)

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15
Q

set gypsum? disinfectant? alc?

Beware of Interactions when pouring cast

A

*Gypsum that has already set acts as a catalyst when in contact with unset gypsum and can cause changes in the set and working times.
*Excessive disinfectant solution or water can give you unset or powdery gypsum at the surface.
*Make sure that your impressions are clean and only slightly damp before you pour.
*Excessive use of alcohol based surfactants or debubblizers can also create surface issues like softness or chalkiness

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16
Q

Mechanical-Vacuum Mixing of Gypsum

A

*Helps eliminate porosity
*Strengthens the cast
*20 seconds / 425 rpm / >25mmHg
*Over-spatulation → decreased
working time

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17
Q

Dimensional Accuracy and Strength

A

*Minimal expansion for procedure
*Surface should be hard and smooth when removed from impression
*Wet strength – Dry strength
*Strength doubles 1H → 24H
*Set in an upright position
*Prevents stone slumping from cusps

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18
Q

Alginate Impressions: 2-Pour Technique

A

*Anatomic pour with Type III Stone: cover vestibule; stack up stone; add
nodules
*Base: 2omix after initial set of anatomic pour or after separation from
impression (45 min).

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19
Q

Solubility: Gypsum immersion in water effect on linear deminsion

A

Linear dimension ↓ per every 20 minutes of immersion

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20
Q

Immersion in water saturated with calcium sulfate (slurry) will decrease what quality?

A

Immersion in water saturated with calcium sulfate (slurry) will decrease
solubility

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21
Q

*Avoid _______ formation (cast trimming)

A

*Avoid sludge formation (cast trimming)

22
Q

*Scrubbing cast will remove

A

*Scrubbing cast will remove surface detail

23
Q

Resistance to Abrasion
*Surface hardness ≠
*Surface impregnation?
*Strengthened products?

A

*Surface hardness ≠ abrasion resistance
*Surface impregnation**- Cyanoacrylate cement
Strengthened products- Resin (CAD-CAM)

24
Q

Pour the impression twice…
*Check _______ contacts
*Verify fit of?
*Can be used if?

A

*Check interproximal contacts, solder relation on rigid cast.
*Verify fit of casting or margin at try -in.
*Can be used if original is damaged.

25
Q

Indirect cast/Die Systems

A

*Removable Dies
*Solid Cast / Separate Dies (Multiple Pour System)

26
Q

*Removable Dies
*Retained by?
*One die used for?

A

*Removable Dies
*Retained by pins in a base (stone or plastic)
*One die used for entire wax pattern - proximal contacts, occlusion and margins

27
Q

*Solid Cast / Separate Dies (Multiple Pour System)
*Single (separate) die?
*Solid cast for?

A

*Single (separate) die for wax coping and margins
*Solid cast for waxing proximal contacts and occlusion

28
Q

Solid Cast – Separate Die System
Advantages:
*fabrication?
*Provides what for FPD components?

A

Solid Cast – Separate Die System
Advantages:
*Simple fabrication - requires minimum
trimming
*Provides a rigid relation for FPD components

29
Q

Removable Die Systems
die can be?
manipulation?

A

*The die can be lifted and replaced in the master cast with embedded pins or dowels.

*Requires less manipulation of wax pattern
- Reduces chance of breakage and distortion
-Handling of restorations is easier (porcelain margins)

30
Q

Removable Die Systems
*Disadvantages:
Technique?
*Error?
*Margin or pin damage?

A

Removable Die Systems
*Disadvantage: Technique sensitive
*Error in pattern if die does not re-seat accurately
*Margin or pin damage by improper saw cuts

31
Q

Loose, poorly adapted pins cause?

A

Loose, poorly adapted pins – die rotation

32
Q

Saw-cut through pin areas causes

A

Saw-cut through pin areas –
pins dislodged

33
Q

Digitally Milled Casts

A

*Digital impression systems

*CAM process (Cadent)
-Milled resin cast
-Sectioned dies
-Articulation

34
Q

Requirements for Removable Die Systems
*Dies must return to?
*Dies must remain? .
*Master cast must be easily?
.

A

Requirements for Removable Die Systems
*Dies must return to exact
original position.
*Dies must remain stable,
even when inverted.
*Master cast must be easily
mounted on an articulator.

35
Q

Definitive Cast and Die Preparation
Pindex Technique

A
  1. Pouring the impression / cast trimming
  2. “Pin” the cast and pour base
  3. Section the cast by sawing
  4. Die Preparation
    *Die trimming
    *Mark finish line
  5. Articulate the master cast
    *Interocclusal record in MIP
  6. Preparation for waxing
    *Die relief (cement spacer)
    *Die hardening (finish line)
36
Q

base poured after? 1st pour seperated from? cast-base interface free of

Definitive Cast Preparation: Pindex Base

A

*Base is poured after pins/sleeves are
cemented.
*1st pour carefully separated from cast base.
*Cast base interface should be free of voids.

37
Q

Definitive Cast Preparation: Pindex Section Dies
*Each die section must?
*Yet have ?
*Avoid cutting or abrading a?
*All sections are independently?
*Die base should seat?

A

*Each die section must slide out independently -
*Yet have adequate stone around pins for strength -
*Avoid cutting or abrading a margin.
*All sections are independently removable from the base.
*Die base should seat flush and be perpendicular to cast base.

38
Q

Definitive Cast Preparation:
Solid Cast – Separate Die
*Pour individual?
*Separate cast from?
*The first pour is?
*The 2ndpour is completed as?
*The solid cast (full arch) is mounted on?

A

*Pour individual die section (1stpour)
*Separate cast from impression and re-pour impression
*The first pour is sectioned/trimmed into individual die
*The 2ndpour is completed as a full arch cast with base
*The solid cast (full arch) is mounted on articulator

39
Q

Definitive Cast Preparation:
Solid Cast – Separate Die 1st pour build up of stone mass

A

Stone mass is built up to a height of about 1 inch to make a handle

40
Q

Definitive Cast – Die Trimming
*Die is trimmed to remove? .
*Die contour approximates?
*Provides access to?
*Smooth?

A

*Die is trimmed to remove areas corresponding to the gingival tissue.
*Die contour approximates the root and emergence profile.
*Provides access to margin.
*Smooth surface

41
Q

Die Trimming: Emergence Profile
*The surface of the “un-prepared” tooth apical to?
*Stone is removed with?

A

*The surface of the “un-prepared” tooth apical to the finish line is left intact.
*Stone is removed with scalpel blade below this line.

42
Q

Cervical Margin: Emergence Profile
*A properly trimmed die must have same contour as?
*Adequate access to the _____ is necessary for _______ to
proper emergence profile.
*≈ ___mm below finish line

A

*A properly trimmed die must have the same cervical contour as the tooth.
*Adequate access to the margin is necessary for carving the wax to the
proper emergence profile.
*≈ 5mm below finish line

43
Q

Definitive Cast – Die Trimming
*Trimmed from?
*Leave what below margin?
*Margin trimming is finished with?

A

*Trimmed from below and parallel to the margin.
*Leave small lip of stone below margin.
*Margin trimming is finished with Bard-Parker #25 blade.

44
Q

AVOID: Sharp _______ of the die apical to the margin
→ what contouring occurs?
→ strenght of die?

A

AVOID: Sharp ditching of the die apical to the margin
→ over-contouring (angulation of wax carver)
→ weakening of the die

45
Q

Definitive Cast: Articulation
*Ensure? .
*Verify contact of ? .
*Accuracy of mounting is critical to?
*Compare?

A

*Ensure accurate tooth - tooth contact.
*Verify contact of incisal pin.
*Accuracy of mounting is critical to accurate occlusion in final restoration.
*Compare intraoral and articulated cast occlusal contacts.

46
Q

Interocclusal Records for Orienting Casts on Articulator

A

An interocclusal registration is necessary to orient dies of prepared
teeth to the opposing occlusion.

47
Q

Interocclusal Records: Materials
*Material Requirements:
*R to closure?
*Rigid when?
*Dimensional?

A

*No resistance to closure
*Rigid when set
*Dimensional stability / accurac

48
Q

Interocclusal Records: Materials

A

*Rigid, Fast-set VPS
*Plaster (Removable Prostheses)
*ZnOE paste; Resin (rigid)
*Wax - should not be used for fixed
prosth

49
Q

Definitive Cast: Occlusal Registration(MIP)
*Record the maxillary and mandibular teeth in?
*Stone - stone contact with hand articulation?
*Place record material between? .

A

*Record the maxillary and mandibular teeth in total contact.
*Stone - stone contact with hand articulation where possible.
*Place record material between prepared and opposing teeth only.

50
Q

Definitive Cast: Occlusal Registration
*Reduce record to include only?
*Cut back? to visualize?
*Ensure? how?

A

*Reduce record to include only cusp tips for proper seating.
*Cut back facial to visualize seating.
*Ensure accurate tooth - tooth contact elsewhere- Mark with articulating paper
and Check with shimstock

51
Q

Definitive Cast: Occlusal Registration
*Articulation of?

A

*Articulation of the mandibular master cast with the maxillary diagnostic cast.

52
Q

deminsions of the definitive casts

A

fixed pros. (11 decks)

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