def cast and dies Flashcards by Caleb Houghton

Definitive (Master or Working)
Cast

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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Die:

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

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A good cast must be:

Bubble free
Distortion free

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cast must reporduce which surfaces?

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

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occluding surfaces of casts must allow for

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

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soft tissues of cast

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

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

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

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

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Classification of gypsum products according
to ADA Specification No-25

*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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Desirable Properties of Cast / Die Materials

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

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*Strong and durable cast qualities

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

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*Color of cast

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

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Water : Powder Ratio

*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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Properties related to water:powder ratio

*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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set gypsum? disinfectant? alc?

Beware of Interactions when pouring cast

*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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Mechanical-Vacuum Mixing of Gypsum

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

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Dimensional Accuracy and Strength

*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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Alginate Impressions: 2-Pour Technique

*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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Solubility: Gypsum immersion in water effect on linear deminsion

Linear dimension ↓ per every 20 minutes of immersion

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

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

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*Avoid _______ formation (cast trimming)

*Avoid sludge formation (cast trimming)

*Scrubbing cast will remove

*Scrubbing cast will remove surface detail

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

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

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

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

Indirect cast/Die Systems

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

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

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

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

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

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

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

Removable Die Systems die can be? manipulation?

*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)

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

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

Loose, poorly adapted pins cause?

Loose, poorly adapted pins – die rotation

Saw-cut through pin areas causes

Saw-cut through pin areas – pins dislodged

Digitally Milled Casts

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

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

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.

Definitive Cast and Die Preparation Pindex Technique

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)

# base poured after? 1st pour seperated from? cast-base interface free of Definitive Cast Preparation: Pindex Base

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

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?

*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.

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?

*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

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

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

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

*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

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

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

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 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

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

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

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

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

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

*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.

Interocclusal Records for Orienting Casts on Articulator

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

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

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

Interocclusal Records: Materials

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

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

*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.

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

*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

Definitive Cast: Occlusal Registration *Articulation of?

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

deminsions of the definitive casts