Introduction to Impressions for FPDs - Mohammed...

Mohammed AlfarsiBDS, MDSc(Pros), PhD

www.DrMohdAlfarsi.comwww.محمدالفارسي.com

[email protected]@DrMohdAlfarsiDrMohdAlfarsi056 224 2227

Introduction to Impressions for FPDs

Friday, 7 March 14

http://www.DrMohdAlfarsi.com




Why Do We Take Impressions?Overview

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Why Do We Take Impressions?Overview

Requirements:- Should be biocompatible.- Should be cost-effective.- Be fluidly enough to adapt to the oral tissues- Be viscous enough to be contained in the impression tray.- Set in reasonable time.- Should not be distorted when removed after setting.- Should remain dimensionally stable until poured.- Should reproduce surface details.

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Types of ImpressionsIntroduction

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Reversible Irreversible

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Impression compound

(green sticks)

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Impression compound

(green sticks)

Reversible hydrocolloid

(agar)

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Impression compound

(green sticks)


(agar)

Irreversible hydrocolloid

(alginate)

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Impression compound

(green sticks)


(agar)


(alginate)

Elastomeric impression

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Impression compound

(green sticks)


(agar)


(alginate)


Polysulfide

Silicone

Polyether

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Impression compound

(green sticks)


(agar)


(alginate)


Polysulfide

Silicone

Polyether

Condensation silicone

Addition silicone

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Impression compound

(green sticks)


(agar)


(alginate)


Zinc oxide-eugenol impression

Polysulfide

Silicone

Polyether


Addition silicone

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Impression compound

(green sticks)


(agar)


(alginate)


Zinc oxide-eugenol impression

Impression plaster

Polysulfide

Silicone

Polyether


Addition silicone

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Impression materials

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AlginateImpression materials

- Inexpensive- Easy to manipulate- Requires simple equipment- Hydrophilic- Comfortable for the patient

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AlginateImpression materials

- Inexpensive- Easy to manipulate- Requires simple equipment- Hydrophilic- Comfortable for the patient

- Can not reproduce fine details- Mixing time can affect the strength- Water temp. can affect setting time- Must be poured within an hour- Second pour is not as accurate- Sudden removal is required

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Addition SiliconeImpression materials

- Accurate reproduction of surface details.- Does not require immediate pour.- Can be poured more than once, most accurate is first one.- Easy pouring, if hydrophilic surfactant is incorporated.- Stays dimesionally stable for long time.

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Addition SiliconeImpression materials

- Accurate reproduction of surface details.- Does not require immediate pour.- Can be poured more than once, most accurate is first one.- Easy pouring, if hydrophilic surfactant is incorporated.- Stays dimesionally stable for long time.

- Relatively expensive.- Releases hydrogen gas. But recent materials do not.- Hydrophobic. But recent material are hydrophilic- Latex gloves inhibit the setting.- Can be technique sensitive.

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PolyetherImpression materials

- First elastomer developed to be impression material.- Hydrophilic.- Very accurate reproduction of surface details.- Dimensionally stable.- Can be poured more than once.

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PolyetherImpression materials

- First elastomer developed to be impression material.- Hydrophilic.- Very accurate reproduction of surface details.- Dimensionally stable.- Can be poured more than once.

- Expensive.- Stiff, should not be used if there are undercuts.

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ViscositiesImpression materials

- Light.- Medium.- Heavy.- Extra heavy (Putty).

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ViscositiesImpression materials

- Light.- Medium.- Heavy.- Extra heavy (Putty).

Shear-thinning(pseudo-plasticity)

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Impression techniques

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How to Take an Impression for a FPD?Impression techniques

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Troubleshooting

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What can go wrong?Troubleshooting

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The End

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The End

References

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Introduction to Impressions for FPDs - Mohammed...

Documents

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