UNIT 7 - impression materials - IMPORTANT FOR PRACTICAL EXAM

What are impression materials used for?

To accurately record the shape of oral structures.

What are the two purposes of impression materials?

• Obtaining a model to work with outside the patient’s mouth.

• Recording positions: keys and occlusion records.

Why are traditional impression materials still used despite the development of new technologies?

New technologies may be out of reach for some due to economic and technical reasons, and certain processes are faster and more cost-effective using traditional methods.

requirements

What biological requirements should impression materials meet?

Compatibility and non-toxicity.

requirements

What two aspects make up the accuracy requirement for impression materials?

• Reproducibility of details, which depends on the viscosity of the material.

• Dimensional stability.

requirements

What plastic and elastic properties should impression materials have?

Plasticity to adapt to tissues and elasticity for easy removal from the mouth.

requirements

What strength requirement should impression materials meet?

Strength, especially tear resistance, i.e. tensile strength.

requirements

What working and reaction times are required for impression materials?

Sufficient working time to perform the necessary procedures and the shortest possible reaction time.

requirements

What sensory requirements should impression materials meet?

Pleasant taste and odour.

requirements

What compatibility requirement should impression materials meet?

Compatibility with model materials.

requirements

What practical and economic requirements should impression materials meet?

Cost-effectiveness, easy handling and long shelf life.

classification

How are impression materials classified according to their setting reaction?

• Setting through a chemical reaction.

• Setting through temperature variation.

classification

How are impression materials classified according to their properties before setting?

• Fluids, if they do not compress soft tissues.

• Viscous or muco-compressive materials.

classification

What are the two main categories of impression materials according to their properties after setting?

Rigid materials and elastic materials.

classification

Which materials are classified as rigid impression materials? (5)

• Plaster for impressions.

• Cinquenolic paste.

• Resins.

• Modelling compound (godiva).

• Waxes.

classification

Which materials are classified as elastic impression materials? (5)

• Hydrocolloids.

• Elastomers.

• Silicones.

• Polyesters.

• Polysulfides or mercaptans.

classification

What are the two types of hydrocolloids?

• Reversible: agar-agar.

• Irreversible: alginate.

classification

How are silicones classified according to their setting reaction?

• By condensation.

• By addition.

classification

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Plaster for impressions - FOR PRACTICAL EXAM

What is impression plaster made of?

Calcium sulfate hemihydrate of the beta type.

Plaster for impressions - FOR PRACTICAL EXAM

What is the setting time of impression plaster?

2–3 minutes.

Plaster for impressions - FOR PRACTICAL EXAM

What is the manual spatulation time for impression plaster?

30–40 seconds.

Plaster for impressions - FOR PRACTICAL EXAM

What is the water/powder ratio for impression plaster?

50–60 ml of water per 100 g of powder, according to the manufacturer.

Plaster for impressions - FOR PRACTICAL EXAM

What are the properties of impression plaster?

• Good reproduction of details.

• Good dimensional stability.

• Clean fracture line.

Plaster for impressions - FOR PRACTICAL EXAM

What is required when using impression plaster?

The use of a spacer.

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Cinquenolic paste

What are the three components of the base paste in cinquenolic paste?

• Zinc oxide.

• Inert oils.

• Accelerators.

Cinquenolic paste

What are the components listed for the catalyst paste in cinquenolic paste?

• Eugenol.

• Resins.

• Oils.

• Fillers.

• Accelerators.

Cinquenolic paste

What allergic reaction warning is written beside eugenol

Eugenol can cause an allergic reaction.

Cinquenolic paste - properties

How thick can cinquenolic paste be used?

It allows working in very thin thicknesses because it is fluid.

Cinquenolic paste - properties

What is the contraction of cinquenolic paste?

0.1%.

Cinquenolic paste - properties

How well does cinquenolic paste reproduce details?

It reproduces details very well.

Cinquenolic paste - properties

What taste and odour does cinquenolic paste have?

Unpleasant taste and odour.

Cinquenolic paste - properties

Is here an allergic reaction risk associated

yes

Cinquenolic paste - properties

How difficult is cinquenolic paste to manipulate?

It is difficult to manipulate.

Cinquenolic paste - properties

What can cinquenolic paste react with?

Some model materials.

Cinquenolic paste - Handling

What is the commercial presentation of cinquenolic paste?

Two containers.

Cinquenolic paste - Handling

What is the dosage ratio when dispensing cinquenolic paste from its two tubes?

Equal lengths from both tubes, in a 1:1 ratio.

Cinquenolic paste - Handling

How much cinquenolic paste is needed for an upper edentulous case?

75–100 mm.

Cinquenolic paste - Handling

What is the spatulation time for cinquenolic paste?

20–30 seconds.

Cinquenolic paste - Handling

What must be achieved when spatulating cinquenolic paste?

A uniform colour.

Cinquenolic paste - Handling

What is the working time of cinquenolic paste?

135–150 seconds.

Cinquenolic paste - Handling

What is the setting time of cinquenolic paste?

4–5 minutes.

Cinquenolic paste - Handling

When should cinquenolic paste ideally be cast?

Within 30 minutes.

Cinquenolic paste - Handling

How should the model be separated from a cinquenolic paste impression?

Place the cast impression in a 60°C bath for 5 minutes before demoulding.

Cinquenolic paste - Handling

Mix until a uniform colour and consistency are achieved.

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Cinquenolic paste - uses

Which trays are used with cinquenolic paste to take impressions in edentulous arches?

Special trays.

Cinquenolic paste - uses

Which type of prosthesis is another use of cinquenolic paste?

Partial removable prostheses.

Resins - properties

What dimensional change occurs during resin polymerisation?

Polymerisation shrinkage.

Resins - properties

What thermal effect occurs during resin polymerisation?

Polymerisation exotherm.

Resins - properties

What can the polymerisation exotherm do to tissues?

It can damage tissues.

Resins - properties

What taste and odour do resins have?

Unpleasant taste and odour.

Resins - properties

What allergic reaction risk is associated with resins?

Possibility of an allergic reaction.

Resins - uses

What technique uses patterns created from resins?

The lost-wax micro-casting technique.

Resins - uses

How are resins used with implant transfers in impressions?

For splinting implant transfers.

Resins - uses

Which type of crowns can be made using resins?

Provisional crowns.

Resins - uses

What two items can be fabricated using resins?

Individual trays and base plates.

Resins - Handling

How difficult are resins to handle?

They are difficult to handle.

Resins - Handling

What should be followed when handling resins to achieve the best results?

The manufacturer's recommended technique.

Resins - Handling

What is the gelation time for resins used for provisional restorations?

4–5 minutes.

Resins - Handling

What is the working time for resins used for provisional restorations?

6–7 minutes.

Resins - Handling

What is the normal setting time for resins used for provisional restorations?

8–9 minutes.

Resins - Handling

What is the maximum heat time listed for resins used for provisional restorations?

10–11 minutes.

Resins - Handling

What is the flash point listed for resins used for provisional restorations?

10°C.

How are resins used to make individual trays and base plates typically cured?Resins - Handling

They are typically light-cured.

Resins - Handling

What is the recommended curing time for resins used to make individual trays and base plates?

5 minutes

Resins - Handling

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Godiva (Impression Compound)

What type of material is Godiva?

A thermoplastic material and muco-compressive.

Godiva (Impression Compound) - uses

What are the uses of Godiva?

Auxiliary impression techniques and individualisation of standard trays.

Godiva (Impression Compound) - commercial presentation

What forms is Godiva commercially available in?

Bars or sticks, and sheets.

Godiva (Impression Compound) - commercial presentation

What colour are Godiva bars or sticks?

Green.

Godiva (Impression Compound) - commercial presentation

How are Godiva bars or sticks softened?

With a lighter flame.

Godiva (Impression Compound) - commercial presentation

What colours are Godiva sheets?

Brown or red.

Godiva (Impression Compound) - commercial presentation

How are Godiva sheets softened?

In water at 65°C.

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Waxes

What type of material are waxes?

Thermoplastic material.

Waxes - properties

What is the thermal expansion coefficient of waxes?

0.6% from 25°C to 37°C.

Waxes - properties

What does the PowerPoint state about wax shrinkage

High shrinkage.

Waxes - properties

What should waxes not do at working temperatures?

Scale, break, or distort.

Waxes - properties

What should the consistency of waxes be at room temperature?

Rigid.

Waxes - properties

What are waxes used to make?

Records.

Waxes - commercial presentation

In what two forms are waxes commercially presented?

Sheets and bars.

Waxes - commercial presentation

What does the image show about softening wax sheets?

Wax sheets being softened by immersion in water.

Waxes - commercial presentation

What are softened wax sheets used for

Making bite registrations.

Waxes - commercial presentation

What precaution should be taken when heating wax in a flame or in water?

There is a possibility of losing volatile components, or soluble components in the case of water.

Hydrocolloids

What is the dispersing phase of hydrocolloids?

Water.

Hydrocolloids

What is the particle size range of colloid particles in hydrocolloids?

1–200 nm.

Hydrocolloids

What transformation occurs when a hydrocolloid sets?

A sol-gel transformation, from a flowable state to a solid state.

Hydrocolloids

What are the two types of hydrocolloids

Reversible hydrocolloids and irreversible hydrocolloids.

Hydrocolloids

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Reversible Hydrocolloids

What type of process causes gelation in reversible hydrocolloids?

A thermal process.

Reversible Hydrocolloids

What happens during gelation in reversible hydrocolloids?

The transition from sol to gel involves increasing and decreasing temperature.

Reversible Hydrocolloids

How does the liquefaction temperature compare with the gelation temperature in reversible hydrocolloids?

he liquefaction temperature is higher than the gelation temperature.

Reversible Hydrocolloids

What is the temperature difference between liquefaction and gelation called?

Hysteresis.

Reversible Hydrocolloids

Through which two processes do reversible hydrocolloids experience significant water loss?

Evaporation and syneresis.

Reversible Hydrocolloids

Why do reversible hydrocolloids have poor dimensional stability?

Due to water loss or gain.

Reversible Hydrocolloids

What is one use of reversible hydrocolloids?

Duplicating models.

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Irreversible Hydrocolloids (Alginates)

What type of process causes gelation in irreversible hydrocolloids (alginates)?

A chemical process.

Irreversible Hydrocolloids (Alginates)

Through which two processes do alginates experience water loss?

Evaporation and syneresis.