Final Impression in Prosthodontics Lecture Quiz

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Questions and Answers

What is the primary purpose of using a light consistency impression material?

To inject over the prepared teeth and remaining dental arch (correct)

To act as a catalyst for the base material

To provide a heavy consistency for the final impression

To use as a tray material for seating the final impression

What is the main advantage of polysulfide impression materials?

Long working time for multiple preparations (correct)

Excellent dimensional stability after setting

Minimal shrinkage towards the tray

Short working time for single preparations

Which statement about polyether impression materials is true?

They are supplied as a single paste system

They have excellent dimensional stability upon polymerization (correct)

They have poor dimensional stability upon polymerization

They are recommended for use with a spacer-less tray

What is a disadvantage of polysulfide impression materials?

Objectionable odor and messiness Signup and view all the answers

Which impression material is recommended for use with a special tray with a 4 mm spacer?

Polysulfide Signup and view all the answers

What is the recommended method for removing a polysulfide impression from the mouth?

Single swift pull Signup and view all the answers

Which statement about polysulfide impression materials is true?

They exhibit dimensional stability after setting Signup and view all the answers

What is the recommended viscosity of impression material to use as a tray material during the final impression procedure?

Putty or heavy body Signup and view all the answers

What is the main advantage of the Direct (intra oral) digital impression method?

It eliminates the need for taking a physical impression and fabricating a cast. Signup and view all the answers

What is the primary disadvantage of the Direct (intra oral) digital impression method?

Tongue and saliva may pose problems during scanning. Signup and view all the answers

What is the term used to describe the process of fabricating a restoration using digital impression data and CAD/CAM technology?

CAD-CAM Signup and view all the answers

In the context of digital impressions, what does the acronym 'CAD' stand for?

Computer Aided Designing Signup and view all the answers

Which system is mentioned in the text as being widely used for Direct (intra oral) digital impressions?

Cerec System Signup and view all the answers

What is the term used to describe the process of capturing a digital impression directly from the prepared tooth?

Optical Impression Signup and view all the answers

Where can the digital impression data be transferred after capture?

Either to an in-office CAD/CAM system or an external lab CAD/CAM facility Signup and view all the answers

What is the term used to describe the method of taking a physical impression and fabricating a cast?

The text does not provide a term for this method Signup and view all the answers

What is the first step in the spaced putty-wash impression technique?

Take a putty impression of the dental arch before tooth preparation Signup and view all the answers

How is the space created inside the putty impression for the wash (light body) layer?

By using a polyethylene spacer placed over the putty Signup and view all the answers

What is the purpose of creating a space inside the putty impression?

To create a reservoir for the wash (light body) impression material Signup and view all the answers

What is the difference between an unspaced putty impression and a spaced putty impression?

An unspaced putty impression does not have a space for the wash layer, while a spaced putty impression does Signup and view all the answers

When should the putty impression be taken in relation to tooth preparation?

The putty impression can be taken either before or after tooth preparation Signup and view all the answers

What is the purpose of the wash (light body) impression material in this technique?

To provide a more accurate impression of the prepared tooth or teeth Signup and view all the answers

What is the purpose of using a polyethylene spacer in the spaced putty impression technique?

To create a space for the wash (light body) impression material Signup and view all the answers

What is the difference between the spaced putty impression technique and the unspaced putty impression technique?

The spaced technique involves creating a space for the wash layer, while the unspaced technique does not Signup and view all the answers

What does the image on the monitor show?

If all the needed details have been captured before sending to the lab Signup and view all the answers

What allows the laboratory technician to fabricate a restoration with excellent marginal fit and accurate occlusion?

The accuracy of mounting, bite registration, and die stability Signup and view all the answers

What advantage of digital impressions is mentioned in the text?

The ability to see if proper occlusal reduction has been achieved Signup and view all the answers

How are digital impressions stored according to the text?

On PCs Signup and view all the answers

What issue is eliminated with a digital impression system?

The need for disinfection of impressions Signup and view all the answers

What is a disadvantage of digital impression systems mentioned in the text?

The large size and weight of the camera head Signup and view all the answers

What is required to operate and maintain a digital impression system according to the text?

A trained operator Signup and view all the answers

What is mentioned as a disadvantage of digital impression systems in the text?

High cost Signup and view all the answers

What is the main purpose of a conventional impression in crown and bridge prosthodontics?

To provide an exact duplication of the prepared tooth and surrounding oral tissues Signup and view all the answers

Why is it important for an impression in crown and bridge prosthodontics to include uncut tooth surface beyond the preparation?

To allow for proper contouring of the restoration Signup and view all the answers

What role does the hydrophilicity of impression material play in crown and bridge prosthodontics?

It allows good surface wetting and high surface detail Signup and view all the answers

Why must the impression material used for crowns and bridges be elastic?

To allow for easy removal from undercut regions on the tooth Signup and view all the answers

The spacer is removed before taking the putty impression in the spaced putty-wash technique.

True Signup and view all the answers

In the unspaced putty-wash technique, a space is created after teeth preparation.

False Signup and view all the answers

The light body impression material is injected before the heavy body impression material in the putty-wash technique.

False Signup and view all the answers

A spacer is used when taking impressions for post crowns to facilitate insertion into tiny canals.

False Signup and view all the answers

The light body impression material is removed from the patient's mouth before it is completely set.

False Signup and view all the answers

Impression materials for crowns and bridges need to be rigid to prevent distortion during removal.

False Signup and view all the answers

The putty impression should not include uncut tooth surfaces beyond the preparation.

False Signup and view all the answers

Digital impressions are typically stored in physical storage units according to the text.

False Signup and view all the answers

In crown and bridge prosthodontics, a good impression should only include the prepared tooth without considering the surrounding teeth and tissues.

False Signup and view all the answers

Bubble-free impressions are crucial in crown and bridge work to ensure accuracy, especially at the area of the finish line.

True Signup and view all the answers

The material used for final impressions in crown and bridges should not be elastic after placement in the mouth.

False Signup and view all the answers

Hydrophilic impression materials have a low affinity for moisture and do not provide good surface wetting.

False Signup and view all the answers

Digital impressions are stored in physical trays according to the text.

False Signup and view all the answers

Polysulfide impression materials are not suitable for crown and bridge prosthodontics.

False Signup and view all the answers

A light body impression material is primarily used for creating the main body of the impression in crown and bridge work.

False Signup and view all the answers

Accurate articulation of the cast is not important when taking impressions for crown and bridge prosthetics.

False Signup and view all the answers

A plastic post can be used as reinforcement for the impression material.

False Signup and view all the answers

Air bubble presence in the area of preparation is not a concern when inspecting the impression.

False Signup and view all the answers

To obtain a good final impression, a wet field of operation is recommended.

False Signup and view all the answers

Digital impressions represent an outdated development in Dentistry.

False Signup and view all the answers

Digital impressions convert the shape of prepared teeth into two-dimensional images.

False Signup and view all the answers

Hydrocolloids are hydrophobic and displace moisture.

False Signup and view all the answers

The main purpose of using a light consistency impression material is to create voids in the impression.

False Signup and view all the answers

A special tray is not required when obtaining a good final impression.

False Signup and view all the answers

Polyether and hydrophilic addition silicon impression materials should be submerged in a glutaraldehyde solution for disinfection.

False Signup and view all the answers

Impression material should be immediately rinsed with tap water after removal from the patient's mouth.

True Signup and view all the answers

It is necessary to follow the manufacturer's recommendations when using disinfecting solutions or sprays on impression material.

True Signup and view all the answers

All impression materials come in contact with body fluid when removed from the patient's mouth.

True Signup and view all the answers

Glutaraldehyde Solution 10 should not be used for disinfection of impression materials.

False Signup and view all the answers

Disinfecting impression materials for too long can lead to dimensional and surface changes, affecting accuracy in dies and models.

True Signup and view all the answers

Polyether and hydrophilic addition silicon impression materials are not suitable for being sprayed and stored in a plastic bag for disinfection.

False Signup and view all the answers

The impression material used for crowns and bridges should not be elastic.

False Signup and view all the answers

CAD-CAM stands for Computer Aided Designing - Computer Aided Milling.

False Signup and view all the answers

CAD/CAM systems consist of scanning, designing, and casting phases.

False Signup and view all the answers

Digital scanning can be divided into Direct (intra oral) and Indirect (extra oral) digital impressions.

True Signup and view all the answers

The introduction of CAD/CAM systems to dental field was in the 1990s.

False Signup and view all the answers

Indirect digital impression systems scan a stone cast or die of the prepared tooth in the patient's mouth.

False Signup and view all the answers

Direct digital impression systems require the dental technician to add porcelain for individualization of restorations.

False Signup and view all the answers

Master cast fabrication is a quick and error-free method in digital scanning.

False Signup and view all the answers

CAD CAM systems eliminate the need for preparation of abutment teeth in traditional impression techniques.

False Signup and view all the answers

Study Notes

Impression Materials and Techniques

Shadowing effect limits the use of extra-oral digitization methods.
Direct (intra-oral) digital impression:
- Uses an intra-oral camera (scanner) to capture the desired image (optical impression).
- Transfers the image electronically to CAD/CAM for fabrication.
- Advantages: takes data directly from prepared tooth, eliminates need for impression and cast fabrication.
- Disadvantage: tongue and saliva may pose problems.
Polysulfide impression material:
- Supplied as a two-paste system (base and catalyst).
- Available in various viscosities (light, medium, heavy).
- Advantages: accurate, long working time, excellent tear resistance.
- Disadvantages: messy, objectionable odor, long setting time, shrinkage towards tray.
Polyether impression material:
- Excellent dimensional stability.
- Techniques: spaced putty impression, un-spaced putty impression.
- Advantages: high accuracy, minimal distortion.
- Disadvantages: complex procedure, operator skill required.

Digital Impression

Advantages:
- Allows for single-appointment restoration fabrication.
- Eliminates impression fabrication and disinfection steps.
- Enables digital record-keeping and storage.
- Reduces chairside time.
Disadvantages:
- Large camera size and weight.
- Complex equipment requires trained operator.
- High cost.

Conventional Impression

Requirements for a good impression in crown and bridge prosthodontics:
- Accurate duplication of prepared tooth and surrounding tissues.
- Bubble-free impression.
- Registration of undercut surfaces without distortion or fracture.
Properties of material used for final impression in crowns and bridges:
- Elastic after placement in the mouth.
- Hydrophilicity for good surface wetting and detail.

Impression Procedure

Spaced putty wash technique:
- Record putty impression of dental arch, including prepared tooth.
- Create space inside impression using a spacer or scalpel.
- Mix light body impression material and inject around preparation and dental arch.
Un-spaced putty wash technique:
- Record putty impression after teeth preparation.
- No space creation, direct injection of light body material.

Post-Crown Impression

Requires impression for root canal space.
Difficulty in inserting and removing impression material from canal.
Use of reinforcement (plastic post or stainless wire) to support impression material.

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Description

Test your knowledge on final impressions in prosthodontics, focusing on conventional and digital impression techniques. Learn about the requirements for a good impression in crown and bridge prosthodontics.