EFDA - Expanded Function Dental Auxiliary Impression Materials and Techniques Questions and Answers

Question 1

An EFDA is taking a final impression for a single crown.
Upon removing the impression, they notice a "drag" or "pull" distortion near the margin of the prepared tooth.
What is the most likely cause of this specific error?

Accepted Answer

The impression material began to set while the tray was being seated.

Answer

Premature removal of the tray from the mouth.

Answer

Moisture contamination from saliva or blood.

Answer

The tray was removed with a slow, teasing motion.

Question 2

Which of the following impression materials is classified as an irreversible hydrocolloid and is primarily used for diagnostic casts, preliminary impressions for custom trays, and opposing arch models?

Accepted Answer

Alginate

Answer

Polyether

Answer

Polyvinyl siloxane (PVS)

Answer

Reversible hydrocolloid (Agar)

Question 3

An EFDA has just taken an alginate impression. To ensure maximum dimensional accuracy before pouring the model, what is the most appropriate next step?

Accepted Answer

Disinfect the impression, rinse, and pour it immediately or store it in 100% humidity.

Answer

Leave the impression on the counter to air dry for 15 minutes.

Answer

Submerge the impression in a bowl of warm water until it can be poured.

Answer

Wrap the impression in a dry paper towel to absorb excess moisture.

Question 4

A dentist requires a highly accurate and dimensionally stable final impression for a three-unit bridge. The material must have excellent tear strength and allow for multiple pours of the model if needed. Which material best fits this description?

Accepted Answer

Polyvinyl siloxane (PVS)

Answer

Polysulfide

Answer

Alginate

Answer

Zinc oxide-eugenol (ZOE)

Question 5

When an EFDA dispenses material for a bite registration, what is the primary goal of this procedure?

Accepted Answer

To record the occlusal relationship between the maxillary and mandibular arches in centric occlusion.

Answer

To create a detailed model of the patient's gingival contours.

Answer

To serve as a mold for fabricating a provisional restoration.

Answer

To capture the undercuts of the teeth for designing a removable partial denture.

Question 6

An EFDA is assisting with a final impression using a polyether material. Which of the following is a key characteristic of this material that must be considered when handling the final impression?

Accepted Answer

It is very rigid when set and can be difficult to remove from the mouth, especially around undercuts.

Answer

It is highly hydrophobic and repels all moisture.

Answer

It has a very long setting time, often exceeding 15 minutes.

Answer

It must be poured within 5 minutes due to poor dimensional stability.