ABE Endodontic Materials 5

Question 1

The presence of a precipitate when mixing chlorhexidine and sodium hypochlorite irrigants in the canal results in formation of:

Accepted Answer

Para-chloroaniline, a potentially carcinogenic compound

Answer

Mixing NaOCl and chlorhexidine creates a brown precipitate of para-chloroaniline (PCA), which is potentially toxic and can stain tooth structure.

Question 2

The dimensional stability of zinc oxide eugenol temporary restorations is most adversely affected by:

Accepted Answer

Moisture contamination during setting

Answer

Moisture contamination during the setting of ZOE materials accelerates the reaction unevenly and can lead to dimensional instability and reduced strength.

Question 3

In the context of root canal obturation, the term 'apical plug' refers to a technique where:

Accepted Answer

MTA or bioceramic material is condensed at the apex to create a barrier

Answer

An apical plug technique places 3-4mm of MTA or bioceramic material at the apex to create a barrier before backfilling, commonly used in open-apex cases.

Question 4

Paraformaldehyde-containing pastes (e.g., N2, Endomethasone) are controversial in endodontics primarily because they:

Accepted Answer

Release formaldehyde which is mutagenic and can cause severe tissue injury

Answer

Paraformaldehyde releases formaldehyde which is a recognized mutagen and carcinogen; periapical extrusion can cause severe neurotoxicity and tissue necrosis.

Question 5

The working time of AH Plus epoxy resin sealer at room temperature (23°C) is approximately:

Accepted Answer

4 hours

Answer

AH Plus has a working time of approximately 4 hours at room temperature (23°C), though it sets faster at body temperature.

(ABE) American Board of Endodontics Practice Test

(ABE) American Board of Endodontics Practice Test

ABE Endodontic Materials 5