NBDE Endodontics 2

Question 1

Which radiographic finding is most characteristic of a periapical abscess compared to a periapical granuloma?

Accepted Answer

Diffuse radiolucency with poorly defined margins

Answer

Periapical abscesses typically appear as diffuse, poorly defined radiolucencies due to rapid bone destruction, whereas granulomas have more defined borders.

Question 2

A patient presents with a tooth that tests vital with cold but has a periapical radiolucency. What is the most likely diagnosis?

Accepted Answer

Non-odontogenic lesion or anatomical landmark

Answer

A vital pulp response with a periapical radiolucency suggests a non-odontogenic etiology or an anatomical structure (e.g., mental foramen, incisive canal) rather than pulpal pathology.

Question 3

During root canal preparation, the working length shortens by 2mm unexpectedly. What is the most likely cause?

Accepted Answer

Ledge formation

Answer

Ledge formation creates a false canal wall that blocks instrument passage to the apex, causing an apparent reduction in working length.

Question 4

Which irrigant is most effective at dissolving organic pulp tissue remnants during root canal treatment?

Accepted Answer

Sodium hypochlorite (5.25%)

Answer

Sodium hypochlorite is the only endodontic irrigant with proven ability to dissolve organic tissue due to its proteolytic action.

Question 5

What is the primary purpose of the smear layer removal step using EDTA in root canal treatment?

Accepted Answer

Open dentinal tubules to improve sealer penetration

Answer

EDTA chelates calcium ions and removes the inorganic smear layer, exposing dentinal tubule openings to allow deeper sealer penetration.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

NBDE Endodontics 2