FREE NBDE Endodontics Questions and Answers

Question 1

A patient presents with a chief complaint of a severe, spontaneous toothache in the lower right quadrant that awakens them at night.
A cold stimulus applied to tooth #30 elicits a sharp pain that lingers for over 30 seconds.
The tooth is not tender to percussion.
Radiographs reveal a deep composite restoration but no periapical radiolucency.
What is the most likely pulpal diagnosis?

Accepted Answer

Symptomatic Irreversible Pulpitis

Answer

Reversible Pulpitis

Answer

Pulp Necrosis

Answer

Asymptomatic Apical Periodontitis

Question 2

Which of the following is the primary active ingredient in endodontic irrigating solutions responsible for dissolving necrotic pulp tissue and the organic components of the smear layer?

Accepted Answer

Sodium hypochlorite (NaOCl)

Answer

Ethylenediaminetetraacetic acid (EDTA)

Answer

Chlorhexidine gluconate

Answer

Calcium hydroxide

Question 3

A dentist is performing a root canal on a mandibular first molar. Based on typical root and canal morphology, what is the most common configuration they should expect to find?

Accepted Answer

Two roots; one mesial root with two canals and one distal root with one or two canals

Answer

One root with one canal

Answer

Three separate roots (MB, DB, and Palatal)

Answer

Two roots; one mesial and one distal, with one canal in each root

Question 4

A 12-year-old patient presents with an avulsed permanent maxillary central incisor (#8) with a closed apex. The tooth was stored dry for 75 minutes before presentation. According to current IADT guidelines, what is the primary therapeutic goal of replanting this tooth?

Accepted Answer

To maintain the alveolar bone contour via eventual ankylosis and replacement resorption.

Answer

To encourage revascularization of the pulpal tissue.

Answer

To allow for regeneration of the periodontal ligament.

Answer

To ensure the immediate return of normal proprioceptive function.

Question 5

The primary purpose of using a 17% EDTA solution as a final rinse during chemo-mechanical debridement of a root canal is to:

Accepted Answer

Remove the inorganic, mineralized component of the smear layer.

Answer

Kill resistant bacterial strains like E. faecalis.

Answer

Dissolve any remaining vital pulp tissue.

Answer

Act as a long-term intracanal medicament between appointments.

Question 6

Which of the following microorganisms is a facultative anaerobe most frequently implicated in persistent or secondary endodontic infections and is known for its resistance to common intracanal medicaments?

Accepted Answer

Enterococcus faecalis

Answer

Porphyromonas gingivalis

Answer

Streptococcus mutans

Answer

Actinomyces israelii