NBDE Periodontics and Endodontics Questions and Answers

Question 1

A 45-year-old patient presents with a chief complaint of a "gummy smile." Clinical examination reveals probing depths of 2-3 mm, minimal bleeding on probing, and a gingival margin located significantly coronal to the CEJ. Bone sounding reveals a distance of 5 mm from the gingival margin to the alveolar crest. What is the most likely diagnosis?

Accepted Answer

Altered Passive Eruption

Answer

Altered passive eruption occurs when the gingival margin fails to migrate apically to the CEJ after tooth eruption, resulting in short clinical crowns and excessive gingival display. The key diagnostic finding here is the excessive gingival tissue coronal to the CEJ despite normal probing depths, which rules out periodontitis. The significant distance from the gingival margin to the alveolar crest confirms an excess of supracrestal soft tissue.

Question 2

Which of the following is the primary purpose of using 17% Ethylenediaminetetraacetic acid (EDTA) as an irrigant during root canal therapy?

Accepted Answer

To remove the inorganic component of the smear layer.

Answer

EDTA is a chelating agent that specifically binds with calcium ions in dentin. Its primary function in endodontics is to remove the inorganic, mineralized component of the smear layer created during canal instrumentation. This action unplugs the dentinal tubules, allowing for better adaptation of obturating materials and deeper penetration of disinfectants like sodium hypochlorite, which dissolves the organic tissue.

Question 3

A clinician is evaluating a maxillary molar with a Nabers probe. The probe passes completely through the furcation from the buccal to the mesiopalatal aspect, and the entrance to the furcation is clinically visible due to significant gingival recession. According to Glickman's classification, what is the correct classification for this furcation involvement?

Accepted Answer

Class IV

Answer

Glickman's classification defines a Class IV furcation as a through-and-through involvement that is clinically visible because of gingival recession. A Class III furcation is also a through-and-through defect, but it is covered by soft tissue and not clinically visible. Class I is incipient involvement, and Class II is partial penetration into the furcation.

Question 4

A 22-year-old patient reports sharp, lingering pain in tooth #30 that lasts for several minutes after a cold stimulus is removed. The pain also occurs spontaneously and has awakened the patient from sleep. Percussion and palpation tests are within normal limits. A periapical radiograph shows a deep composite restoration but no periapical radiolucency. Based on these findings, what are the most likely pulpal and periapical diagnoses?

Accepted Answer

Symptomatic Irreversible Pulpitis and Normal Apical Tissues

Answer

The key signs of symptomatic irreversible pulpitis are spontaneous pain and lingering pain to thermal stimuli. Since the percussion and palpation tests are normal and there is no radiographic evidence of periapical pathosis, the diagnosis for the periapical tissues is Normal Apical Tissues. Symptomatic Apical Periodontitis would present with pain on percussion, indicating inflammation has reached the periapical ligament.

Question 5

Which of the following clinical scenarios is most indicative of a primary periodontal lesion with secondary endodontic involvement?

Accepted Answer

A vital tooth with generalized severe bone loss and a wide, conical periodontal pocket.

Answer

A primary periodontal lesion begins with marginal periodontitis. This would be characterized by generalized bone loss and wide pocketing around a tooth that initially tests vital. The infection can then progress apically to involve the pulp via lateral canals or the apical foramen, causing a secondary endodontic lesion where the pulp becomes necrotic. A deep, isolated pocket on a non-vital tooth suggests a primary endodontic lesion draining coronally.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

NBDE Periodontics and Endodontics Questions and Answers