NBDE Periodontics and Endodontics 3 — Questions and Answers
Question 1: Which test result pattern is MOST consistent with a diagnosis of reversible pulpitis?
- No response to cold, lingering pain
- Exaggerated response to cold that resolves quickly (Correct answer)
- Spontaneous pain unrelated to stimuli
- Positive percussion, negative cold test
Correct answer: Exaggerated response to cold that resolves quickly
Reversible pulpitis produces a heightened but transient response to thermal stimuli that subsides quickly upon removal of the stimulus, indicating the pulp can recover.
Question 2: What is 'biologic width' and why is it clinically significant in restorative dentistry?
- The minimum root length needed for a crown
- The combined height of junctional epithelium and connective tissue attachment above bone (Correct answer)
- The ideal crown-to-root ratio for a fixed prosthesis
- The distance from the CEJ to the alveolar crest
Correct answer: The combined height of junctional epithelium and connective tissue attachment above bone
Biologic width (~2mm) is the combined dimension of the junctional epithelium (~1mm) and connective tissue attachment (~1mm) that must be respected when placing restoration margins.
Question 3: During root canal shaping, which concept describes enlarging the canal more at the coronal third to improve irrigation and reduce ledging?
- Step-back technique
- Crown-down technique (Correct answer)
- Balanced force technique
- Passive step-back
Correct answer: Crown-down technique
The crown-down technique shapes the canal from the orifice downward, removing coronal interferences first to improve irrigant access, reduce apical debris extrusion, and minimize ledging.
Question 4: A healthy sulcus depth is generally considered to be:
- 0–1 mm
- 1–3 mm (Correct answer)
- 4–5 mm
- Greater than 5 mm
Correct answer: 1–3 mm
A healthy gingival sulcus typically measures 1–3 mm in depth; depths exceeding 3 mm with attachment loss are considered pathologic periodontal pockets.
Question 5: What is the MOST common cause of endodontic treatment failure?
- Instrument fracture within the canal
- Incomplete removal of infected tissue and inadequate seal (Correct answer)
- Overfill of the root canal system
- Perforation of the root
Correct answer: Incomplete removal of infected tissue and inadequate seal
The most common cause of endodontic failure is inadequate debridement leaving residual infected tissue combined with a poor coronal or apical seal allowing recontamination.
Question 6: Which systemic condition is MOST strongly associated with generalized aggressive periodontitis?
- Hypertension
- Neutrophil functional defects (Correct answer)
- Hyperthyroidism
- Iron deficiency anemia
Correct answer: Neutrophil functional defects
Aggressive periodontitis is strongly associated with neutrophil functional defects (chemotaxis or phagocytosis abnormalities) that impair the host's ability to control periodontal pathogens.
Question 7: In the step-back technique for root canal preparation, the working length is established at which file size?
- The largest file used
- The master apical file (MAF) (Correct answer)
- The first file to bind at the apex
- The size 10 K-file
Correct answer: The master apical file (MAF)
In the step-back technique, the master apical file (MAF) is the largest file used at the full working length, establishing the final apical preparation size.
NBDE Periodontics and Endodontics 3
Which test result pattern is MOST consistent with a diagnosis of reversible pulpitis?