NBDE General Practice 4 — Questions and Answers
Question 1: Which class of antibiotics inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins?
- Macrolides
- Beta-lactams (Correct answer)
- Fluoroquinolones
- Tetracyclines
Correct answer: Beta-lactams
Beta-lactam antibiotics (penicillins, cephalosporins) inhibit transpeptidation by binding to penicillin-binding proteins, preventing cross-linking of peptidoglycan in the bacterial cell wall.
Question 2: A patient develops an allergic reaction to amoxicillin. Which antibiotic is the BEST alternative for a dental infection?
- Cephalexin
- Ampicillin
- Clindamycin (Correct answer)
- Nafcillin
Correct answer: Clindamycin
Clindamycin is the preferred alternative for penicillin-allergic patients in dentistry due to its activity against oral anaerobes and streptococci without cross-reactivity.
Question 3: In which patient population is nitrous oxide/oxygen sedation contraindicated?
- Patients with mild hypertension
- Patients with COPD relying on hypoxic drive (Correct answer)
- Patients with controlled asthma
- Pediatric patients over age 5
Correct answer: Patients with COPD relying on hypoxic drive
Patients with severe COPD who depend on hypoxic drive for respiratory stimulation may have respiratory depression suppressed by supplemental oxygen delivered with nitrous oxide.
Question 4: What is the significance of the 'danger space' (space 4) in the context of deep neck infections?
- It communicates directly with the submandibular space
- It provides a direct pathway for infection to spread to the posterior mediastinum (Correct answer)
- It is the primary site of Ludwig's angina
- It is bounded anteriorly by the hyoid bone
Correct answer: It provides a direct pathway for infection to spread to the posterior mediastinum
The danger space (space 4) extends from the skull base to the diaphragm, providing a direct pathway for infection to spread into the posterior mediastinum, making it life-threatening.
Question 5: A child presents after a fall with an avulsed permanent maxillary central incisor. The tooth has been out of the socket for 35 minutes and was stored dry. What is the best immediate action?
- Reimplant immediately without any soaking
- Soak in Hank's balanced salt solution for 30 minutes, then reimplant (Correct answer)
- Reimplant after soaking in sodium hypochlorite
- Do not reimplant; refer for a space maintainer
Correct answer: Soak in Hank's balanced salt solution for 30 minutes, then reimplant
Teeth dry for more than 60 minutes have non-viable PDL cells; soaking in HBSS or milk for 30 minutes can help rehydrate cells and improve prognosis before reimplantation.
Question 6: Which of the following instruments is used to detect subgingival calculus during a periodontal examination?
- Periodontal probe
- Explorer (shepherd's hook) (Correct answer)
- Gracey curette
- Sickle scaler
Correct answer: Explorer (shepherd's hook)
A dental explorer, particularly the #17 or #3A shepherd's hook, is the instrument of choice for tactile detection of subgingival calculus deposits.
Question 7: A patient presents with a chief complaint of pain on biting and extreme sensitivity to cold that lingers for 30+ seconds. The most likely diagnosis is:
- Reversible pulpitis
- Irreversible pulpitis (Correct answer)
- Pulp necrosis
- Dentin hypersensitivity
Correct answer: Irreversible pulpitis
Lingering cold pain lasting more than 10–15 seconds, combined with spontaneous pain, is a hallmark of irreversible pulpitis, indicating pulpectomy or extraction is required.
NBDE General Practice 4
Which class of antibiotics inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins?