NBDE Knowledge 5 — Questions and Answers
Question 1: Which of the following is the correct order of tooth development stages?
- Initiation, proliferation, histodifferentiation, morphodifferentiation, apposition, maturation (Correct answer)
- Proliferation, initiation, morphodifferentiation, histodifferentiation, apposition, maturation
- Initiation, histodifferentiation, proliferation, apposition, morphodifferentiation, maturation
- Initiation, proliferation, apposition, histodifferentiation, morphodifferentiation, maturation
Correct answer: Initiation, proliferation, histodifferentiation, morphodifferentiation, apposition, maturation
Tooth development proceeds in sequence: initiation → proliferation → histodifferentiation → morphodifferentiation → apposition → maturation.
Question 2: The mucogingival junction can be identified by:
- A color change from pink keratinized gingiva to red alveolar mucosa (Correct answer)
- Probing depth greater than 3mm
- The cementoenamel junction location
- The presence of stippling
Correct answer: A color change from pink keratinized gingiva to red alveolar mucosa
The mucogingival junction is a visible line demarcating the pale pink keratinized attached gingiva from the darker, more mobile alveolar mucosa.
Question 3: Nitrous oxide produces its analgesic and anxiolytic effects primarily by:
- Activating opioid receptors and inhibiting NMDA receptors (Correct answer)
- Blocking sodium channels
- Enhancing GABA activity at GABA-A receptors
- Inhibiting acetylcholinesterase
Correct answer: Activating opioid receptors and inhibiting NMDA receptors
Nitrous oxide analgesia is mediated through endogenous opioid release and NMDA receptor antagonism, not primarily through GABA-A receptors.
Question 4: Which of the following describes a true cyst?
- A pathological cavity lined by epithelium (Correct answer)
- A fluid-filled space lacking an epithelial lining
- A solid mass of epithelial cells
- A granulomatous inflammation around a root apex
Correct answer: A pathological cavity lined by epithelium
By definition, a true cyst is a pathological cavity lined by epithelium, distinguishing it from pseudocysts which lack epithelial lining.
Question 5: The resting membrane potential of a nerve cell is approximately:
- -70 mV (Correct answer)
- +40 mV
- -30 mV
- 0 mV
Correct answer: -70 mV
The resting membrane potential of neurons is approximately -70 mV, maintained primarily by the Na+/K+ ATPase pump and selective membrane permeability.
Question 6: Which salivary gland produces the highest proportion of mucous secretion?
- Sublingual gland (Correct answer)
- Parotid gland
- Submandibular gland
- Minor salivary glands of the palate
Correct answer: Sublingual gland
The sublingual gland is primarily mucous-secreting, while the parotid is purely serous and the submandibular is mixed (predominantly serous).
Question 7: Which condition is characterized by multiple dentigerous cysts, odontogenic keratocysts, and basal cell carcinomas of the skin?
- Gorlin-Goltz syndrome (nevoid basal cell carcinoma syndrome) (Correct answer)
- Gardner syndrome
- Treacher Collins syndrome
- Cleidocranial dysplasia
Correct answer: Gorlin-Goltz syndrome (nevoid basal cell carcinoma syndrome)
Gorlin-Goltz syndrome is an autosomal dominant condition caused by PTCH1 mutations, featuring multiple odontogenic keratocysts, basal cell carcinomas, and skeletal anomalies.
NBDE Knowledge 5
Which of the following is the correct order of tooth development stages?