NBDE MCQ 5 — Questions and Answers
Question 1: Which periodontal fiber group runs parallel to the long axis of the tooth and resists intrusive forces?
- Oblique fibers
- Alveolar crest fibers
- Apical fibers (Correct answer)
- Interradicular fibers
Correct answer: Apical fibers
Apical fibers radiate from the apex of the root to the surrounding alveolar bone and resist intrusive (axial) loading forces applied to the tooth.
Question 2: Ranula is a mucous retention or extravasation phenomenon most commonly associated with which salivary gland?
- Parotid gland
- Submandibular gland
- Sublingual gland (Correct answer)
- Minor salivary glands of the palate
Correct answer: Sublingual gland
Ranulas form in the floor of the mouth primarily from the sublingual gland; plunging ranulas extend through the mylohyoid muscle.
Question 3: Which disinfectant is most effective for sterilization of heat-sensitive dental instruments?
- Glutaraldehyde 2% (10-hour immersion) (Correct answer)
- Isopropyl alcohol 70%
- Sodium hypochlorite 5.25%
- Quaternary ammonium compounds
Correct answer: Glutaraldehyde 2% (10-hour immersion)
2% activated glutaraldehyde achieves sterilization after a 10-hour immersion and is one of the few chemical agents capable of destroying all microbial life including spores.
Question 4: Amelogenesis imperfecta affects which dental structure and its inheritance pattern includes:
- Dentin; autosomal dominant only
- Enamel; X-linked, autosomal dominant, or autosomal recessive (Correct answer)
- Cementum; autosomal recessive only
- Pulp; X-linked recessive
Correct answer: Enamel; X-linked, autosomal dominant, or autosomal recessive
Amelogenesis imperfecta affects enamel formation and can follow X-linked, autosomal dominant, or autosomal recessive inheritance depending on the gene involved.
Question 5: The zone of coagulation necrosis in thermal injury to pulp tissue, followed by the zone of stasis, is BEST described as:
- Zones seen in reversible pulpitis from caries
- A histopathologic pattern of acute pulpal inflammation
- Jackson's burn zones applied to pulp thermal injury (Correct answer)
- The spread pattern of periapical abscess
Correct answer: Jackson's burn zones applied to pulp thermal injury
Jackson's burn model (coagulation, stasis, hyperemia) describes the three concentric zones of tissue injury from thermal trauma, applicable to heat-induced pulp damage.
Question 6: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) most frequently occurs in which location?
- Anterior maxilla
- Posterior maxilla
- Posterior mandible (Correct answer)
- Anterior mandible
Correct answer: Posterior mandible
BRONJ occurs most commonly in the posterior mandible, particularly in the molar region, likely due to thinner mucosa, less vascularity, and greater mechanical stress.
Question 7: During the mixed dentition stage, the 'ugly duckling' stage refers to:
- Spacing between all primary teeth
- Flaring of maxillary central incisors with midline diastema before canine eruption (Correct answer)
- Crowding of mandibular incisors before lateral eruption
- Crossbite developing during primary molar eruption
Correct answer: Flaring of maxillary central incisors with midline diastema before canine eruption
The 'ugly duckling' stage is a normal developmental phenomenon where maxillary central incisors flare distally and create a midline diastema, which usually self-corrects when the canines erupt.
NBDE MCQ 5
Which periodontal fiber group runs parallel to the long axis of the tooth and resists intrusive forces?