NBDE Trivia 4 — Questions and Answers
Question 1: Which periodontal fiber group runs from the alveolar crest obliquely to the cementum in an apical direction?
- Horizontal fibers
- Oblique fibers (Correct answer)
- Apical fibers
- Transseptal fibers
Correct answer: Oblique fibers
Oblique fibers are the most numerous PDL fibers, running from alveolar bone coronally to insert into cementum, resisting axial forces.
Question 2: Which radiographic technique provides the most accurate image of the true mesiodistal width of interproximal bone loss?
- Panoramic radiograph
- Occlusal radiograph
- Bitewing radiograph (Correct answer)
- Lateral cephalometric radiograph
Correct answer: Bitewing radiograph
Bitewing radiographs show the crestal bone of both arches with minimal distortion, making them optimal for assessing interproximal bone levels.
Question 3: In operative dentistry, a beveled cavosurface margin is indicated for which restorative material?
- Amalgam
- Glass ionomer cement
- Cast gold (Correct answer)
- Resin-modified glass ionomer
Correct answer: Cast gold
Beveled cavosurface margins increase the surface area of the gold-tooth interface and improve marginal seal for cast gold restorations.
Question 4: Which immunoglobulin class is predominant in saliva and provides the first line of mucosal defense?
- IgG
- IgM
- IgA (secretory) (Correct answer)
- IgE
Correct answer: IgA (secretory)
Secretory IgA (sIgA) is the predominant antibody in saliva, resisting proteolysis and neutralizing pathogens on mucosal surfaces.
Question 5: The Koplik spots seen in measles are pathognomonic lesions found on which oral surface?
- Dorsal tongue
- Hard palate
- Buccal mucosa opposite the lower molars (Correct answer)
- Gingiva
Correct answer: Buccal mucosa opposite the lower molars
Koplik spots appear as small white papules on the buccal mucosa near the lower molars and precede the skin rash of measles.
Question 6: Which material property describes a material's resistance to permanent deformation under load?
- Hardness (Correct answer)
- Toughness
- Ductility
- Resilience
Correct answer: Hardness
Hardness is defined as a material's resistance to permanent surface deformation or indentation, commonly measured by Vickers or Brinell scales.
Question 7: Which embryonic structure gives rise to the enamel organ?
- Dental papilla
- Dental sac
- Dental lamina (Correct answer)
- Hertwig's epithelial root sheath
Correct answer: Dental lamina
The dental lamina, an ingrowth of oral ectoderm, gives rise to the enamel organ which produces enamel via ameloblasts.
NBDE Trivia 4
Which periodontal fiber group runs from the alveolar crest obliquely to the cementum in an apical direction?