NBDE Part II 4 — Questions and Answers
Question 1: During endodontic treatment of a maxillary first molar, which root canal is MOST likely to have a second canal?
- Distobuccal root
- Palatal root
- Mesiobuccal root (Correct answer)
- Mesiopalatal root
Correct answer: Mesiobuccal root
The mesiobuccal root of the maxillary first molar has a second canal (MB2) in approximately 60–95% of cases and is clinically the most commonly missed canal.
Question 2: Which material is contraindicated as a base under composite resin restorations due to inhibition of polymerization?
- Glass ionomer cement
- Resin-modified glass ionomer
- Zinc oxide eugenol (ZOE) (Correct answer)
- Calcium hydroxide liner
Correct answer: Zinc oxide eugenol (ZOE)
Eugenol from ZOE inhibits the free-radical polymerization of composite resins, leading to a soft, unset surface layer at the interface.
Question 3: A patient presents with a chief complaint of pain in the upper left quadrant. On examination, tooth #14 is non-vital, has a sinus tract, and shows a periapical radiolucency. The sinus tract most likely originates from:
- The palatal root
- The mesiobuccal root
- The distobuccal root
- Cannot be determined without a GP trace (Correct answer)
Correct answer: Cannot be determined without a GP trace
Placing a gutta-percha point into the sinus tract and tracing it radiographically is the definitive method to identify the exact origin of the sinus tract.
Question 4: The maximum recommended dose of lidocaine with epinephrine for a healthy 70 kg adult patient is approximately:
- 100 mg
- 300 mg
- 500 mg (Correct answer)
- 700 mg
Correct answer: 500 mg
The maximum dose of lidocaine with epinephrine is 7 mg/kg with an absolute maximum of 500 mg in a healthy adult.
Question 5: Which of the following is the primary reason for placing a rubber dam during endodontic treatment?
- To improve patient comfort and airway protection
- To prevent salivary contamination of the root canal system (Correct answer)
- To improve visualization of the access cavity
- To reduce radiation exposure
Correct answer: To prevent salivary contamination of the root canal system
Rubber dam isolation is mandatory in endodontics primarily to prevent microbial contamination of the canal from saliva, which would compromise treatment outcomes.
Question 6: A 30-year-old presents with 6 mm attachment loss in the anterior region and no pocketing. This patient most likely has:
- Active periodontitis
- Gingival recession with no periodontitis (Correct answer)
- Gingivitis on a reduced periodontium
- Necrotizing ulcerative periodontitis
Correct answer: Gingival recession with no periodontitis
Attachment loss without pocketing indicates that the gingival margin has receded apically, exposing root surface without a pathologic pocket.
Question 7: Which occlusal scheme is most appropriate for a fully balanced complete denture?
- Mutually protected occlusion
- Lingualized occlusion (Correct answer)
- Group function occlusion
- Canine-protected occlusion
Correct answer: Lingualized occlusion
Lingualized occlusion provides bilateral balance during excursive movements while reducing lateral forces on the denture base, making it the preferred scheme for complete dentures.
NBDE Part II 4
During endodontic treatment of a maxillary first molar, which root canal is MOST likely to have a second canal?