NBDE Part II 5 — Questions and Answers
Question 1: A 10-year-old patient has a pulp exposure on tooth #19 (mandibular first permanent molar) due to caries. The tooth is asymptomatic and radiographs show no periapical pathology. The treatment of choice is:
- Pulpotomy with mineral trioxide aggregate (MTA) (Correct answer)
- Pulpectomy with zinc oxide eugenol fill
- Direct pulp cap with calcium hydroxide only
- Immediate extraction and space maintenance
Correct answer: Pulpotomy with mineral trioxide aggregate (MTA)
MTA pulpotomy is the treatment of choice for carious pulp exposures in young permanent teeth with closed or open apices, providing the best success rates for vital pulp therapy.
Question 2: Which of the following describes the working width (apical enlargement) principle during root canal preparation?
- The master apical file should match the original canal diameter exactly
- The canal should be enlarged at least 3 ISO sizes larger than the first file to bind at the apex (Correct answer)
- The apical preparation should stop at 2 mm from the radiographic apex
- All canals should be prepared to a minimum size 25 file regardless of anatomy
Correct answer: The canal should be enlarged at least 3 ISO sizes larger than the first file to bind at the apex
Enlarging at least 3 ISO sizes beyond the initial apical binding file ensures adequate debridement and disinfection of the apical third.
Question 3: Which class of malocclusion is characterized by a mesially positioned mandibular first molar relative to the maxillary first molar?
- Class I
- Class II Division 1
- Class II Division 2
- Class III (Correct answer)
Correct answer: Class III
Angle Class III malocclusion is defined by the mesiobuccal cusp of the maxillary first molar occluding posterior to the buccal groove of the mandibular first molar, indicating a mesial molar relationship.
Question 4: Which type of bone graft has both osteogenic and osteoinductive properties and is considered the gold standard in periodontal regeneration?
- Alloplast (synthetic hydroxyapatite)
- Xenograft (bovine-derived mineral)
- Autograft from the iliac crest or intraoral sites (Correct answer)
- Demineralized freeze-dried bone allograft (DFDBA)
Correct answer: Autograft from the iliac crest or intraoral sites
Autografts contain living osteogenic cells and growth factors, providing osteogenesis, osteoinduction, and osteoconduction — the only graft with all three properties.
Question 5: A dentist notices an asymptomatic, well-defined unilocular radiolucency at the apex of a vital tooth #8. The MOST likely diagnosis is:
- Periapical granuloma
- Periapical abscess
- Lateral periodontal cyst
- Nasopalatine duct cyst (Correct answer)
Correct answer: Nasopalatine duct cyst
The nasopalatine duct cyst appears as a heart-shaped or round radiolucency between the maxillary central incisors in a vital tooth and is the most common non-odontogenic cyst of the jaws.
Question 6: During an inferior alveolar nerve block, which muscle is the target landmark for needle insertion depth?
- Masseter muscle
- Medial pterygoid muscle (Correct answer)
- Buccinator muscle
- Temporalis muscle
Correct answer: Medial pterygoid muscle
The needle is advanced through the pterygomandibular space toward the mandibular foramen, using the medial pterygoid muscle as the posterior border landmark for injection depth.
Question 7: A patient with poorly controlled Type 2 diabetes presents for periodontal therapy. Which of the following is the most accurate bidirectional relationship between diabetes and periodontitis?
- Diabetes increases susceptibility to periodontal disease, but periodontitis does not affect glycemic control
- Periodontitis increases insulin resistance, and diabetes impairs the host immune response to periodontal pathogens (Correct answer)
- Only Type 1 diabetes is associated with periodontal disease progression
- Glycemic control must be perfect before any periodontal treatment can be initiated
Correct answer: Periodontitis increases insulin resistance, and diabetes impairs the host immune response to periodontal pathogens
The relationship is bidirectional: hyperglycemia impairs neutrophil function and increases cytokine production, while periodontal inflammation worsens insulin resistance through systemic inflammatory mediators.
NBDE Part II 5
A 10-year-old patient has a pulp exposure on tooth #19 (mandibular first permanent molar) due to caries.
The tooth is asymptomatic and radiographs show no periapical pathology.
The treatment of choice is: