NBDE Diagnosis and Treatment Planning 3 — Questions and Answers
Question 1: A radiograph of a mandibular molar shows a periapical radiolucency with the root apex appearing to project through the inferior alveolar canal. What is the most important diagnostic consideration?
- Root perforation requiring surgical repair
- Proximity of roots to the inferior alveolar nerve before endodontic surgery (Correct answer)
- Condensing osteitis secondary to chronic pulpitis
- Vertical root fracture requiring extraction
Correct answer: Proximity of roots to the inferior alveolar nerve before endodontic surgery
When apices appear to overlap or project through the inferior alveolar canal, the dentist must assess the proximity to avoid neurovascular injury during endodontic or surgical procedures.
Question 2: Which systemic condition most directly contraindicates elective dental treatment under local anesthesia alone, requiring medical clearance first?
- Controlled Type 2 diabetes with HbA1c of 7.2%
- Stable angina with recent myocardial infarction 3 weeks ago (Correct answer)
- Well-controlled hypertension on ACE inhibitors
- Hypothyroidism managed with levothyroxine
Correct answer: Stable angina with recent myocardial infarction 3 weeks ago
Elective dental procedures should be deferred for at least 6 months after a myocardial infarction due to elevated risk of reinfarction under stress.
Question 3: A patient presents with multiple missing posterior teeth and requests implants. Panoramic radiograph reveals inadequate vertical bone height in the posterior maxilla. What diagnostic imaging is most essential before treatment planning implants?
- Periapical radiographs of adjacent teeth
- CBCT of the posterior maxilla to assess sinus floor proximity (Correct answer)
- Lateral cephalometric radiograph for skeletal assessment
- Occlusal radiograph for buccolingual bone width
Correct answer: CBCT of the posterior maxilla to assess sinus floor proximity
CBCT provides three-dimensional assessment of residual bone height, width, and proximity to the maxillary sinus, which is critical for implant placement planning in this region.
Question 4: A 12-year-old presents with a periapical abscess on a maxillary first permanent molar with an open apex. Which treatment approach best preserves the tooth's developmental potential?
- Conventional root canal therapy followed by apical plug
- Apexification with calcium hydroxide or MTA (Correct answer)
- Extraction and implant placement
- Pulpotomy with formocresol
Correct answer: Apexification with calcium hydroxide or MTA
Apexification with calcium hydroxide or MTA creates an apical barrier, allowing the dentist to obturate the canal while preserving the tooth until root development completes or is simulated.
Question 5: During treatment planning for a full-arch fixed implant prosthesis, what is the most important occlusal consideration?
- Establishing a Class I canine relationship
- Providing group function occlusion on the working side
- Minimizing lateral forces through mutually protected occlusion (Correct answer)
- Ensuring bilateral balanced occlusion in all excursions
Correct answer: Minimizing lateral forces through mutually protected occlusion
Implant-supported prostheses lack periodontal ligament proprioception, so mutually protected occlusion minimizes destructive lateral forces on implants and prosthetic components.
Question 6: A patient presents with a chief complaint of 'cracking sounds' in the jaw and difficulty opening widely. The maximum opening is 28 mm with deviation to the left. What is the most likely diagnosis?
- Myofascial pain disorder
- Anterior disc displacement with reduction on the left
- Anterior disc displacement without reduction on the left (Correct answer)
- Osteoarthritis of the right temporomandibular joint
Correct answer: Anterior disc displacement without reduction on the left
Limited opening with deflection (not deviation correcting at maximum opening) and absence of clicking suggests disc displacement without reduction (closed lock) on the ipsilateral side.
Question 7: Which caries risk assessment factor most significantly elevates a patient's caries risk classification from moderate to high?
- Presence of Class II restorations
- Wearing a removable partial denture
- Salivary flow rate below 0.1 mL/min (hyposalivation) (Correct answer)
- Consuming one sugary beverage per day
Correct answer: Salivary flow rate below 0.1 mL/min (hyposalivation)
Severe xerostomia (salivary flow < 0.1 mL/min) dramatically increases caries risk because saliva is the primary defense against acid demineralization.
NBDE Diagnosis and Treatment Planning 3
A radiograph of a mandibular molar shows a periapical radiolucency with the root apex appearing to project through the inferior alveolar canal.
What is the most important diagnostic consideration?