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NDEB EXAM (NATIONAL DENTAL EXAMINING BOARD OF
CANADA) | NEWEST 2026 | VERIFIED QUESTIONS &
ANSWERS WITH DETAILED RATIONALES | GRADED A+
1. A 45-year-old patient presents with a chief complaint of pain in the maxillary right posterior
region that is exacerbated by biting and relieved by lying down. Radiographic examination
reveals a radiolucency associated with the distal root of tooth #3, with loss of the lamina dura.
The tooth does not respond to cold or electric pulp testing. What is the most likely diagnosis?
A. Reversible pulpitis
B. Irreversible pulpitis with symptomatic apical periodontitis
C. Chronic apical abscess
D. Periapical granuloma
☑ Correct Answer: B
☑ Explanation: The absence of response to pulp testing indicates non-vital pulp
(irreversible pulpitis). The pain on biting and relief when lying down are characteristic of
symptomatic apical periodontitis, where inflammatory exudate accumulates in the periapical
region and pressure increases in the supine position. A chronic apical abscess (C) would typically
present with a sinus tract. A periapical granuloma (D) is usually asymptomatic.
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2. On a bite-wing radiograph of posterior teeth, which of the following structures is most likely
to be misdiagnosed as proximal caries?
A. Cemento-enamel junction
B. Marginal ridge
C. Carabelli cusp
D. Cemental tear
☑ Correct Answer: A
☑ Explanation: The cemento-enamel junction (CEJ) can appear as a radiolucent line on
bite-wing radiographs that may be mistaken for proximal caries. The CEJ is a normal anatomical
landmark where the enamel and cementum meet, and its radiographic appearance can mimic
early carious lesions. The marginal ridge (B) is a raised border of enamel, not typically confused
with caries. Carabelli cusp (C) is an accessory cusp on maxillary molars. A cemental tear (D) is a
separation of cementum from the root surface.
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3. Which of the following local anaesthetic agents has the longest duration of action and is
most suitable for prolonged surgical procedures?
A. Lidocaine 2% with 1:100,000 epinephrine
B. Mepivacaine 3% plain
C. Bupivacaine 0.5% with 1:200,000 epinephrine
D. Prilocaine 4% with 1:200,000 epinephrine
☑ Correct Answer: C
☑ Explanation: Bupivacaine 0.5% with epinephrine has the longest duration of action
among commonly used dental local anaesthetics, providing 3–6 hours of pulpal anaesthesia.
Lidocaine (A) provides 1–2 hours, mepivacaine plain (B) provides 20–40 minutes, and prilocaine
(D) provides 1–2 hours. Bupivacaine is the agent of choice for prolonged surgical procedures
requiring extended postoperative analgesia.
4. In a Class II amalgam restoration, which of the following is the primary factor determining the
resistance form of the preparation?
A. The depth of the occlusal isthmus
B. The convergence of the buccal and lingual walls
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C. The presence of a gingival seat
D. The placement of retentive grooves
☑ Correct Answer: B
☑ Explanation: Resistance form refers to the features of a cavity preparation that enable
the restoration to withstand masticatory forces without fracture or displacement. The
convergence of the buccal and lingual walls toward the occlusal surface provides the primary
resistance form by ensuring that the restoration is supported by sound tooth structure. The
depth of the occlusal isthmus (A) primarily affects retention form. The gingival seat (C) and
retentive grooves (D) are secondary factors.
5. A 30-year-old patient presents with a painless, slowly enlarging swelling of the left mandible.
Radiographic examination reveals a unilocular radiolucency with scalloped borders extending
between the roots of the mandibular premolars and molars. The lesion is not associated with
an unerupted tooth. Incisional biopsy shows odontogenic epithelium with a characteristic
"picket-fence" arrangement of columnar cells. What is the most likely diagnosis?
A. Ameloblastoma
B. Odontogenic keratocyst (OKC)
NDEB EXAM (NATIONAL DENTAL EXAMINING BOARD OF
CANADA) | NEWEST 2026 | VERIFIED QUESTIONS &
ANSWERS WITH DETAILED RATIONALES | GRADED A+
1. A 45-year-old patient presents with a chief complaint of pain in the maxillary right posterior
region that is exacerbated by biting and relieved by lying down. Radiographic examination
reveals a radiolucency associated with the distal root of tooth #3, with loss of the lamina dura.
The tooth does not respond to cold or electric pulp testing. What is the most likely diagnosis?
A. Reversible pulpitis
B. Irreversible pulpitis with symptomatic apical periodontitis
C. Chronic apical abscess
D. Periapical granuloma
☑ Correct Answer: B
☑ Explanation: The absence of response to pulp testing indicates non-vital pulp
(irreversible pulpitis). The pain on biting and relief when lying down are characteristic of
symptomatic apical periodontitis, where inflammatory exudate accumulates in the periapical
region and pressure increases in the supine position. A chronic apical abscess (C) would typically
present with a sinus tract. A periapical granuloma (D) is usually asymptomatic.
,2
2. On a bite-wing radiograph of posterior teeth, which of the following structures is most likely
to be misdiagnosed as proximal caries?
A. Cemento-enamel junction
B. Marginal ridge
C. Carabelli cusp
D. Cemental tear
☑ Correct Answer: A
☑ Explanation: The cemento-enamel junction (CEJ) can appear as a radiolucent line on
bite-wing radiographs that may be mistaken for proximal caries. The CEJ is a normal anatomical
landmark where the enamel and cementum meet, and its radiographic appearance can mimic
early carious lesions. The marginal ridge (B) is a raised border of enamel, not typically confused
with caries. Carabelli cusp (C) is an accessory cusp on maxillary molars. A cemental tear (D) is a
separation of cementum from the root surface.
,3
3. Which of the following local anaesthetic agents has the longest duration of action and is
most suitable for prolonged surgical procedures?
A. Lidocaine 2% with 1:100,000 epinephrine
B. Mepivacaine 3% plain
C. Bupivacaine 0.5% with 1:200,000 epinephrine
D. Prilocaine 4% with 1:200,000 epinephrine
☑ Correct Answer: C
☑ Explanation: Bupivacaine 0.5% with epinephrine has the longest duration of action
among commonly used dental local anaesthetics, providing 3–6 hours of pulpal anaesthesia.
Lidocaine (A) provides 1–2 hours, mepivacaine plain (B) provides 20–40 minutes, and prilocaine
(D) provides 1–2 hours. Bupivacaine is the agent of choice for prolonged surgical procedures
requiring extended postoperative analgesia.
4. In a Class II amalgam restoration, which of the following is the primary factor determining the
resistance form of the preparation?
A. The depth of the occlusal isthmus
B. The convergence of the buccal and lingual walls
, 4
C. The presence of a gingival seat
D. The placement of retentive grooves
☑ Correct Answer: B
☑ Explanation: Resistance form refers to the features of a cavity preparation that enable
the restoration to withstand masticatory forces without fracture or displacement. The
convergence of the buccal and lingual walls toward the occlusal surface provides the primary
resistance form by ensuring that the restoration is supported by sound tooth structure. The
depth of the occlusal isthmus (A) primarily affects retention form. The gingival seat (C) and
retentive grooves (D) are secondary factors.
5. A 30-year-old patient presents with a painless, slowly enlarging swelling of the left mandible.
Radiographic examination reveals a unilocular radiolucency with scalloped borders extending
between the roots of the mandibular premolars and molars. The lesion is not associated with
an unerupted tooth. Incisional biopsy shows odontogenic epithelium with a characteristic
"picket-fence" arrangement of columnar cells. What is the most likely diagnosis?
A. Ameloblastoma
B. Odontogenic keratocyst (OKC)
