NDEB WRITTEN EXAM 2026/2027 | 300
PRACTICE QUESTIONS & ANSWERS WITH
RATIONALES | NATIONAL DENTAL
EXAMINING BOARD OF CANADA PREP|
INSTANT DOWNLOAD | NEWEST!
Questions — 1–25
1. Which microorganism is most strongly associated with the initiation of dental caries?
A. Porphyromonas gingivalis
B. Streptococcus mutans
C. Treponema denticola
D. Aggregatibacter actinomycetemcomitans
Answer: B. Streptococcus mutans
Rationale: S. mutans is an important cariogenic bacterium because it metabolizes
fermentable carbohydrates, produces acid, and contributes to enamel demineralization.
2. Which cranial nerve provides the primary sensory innervation to the maxillary teeth?
A. Facial nerve (CN VII)
B. Glossopharyngeal nerve (CN IX)
C. Maxillary division of the trigeminal nerve (CN V2)
D. Mandibular division of the trigeminal nerve (CN V3)
Answer: C. Maxillary division of the trigeminal nerve (CN V2)
Rationale: The maxillary division of CN V supplies sensory innervation to the maxillary teeth
and associated oral structures.
3. Which permanent tooth generally has the longest root?
A. Maxillary central incisor
B. Maxillary canine
C. Mandibular first molar
D. Mandibular canine
,Answer: B. Maxillary canine
Rationale: The maxillary canine typically has the longest root of any permanent tooth.
4. A patient presents with spontaneous, lingering pain after exposure to cold. Which
pulpal diagnosis is most consistent with these findings?
A. Normal pulp
B. Reversible pulpitis
C. Symptomatic irreversible pulpitis
D. Pulp necrosis
Answer: C. Symptomatic irreversible pulpitis
Rationale: Spontaneous pain and prolonged lingering thermal pain are characteristic
findings associated with symptomatic irreversible pulpitis.
5. Which radiographic feature is most characteristic of a periapical cyst?
A. Diffuse radiopacity surrounding the apex
B. Well-defined unilocular radiolucency associated with the tooth apex
C. Generalized loss of lamina dura
D. Radiopaque mass fused to the root
Answer: B. Well-defined unilocular radiolucency associated with the tooth apex
Rationale: A radicular/periapical cyst commonly presents as a well-circumscribed
radiolucency at the apex of a non-vital tooth, although radiographic appearance alone
cannot establish a definitive histopathologic diagnosis.
6. Which periodontal ligament fiber group primarily resists intrusive forces?
A. Alveolar crest fibers
B. Horizontal fibers
C. Oblique fibers
D. Apical fibers
Answer: C. Oblique fibers
Rationale: Oblique periodontal ligament fibers are the largest fiber group and are
particularly important in resisting vertical or intrusive occlusal forces.
,7. Which fluoride mechanism has the greatest direct effect on reducing enamel
demineralization?
A. Increasing plaque thickness
B. Increasing enamel solubility
C. Enhancing remineralization and reducing mineral dissolution
D. Increasing bacterial carbohydrate metabolism
Answer: C. Enhancing remineralization and reducing mineral dissolution
Rationale: Fluoride promotes remineralization and makes the tooth mineral more resistant to
acid-mediated dissolution.
8. Which local anesthetic is an amide anesthetic?
A. Procaine
B. Benzocaine
C. Lidocaine
D. Tetracaine
Answer: C. Lidocaine
Rationale: Lidocaine is an amide-type local anesthetic. Procaine, benzocaine, and tetracaine
are ester-type anesthetics.
9. Which structure forms the majority of the tooth's internal hard tissue?
A. Enamel
B. Dentin
C. Cementum
D. Pulp
Answer: B. Dentin
Rationale: Dentin forms the bulk of the tooth and surrounds the pulp chamber and root
canals.
10. Which cells are responsible for producing dentin?
A. Ameloblasts
B. Cementoblasts
C. Odontoblasts
D. Osteoclasts
, Answer: C. Odontoblasts
Rationale: Odontoblasts are specialized cells located along the peripheral pulp and are
responsible for dentin formation.
11. Which condition is characterized by generalized inflammation of the gingiva
without attachment loss?
A. Gingivitis
B. Periodontitis
C. Peri-implantitis
D. Alveolar osteitis
Answer: A. Gingivitis
Rationale: Gingivitis involves inflammation of the gingival tissues without the periodontal
attachment loss that characterizes periodontitis.
12. Which microorganism is strongly associated with aggressive forms of periodontitis?
A. Streptococcus salivarius
B. Aggregatibacter actinomycetemcomitans
C. Lactobacillus acidophilus
D. Candida albicans
Answer: B. Aggregatibacter actinomycetemcomitans
Rationale: A. actinomycetemcomitans has been associated with certain rapidly progressive
periodontal conditions and possesses virulence factors that contribute to periodontal tissue
destruction.
13. Which permanent tooth most commonly has two roots?
A. Maxillary first premolar
B. Maxillary central incisor
C. Mandibular central incisor
D. Maxillary canine
Answer: A. Maxillary first premolar
Rationale: The maxillary first premolar commonly has two roots, although anatomical
variation occurs.
PRACTICE QUESTIONS & ANSWERS WITH
RATIONALES | NATIONAL DENTAL
EXAMINING BOARD OF CANADA PREP|
INSTANT DOWNLOAD | NEWEST!
Questions — 1–25
1. Which microorganism is most strongly associated with the initiation of dental caries?
A. Porphyromonas gingivalis
B. Streptococcus mutans
C. Treponema denticola
D. Aggregatibacter actinomycetemcomitans
Answer: B. Streptococcus mutans
Rationale: S. mutans is an important cariogenic bacterium because it metabolizes
fermentable carbohydrates, produces acid, and contributes to enamel demineralization.
2. Which cranial nerve provides the primary sensory innervation to the maxillary teeth?
A. Facial nerve (CN VII)
B. Glossopharyngeal nerve (CN IX)
C. Maxillary division of the trigeminal nerve (CN V2)
D. Mandibular division of the trigeminal nerve (CN V3)
Answer: C. Maxillary division of the trigeminal nerve (CN V2)
Rationale: The maxillary division of CN V supplies sensory innervation to the maxillary teeth
and associated oral structures.
3. Which permanent tooth generally has the longest root?
A. Maxillary central incisor
B. Maxillary canine
C. Mandibular first molar
D. Mandibular canine
,Answer: B. Maxillary canine
Rationale: The maxillary canine typically has the longest root of any permanent tooth.
4. A patient presents with spontaneous, lingering pain after exposure to cold. Which
pulpal diagnosis is most consistent with these findings?
A. Normal pulp
B. Reversible pulpitis
C. Symptomatic irreversible pulpitis
D. Pulp necrosis
Answer: C. Symptomatic irreversible pulpitis
Rationale: Spontaneous pain and prolonged lingering thermal pain are characteristic
findings associated with symptomatic irreversible pulpitis.
5. Which radiographic feature is most characteristic of a periapical cyst?
A. Diffuse radiopacity surrounding the apex
B. Well-defined unilocular radiolucency associated with the tooth apex
C. Generalized loss of lamina dura
D. Radiopaque mass fused to the root
Answer: B. Well-defined unilocular radiolucency associated with the tooth apex
Rationale: A radicular/periapical cyst commonly presents as a well-circumscribed
radiolucency at the apex of a non-vital tooth, although radiographic appearance alone
cannot establish a definitive histopathologic diagnosis.
6. Which periodontal ligament fiber group primarily resists intrusive forces?
A. Alveolar crest fibers
B. Horizontal fibers
C. Oblique fibers
D. Apical fibers
Answer: C. Oblique fibers
Rationale: Oblique periodontal ligament fibers are the largest fiber group and are
particularly important in resisting vertical or intrusive occlusal forces.
,7. Which fluoride mechanism has the greatest direct effect on reducing enamel
demineralization?
A. Increasing plaque thickness
B. Increasing enamel solubility
C. Enhancing remineralization and reducing mineral dissolution
D. Increasing bacterial carbohydrate metabolism
Answer: C. Enhancing remineralization and reducing mineral dissolution
Rationale: Fluoride promotes remineralization and makes the tooth mineral more resistant to
acid-mediated dissolution.
8. Which local anesthetic is an amide anesthetic?
A. Procaine
B. Benzocaine
C. Lidocaine
D. Tetracaine
Answer: C. Lidocaine
Rationale: Lidocaine is an amide-type local anesthetic. Procaine, benzocaine, and tetracaine
are ester-type anesthetics.
9. Which structure forms the majority of the tooth's internal hard tissue?
A. Enamel
B. Dentin
C. Cementum
D. Pulp
Answer: B. Dentin
Rationale: Dentin forms the bulk of the tooth and surrounds the pulp chamber and root
canals.
10. Which cells are responsible for producing dentin?
A. Ameloblasts
B. Cementoblasts
C. Odontoblasts
D. Osteoclasts
, Answer: C. Odontoblasts
Rationale: Odontoblasts are specialized cells located along the peripheral pulp and are
responsible for dentin formation.
11. Which condition is characterized by generalized inflammation of the gingiva
without attachment loss?
A. Gingivitis
B. Periodontitis
C. Peri-implantitis
D. Alveolar osteitis
Answer: A. Gingivitis
Rationale: Gingivitis involves inflammation of the gingival tissues without the periodontal
attachment loss that characterizes periodontitis.
12. Which microorganism is strongly associated with aggressive forms of periodontitis?
A. Streptococcus salivarius
B. Aggregatibacter actinomycetemcomitans
C. Lactobacillus acidophilus
D. Candida albicans
Answer: B. Aggregatibacter actinomycetemcomitans
Rationale: A. actinomycetemcomitans has been associated with certain rapidly progressive
periodontal conditions and possesses virulence factors that contribute to periodontal tissue
destruction.
13. Which permanent tooth most commonly has two roots?
A. Maxillary first premolar
B. Maxillary central incisor
C. Mandibular central incisor
D. Maxillary canine
Answer: A. Maxillary first premolar
Rationale: The maxillary first premolar commonly has two roots, although anatomical
variation occurs.
