NBDHE EXAM NATIONAL BOARD DENTAL HYGIENE EXAM
2025/2026 | COMPLETE QUESTIONS AND CORRECT
ANSWERS WITH RATIONALES | VERIFIED ANSWERS |
NEWEST VERSION | BRAND NEW VERSION
Question 1
Which of the following describes the primary mechanism of action of fluoride
in preventing dental caries?
A) Killing cariogenic bacteria directly
B) Buffering acids in the oral cavity
C) Inhibiting plaque formation
D) Enhancing remineralization and decreasing demineralization of enamel
E) Increasing salivary flow
Correct Answer: D) Enhancing remineralization and decreasing
demineralization of enamel
Rationale: Fluoride primarily works by incorporating into the enamel
to form fluorapatite, which is more resistant to acid
demineralization, and by promoting the remineralization of early
carious lesions.
Question 2
A patient presents with generalized moderate gingivitis. Which of the
following is the most appropriate initial treatment?
A) Oral surgery and antibiotics
B) Scaling and root planing with local anesthesia
C) Oral hygiene instructions and supragingival scaling
D) Systemic antibiotics only
E) Chlorhexidine gluconate rinse without debridement
Correct Answer: C) Oral hygiene instructions and supragingival scaling
Rationale: Gingivitis is an inflammatory condition limited to the
gingiva. Initial treatment focuses on removing the etiologic factor
(plaque) through effective oral hygiene and professional
supragingival debridement (scaling).
,Question 3
Which cranial nerve is primarily responsible for the sensation of taste from
the anterior two-thirds of the tongue?
A) Trigeminal nerve (CN V)
B) Facial nerve (CN VII)
C) Glossopharyngeal nerve (CN IX)
D) Vagus nerve (CN X)
E) Hypoglossal nerve (CN XII)
Correct Answer: B) Facial nerve (CN VII)
Rationale: The chorda tympani, a branch of the facial nerve (CN VII),
innervates the taste buds on the anterior two-thirds of the tongue.
Question 4
A patient reports a persistent dry mouth (xerostomia). Which of the following
is the MOST common cause of xerostomia?
A) Sjögren's syndrome
B) Radiation therapy to the head and neck
C) Medications (e.g., anticholinergics, antidepressants)
D) Diabetes mellitus
E) Vitamin B deficiency
Correct Answer: C) Medications (e.g., anticholinergics,
antidepressants)
Rationale: Medication use is the most common cause of xerostomia,
with hundreds of commonly prescribed drugs listing dry mouth as a
side effect.
Question 5
When taking a panoramic radiograph, what is the MOST common patient
positioning error that results in an exaggerated smile line?
A) Chin placed too high
B) Chin placed too low
C) Patient slumped forward
,D) Tongue not placed on the roof of the mouth
E) Patient head tilted
Correct Answer: A) Chin placed too high
Rationale: When the chin is positioned too high during a panoramic
radiograph, the Frankfort plane is angled upward, resulting in an
exaggerated smile line on the image.
Question 6
Which classification of carious lesions typically involves the incisal edges of
anterior teeth or cusp tips of posterior teeth without involving pits or
fissures?
A) Class I
B) Class II
C) Class III
D) Class IV
E) Class VI
Correct Answer: E) Class VI
Rationale: Class VI carious lesions (according to G.V. Black's
classification) are found on the incisal edges of anterior teeth and
cusp tips of posterior teeth.
Question 7
What is the recommended probing depth for healthy gingiva?
A) 0-1 mm
B) 1-3 mm
C) 3-5 mm
D) 5-7 mm
E) Greater than 7 mm
Correct Answer: B) 1-3 mm
Rationale: Healthy gingiva typically exhibits sulcus depths of 1-3 mm
with no bleeding upon probing.
, Question 8
Which of the following local anesthetics is CONTRAINDICATED for patients
with a sulfite allergy?
A) Lidocaine
B) Mepivacaine
C) Bupivacaine
D) Articaine
E) Epinephrine-containing local anesthetics
Correct Answer: E) Epinephrine-containing local anesthetics
Rationale: Epinephrine-containing local anesthetics often contain
sodium bisulfite as an antioxidant. Patients with a true sulfite
allergy (rare) should avoid these and use plain local anesthetics.
Question 9
The primary function of cementum is to:
A) Support the tooth in the alveolar bone
B) Provide sensation to the tooth
C) Form the bulk of the tooth crown
D) Protect the pulp from thermal changes
E) Facilitate mastication
Correct Answer: A) Support the tooth in the alveolar bone
Rationale: Cementum covers the root surface and serves as the
attachment for periodontal ligament fibers, which anchor the tooth
to the alveolar bone.
Question 10
A patient presents with a localized, painful, fluid-filled lesion on the labial
mucosa that ruptures and crusts over. This is most likely:
A) Apthous ulcer
B) Herpes simplex labialis
C) Frictional keratosis
D) Mucocele
2025/2026 | COMPLETE QUESTIONS AND CORRECT
ANSWERS WITH RATIONALES | VERIFIED ANSWERS |
NEWEST VERSION | BRAND NEW VERSION
Question 1
Which of the following describes the primary mechanism of action of fluoride
in preventing dental caries?
A) Killing cariogenic bacteria directly
B) Buffering acids in the oral cavity
C) Inhibiting plaque formation
D) Enhancing remineralization and decreasing demineralization of enamel
E) Increasing salivary flow
Correct Answer: D) Enhancing remineralization and decreasing
demineralization of enamel
Rationale: Fluoride primarily works by incorporating into the enamel
to form fluorapatite, which is more resistant to acid
demineralization, and by promoting the remineralization of early
carious lesions.
Question 2
A patient presents with generalized moderate gingivitis. Which of the
following is the most appropriate initial treatment?
A) Oral surgery and antibiotics
B) Scaling and root planing with local anesthesia
C) Oral hygiene instructions and supragingival scaling
D) Systemic antibiotics only
E) Chlorhexidine gluconate rinse without debridement
Correct Answer: C) Oral hygiene instructions and supragingival scaling
Rationale: Gingivitis is an inflammatory condition limited to the
gingiva. Initial treatment focuses on removing the etiologic factor
(plaque) through effective oral hygiene and professional
supragingival debridement (scaling).
,Question 3
Which cranial nerve is primarily responsible for the sensation of taste from
the anterior two-thirds of the tongue?
A) Trigeminal nerve (CN V)
B) Facial nerve (CN VII)
C) Glossopharyngeal nerve (CN IX)
D) Vagus nerve (CN X)
E) Hypoglossal nerve (CN XII)
Correct Answer: B) Facial nerve (CN VII)
Rationale: The chorda tympani, a branch of the facial nerve (CN VII),
innervates the taste buds on the anterior two-thirds of the tongue.
Question 4
A patient reports a persistent dry mouth (xerostomia). Which of the following
is the MOST common cause of xerostomia?
A) Sjögren's syndrome
B) Radiation therapy to the head and neck
C) Medications (e.g., anticholinergics, antidepressants)
D) Diabetes mellitus
E) Vitamin B deficiency
Correct Answer: C) Medications (e.g., anticholinergics,
antidepressants)
Rationale: Medication use is the most common cause of xerostomia,
with hundreds of commonly prescribed drugs listing dry mouth as a
side effect.
Question 5
When taking a panoramic radiograph, what is the MOST common patient
positioning error that results in an exaggerated smile line?
A) Chin placed too high
B) Chin placed too low
C) Patient slumped forward
,D) Tongue not placed on the roof of the mouth
E) Patient head tilted
Correct Answer: A) Chin placed too high
Rationale: When the chin is positioned too high during a panoramic
radiograph, the Frankfort plane is angled upward, resulting in an
exaggerated smile line on the image.
Question 6
Which classification of carious lesions typically involves the incisal edges of
anterior teeth or cusp tips of posterior teeth without involving pits or
fissures?
A) Class I
B) Class II
C) Class III
D) Class IV
E) Class VI
Correct Answer: E) Class VI
Rationale: Class VI carious lesions (according to G.V. Black's
classification) are found on the incisal edges of anterior teeth and
cusp tips of posterior teeth.
Question 7
What is the recommended probing depth for healthy gingiva?
A) 0-1 mm
B) 1-3 mm
C) 3-5 mm
D) 5-7 mm
E) Greater than 7 mm
Correct Answer: B) 1-3 mm
Rationale: Healthy gingiva typically exhibits sulcus depths of 1-3 mm
with no bleeding upon probing.
, Question 8
Which of the following local anesthetics is CONTRAINDICATED for patients
with a sulfite allergy?
A) Lidocaine
B) Mepivacaine
C) Bupivacaine
D) Articaine
E) Epinephrine-containing local anesthetics
Correct Answer: E) Epinephrine-containing local anesthetics
Rationale: Epinephrine-containing local anesthetics often contain
sodium bisulfite as an antioxidant. Patients with a true sulfite
allergy (rare) should avoid these and use plain local anesthetics.
Question 9
The primary function of cementum is to:
A) Support the tooth in the alveolar bone
B) Provide sensation to the tooth
C) Form the bulk of the tooth crown
D) Protect the pulp from thermal changes
E) Facilitate mastication
Correct Answer: A) Support the tooth in the alveolar bone
Rationale: Cementum covers the root surface and serves as the
attachment for periodontal ligament fibers, which anchor the tooth
to the alveolar bone.
Question 10
A patient presents with a localized, painful, fluid-filled lesion on the labial
mucosa that ruptures and crusts over. This is most likely:
A) Apthous ulcer
B) Herpes simplex labialis
C) Frictional keratosis
D) Mucocele
