DENTAL HYGIENIST LICENCING EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS) PLUS CORRECT
RATIONALE IN ITALICS.
1. Which of the following is the primary mineral component of enamel?
A. Collagen
B. Hydroxyapatite
C. Keratin
D. Calcium carbonate
Correct answer: B. Hydroxyapatite
Rationale: Enamel is composed primarily of hydroxyapatite crystals, which provide hardness
and resistance to demineralization.
2. Which tooth surface is closest to the tongue?
A. Distal
B. Buccal
C. Lingual
D. Occlusal
Correct answer: C. Lingual
Rationale: The lingual surface faces the tongue, while the buccal surface faces the cheeks.
3. Which periodontal fiber resists vertical and intrusive forces on the tooth?
A. Horizontal
B. Apical
C. Oblique
D. Interradicular
Correct answer: C. Oblique
Rationale: Oblique fibers absorb vertical stress and help resist tooth intrusion into the socket.
4. What is the primary cause of dental caries?
A. Plaque accumulation
B. Poor brushing technique
C. High fluoride exposure
D. Dietary fat
Correct answer: A. Plaque accumulation
Rationale: Dental caries result from bacterial plaque metabolizing sugars into acids that
demineralize tooth enamel.
,5. Which of the following is a gram-positive facultative anaerobe strongly associated with dental
caries?
A. Streptococcus mutans
B. Porphyromonas gingivalis
C. Actinobacillus actinomycetemcomitans
D. Treponema denticola
Correct answer: A. Streptococcus mutans
Rationale: S. mutans metabolizes sucrose to produce acids that initiate enamel demineralization.
6. Which fluoride compound is most commonly used in community water fluoridation?
A. Sodium fluoride
B. Stannous fluoride
C. Acidulated phosphate fluoride
D. Sodium silicofluoride
Correct answer: D. Sodium silicofluoride
Rationale: Sodium silicofluoride and hydrofluosilicic acid are most often used due to cost-
effectiveness and stability.
7. Which instrument is best suited for removing supragingival calculus?
A. Gracey curette
B. Sickle scaler
C. Universal curette
D. Probe
Correct answer: B. Sickle scaler
Rationale: Sickle scalers have pointed tips designed for efficient removal of supragingival
deposits.
8. The Gracey 11/12 curette is designed for which area?
A. Anterior teeth
B. Posterior mesial surfaces
C. Posterior distal surfaces
D. All surfaces
Correct answer: B. Posterior mesial surfaces
Rationale: Gracey 11/12 is specifically angled for mesial surfaces of posterior teeth.
, 9. Which of the following indices measures the thickness of plaque at the gingival margin?
A. Plaque Control Record
B. Plaque Index (Silness and Löe)
C. OHI-S
D. DMFT
Correct answer: B. Plaque Index (Silness and Löe)
Rationale: The Plaque Index measures plaque thickness at the gingival area of each tooth.
10. The main purpose of a dental sealant is to:
A. Strengthen enamel
B. Seal pits and fissures
C. Re-mineralize enamel
D. Remove plaque
Correct answer: B. Seal pits and fissures
Rationale: Sealants provide a physical barrier preventing bacteria from colonizing occlusal pits.
11. Which nerve supplies sensation to the mandibular teeth?
A. Infraorbital nerve
B. Maxillary nerve
C. Mandibular nerve
D. Lingual nerve
Correct answer: C. Mandibular nerve
Rationale: The mandibular division (V3) of the trigeminal nerve innervates the lower teeth.
12. What is the primary goal of periodontal therapy?
A. Eliminate all bacteria
B. Promote new bone formation
C. Reduce inflammation and pocket depth
D. Whiten the teeth
Correct answer: C. Reduce inflammation and pocket depth
Rationale: The goal is to restore periodontal health by reducing bacterial load and tissue
inflammation.
13. Which of the following is the best indicator of current periodontal disease activity?
A. Tooth mobility
B. Bleeding on probing
C. Calculus deposits
D. Gingival color
CORRECT ANSWERS (VERIFIED ANSWERS) PLUS CORRECT
RATIONALE IN ITALICS.
1. Which of the following is the primary mineral component of enamel?
A. Collagen
B. Hydroxyapatite
C. Keratin
D. Calcium carbonate
Correct answer: B. Hydroxyapatite
Rationale: Enamel is composed primarily of hydroxyapatite crystals, which provide hardness
and resistance to demineralization.
2. Which tooth surface is closest to the tongue?
A. Distal
B. Buccal
C. Lingual
D. Occlusal
Correct answer: C. Lingual
Rationale: The lingual surface faces the tongue, while the buccal surface faces the cheeks.
3. Which periodontal fiber resists vertical and intrusive forces on the tooth?
A. Horizontal
B. Apical
C. Oblique
D. Interradicular
Correct answer: C. Oblique
Rationale: Oblique fibers absorb vertical stress and help resist tooth intrusion into the socket.
4. What is the primary cause of dental caries?
A. Plaque accumulation
B. Poor brushing technique
C. High fluoride exposure
D. Dietary fat
Correct answer: A. Plaque accumulation
Rationale: Dental caries result from bacterial plaque metabolizing sugars into acids that
demineralize tooth enamel.
,5. Which of the following is a gram-positive facultative anaerobe strongly associated with dental
caries?
A. Streptococcus mutans
B. Porphyromonas gingivalis
C. Actinobacillus actinomycetemcomitans
D. Treponema denticola
Correct answer: A. Streptococcus mutans
Rationale: S. mutans metabolizes sucrose to produce acids that initiate enamel demineralization.
6. Which fluoride compound is most commonly used in community water fluoridation?
A. Sodium fluoride
B. Stannous fluoride
C. Acidulated phosphate fluoride
D. Sodium silicofluoride
Correct answer: D. Sodium silicofluoride
Rationale: Sodium silicofluoride and hydrofluosilicic acid are most often used due to cost-
effectiveness and stability.
7. Which instrument is best suited for removing supragingival calculus?
A. Gracey curette
B. Sickle scaler
C. Universal curette
D. Probe
Correct answer: B. Sickle scaler
Rationale: Sickle scalers have pointed tips designed for efficient removal of supragingival
deposits.
8. The Gracey 11/12 curette is designed for which area?
A. Anterior teeth
B. Posterior mesial surfaces
C. Posterior distal surfaces
D. All surfaces
Correct answer: B. Posterior mesial surfaces
Rationale: Gracey 11/12 is specifically angled for mesial surfaces of posterior teeth.
, 9. Which of the following indices measures the thickness of plaque at the gingival margin?
A. Plaque Control Record
B. Plaque Index (Silness and Löe)
C. OHI-S
D. DMFT
Correct answer: B. Plaque Index (Silness and Löe)
Rationale: The Plaque Index measures plaque thickness at the gingival area of each tooth.
10. The main purpose of a dental sealant is to:
A. Strengthen enamel
B. Seal pits and fissures
C. Re-mineralize enamel
D. Remove plaque
Correct answer: B. Seal pits and fissures
Rationale: Sealants provide a physical barrier preventing bacteria from colonizing occlusal pits.
11. Which nerve supplies sensation to the mandibular teeth?
A. Infraorbital nerve
B. Maxillary nerve
C. Mandibular nerve
D. Lingual nerve
Correct answer: C. Mandibular nerve
Rationale: The mandibular division (V3) of the trigeminal nerve innervates the lower teeth.
12. What is the primary goal of periodontal therapy?
A. Eliminate all bacteria
B. Promote new bone formation
C. Reduce inflammation and pocket depth
D. Whiten the teeth
Correct answer: C. Reduce inflammation and pocket depth
Rationale: The goal is to restore periodontal health by reducing bacterial load and tissue
inflammation.
13. Which of the following is the best indicator of current periodontal disease activity?
A. Tooth mobility
B. Bleeding on probing
C. Calculus deposits
D. Gingival color
