Latest 2026/2027 NBDHE (National Board Dental Hygiene Examination] with
correct answers and rationales updated this month
1. Which microorganism is most strongly associated with the initiation of dental caries?
A. Porphyromonas gingivalis
B. Streptococcus mutans
C. Treponema pallidum
D. Candida albicans
Correct answer: B. Streptococcus mutans
Rationale: S. mutans is a major cariogenic bacterium that metabolizes fermentable
carbohydrates and produces acids that contribute to enamel demineralization.
2. The primary mineral component of enamel is:
A. Calcium carbonate
B. Hydroxyapatite
C. Collagen
D. Keratin
Correct answer: B. Hydroxyapatite
Rationale: Enamel is primarily composed of crystalline calcium phosphate in the form of
hydroxyapatite.
3. Which tooth tissue is the hardest?
A. Cementum
B. Dentin
C. Enamel
D. Pulp
Correct answer: C. Enamel
Rationale: Enamel is the hardest tissue in the human body because of its high mineral content.
4. The primary function of the periodontal ligament is to:
A. Produce saliva
B. Attach the tooth to the alveolar bone and absorb functional forces
C. Form enamel
D. Protect the pulp from bacteria
,Correct answer: B. Attach the tooth to the alveolar bone and absorb functional forces
Rationale: The periodontal ligament connects cementum to alveolar bone and helps support the
tooth while absorbing occlusal forces.
5. Which cell is primarily responsible for bone resorption?
A. Osteoblast
B. Osteocyte
C. Osteoclast
D. Fibroblast
Correct answer: C. Osteoclast
Rationale: Osteoclasts break down and resorb bone tissue.
6. A patient has bleeding on probing, redness, and edema limited to the gingiva, with no
clinical attachment loss. This is most consistent with:
A. Periodontitis
B. Gingivitis
C. Necrotizing periodontitis
D. Periapical abscess
Correct answer: B. Gingivitis
Rationale: Gingivitis is inflammation confined to the gingiva without loss of periodontal
attachment.
7. The most important etiologic factor in plaque-induced gingivitis is:
A. Dental biofilm
B. Tooth color
C. Occlusal anatomy alone
D. Salivary flow alone
Correct answer: A. Dental biofilm
Rationale: Accumulation of pathogenic dental biofilm is the primary initiating factor in plaque-
induced gingival inflammation.
8. Which microorganism is strongly associated with advanced periodontal disease?
A. Porphyromonas gingivalis
B. Streptococcus salivarius
, C. Lactobacillus acidophilus
D. Staphylococcus epidermidis
Correct answer: A. Porphyromonas gingivalis
Rationale: P. gingivalis is a recognized periodontal pathogen associated with dysbiosis and
destructive periodontal disease.
9. A periodontal pocket is best described as:
A. A normal gingival sulcus
B. A pathologically deepened gingival sulcus
C. A cavity in the enamel
D. A fracture of the root
Correct answer: B. A pathologically deepened gingival sulcus
Rationale: Periodontal pockets result from apical migration of the junctional epithelium and loss
of periodontal attachment.
10. Which instrument is primarily designed for removing supragingival calculus?
A. Universal curet
B. Gracey curet
C. Sickle scaler
D. Periodontal probe
Correct answer: C. Sickle scaler
Rationale: Sickle scalers have a pointed tip and are primarily used for supragingival calculus
removal.
11. A periodontal probe is used primarily to:
A. Remove calculus
B. Measure periodontal pocket depths and assess periodontal tissues
C. Polish teeth
D. Remove caries
Correct answer: B. Measure periodontal pocket depths and assess periodontal tissues
Rationale: Periodontal probes are used to assess pocket depth, attachment levels, bleeding, and
other periodontal findings.
12. Which fluoride mechanism helps prevent dental caries?
correct answers and rationales updated this month
1. Which microorganism is most strongly associated with the initiation of dental caries?
A. Porphyromonas gingivalis
B. Streptococcus mutans
C. Treponema pallidum
D. Candida albicans
Correct answer: B. Streptococcus mutans
Rationale: S. mutans is a major cariogenic bacterium that metabolizes fermentable
carbohydrates and produces acids that contribute to enamel demineralization.
2. The primary mineral component of enamel is:
A. Calcium carbonate
B. Hydroxyapatite
C. Collagen
D. Keratin
Correct answer: B. Hydroxyapatite
Rationale: Enamel is primarily composed of crystalline calcium phosphate in the form of
hydroxyapatite.
3. Which tooth tissue is the hardest?
A. Cementum
B. Dentin
C. Enamel
D. Pulp
Correct answer: C. Enamel
Rationale: Enamel is the hardest tissue in the human body because of its high mineral content.
4. The primary function of the periodontal ligament is to:
A. Produce saliva
B. Attach the tooth to the alveolar bone and absorb functional forces
C. Form enamel
D. Protect the pulp from bacteria
,Correct answer: B. Attach the tooth to the alveolar bone and absorb functional forces
Rationale: The periodontal ligament connects cementum to alveolar bone and helps support the
tooth while absorbing occlusal forces.
5. Which cell is primarily responsible for bone resorption?
A. Osteoblast
B. Osteocyte
C. Osteoclast
D. Fibroblast
Correct answer: C. Osteoclast
Rationale: Osteoclasts break down and resorb bone tissue.
6. A patient has bleeding on probing, redness, and edema limited to the gingiva, with no
clinical attachment loss. This is most consistent with:
A. Periodontitis
B. Gingivitis
C. Necrotizing periodontitis
D. Periapical abscess
Correct answer: B. Gingivitis
Rationale: Gingivitis is inflammation confined to the gingiva without loss of periodontal
attachment.
7. The most important etiologic factor in plaque-induced gingivitis is:
A. Dental biofilm
B. Tooth color
C. Occlusal anatomy alone
D. Salivary flow alone
Correct answer: A. Dental biofilm
Rationale: Accumulation of pathogenic dental biofilm is the primary initiating factor in plaque-
induced gingival inflammation.
8. Which microorganism is strongly associated with advanced periodontal disease?
A. Porphyromonas gingivalis
B. Streptococcus salivarius
, C. Lactobacillus acidophilus
D. Staphylococcus epidermidis
Correct answer: A. Porphyromonas gingivalis
Rationale: P. gingivalis is a recognized periodontal pathogen associated with dysbiosis and
destructive periodontal disease.
9. A periodontal pocket is best described as:
A. A normal gingival sulcus
B. A pathologically deepened gingival sulcus
C. A cavity in the enamel
D. A fracture of the root
Correct answer: B. A pathologically deepened gingival sulcus
Rationale: Periodontal pockets result from apical migration of the junctional epithelium and loss
of periodontal attachment.
10. Which instrument is primarily designed for removing supragingival calculus?
A. Universal curet
B. Gracey curet
C. Sickle scaler
D. Periodontal probe
Correct answer: C. Sickle scaler
Rationale: Sickle scalers have a pointed tip and are primarily used for supragingival calculus
removal.
11. A periodontal probe is used primarily to:
A. Remove calculus
B. Measure periodontal pocket depths and assess periodontal tissues
C. Polish teeth
D. Remove caries
Correct answer: B. Measure periodontal pocket depths and assess periodontal tissues
Rationale: Periodontal probes are used to assess pocket depth, attachment levels, bleeding, and
other periodontal findings.
12. Which fluoride mechanism helps prevent dental caries?
