Integrated National Board Dental
Examination (INBDE) Questions And
Correct Answers Plus Rationales 2026
1. Which immunoglobulin is primarily responsible for mucosal immunity?
A. IgG
B. IgM
C. IgA
D. IgE
Rationale: IgA is the dominant antibody in saliva and mucosal surfaces,
providing first-line defense against pathogens.
2. The primary function of the periodontal ligament is to:
A. Produce keratin
B. Protect the pulp
C. Support the tooth and resist functional forces
D. Form enamel
Rationale: The PDL suspends the tooth in its socket and absorbs occlusal forces.
3. A patient with angular cheilitis is most likely deficient in:
A. Vitamin C
B. Vitamin B2 (riboflavin)
C. Vitamin A
D. Vitamin K
,Rationale: Riboflavin deficiency commonly presents with angular cheilitis and
glossitis.
4. Which bacteria is most associated with initiation of dental caries?
A. Lactobacillus casei
B. Streptococcus mutans
C. Actinomyces viscosus
D. Prevotella intermedia
Rationale: S. mutans initiates enamel caries due to acid production and biofilm
formation.
5. The most common cause of irreversible pulpitis is:
A. Trauma
B. Deep caries
C. Bruxism
D. Periodontal disease
Rationale: Deep caries introduces bacteria and toxins into the pulp, leading to
irreversible inflammation.
6. Which muscle opens the jaw?
A. Masseter
B. Temporalis
C. Medial pterygoid
D. Lateral pterygoid
Rationale: The lateral pterygoid protrudes and depresses the mandible, opening
the mouth.
, 7. Which radiographic finding is most indicative of periapical pathology?
A. Widened PDL coronally
B. Radiolucency at the apex
C. Hypercementosis
D. Condensing osteitis
Rationale: A periapical radiolucency suggests necrotic pulp and apical
periodontitis.
8. The main component of dental plaque is:
A. Mineral
B. Bacteria
C. Food debris
D. Pellicle
Rationale: Plaque is a dense community of bacteria embedded in a biofilm
matrix.
9. The most common oral manifestation of HIV is:
A. Oral lichen planus
B. Oral candidiasis
C. SCC
D. Fordyce granules
Rationale: Immunosuppression increases susceptibility to Candida infections.
10. Which artery supplies the maxillary teeth?
A. Facial artery
B. Posterior superior alveolar artery
C. Lingual artery
Examination (INBDE) Questions And
Correct Answers Plus Rationales 2026
1. Which immunoglobulin is primarily responsible for mucosal immunity?
A. IgG
B. IgM
C. IgA
D. IgE
Rationale: IgA is the dominant antibody in saliva and mucosal surfaces,
providing first-line defense against pathogens.
2. The primary function of the periodontal ligament is to:
A. Produce keratin
B. Protect the pulp
C. Support the tooth and resist functional forces
D. Form enamel
Rationale: The PDL suspends the tooth in its socket and absorbs occlusal forces.
3. A patient with angular cheilitis is most likely deficient in:
A. Vitamin C
B. Vitamin B2 (riboflavin)
C. Vitamin A
D. Vitamin K
,Rationale: Riboflavin deficiency commonly presents with angular cheilitis and
glossitis.
4. Which bacteria is most associated with initiation of dental caries?
A. Lactobacillus casei
B. Streptococcus mutans
C. Actinomyces viscosus
D. Prevotella intermedia
Rationale: S. mutans initiates enamel caries due to acid production and biofilm
formation.
5. The most common cause of irreversible pulpitis is:
A. Trauma
B. Deep caries
C. Bruxism
D. Periodontal disease
Rationale: Deep caries introduces bacteria and toxins into the pulp, leading to
irreversible inflammation.
6. Which muscle opens the jaw?
A. Masseter
B. Temporalis
C. Medial pterygoid
D. Lateral pterygoid
Rationale: The lateral pterygoid protrudes and depresses the mandible, opening
the mouth.
, 7. Which radiographic finding is most indicative of periapical pathology?
A. Widened PDL coronally
B. Radiolucency at the apex
C. Hypercementosis
D. Condensing osteitis
Rationale: A periapical radiolucency suggests necrotic pulp and apical
periodontitis.
8. The main component of dental plaque is:
A. Mineral
B. Bacteria
C. Food debris
D. Pellicle
Rationale: Plaque is a dense community of bacteria embedded in a biofilm
matrix.
9. The most common oral manifestation of HIV is:
A. Oral lichen planus
B. Oral candidiasis
C. SCC
D. Fordyce granules
Rationale: Immunosuppression increases susceptibility to Candida infections.
10. Which artery supplies the maxillary teeth?
A. Facial artery
B. Posterior superior alveolar artery
C. Lingual artery
