INBDE Endodontics Practice Exam 2026
| 100 Advanced Questions & Answers
with Detailed Rationales | Integrated
National Board Dental Examination
Prep & Study Guide
1. A patient presents with spontaneous, lingering pain to cold in the
mandibular first molar. The tooth is not tender to percussion, and the pain
persists for several minutes after removal of the stimulus. Which pulpal
diagnosis is most appropriate?
A. Reversible pulpitis
B. Symptomatic apical periodontitis
C. Symptomatic irreversible pulpitis
D. Pulp necrosis
Answer: C. Symptomatic irreversible pulpitis
Rationale: Lingering, spontaneous thermal pain is characteristic of symptomatic
irreversible pulpitis. The absence of percussion sensitivity indicates that apical
inflammation has not yet become clinically evident.
, 2. A maxillary premolar has no response to cold or electric pulp testing and is
tender to percussion. Radiographically, there is a well-defined periapical
radiolucency. What is the most likely diagnosis?
A. Normal pulp with symptomatic apical periodontitis
B. Pulp necrosis with asymptomatic apical periodontitis
C. Previously treated tooth with acute apical abscess
D. Reversible pulpitis with chronic apical abscess
Answer: B. Pulp necrosis with asymptomatic apical periodontitis
Rationale: Loss of pulp sensibility indicates necrosis, while the well-defined
asymptomatic periapical radiolucency is consistent with asymptomatic apical
periodontitis.
3. During access preparation of a mandibular molar, a clinician suspects a
second distal canal. Which finding most strongly suggests the presence of
an additional canal?
A. Large pulp chamber
B. A single apical foramen
C. A developmental groove extending from the chamber floor toward the distal
root
D. Increased tooth mobility
Answer: C. A developmental groove extending from the chamber floor toward
the distal root
Rationale: Developmental grooves, color changes, and canal orifice symmetry
on the chamber floor can provide important clues to additional canals. Careful
examination of the chamber floor is critical.
4. A patient with a necrotic mandibular molar develops rapidly increasing
swelling, fever, and malaise. What is the most appropriate management?
A. Antibiotics alone
B. Occlusal adjustment only
,C. Delay treatment until swelling resolves
D. Establish drainage and perform definitive endodontic treatment when
possible, with systemic antibiotics when systemic involvement is present
Answer: D. Establish drainage and perform definitive endodontic treatment
when possible, with systemic antibiotics when systemic involvement is present
Rationale: Local source control through drainage and endodontic treatment is
essential. Systemic antibiotics are indicated when infection produces systemic
manifestations such as fever or malaise.
5. Which irrigant property is primarily responsible for sodium hypochlorite's
ability to dissolve organic tissue?
A. Chelation
B. Surface tension reduction
C. Proteolysis and saponification reactions
D. Demineralization of inorganic dentin
Answer: C. Proteolysis and saponification reactions
Rationale: Sodium hypochlorite dissolves organic tissue through chemical
reactions involving proteolysis and saponification. EDTA, rather than sodium
hypochlorite, is primarily responsible for chelation of inorganic components.
6. What is the primary purpose of EDTA during root canal preparation?
A. Dissolution of pulp tissue
B. Elimination of all intracanal bacteria
C. Chelation and removal of the inorganic component of the smear layer
D. Obturation of dentinal tubules
Answer: C. Chelation and removal of the inorganic component of the smear
layer
Rationale: EDTA chelates calcium ions and facilitates removal of the inorganic
component of the smear layer, improving penetration of irrigants and sealers
into dentinal irregularities.
, 7. A clinician instruments a curved canal aggressively with a large stainless-
steel file and subsequently observes a deviation of the canal from its
original path. Which complication has most likely occurred?
A. Apical plug formation
B. Canal transportation
C. Internal resorption
D. Vertical root fracture
Answer: B. Canal transportation
Rationale: Canal transportation occurs when instrumentation removes dentin
preferentially from one side of a curved canal, causing deviation from its
original trajectory and potentially compromising apical cleaning and obturation.
8. Which characteristic makes nickel-titanium instruments particularly useful
in curved root canals?
A. Greater cutting efficiency than all stainless-steel instruments
B. Complete resistance to cyclic fatigue
C. Superior flexibility and shape-memory behavior
D. Ability to dissolve dentin chemically
Answer: C. Superior flexibility and shape-memory behavior
Rationale: NiTi instruments have greater flexibility than stainless-steel
instruments, allowing better maintenance of canal curvature. However, they
remain susceptible to cyclic and torsional fatigue.
9. A file fractures inside a curved canal because its tip binds while the shank
continues rotating. What type of failure is primarily involved?
A. Cyclic fatigue
B. Corrosion
C. Torsional failure
D. Thermal fatigue
Answer: C. Torsional failure
| 100 Advanced Questions & Answers
with Detailed Rationales | Integrated
National Board Dental Examination
Prep & Study Guide
1. A patient presents with spontaneous, lingering pain to cold in the
mandibular first molar. The tooth is not tender to percussion, and the pain
persists for several minutes after removal of the stimulus. Which pulpal
diagnosis is most appropriate?
A. Reversible pulpitis
B. Symptomatic apical periodontitis
C. Symptomatic irreversible pulpitis
D. Pulp necrosis
Answer: C. Symptomatic irreversible pulpitis
Rationale: Lingering, spontaneous thermal pain is characteristic of symptomatic
irreversible pulpitis. The absence of percussion sensitivity indicates that apical
inflammation has not yet become clinically evident.
, 2. A maxillary premolar has no response to cold or electric pulp testing and is
tender to percussion. Radiographically, there is a well-defined periapical
radiolucency. What is the most likely diagnosis?
A. Normal pulp with symptomatic apical periodontitis
B. Pulp necrosis with asymptomatic apical periodontitis
C. Previously treated tooth with acute apical abscess
D. Reversible pulpitis with chronic apical abscess
Answer: B. Pulp necrosis with asymptomatic apical periodontitis
Rationale: Loss of pulp sensibility indicates necrosis, while the well-defined
asymptomatic periapical radiolucency is consistent with asymptomatic apical
periodontitis.
3. During access preparation of a mandibular molar, a clinician suspects a
second distal canal. Which finding most strongly suggests the presence of
an additional canal?
A. Large pulp chamber
B. A single apical foramen
C. A developmental groove extending from the chamber floor toward the distal
root
D. Increased tooth mobility
Answer: C. A developmental groove extending from the chamber floor toward
the distal root
Rationale: Developmental grooves, color changes, and canal orifice symmetry
on the chamber floor can provide important clues to additional canals. Careful
examination of the chamber floor is critical.
4. A patient with a necrotic mandibular molar develops rapidly increasing
swelling, fever, and malaise. What is the most appropriate management?
A. Antibiotics alone
B. Occlusal adjustment only
,C. Delay treatment until swelling resolves
D. Establish drainage and perform definitive endodontic treatment when
possible, with systemic antibiotics when systemic involvement is present
Answer: D. Establish drainage and perform definitive endodontic treatment
when possible, with systemic antibiotics when systemic involvement is present
Rationale: Local source control through drainage and endodontic treatment is
essential. Systemic antibiotics are indicated when infection produces systemic
manifestations such as fever or malaise.
5. Which irrigant property is primarily responsible for sodium hypochlorite's
ability to dissolve organic tissue?
A. Chelation
B. Surface tension reduction
C. Proteolysis and saponification reactions
D. Demineralization of inorganic dentin
Answer: C. Proteolysis and saponification reactions
Rationale: Sodium hypochlorite dissolves organic tissue through chemical
reactions involving proteolysis and saponification. EDTA, rather than sodium
hypochlorite, is primarily responsible for chelation of inorganic components.
6. What is the primary purpose of EDTA during root canal preparation?
A. Dissolution of pulp tissue
B. Elimination of all intracanal bacteria
C. Chelation and removal of the inorganic component of the smear layer
D. Obturation of dentinal tubules
Answer: C. Chelation and removal of the inorganic component of the smear
layer
Rationale: EDTA chelates calcium ions and facilitates removal of the inorganic
component of the smear layer, improving penetration of irrigants and sealers
into dentinal irregularities.
, 7. A clinician instruments a curved canal aggressively with a large stainless-
steel file and subsequently observes a deviation of the canal from its
original path. Which complication has most likely occurred?
A. Apical plug formation
B. Canal transportation
C. Internal resorption
D. Vertical root fracture
Answer: B. Canal transportation
Rationale: Canal transportation occurs when instrumentation removes dentin
preferentially from one side of a curved canal, causing deviation from its
original trajectory and potentially compromising apical cleaning and obturation.
8. Which characteristic makes nickel-titanium instruments particularly useful
in curved root canals?
A. Greater cutting efficiency than all stainless-steel instruments
B. Complete resistance to cyclic fatigue
C. Superior flexibility and shape-memory behavior
D. Ability to dissolve dentin chemically
Answer: C. Superior flexibility and shape-memory behavior
Rationale: NiTi instruments have greater flexibility than stainless-steel
instruments, allowing better maintenance of canal curvature. However, they
remain susceptible to cyclic and torsional fatigue.
9. A file fractures inside a curved canal because its tip binds while the shank
continues rotating. What type of failure is primarily involved?
A. Cyclic fatigue
B. Corrosion
C. Torsional failure
D. Thermal fatigue
Answer: C. Torsional failure
