DMD DMD Endodontics and Pulp Biology 2 — Questions and Answers
Question 1: What is the purpose of the working length in root canal therapy?
- To determine the length to which instrumentation and obturation should extend, ideally 0.5–1 mm from the radiographic apex (Correct answer)
- To measure the crown-to-root ratio
- To confirm pulp vitality
- To identify canal curvature
Correct answer: To determine the length to which instrumentation and obturation should extend, ideally 0.5–1 mm from the radiographic apex
The working length defines the distance from a reference point to the apical stop, typically 0.5–1 mm short of the radiographic apex, to prevent overextension.
Question 2: Which irrigant is considered the gold standard for root canal disinfection?
- Sodium hypochlorite (NaOCl) (Correct answer)
- Chlorhexidine
- EDTA
- Hydrogen peroxide
Correct answer: Sodium hypochlorite (NaOCl)
Sodium hypochlorite is the gold standard root canal irrigant due to its ability to dissolve organic tissue and kill a broad spectrum of microorganisms.
Question 3: What is the role of EDTA in root canal treatment?
- To remove the smear layer by chelating calcium ions from dentin (Correct answer)
- To dissolve necrotic pulp tissue
- To kill bacteria in the canal
- To obturate the canal
Correct answer: To remove the smear layer by chelating calcium ions from dentin
EDTA (ethylenediaminetetraacetic acid) is a chelating agent that removes the inorganic smear layer from canal walls, enhancing irrigant penetration.
Question 4: Which obturation technique uses a heated carrier to deliver gutta-percha into the canal?
- Thermafil technique
- Cold lateral condensation
- Carrier-based obturator technique
- Both A and C (Correct answer)
Correct answer: Both A and C
Both Thermafil and carrier-based obturator techniques use a heated plastic or metal carrier coated with gutta-percha that is inserted into the canal.
Question 5: Which sealer property is most critical for a successful root canal obturation?
- Good adhesion and adequate sealing of lateral and accessory canals (Correct answer)
- High radiopacity
- Fast set time
- Antimicrobial activity
Correct answer: Good adhesion and adequate sealing of lateral and accessory canals
An ideal endodontic sealer must adhere well to dentin and gutta-percha and seal lateral and accessory canals to prevent bacterial re-colonization.
Question 6: In which situation is a single-visit root canal treatment contraindicated?
- Acute apical abscess with systemic involvement (Correct answer)
- Vital pulp with irreversible pulpitis
- Previously initiated treatment
- Calcified canals
Correct answer: Acute apical abscess with systemic involvement
An acute apical abscess with systemic signs (fever, lymphadenopathy) is a contraindication to single-visit treatment because the infection requires drainage and may need adjunctive antibiotics.
DMD DMD Endodontics and Pulp Biology 2
What is the purpose of the working length in root canal therapy?