INBDE Endodontics 2 — Questions and Answers
Question 1: Which material is most commonly used as an intracanal medicament between appointments in root canal therapy?
- Formocresol
- Zinc oxide eugenol
- Calcium hydroxide (Correct answer)
- Iodoform paste
Correct answer: Calcium hydroxide
Calcium hydroxide is the most widely used intracanal medicament because its high pH (~12.5) is bactericidal, promotes periapical healing, and prevents reinfection between visits.
Question 2: What is the primary purpose of EDTA in root canal treatment?
- Antimicrobial activity
- Dissolution of organic tissue
- Removal of the smear layer (chelation of inorganic components) (Correct answer)
- Lubrication of instruments
Correct answer: Removal of the smear layer (chelation of inorganic components)
EDTA (ethylenediaminetetraacetic acid) chelates calcium ions in the smear layer and dentinal walls, removing the inorganic component to open dentinal tubules.
Question 3: A maxillary first molar most commonly has how many canals?
- 2
- 3
- 4 (Correct answer)
- 5
Correct answer: 4
The maxillary first molar typically has 3 roots and most commonly 4 canals (2 in the mesiobuccal root — MB1 and MB2, 1 in the distobuccal, 1 in the palatal).
Question 4: Internal root resorption appears radiographically as:
- A radiolucency with irregular borders around the root
- A symmetric oval or round radiolucency within the root canal space (Correct answer)
- Blunting of the root apex
- External notching of the root surface
Correct answer: A symmetric oval or round radiolucency within the root canal space
Internal resorption appears as a smooth, round-to-oval radiolucent enlargement within the root canal, caused by clastic cells activated within the pulp.
Question 5: What is the working length in endodontics?
- The length of the root as measured on the radiograph
- The distance from a reference point to the apical constriction where instrumentation ends (Correct answer)
- The full length of the root canal from orifice to apex
- The length of gutta-percha used for obturation
Correct answer: The distance from a reference point to the apical constriction where instrumentation ends
Working length is the measured distance from an occlusal/incisal reference point to the apical stop (apical constriction), establishing the limit of instrumentation.
Question 6: Which bacteria is most commonly found in failed root canal treatments?
- Porphyromonas gingivalis
- Enterococcus faecalis (Correct answer)
- Streptococcus mutans
- Fusobacterium nucleatum
Correct answer: Enterococcus faecalis
Enterococcus faecalis is the most frequently isolated organism in failed root canals due to its ability to survive in the alkaline environment created by calcium hydroxide.
INBDE Endodontics 2
Which material is most commonly used as an intracanal medicament between appointments in root canal therapy?