ABE Clinical Endodontics 3 — Questions and Answers
Question 1: When using the 'balanced force' technique for root canal preparation, the sequence of motions is:
- 90° clockwise to engage, 120–180° counterclockwise with apical pressure, then clockwise to release (Correct answer)
- Full clockwise rotation, then full counterclockwise rotation without apical pressure
- Alternating 45° clockwise and counterclockwise without apical progression
- Clockwise 360° continuous rotation with constant apical pressure
Correct answer: 90° clockwise to engage, 120–180° counterclockwise with apical pressure, then clockwise to release
The balanced force technique uses a clockwise quarter-turn to engage dentin, followed by a counterclockwise rotation with apical pressure to cut and remove debris.
Question 2: Which of the following best describes the concept of 'apical patency' in endodontic treatment?
- Confirming the apical foramen is located at the radiographic apex
- Maintaining a glide path through the entire root canal to the apical foramen
- Ensuring no debris is extruded beyond the apical foramen during irrigation
- Keeping the foramen open and free of debris with a small file (Correct answer)
Correct answer: Keeping the foramen open and free of debris with a small file
Apical patency refers to maintaining an open, debris-free apical foramen by passively passing a small file (e.g., #10 K-file) through the constricture.
Question 3: EDTA is used in root canal preparation primarily to:
- Kill bacteria in the canal system
- Remove the smear layer by chelating calcium ions (Correct answer)
- Dissolve organic tissue remnants
- Lubricate and prevent instrument fracture only
Correct answer: Remove the smear layer by chelating calcium ions
EDTA chelates calcium ions in mineralized dentin, effectively removing the inorganic component of the smear layer.
Question 4: A radiograph of a maxillary first molar shows a well-defined radiolucency associated with the MB root that does not respond to vitality testing. Probing depths are within normal limits. This most likely represents:
- Periapical cyst
- Periapical granuloma (Correct answer)
- Lateral periodontal cyst
- Focal sclerosing osteomyelitis
Correct answer: Periapical granuloma
A well-defined periapical radiolucency on a non-vital tooth with normal probing is classically a periapical granuloma, the most common periapical lesion.
Question 5: The master apical file (MAF) size is typically selected to achieve which goal?
- Match the largest instrument that fits to working length without binding
- Be at least three sizes larger than the first file that binds at working length (Correct answer)
- Equal the ISO size of the apical foramen as confirmed by electronic apex locator
- Be the same size used for the initial glide path
Correct answer: Be at least three sizes larger than the first file that binds at working length
The MAF is typically selected to be at least three ISO sizes larger than the first file that binds at working length, ensuring adequate canal shaping.
Question 6: Which of the following root morphologies is most commonly associated with missed canals in mandibular incisors?
- Single canal with round cross-section
- Two canals joining apically into one (Vertucci Type II) (Correct answer)
- Three separate canals with independent foramina
- One canal with an oval cross-section
Correct answer: Two canals joining apically into one (Vertucci Type II)
Mandibular incisors frequently exhibit a Vertucci Type II configuration (2-1), where two canals merge into one near the apex, making the second canal easy to miss.
Question 7: When performing warm vertical compaction, the 'fit' of the master gutta-percha cone is most critical at which location?
- The coronal third
- The junction of the middle and apical third
- The apical 3–5 mm (apical stop) (Correct answer)
- The canal orifice
Correct answer: The apical 3–5 mm (apical stop)
The master cone must have 'tug-back' resistance at the apical stop (apical 3–5 mm) to ensure proper apical seal during warm vertical compaction.
ABE Clinical Endodontics 3
When using the 'balanced force' technique for root canal preparation, the sequence of motions is: