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Endodontics: INBDE study notes and practice questions

Endodontic questions start with diagnosis: you are given symptoms and test results and must name the pulpal and periapical status. They then move on to treatment steps, materials, complications and traumatic injuries.

706 practice questions · 24 patient cases

Practice Endodontics

Where it fits in the official INBDE blueprint

Oral Health Management (endodontic conditions and procedures). Nearest foundation knowledge areas: FK 6, FK 7. See the content outline for the official weights. This mapping is approximate: real items combine a clinical area with a foundation area.

What this area tests

High-yield checklist

Common traps

These notes are original study aids, not official exam content. Confirm clinical details against current guidelines.

Sample questions

1. Calcium hydroxide performs its endodontic function due to:

  1. An acidic pH of 2.5
  2. A neutral pH of 7
  3. A basic pH of 12.5
  4. Calcium hydroxide is not routinely used in endodontics
Show answer and explanation

Correct answer: C. A basic pH of 12.5

Calcium hydroxide has a highly basic pH of ~12.5, which is bactericidal against anaerobic organisms by denaturing bacterial proteins and inactivating LPS. Clinical uses: antimicrobial dressing, apexification, management of root resorption, and pulp capping.

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2. The BEST predictor of long-term success for an endodontically treated tooth is:

  1. Quality of root canal obturation on post-op radiograph
  2. Placement of a full-coverage restoration
  3. Canal fill length within 2 mm of the apex
  4. Absence of periapical lesion at 6 months
Show answer and explanation

Correct answer: B. Placement of a full-coverage restoration

While quality obturation, absence of periapical pathology, and proper length are all important, the BEST predictor of long-term success of an endodontically treated tooth is placement of a full-coverage restoration (crown). Teeth without full coverage have significantly higher rates of fracture and tooth loss — the tooth structure remaining after RCT makes the tooth brittle and fracture-prone without crown protection.
  • A. Quality of obturation is important but not the best predictor of long-term tooth survival — coronal seal and restoration are equally or more critical.
  • B. CORRECT. Full-coverage restoration (crown) is the best predictor of long-term success. It protects weakened tooth structure from fracture and maintains the coronal seal — both critical for long-term tooth survival.
  • C. Canal fill length within 2 mm of apex is a technical obturation goal but is not the best overall predictor of tooth survival.
  • D. Absence of periapical lesion at 6 months indicates endodontic healing, but without proper coronal restoration the tooth remains at high risk for fracture.

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3. What is the BEST predictor of long-term success for an endodontically treated tooth?

  1. Full-coverage (crown) restoration
  2. Post and core placement
  3. Periapical healing on X-ray
  4. Absence of symptoms
Show answer and explanation

Correct answer: A. Full-coverage (crown) restoration

✓ A) Full-coverage restoration is the best predictor.
Numerous studies consistently show that the RESTORATION placed after RCT is the strongest predictor of tooth survival. Teeth with full-coverage crowns after RCT have significantly higher survival rates than teeth restored with only a filling. This is because RCT-treated teeth are more brittle (loss of moisture, lack of proprioceptive feedback), prone to fracture under occlusal loads, and the crown protects the remaining tooth structure, seals the coronal access, and maintains function. Early coronal seal and full coverage dramatically improve long-term prognosis.

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4. What is the minimum recommended ferrule height for adequate crown retention and fracture resistance of an endodontically treated tooth?

  1. 0.5 mm
  2. 1.0 mm
  3. 2.0 mm
  4. 3.0 mm
Show answer and explanation

Correct answer: C. 2.0 mm

The literature consistently recommends a minimum ferrule height of 2.0 mm (360 degrees around the tooth preparation) to provide adequate fracture resistance and retention for crowns on endodontically treated teeth. The ferrule effect involves the metal collar of the crown encircling sound tooth structure above the crown margin, counteracting the wedging forces of the post and resisting fracture under occlusal loading. A 1.5 mm ferrule provides some benefit but is considered the absolute minimum; 2.0 mm is the standard clinical recommendation per Carranza's and multiple biomechanical studies.

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5. A patient has a fixed bridge from the upper second premolar to the second molar. The second premolar abutment was previously root canal treated and now has a 9 mm vertical bone defect on the mesial. The root has adequate length remaining. What is the best treatment for this abutment tooth?

  1. Extract the tooth and remake the bridge or place an implant
  2. Perform periodontal regenerative surgery only
  3. Re-treat the root canal and restore with a new post and core
  4. Observe and recall every 3 months
Show answer and explanation

Correct answer: A. Extract the tooth and remake the bridge or place an implant

A 9 mm vertical (angular) bone defect on the mesial of an endodontically treated bridge abutment carries a poor prognosis. While vertical bone defects can sometimes be treated with regenerative periodontal therapy (GTR, bone grafting), a 9 mm defect with the tooth under occlusal load as a bridge abutment makes: (1) the tooth structure severely compromised; (2) the bone support critically reduced; (3) re-treating the RCT unhelpful as it does not address the bone defect. Extraction of the compromised abutment and replacement with an implant or redesigned bridge is the most definitive treatment. Re-treating the root canal alone would fail to address the primary problem — the 9 mm vertical bone loss that has destroyed the structural foundation of the tooth.

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6. What is the ACCESS CAVITY SHAPE for the mandibular lateral incisor that is DIFFERENT from the others listed (maxillary premolars, maxillary canine)?

  1. Maxillary premolar — ovoid (different)
  2. Maxillary canine — oval (different)
  3. Mandibular lateral incisor — oval (different from maxillary premolars/canines shape-wise)
  4. All have the same access cavity shape
  5. Mandibular lateral incisor has a unique ovoid/lozenge shape different from the oval maxillary teeth
Show answer and explanation

Correct answer: E. Mandibular lateral incisor has a unique ovoid/lozenge shape different from the oval maxillary teeth

✓ E) Mandibular lateral incisor has a different access cavity shape.
Access cavity shapes: Maxillary central incisor = triangular; Maxillary lateral/canine = oval; Maxillary first premolar = ovoid/elongated; Mandibular incisors = OVAL to lozenge shape. The mandibular lateral incisor has a narrower, more elongated oval/lozenge access. Mandibular incisors frequently have TWO canals (look for labial and lingual canals). This anatomical variation makes mandibular incisor endodontics tricky. Always check for second canal. The PDF notes mandibular lateral is the exception among the listed options.

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7. Which statement is NOT true about taurodontism?

  1. It results from failure of Hertwig's root sheath to invaginate at the proper level
  2. The pulp chamber is enlarged with apical displacement of the pulpal floor
  3. Taurodontism exclusively affects primary teeth
  4. Roots are shortened compared to normal teeth
Show answer and explanation

Correct answer: C. Taurodontism exclusively affects primary teeth

Taurodontism is a developmental anomaly characterized by an enlarged pulp chamber with apical displacement of the pulpal floor and bifurcation/trifurcation, shortened roots, and absence of the normal cervical constriction at the cementoenamel junction. It results from failure of Hertwig's epithelial root sheath to invaginate at the proper horizontal level during root development. Taurodontism can affect both primary and permanent dentition; it is NOT exclusive to primary teeth. It is most commonly seen in permanent molars. It may occur as an isolated finding or in association with syndromes such as amelogenesis imperfecta, Klinefelter syndrome, and tricho-dento-osseous syndrome.

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8. What anatomical landmark is most commonly used to locate the apex of the mesiobuccal root of a mandibular first molar?

  1. Central groove
  2. Buccal developmental groove
  3. Mesiobuccal cusp tip
  4. Mesiolingual cusp tip
Show answer and explanation

Correct answer: C. Mesiobuccal cusp tip

For mandibular first molars, the apex of the mesiobuccal root is located approximately beneath the mesiobuccal cusp tip when viewing the tooth from the buccal aspect. This landmark is used clinically and radiographically to estimate root length and working length during endodontic procedures. The mesiobuccal root tends to curve distally in its apical third, but the coronal projection of the apex aligns with the mesiobuccal cusp tip. The central groove and buccal developmental groove serve as landmarks for fissure sealants and the mesiobuccal root entrance on the pulpal floor, respectively.

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Patient cases

All Endodontics questions (706)