DHA Endodontics exam questions

6 worked Endodontics practice questions

Original exam-style questions from the bank, spread across the blueprint domains. They are not real or recalled exam questions. Try each one, then open the answer for the rationale and reference. None of them appear in the free mock exam, so reading them will not spoil it.

1. Question 1 · Cleaning, Shaping and Irrigation

   A clinician irrigates with 2% chlorhexidine immediately after 3% sodium hypochlorite and notices an orange-brown precipitate in the canal. How should this be prevented?

   1. AWarm the chlorhexidine before using it
   2. BUse 5.25% hypochlorite instead of 3%
   3. CUse chlorhexidine before hypochlorite
   4. DFlush with saline or water between irrigants
   Show answer and explanation

   Correct answer: D. Flush with saline or water between irrigants

   Chlorhexidine reacts with sodium hypochlorite to form a precipitate containing parachloroaniline that can block tubules and stain; flushing with water, saline or alcohol between them prevents this. Reversing the order does not prevent the reaction when residual irrigant remains.

   Reference: Basrani BR et al. J Endod 2007

2. Question 2 · Endodontic Microbiology and Pathology

   Which classic study demonstrated that exposed pulps in germ-free rats did not develop pulp necrosis or periapical lesions, whereas conventional rats did?

   1. AKakehashi, Stanley and Fitzgerald 1965
   2. BSundqvist G, doctoral thesis 1976
   3. CNair PNR and colleagues 2004
   4. DRicucci D and Siqueira JF 2010
   Show answer and explanation

   Correct answer: A. Kakehashi, Stanley and Fitzgerald 1965

   Kakehashi and colleagues showed in 1965 that bacteria are essential for the development of pulpal and periapical disease, using germ-free and conventional rats. Sundqvist later confirmed the role of bacteria in necrotic human teeth with intact crowns.

   Reference: Kakehashi S, Stanley HR, Fitzgerald RJ. Oral Surg Oral Med Oral Pathol 1965

3. Question 3 · Obturation and Restoration of Treated Teeth

   Which restoration most improves the long-term survival of a root-filled mandibular molar with a large MOD cavity?

   1. AGlass ionomer only
   2. BComposite without cusp coverage
   3. CAmalgam without cusp coverage
   4. DA restoration with cuspal coverage
   Show answer and explanation

   Correct answer: D. A restoration with cuspal coverage

   Root-filled posterior teeth with substantial tooth loss have significantly better survival when restored with cuspal coverage such as a crown or onlay. Intracoronal restorations without cuspal coverage leave the tooth vulnerable to cusp fracture.

   Reference: Aquilino SA, Caplan DJ. J Prosthet Dent 2002

4. Question 4 · Endodontic Microbiology and Pathology

   Histology of a periapical lesion shows an epithelium-lined cavity that is completely enclosed and has no communication with the root canal. Which statement about this lesion is most accurate?

   1. AIt is a pocket cyst likely to heal after orthograde treatment
   2. BIt is a granuloma that always heals non-surgically
   3. CIt is a true cyst that may not heal without surgery
   4. DIt is a scar that needs no further treatment
   Show answer and explanation

   Correct answer: C. It is a true cyst that may not heal without surgery

   A true radicular cyst is fully enclosed by epithelium with no connection to the canal, so it is considered self-sustaining and may persist after non-surgical treatment. A pocket (bay) cyst opens into the root canal and may heal once the canal infection is removed.

   Reference: Nair PNR. Periodontol 2000, 1997 (apical periodontitis pathogenesis)

5. Question 5 · Obturation and Restoration of Treated Teeth

   When preparing a post space in a root-filled canine, what minimum length of gutta-percha should remain apically to maintain an apical seal?

   1. A4-5 mm
   2. B1 mm
   3. C2 mm
   4. D10 mm
   Show answer and explanation

   Correct answer: A. 4-5 mm

   At least 4-5 mm of gutta-percha should be retained apically after post space preparation because shorter remaining lengths show increased leakage. Leaving 10 mm would usually make the post too short for adequate retention.

   Reference: Cohen's Pathways of the Pulp, 12th ed.

6. Question 6 · Pulpal and Periapical Diagnosis

   A 45-year-old has sharp pain on chewing tough food in tooth 37, worst when releasing the bite. The tooth has a large MOD amalgam, responds normally to cold and has no caries or radiographic lesion. Biting on one cusp with a bite-test device reproduces the pain. What is the most likely diagnosis?

   1. AVertical root fracture
   2. BAcute apical abscess
   3. CReversible pulpitis from caries
   4. DCracked tooth
   Show answer and explanation

   Correct answer: D. Cracked tooth

   Pain on biting, especially on release, reproduced by loading a single cusp in a vital tooth with a large intracoronal restoration is classic for a cracked tooth. Vertical root fracture usually occurs in root-filled teeth and causes deep isolated probing defects.

   Reference: AAE Colleagues for Excellence: Cracking the Cracked Tooth Code 2008