Endodontics · patient case with 5 questions
The tooth that bled during shaping
demo: 38-year-old male
chief: Referred for root canal treatment of a mandibular molar with a necrotic pulp.
history: Unremarkable. No allergies.
meds: None.
findings: Tooth 19 fails to respond to cold and is tender to percussion. Access is completed and the canals are irrigated. Partway through cleaning and shaping the patient reports sudden severe pain and the operator notices brisk bleeding from the canal along with rapid swelling of the cheek. Separately, tooth 4 in the same patient shows a narrow radiolucency running along the lateral root surface and joining an apical radiolucency.
Question 1
Sudden severe pain, bleeding and rapid swelling during irrigation is most consistent with:
Show answer and explanation
Correct answer: B. A sodium hypochlorite accident
- A. A floor perforation causes bleeding and pain but not the immediate massive tissue swelling produced by extruded hypochlorite.
- B. Correct. A hypochlorite accident occurs when irrigant is extruded past the apex, typically through an open apex, a perforation or from binding the needle and applying pressure. The immediate triad is severe pain, profuse haemorrhage into the tissues and rapid ballooning swelling, followed by ecchymosis. Management is reassurance, analgesia, cold then warm compresses, and close monitoring, with antibiotics if infection supervenes.
- C. A vasovagal faint gives pallor, sweating, bradycardia and loss of consciousness, without pain or bleeding.
- D. Anaphylaxis presents with urticaria, angioedema, bronchospasm and hypotension, not with bleeding from the canal, and it would have begun near the time of injection.
Note: Prevention: use a side-vented needle, keep it loose in the canal, stay 2 to 3 mm short of working length and never apply pressure to a bound needle.
Question 2
What is the principal reason sodium hypochlorite is used as an endodontic irrigant?
Show answer and explanation
Correct answer: A. It is bactericidal and dissolves organic pulp tissue
- A. Correct. Hypochlorite is a strong oxidising agent that kills bacteria and dissolves necrotic and vital organic tissue, including the pulp remnants and biofilm in the areas of the canal system that instruments cannot reach. That combination is what makes it irreplaceable.
- B. Substantivity, meaning sustained antimicrobial action after application, is a property of chlorhexidine, not hypochlorite.
- C. Lubrication is a secondary benefit of any irrigant and is not the reason hypochlorite is chosen.
- D. The inorganic component of the smear layer is removed by a chelator, EDTA, which is why the two are used in sequence rather than as alternatives.
Question 3
The lateral radiolucency along the root of tooth 4 joining an apical lesion is most suggestive of:
Show answer and explanation
Correct answer: A. A vertical root fracture
- A. Correct. A vertical root fracture allows bacteria to colonise the fracture line, producing a J-shaped or halo radiolucency that runs along the lateral root surface and joins the apical lesion. A narrow deep isolated probing defect and a sinus tract near the gingival margin complete the picture, and the prognosis is extraction or root resection.
- B. A lateral periodontal cyst is a well-corticated round or teardrop radiolucency between the roots of vital teeth, most often mandibular premolars, and it does not connect to an apical lesion.
- C. External resorption produces a concavity or loss of root outline rather than a linear lucency tracking the length of the root.
- D. A periodontal abscess arises from an existing pocket, giving angular bone loss continuous with the crest rather than an isolated lateral lucency joining the apex.
Question 4
Which is a defining feature of correct endodontic access preparation?
Show answer and explanation
Correct answer: B. Straight-line access to the canal orifices
- A. The floor is preserved carefully. Its developmental grooves and colour change guide the operator to the orifices, and cutting into it risks a furcal perforation.
- B. Correct. Straight-line access lets instruments reach the apical third without deflection, which prevents ledging, transportation and instrument separation. The outline should be conservative but unrestricted along the path the file must travel.
- C. The roof must be removed entirely. Any overhanging roof retains pulp tissue that discolours the crown and shelters bacteria, and it obscures orifices.
- D. Over-extension needlessly weakens the tooth. Access should be as small as possible while still permitting unimpeded instrumentation.
Note: Both removing the entire roof and achieving straight-line access are correct requirements; the recall listed them as competing options. Straight-line access is the broader principle that governs the shape of the whole preparation.
Question 5
All of the following are routes by which bacteria reach the pulp EXCEPT:
Show answer and explanation
Correct answer: C. Anachoresis through the bloodstream
- A. The retrograde periodontal route through lateral and accessory canals and the apical foramen is well recognised and produces combined endodontic-periodontal lesions.
- B. A fracture that exposes dentin opens tubules directly to the oral environment, and one that exposes pulp does so immediately.
- C. Correct as this question is keyed, and this is the exception. Anachoresis, the seeding of an inflamed pulp by circulating bacteria, is a documented experimental phenomenon but is a rare and debated route clinically. Caries is overwhelmingly the dominant pathway.
- D. Caries is the principal route. Bacteria and their products advance through dentinal tubules well before frank exposure.