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Endodontics · single question

Regarding the technique for internal (non-vital) bleaching, which statement is INCORRECT?

  1. Gutta-percha should be removed to approximately 2 mm apical to the cementoenamel junction
  2. A 1 mm cervical barrier is sufficient between the gutta-percha and the bleaching agent
  3. Pulp horns and the pulp chamber must be thoroughly debrided of all necrotic tissue and restorative debris
  4. Rubber dam isolation is required
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Correct answer: B. A 1 mm cervical barrier is sufficient between the gutta-percha and the bleaching agent

  • A. This IS correct. Removing gutta-percha to roughly 2 mm apical to the CEJ (level of the epithelial attachment) allows adequate barrier placement while preserving the apical seal.
  • B. CORRECT — this is INCORRECT technique. The cervical barrier should be at least 2 MM thick (2–3 mm is ideal), not 1 mm. The barrier of glass ionomer, RMGI, or a resin-modified base seals the canal orifice and blocks diffusion of peroxide through the dentinal tubules to the periodontal ligament at the cervical region — the mechanism of external cervical resorption. A thin barrier is the single most common technique error leading to resorption.
  • C. This IS correct. Residual necrotic tissue and old restorative material in the pulp horns are the primary source of discoloration and must be removed for the bleach to work.
  • D. This IS correct. Rubber dam isolation protects the soft tissues from the caustic bleaching agent.

Note: Barrier level should follow the external CEJ contour, not a flat horizontal line — the CEJ is scalloped, higher interproximally.

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