Ferrule Effect — ORE Part 1 MCQ

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ModerateRestorative DentistryFerrule EffectORE Part 1

An endodontically treated tooth is planned for restoration with a post, core and full-coverage crown. What minimum height of sound coronal tooth structure should be engaged circumferentially by the crown to provide an effective ferrule?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — 1.5–2.0 mm

Explanation lettering: E = shown as A · C = shown as B · B = shown as C · A = shown as E

A is correct. A circumferential ferrule of approximately 1.5–2.0 mm of sound coronal dentine is the conventional minimum target for a post-retained crown. It allows the crown to brace the remaining tooth structure and is associated with improved fracture resistance compared with no ferrule. A post provides retention for the core; it does not compensate for absent coronal tooth structure or reliably reinforce the root. Therefore, C is incorrect. B provides too little dentine height to meet the conventional ferrule target. D and E may be present in a favourable tooth and greater height can improve resistance, but they are not the recommended minimum and may require unnecessary removal of supporting tissue or inappropriate crown-lengthening/extrusion. The qualification “circumferentially” is important: a complete ferrule is preferable, although partial ferrule is better than none where anatomy limits its provision.

Reference: Juloski J, Radovic I, Goracci C, Vulicevic ZR, Ferrari M. Ferrule effect: a literature review. Journal of Endodontics. 2012. https://pubmed.ncbi.nlm.nih.gov/22152612/