When the supra-marginal dentine of a root-filled tooth is engaged by a crown, it may create a stronger tooth/restoration complex. This has been termed the ferrule effect. This paper reviews the current evidence for this effect and examines the influence various post and core materials have on it. Means of achieving a ferrule are discussed and the importance of planning for failure is considered.
Clinical relevance: Provision for the ferrule effect when restoring root-filled teeth with a post-retained crown may optimize the strength of the restored tooth.