How repair undercuts during crown preparation?

Two options: An undercut on complete crown is defined as any irregularities in the wall of a prepared tooth that prevent the withdrawal or seating of a wax pattern or casting. Too small a taper may lead to unwanted undercuts; too large will no longer be retentive for the crown. 1 taper the prep enough to eliminate the undercuts. 2. Block the undercuts in the lab during the waxing phase.

Lab: Most commonly the undercuts, if there are any, are blocked out in the lab. Occasionally the lab will make a index/guide for the dentist to use to modify the shape of the tooth before delivery of the crown. Before or during the preparation for a crown, a dentist may use any number of materials to block out undercuts.