Summary of Abutment Modifications  After RPD Designed  Guideplanes  Lower heights of contour to eliminate interferences & improve esthetics  Create undercuts if absolutely necessary (raising heights of contour)  Rest seat preparation

Other Axial Contour Alterations  Lowering Heights of Contour  Rigid elements contacting abutments  Improve esthetics  Prepare guiding planes - most efficient method to lower

Other Axial Contour Alterations  Raising Heights of Contour  Insufficient retention in gingival 1/3 (at least 1mm from gingiva)  Prepare undercut  Add resin above to create undercut

Preparing Retention  Axial surface must be close to parallel the path of insertion

Retentive Preparation Shape  Follows the path of designed retentive tip

Creating Undercuts With Bonded Resins  Axial surface must be close to parallel the path of insertion

VIDEOS  Double Embrasure Rest Seats  Retentive Undercuts  On Your Own: Review Bonded Rest Seat