The marginal-ridge rest seat.

Natural canine crowns are preferred as abutments for removable partial dentures because of their root morphology and bony support. However, preparing the rest seat on the lingual surface of a mandibular canine risks perforating the enamel. An alternative rest-seat preparation, on the marginal ridge of the canine crown, conserves tooth structure and provides a rest seat of adequate length and depth to ensure support for a cast framework. To illustrate why this little-discussed rest-seat preparation has endured locally, the rationale and preparation of the marginal-ridge rest seat is discussed from both historical and clinical perspectives.