Compared to the marginal ridge reduction, how much extra depth is carved from the floor of the rest seat?

Compared to the marginal ridge reduction, how much extra depth is carved from the floor of the rest seat?

• A. 0.25 mm
• B. 0.5 mm
• C. 1.0 mm
• D. 1.5 mm

Answer: (B)

Creating a rest seat involves giving the tooth a defined seating area for the RPD rest. You start by reducing the marginal ridge a small amount to create space and access, then carve the floor of the seat a bit deeper so the rest can sit on solid tooth structure. The extra depth the floor must have beyond the ridge reduction is about 0.5 mm. This provides enough depth to form a stable, properly contoured rest seat while preserving as much tooth substance as possible. Choosing a larger depth would remove too much tooth, while a smaller depth wouldn’t give a functional, well-supported rest seat.

Creating a rest seat involves giving the tooth a defined seating area for the RPD rest. You start by reducing the marginal ridge a small amount to create space and access, then carve the floor of the seat a bit deeper so the rest can sit on solid tooth structure. The extra depth the floor must have beyond the ridge reduction is about 0.5 mm. This provides enough depth to form a stable, properly contoured rest seat while preserving as much tooth substance as possible. Choosing a larger depth would remove too much tooth, while a smaller depth wouldn’t give a functional, well-supported rest seat.