If a ledge-shaped rest seat is placed incisal to the opposing tooth contact, what happens during function?

If a ledge-shaped rest seat is placed incisal to the opposing tooth contact, what happens during function?

• A. A smooth glide occurs during function
• B. A bumpy ride occurs during function
• C. Occlusal contacts are unchanged
• D. It reduces the wear on opposing teeth

Answer: (B)

The rest seat’s location relative to the opposing contact determines whether it will interfere with the bite. Placing a ledge-shaped rest seat incisal to the opposing contact means, as the mandible closes, the rest seat will contact the opposing tooth earlier and act as a stopper. The denture then rides up on that ledge, producing an abrupt, uneven path of closure rather than a smooth, guided motion. This interference creates a “bumpy ride” during function. It’s not a smooth glide, it changes the contact pattern rather than leaving it unchanged, and it doesn’t reduce wear on the opposing teeth; instead it can introduce instability and irregular wear at the contact with the rest seat.

The rest seat’s location relative to the opposing contact determines whether it will interfere with the bite. Placing a ledge-shaped rest seat incisal to the opposing contact means, as the mandible closes, the rest seat will contact the opposing tooth earlier and act as a stopper. The denture then rides up on that ledge, producing an abrupt, uneven path of closure rather than a smooth, guided motion. This interference creates a “bumpy ride” during function. It’s not a smooth glide, it changes the contact pattern rather than leaving it unchanged, and it doesn’t reduce wear on the opposing teeth; instead it can introduce instability and irregular wear at the contact with the rest seat.