Which of the following is NOT one of the clasp designs used in RPDs?

The classification of clasps used in removable partial dentures (RPDs) is an important consideration in dental prosthodontics. Among the options presented, retention clasps do not refer to a specific design of clasps but rather describe the function or role of a clasp in retaining the RPD in place.

Circumferential clasps are a well-known design used for retention and stability, providing support by encircling the abutment tooth. Wrought wire clasps are another specific design known for their flexibility and adaptability, often used in more challenging circumstances such as for teeth that require a more delicate approach. Embrasure clasps are utilized to engage the interproximal space between adjacent teeth, providing another dimension of retention.

In contrast to these specific designs, the term "retention clasp" generally describes the purpose those clasps serve rather than a distinct design itself. Hence, the identification of retention clasps as a non-design choice in the list is justified. Understanding the proper classification of clasps helps in selecting the appropriate clasp design for different clinical situations in RPD fabrication.