A patient with a removable partial denture (RPD) reports that the prosthesis does not fully seat and rocks during chewing. Which component of the RPD is most likely deficient?

In RPD design: RETENTION = resistance to dislodgement in a vertical direction (pulling away from the teeth). If the RPD is loose when pulling up or down, retention is deficient. SUPPORT = resistance to displacement toward the tissues (vertical seating forces). If the RPD sinks into the mucosa, support (occlusal rests) is deficient. STABILITY = resistance to horizontal and lateral forces. If the RPD ROCKS, shifts laterally, or tips during chewing, STABILITY is deficient. In this case, the prosthesis does not seat fully AND moves/rocks during chewing — indicating a stability problem. This is caused by improper minor connector positioning, inadequate indirect retainers, poor bracing arm design, or occlusal interference. Stability is provided by bracing components (rigid minor connectors against proximal tooth surfaces) and proper occlusal design.