A patient reports that their partial denture does not seat properly and moves during chewing. Which prosthetic property is primarily deficient?

Correct answer: D. Stability

• A. Support is the resistance to vertical (occlusal) forces directed toward the residual ridge. A lack of support manifests as the denture sinking into the tissue, not moving laterally during chewing.
• B. Occlusal problems may cause the denture to tip or shift but the primary prosthetic design property addressed is stability, not occlusion per se.
• C. Retention is the resistance to dislodgement along the path of insertion/removal (vertical pullout). A loose denture that falls out when the patient opens is a retention problem; one that moves during chewing is stability.
• D. CORRECT. Stability is the resistance of a prosthesis to lateral (horizontal) forces and to movement during function. A denture that doesn't stay down and moves while chewing has inadequate stability. Stability is provided by rigid major connectors, properly positioned rests, and guide planes.