Which design feature prevents dislodgement of the restoration by lifting or tipping forces?

• A. Beveling
• B. Marginal integrity
• C. Resistance form
• D. Retention form

Answer: (D)

The design feature being tested is retention form. Retention form creates mechanical locks in the cavity—such as undercuts, grooves, or other retentive features—that hold the restoration in place and resist dislodgement from lifting or tipping forces. This is crucial for amalgam restorations because there is no chemical bond to tooth structure, so the restoration must be locked in by the cavity design rather than by adhesion.

Beveling helps margins and esthetics, not securement of the filling. Marginal integrity focuses on preventing leakage at the junction between tooth and restoration, not on preventing dislodgement. Resistance form protects the tooth from fracture under occlusal loads and large chewing forces, not the restoration’s tendency to be pulled out.