What do converging walls prevent?

• A. Marginal leakage
• B. Pulp exposure
• C. Occlusal displacement
• D. Fracture

Answer: (C)

Converging walls give the restoration a mechanical lock by creating a slight undercut that holds the material in place. Since amalgam doesn’t bond to dentin, retention depends on cavity geometry. When the walls taper toward the occlusal surface, the condensed amalgam is resisted from being displaced in the direction of biting, preventing it from moving occlusally out of the cavity. In other words, the shape of the walls helps resist occlusal forces that would push the restoration upward. Other issues like marginal leakage, pulp exposure, or fracture relate more to margins, depth, or material behavior than to this retention geometry.