A posterior tooth with carious undermined cusps requires a restoration that provides maximum strength, durability, and cuspal protection. Cast gold restorations offer excellent marginal adaptation, strength, and resistance to fracture, making them ideal for supporting weakened cusps. They effectively distribute occlusal forces and prevent further cusp breakage. Unlike direct restorations, they can be precisely fabricated to cover and reinforce the undermined tooth structure. Thus, cast gold restorations ensure long-term success in severely compromised posterior teeth.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition.