How much space is required to cap a weakened cusp with amalgam?

To effectively cap a weakened cusp with amalgam, a depth of approximately 2mm is generally needed. This depth ensures that there is enough material to provide a significant structural support to the weakened area of the tooth, thereby restoring its strength and functionality. Having at least 2mm of thickness also helps in achieving optimum resistance to occlusal forces during chewing.

If the depth is less than this, the amalgam restoration may not withstand the forces exerted during mastication, leading to a higher chance of failure, such as fracture or loss of the restoration. Similarly, with more than 2mm, while it might provide adequate support, there is typically no added clinical benefit, and excessive preparation might remove unnecessary tooth structure.