Diamond burs are generally used for reducing tooth structures to place crowns or porcelain veneer. Diamonds may also be used to smooth, refine, and polish composite or porcelain material. Diamond is the hardest of all known materials. When bonded to stainless steel through a special metallurgical process, it can be used to create a cutting edge with superior cutting ability and durability. However, compared with carbide burs, diamond burs usually have a more pronounced decrease in cutting effectiveness over time leading to a shorter lifespan.