Which of the following materials can be routinely used to sharpen carbide instruments?
Diamond is the hardest available abrasive and is the most effective for cutting and shaping hard materials.
It is the only material routinely capable of sharpening carbide as well as steel instruments.

Ref: Sturdevant's art and science of operative dentistry. 4th edition page 317
Arkansas stone
Silicon carbide
Aluminium oxide
Diamond