Yes.  Dentures can be sharpened.
However, it is not normally recommended or done!
The most common sharpening method uses a rotary tool with a special attachment for teeth.
This attachment consists of a carbide or small diamond-tipped drill bit that grinds away at the surface of a tooth, gradually shaping it into the desired shape.
It is very important that you understand occlusion before sharpening teeth!
It is easy to destroy a denture if you do not have a complete understanding of how dentures function. It is recommended to consult with a dental professional before taking any action.