I don't know much about grinder teeth, but i know a bit about steel. The harder steel is, the more brittle it is, and the more carbon it has. The less carbon, the tougher it is, but is more malleable so it will dull quicker. Exactly what Carl said. When dealing with hardened steel, it is almost always best to wet grind, because you are trying to preserve the hardening process. When steel is hardened, it is heated quite hot and then quenched, forming certain grain structures. It is usually then carefully heat treated (tempered) to relax some of the hardening and make it tough enough to be useful. You can technically do this yourself with a forge, but if you don't know exactly what you are doing you will have mixed results. The particular steel used might be an alloy with other elements, so preserving the heat treatment is best. You need to be able to touch it bare handed at all times, very little heat input.