Depend on what it takes to be considered as "destroyed." Destroying all power production, water pipelines, transportation inferstructure (especially bridges), waste treatment, means of communication, etc., you would have basically destroyed Eminor Seven.
You wouldn't have to actually glass the entire surface.
Doesn't Scott say "all habitable areas"? That could possibly mean not just infrastructure, but vegetation as well.
Scotty mentioned that all cities and installations on Eminiar Seven had been targeted, and that the entire inhabited surface of the planet would be destroyed.
As previously mentioned, destroying utilities and infrastructure, as well as cities where government leadership and economic power was centered would probably be sufficient to set an advanced civilization back decades, or even hundreds of years, without having to destroy everything, everywhere.