Is sulfameth good for a toothache?

Do you mean sulfamethoxazole?
Sulfamethoxazole is a sulfonamide antibiotic.
sulfamethoxazole was once a very useful antibiotic but is almost obsolete as a single agent today due to the development of bacterial resistance to its effects. Sulfamethoxazole is now used primarily in combination with trimethoprim, a combination product known as Bactrim or Septra.
Sulfamethoxazole would not be a good choice for toothache.
You are best to see your dentist if the pain continues.
In the mean time try taking Ibuprofen for pain relief - see your pharmacist for more advice.