Sulfamethoxazole for toothache, is this okay?

Not really: Probably not the best antibiotic for a dental infection. If you are not allergic to penicillin type medicines, Amoxicillin would be the preferred antibiotic.

Sulfamethoxazole: The use of that antibiotic is ok. It will only be effective if your tooth is infected. If your tooth is not infected you do not need an antibiotic like that. So if you have a toothache i advise you to see a dentist to diagnose your problem. Good luck with that!

See your dentist: You must treat the source of the infection, not only the symptoms. Therefore, you need to clean out the inside of the tooth to remove the bacteria which is the source of the infection. The antibiotics cannot reach the source of the infection. Ask your dentist for more information.