Does penicillin work for severe toothaches?

Yes in some cases: If you have an abscessed tooth the penicillin will help the pain. It will not cure the problem though. If it is an abcessed tooth you will need root canal or extraction.

Yes...but: If you have a severe toothache, any antibiotic will help...Provided you are getting a strong enough dosage. But this will only limit the time the tooth may bother you. You need to get the toothe fixed (root canal, filling or ?) or get the tooth removed. If you don't and that infection returns..It will come back with greater pain and more bone destruction is quite possible.