Can I take a second z pak for a severe infection caused by an abscessed tooth?

Yes, you can. You may get thrush or if you are female, you could get a yeast infection. Eat lots of yogurt throughout your treatment and you can use monistat or it's equivalent after a few days of treatment. You might want to get the 7 day stuff and use it every 2 or 3 days if you have ever had one before and are prone to them.Z paks are pretty strong anti biotic and it will kill off all bacteria, good and bad, that keep the yeast in check. You don't have to treat for thrush or yeast, just be aware that they could happen and take appropriate measures if it does. There is a really great mouth wash called Biotene, that has NO alcohol, but is antiseptic and is in with the mouthwashes at drug stores and mass retail stores.It will help with the abscess and so will warm salty gargles. Good luck.