What is the worst thing that could happen when you have an abset tooth?

Abscess: If you mean abscess then the bacterial infection can spread even causing a bloodborne infection. You need to get it treated.

Death from infection: With an abscessed tooth you can get tooth loss, jaw bone damage, neighboring tooth damage or loss, sinus problems, brain abscess, heart damage, hospitalization, coma, and even death.

Bye bye tooth: If you have an abcessed tooth and you let it go...You could lose the tooth. But even if you don't...You are still letting an infection in your body go unchecked. Depending on the location of the abcess there are too many things to address, just know that it is not a good situation and really could be worse than just losing a tooth.