How long does it take for a tooth abscesses to go away with penicillin?

7-10 days: If the penicillin is effective, generally the infection decreases (less, or no pain and swelling) within 7-10 days. However, the infection does not go away until the tooth is treated, ie. Removed or a root canal is performed.

Depends: The penicillin will make the abscess smaller over days depending upon how big it was to start with. Small abscess: 3 days. If the abscess is not going down in two to three days then call for an appointment to be reevaluated for a different antibiotic or a dental proceedure.Absc normally the dentist needs to do a proceedure in the mouth to solve the problem : root canal, extraction, gum treatment.