Dental Abscess: Bacteria from a tooth cavity can cause a dental abscess, or infection of the mouth, jaw or face. Symptoms include pain, swelling, facial redness, gum inflammation, pus drainage, and occasional difficulty fully opening the mouth. Unless the abscess ruptures on its own, the abscess will need to be cut open and drained by a health-care professional. Dental abscesses can be deadly if left untreated.