Buy some Bentonite clay at the healthfood store. Moisten it to the point that it's soft but not mudlike. Put some in between the cheek and gum where the tooth with the abscess is.
Depending on the abscess it usually takes a day or two for the abscess to go away. You'll actually notice the clay starts smelling bad as it draws the infection into it. Just keep apply liberal amounts of clay to the area until the abscess goes away - and it will. Works every time.