what is a gum abcess
1 A gum abscess (also called a periodontal abscess) usually is caused by an infection in the space between the tooth and gum. 2  The infection may occur after food gets trapped between the gum and tooth.3  In people with severe periodontal disease, bacteria can build up under the gum and in the bone.hen the inside of your mouth gets hurt or irritated, bacteria may enter and cause an infection. Sometimes you will see a painful swelling filled with pus (a thick, yellowish fluid). If the pus can't drain out, the area will get more swollen and painful. This is known as an abscess.