Dental Abscess? What's That? First, let’s talk about what an abscess is. An abscess is a collection of pus that is caused by an infection. There are two main kinds of dental abscesses. These abscesses are periapical and periodontal abscesses. A periapical abscess happens when the infection originates from the tooth and spreads into the surrounding tissue around the tooth, while a periodontal abscess originates from the gums whilst the tooth remains healthy – up to a certain level. If the abscess continues to spread to the surrounding tissues, the infection can spread from the gum and into the tooth. This is called a perio-endo lesion.