Abscessed Tooth When pus becomes trapped in the tissues of the jaw bone at the tip of an infected tooth, an abscess can occur. Most abscesses are caused by a bacterial infection accumulating in the soft pulp of a tooth. The abscessed portion occurs from dead pulp tissue (usually from tooth decay), broken teeth, tooth decay and other dental issues. Other causes can be a failed root canal treatment. If you have an abscess, we recommend that you call our office to discuss your condition.