Periodontal abscesses differ from periapical abscesses in that the source of infection is the gum and the supporting tissues, and not the pulp. A periodontal abscess is related to:
• pre-existing gum disease (periodontitis)
• bacterial infection from a deep periodontal pocket
• trauma to the gum e.g. from food or debris embedded in the gum
A persistent infection from a periodontal abscess, can track from the deeper tissues of the gum to gain entry into the pulp. Infection of the pulp can therefore occur, even though the tooth has no evidence of decay. Such an infection is called an endodontic-periodontal lesion to reflect the duality of cause.