The most definitive diagnostic test to differentiate between a periapical abscess of pulpal origin and an abscess of periodontal origin is what?

The most definitive diagnostic test to differentiate between a periapical abscess of pulpal origin and an abscess of periodontal origin is the assessment of tooth vitality. This test evaluates the health of the pulp tissue inside the tooth. In cases where the pulp is necrotic or inflamed, the tooth will generally show a lack of vitality, indicating a pulpal origin for the abscess. Conversely, if the tooth is vital, it suggests that the abscess may be related to periodontal issues rather than pulpal ones.

Periodontal probing, while important for assessing the health of the periodontal tissues, primarily provides information about the attachment levels around the tooth and does not directly assess the vitality of the pulp. Radiographic examination offers valuable insights into bone loss and the presence of an abscess but does not definitively distinguish between pulpal and periodontal origin without additional vitality testing. Pain upon percussion can indicate inflammation or abscess presence, but it is not sufficiently specific to determine the origin of the abscess. Therefore, assessing tooth vitality is the most definitive method for differentiating between these two conditions.