For treatment of a periapical abscess, which symptom is a key indicator?

Pain on percussion is a key indicator of a periapical abscess because it suggests inflammation and infection at the apex of a tooth. This symptom indicates that the pulp tissue may be necrotic, leading to an accumulation of pus and subsequently causing pain when the tooth is tapped or subjected to pressure.

In clinical practice, eliciting pain upon percussion is a common diagnostic tool that helps differentiate between conditions affecting the tooth, such as periapical abscesses, and other dental issues. The presence of pain highlights the acute nature of the infection and the inflammatory response in the surrounding periodontal tissues.

While swelling of the gums, persistent fever, and loss of sensitivity can be associated with dental infections, they are not as specific to periapical abscesses as pain on percussion. Swelling may indicate broader inflammation or works in conjunction with other symptoms, fever can signify systemic involvement, and loss of sensitivity is more commonly associated with pulp necrosis rather than specifically indicating an abscess. Therefore, the specific relationship between pain on percussion and periapical abscess makes it the most indicative symptom among the options provided.