Which treatment has low-cost efficacy for arresting asymptomatic (non-symptomatic) caries lesions?

Silver diamine fluoride is a low-cost, minimally invasive topical agent specifically used to arrest active, asymptomatic carious lesions (especially useful in young children, patients who can't tolerate traditional restorative treatment, and root caries) — it's a major recent addition to evidence-based, non-surgical caries management. Sealants prevent new lesions on sound/early enamel rather than arrest existing cavitated lesions, and amalgam/glass ionomer are surgical (restorative) rather than non-invasive arrest approaches.