A 30-year-old patient presents with proximal caries detected radiographically at the dentin-enamel junction (DEJ) with no frank cavitation visible clinically. What is the most minimally invasive treatment?

For a 30-year-old with an early proximal carious lesion at the DEJ (radiographically visible, no clinical cavitation), the most minimally invasive approach is RESIN INFILTRATION (ICON — DMG). This technique: opens the proximal contact, etches with hydrochloric acid gel to open the enamel surface, then infiltrates low-viscosity resin into the porous carious enamel to arrest lesion progression. ICON is indicated for initial-to-moderate enamel caries (ICDAS 1-3) and early dentin lesions without cavitation — precisely this clinical scenario. It is more conservative than cavity preparation and more effective than fluoride alone for arrested DEJ caries. SDF is primarily used in older adults with root caries, pediatric patients, or patients unable to cooperate — and turns carious tissue black. Composite and amalgam require mechanical preparation, which is NOT indicated for a non-cavitated lesion. ICON represents the ideal 'least invasive first' approach for a young adult with early proximal caries.