A 7 mm pocket persists after thorough root planing. Why consider flap surgery? Deep pockets cannot be cleaned by instruments alone - the dentist cannot see or reach the root's depths blind. Flap surgery lifts the gum for direct vision and access, allowing complete debridement, then repositions the gum for a maintainable shallow sulcus. Students learn the indication honestly: surgery is for access and architecture, not magic - it works only after Phase I and with maintained hygiene.