What is the difference between a periodontal cleaning maintenance visit and a deep planing & scaling. deep planning = 5mm.?

Treat VS Maintain: Deep scaling may need to be done if you have ACTIVE gum/periodontal disease. Maintenance is what you do to stay healthy (and keep the gum disease from coming back). Maintenance will be done instead of a "regular cleaning" every few months (your dentist will tell you how often).

Yes big difference: Scaling and Root planing is for initial therapy for active disease, it may have to be repeated until it gets under control, while maintenance is reserved for those who have their symptoms in check, means reduced pocket depth, under 4 mm and no bleeding and no clinical loss of attachment. Some patient may need surgery if pockets remain active or worsens.