For 3 years i use dirty white spot mirror to floss with inhale/exhale toward mirror. can it cause gum recession or less effective invisalign treatment?

No: The mirror will neither cause gingival recession or affect Invisalign treatment.

Mirror not problem: Gum recession is not caused while using a dirty spotted mirror. Gingival recession can be caused by overly aggressive brushing or not brushing and flossing at all.

NO: Gum recession caused by gum disease, improper oral hygiene, and/or expanding teeth off of their bone support. It is not caused by the reflective surface you look into or breathe on. If you have both gum recession and a malocclusion, it is best to be evaluated by a specialist Periodontist and a specialist Orthodontist who will consult with each other to provide you with the best care possible.