Wearing retainers for 2yrs.deep black stains/spots appear mostly near gumline.some appear as spots on entire tooth.cant get it off.anything serious?

Dental exam needed: Have you had your teeth cleaned since you started wearing your retainer? No pain? Ni can't tell you if this is stain, calculus build up or decay, only by having a dental exam can this be determined. See a dentist asap.

Stain or decay: It is either a stain or a decay (cavities) developed where plaque accumulation the most. Is the stain/spots soft or hard? Schedule a cleaning appointment to see if a dentist/hygienist can clean the spot off. If he or she cannot, it is either an arrest caries or decay. If he or she can, it is either a nicotine stain from smoking, caffeine stain from tea and/or coffee, or just water in your area.

See a dentist: I would not hesitate and get in to see your dentist before the stain becomes too severe or contributes to decay. After appointment, i assume that the hygienist and/or the dentist will instruct you on proper home care, possibly including the use of an electric toothbrush. Your stain may also be from the ferrous sulfate or other supplements/meds.