“Do dentures cause gum disease?”

Yes, dentures might affect gums.

Yes if dentures are worn 24/7. Dentures need to be removed for at least 2 hours per day for gums to slough off and rest.  If you wear your dentures overnight, remove the during the day for about two hours.  Do no eat without your dentures.  Use adhesives if you have to. If you leave them out at night, you can wear them all day.  You are to wear your dentures every day.

Dentures cannot cause gum disease. If there is a bone unevenness under the gum, a sore spot can occur, when the denture rubs that area. This is different that gum disease.
Gum disease is the result of bacteria collecting on the gum around a tooth or implant.