One of my first cases was a charming woman of about 70 with bad breath. According to her account, her grandchildren refused to hug and kiss her because of her breath. I met her in the clinic of a colleague (Prof. Arieh Kaufman) and we took her dentures and put them in a plastic bag. After several minutes, her oral odor was reproduced within the bag. In this manner, we were confident that her dentures were to blame.
With time, dentures often develop a characteristic smell. After all, they are pieces of plastic left in your mouth for years and years. They come in continual contact with saliva, food, drink and billions of bacteria. Usually, it is not enough to just brush your dentures and stick it back in the mouth (although brushing is important). Unless your dentist advises otherwise, take your denture(s) out at night, and leave them soaking in an antiseptic solution (several commercial varieties are available) while you sleep. Disinfect and deodorize your dentures, rather than have them dry out in your mouth during the night and develop a film of dried saliva, debris and bacteria. If your dentures already have odor, ask your dentist to treat them in an ultrasonic bath, with some cleaning solution thrown in. Dr. Kaufman did this trick with the grandmother's dentures, and the odor was dramatically improved within minutes.
Research has shown that dentures may harbor various types of enteric bacteria, including Klebsiella.