Which medical condition prevent use of dentures?

Very few: Most people can have dentures with the normal difficulty of wearing these foreign objects. Some diseases where excessive bone growths or jaw formation would change too much altering the fit, the elephant man, etc. Those with little saliva or dry mouth have a very difficult time retaining or wearing with comfort, like sorgrems syndrome. Your dentist can review all medical conditions and discuss.

Many: There is no magic that ensures that when a patients lose their teeth that they will be able to comfortably tolerate dentures.Patients with severe gag reflexes may never be able to function properly. Patients with dexterity and neurological problem have tremendous difficulty. Rapid weight loss or increases will affect retention and function. Blood pressure, edema and diabetes are also problematic.

none specifically: If you are allergic to the acrylic from which the dentures are constructed then that would be one contradindication. Anything that causes dryness in the mouth will not Prohibit you from wearing dentures but will make wearing them and keeping them in uncomfortable.