Dentures are used to replace missing teeth that can be taken out and put back into your mouth. There are generally two types of dentures available: complete dentures and partial dentures. The type that is needed can be determined by your dentist. Typically complete dentures are used to replace all teeth and partial dentures are used when you still have some of your natural teeth in place.
Dentures are employed so that patients who suffer from tooth loss because of periodontal disease (gum disease), tooth decay, or traumatic injury don't have to suffer the negative effects of not having teeth. Besides the obvious reason of eating, replacement teeth are needed so that remaining teeth do not shift and so that a sagging facial appearance does not give the impression of making one appear older than they are.
Dentures have a brief adjustment period and never feel exactly the same as one's natural teeth. However they are designed to be comfortable and functional and have a similar appearance to natural teeth, improving the smile and facial appearance.