It is not clear if diabetes causes dry mouth (xerostomia) but some people with diabetes complain about dry mouth. Since saliva helps wash away food particles and keeps the mouth moist, this can lead to an increased risk of tooth decay.
Additionally, studies have indicated that severe gum disease may be associated with several other health conditions, including diabetes but saying that two conditions are associated is not the same as saying that one causes the other. Well-designed clinical trials are needed to establish whether a cause-and-effect relationship exists and to determine if, or how, treating gum disease may affect your overall health.