Diseases: Decreased saliva and dry mouth are associated with a number of medical and psychologic conditions. A prominent disease which causes oral dryness (and dryness of the eye) is Sjцgren’s (“Showgren’s”) Syndrome. This is an autoimmune condition which is characterized by generalized dryness. The dryness is brought on by damage to the salivary and other similar glands. Sometimes, Sjцgren’s Syndrome is associated with rheumatoid diseases e.g. rheumatoid arthritis, lupus or scleroderma ( a condition in which the skin becomes thick and less pliable). Other diseases which may result in dryness are diabetes, AIDS, bone marrow transplants, dehydration, etc.
Therapeutic Irradiation: Treatment for certain cancers of the head and neck can include radiation, which may damage the salivary glands, and decrease or completely stop the production of saliva. These effects are sometimes irreversible, but some medications may partly restore salivary function.
Ageing: As we get older our mouth tends to produce less saliva. Although this loss is probably not enough to cause oral dryness, per se, it contributes to this condition.
Decrease in our ability to Chew: Chewing, is the normal exercise of the mouth. Like with any other form of exercise, when you don’t use it, things begin to shrivel up. When your arm is in a cast, the muscles shrink in size. And so it is with the salivary glands. If you cut down on your chewing, they will decline in size and produce less saliva. And this induces dryness.
Depression: People who are depressed and/or overly anxious have lower rates of salivary flow.
Since so many factors cause dry mouth, it is evident that the determination of what causes your oral dryness is not a simple matter.