Saliva is one of your body's natural defenses against plaque because it acts to rinse your mouth of cavity-causing bacteria and other harmful materials. Dry mouth (also called Xerostomia) is a fairly common condition that is caused by diminished saliva production. People with medical conditions, such as an eating disorder or diabetes, are often plagued by dry mouth.
Over the Counter products called saliva substitutes bring much welcomed relief to the dry mouth sufferer.