This study will evaluate participants with complaints of dry mouth to determine the cause and severity of their salivary gland dysfunction and their possible eligibility for other NIDCR protocols. Salivary secretions have antibacterial, lubricating, remineralizing, digestive, buffering and cleansing properties. Impaired function of these glands can cause an increase in tooth decay; a variety of oral hard and soft tissue changes, with painful, burning or ulcerated or oral mucosa; problems chewing, swallowing and speaking; and diminished taste and smell.