Waking up at night to lie down the mouth is always dry may be daytime supplemental water is insufficient, periodontal inflammation or other oral diseases caused. 1. Insufficient water supplementation in the daytime: when the daytime diet is too spicy and salty, and drinking too little water, dry mouth may occur at night, and supplemental water can be. 2. Periodontal inflammation: gingivitis, periodontitis, and other inflammatory stimuli can also trigger insufficient secretion of salivary glands, appearing at night to sleep dry mouth. 3. Other diseases of the oral cavity: menopausal women may appear burning mouth syndrome, lichen planus, self-conscious dry mouth, rough oral mucosa, the phenomenon of too little saliva. Dry mouth at night need to go to the hospital to check the condition of the oral cavity and the whole body to determine the cause of the disease.