Dry mouth can have several causes, but it's most frequently a side effect of medications or medical treatments. Treating dry mouth is important, as the saliva that coats your mouth keeps bacteria and fungi under control, minimizing your risk of tooth decay. To combat dry mouth, Dr. Alin Alkass suggests that you drink plenty of water, avoid smoking and using tobacco products, use a humidifier at night, limit your caffeine intake, and breath through your nose as much as possible. You should also brush with fluoride toothpaste and use a fluoride rinse frequently to build up your enamel and fight tooth decay. Lastly, there are saliva substitutes available if necessary.