Can lack of saliva be treated?

Yes: Treatment depends on the cause of your dry mouth.

Hydration: There are very few medical reasons for "lack of saliva." if you are otherwise healthy... I would stay well hydrated. If you are at risk for diabetes that should be checked. If a female, an auto-immune process called sjogren's disease can account for dry mouth.

Control only: It depends upon the cause. Dry mouth can be caused by head and neck radiation treatment, medications, and sjogren's syndrome. Treatment can only help decrease the symptoms. Options include sugar free lozenges, oral sprays, sipping fluids, saliva substitutes, and in certain cases medications. I would suggest seeing a dentist who has experience treating dry mouth or an oral medicine specialist.