Without saliva,
Apart from lubricating your mouth, it helps to prevent tooth decay.
Decay is caused by acids produced by bacteria (plaque) that act on the sugars you eat. Saliva helps to wash away sugars. Importantly, healthy saliva can counteract the acids produced by bacteria thereby reducing the possibility of tooth decay.
If you have dry mouth or saliva that fails to neutralize acids, you may find it useful to use Tooth Mousse.