Is it related to surgery or cancer treatments?
In any case, if it is something that must simply be treated, there are many products on the market to help with salivary flow such as rinses, lozenges and gums. I think the best are those that are sweetened by XYLITOL. This is a sugar that bacteria in the mouth can’t metabolize or use to create the acids that cause cavities. There are other medications that can be prescribed to increase salivary flow, but these seem to have fallen out of favor. The other and most “low-tech” solution is just to keep water on hand and sip as necessary.