in reply to @eileenb1022 Interestingly enough, I found this article last night, and you might want to check it out.
https://www.news-medical.net/news/20231123/Saliva-substitute-from-University-of-Leeds-scientists-offers-major-relief-for-dry-mouth-conditions.aspx
I too have this problem, and recently saw a new rheumatologist after my former one, now a friend, reviewed my medical records and came up with a diagnosis of scleroderma limited. The "new" doctor did not agree with my friend's findings and ran some labs, while admitting that a negative result did not necessarily mean that I do not have this disorder. When the labs did come back negative, I pressed her further and sent he a link from the NIH which discussed that a blood test alone for many autoimmune diseases was insufficient to make a correct diagnosis. Of course the "new" doctor shut down the conversation and told me to discuss the issue with my PCP, but I already know where that discussion will go. Best of luck