How can you prevent getting salivary stones?

The most important thing is to drink plenty - at least 1.5 litres fluid a day. In summer or during physical exertion you should drink much more.

Since having a facelift one cheek always swells up when I am eating. Can there be a connection?

Yes, the literature describes that patients who have had a facelift can have stricture of the excretory duct of the parotid gland caused by scarring. Saliva fistula and cysts of the salivary glands have also been observed after facial rejuvenation surgery. These can generally be treated by endoscopy or with endoscopy assisted surgery.