From time to time (like today!) I get an email or a comment asking for good information about salivary gland damage from RAI, RadioActive Iodine treatment for thyroid cancer.
Unfortunately, post-RAI salivary issues are a lot more common than your doctor may let on. For the most part, the first flare up is (more) severe. Some people have one incidence, post-treatment, but many continue to experience periodic flare-ups, some triggered by eating certain foods (sour, spicy), or sometimes nothing at all.
If you're looking for some good introductory material about this condition, here is an article on ThyCa.org.
Here is the link to the article on MedScape about radiation damage to salivary glands. This is a much more technical article targeted at a medical professionals, but it also includes an illustration of a very beneficial massage technique (figure 7). (MedScape may require free registration.)
Last but not least, I recommend NSAIDs such as ibuprofen (Motrin, Advil) or naproxen sodium (Aleve) as both a preventative immediately after dosing with RAI and for the next 2 days, and as a treatment whenever the salivaries swell up and become painful.
An aside: I had trouble recently distinguishing jaw pain (TMJ/TMD) from salivary gland issues. Some ways to distinguish between the two: salivary gland issues will not cause clicking or popping when you open and close your mouth, as far as I know, and repositioning your jaw or opening or closing your mouth will not change the type of pain/pressure you experience from salivary glands. If you're hearing pops or your jaw joints hurt when you open or close your mouth, you're most likely suffering from TMD. Unfortunately, it's entirely possible to have both issues at the same time!