Yes Christine,
In some more severe cases tongue depressors are great. They're cheap too!
Speaking of Johns Hopkins. I have an entire notebook with information from relieving dry mouth to PT exercises for the arm and shoulder compromised from neck surgery. All I need to do is re-type them into MS Word docs and save to post. Very useful and informative. Of course, checking with your doctors before doing anything is prudent.
Again, from my SLP @ JH.
"T"
Tongue Depressors (only if <30mm MIO)
Use wooden tongue depressors, adding one more each day, hold between upper and lower teeth or gums (about 1/4 of stick in mouth). Try to increase to 30 seconds.
Alternately, use one tongue depressor and slowly turn it from flat to sideways, gently stretching mouth opening to accommodate. Again, hold for 10-30 seconds as tolerated.