I'm really sorry your mom is so much pain.
I'd like to offer a couple suggestions and toss an idea or two out there for you...I am not a doctor nor do I have any training in the medical field, only personal experience and observations.
One thing you may want to check is allergies...it may sound odd but I worked with a girl who smoked about a pack of cigarettes a day and always had headaches. She found out after trying many things, that she was actually having the headaches from the cigarette smoking. She quit smoking...no more headaches.
Another thing is coffee, caffinated beverages, soda, tea, etc...Some people are very sensitive to the caffeine in a beverage without realizing it. I've had 1 to 2 cups of coffee per day for years. If I have too much I get headaches, if I have none i have caffeine withdrawal headaches. Just tossing that out there as a possibility as well.
Sensitive teeth is a painful experience also. If your mom's teeth are sensitive it could be a definate matter for a dentist to discuss options with her about. They take care of teeth and mouth conditions...they're not just for cleaning, capping and pulling teeth. It's a good idea to see a dentist regularly for preventative care instead of just when there is a problem with your teeth and gums.
It may be as simple as changing to a "sensitive teeth" toothpaste and a soft toothbrush. Let's hope that's all it takes.
I truly hope some of this helps you help your mom!