I Have Had Burning Mouth Syndrome For 6 Month Now.

I have had burning mouth syndrome for 6 month now. It started after I had 2 cracked fillings replaced. It's taking a toll on my quality of life. I've tried lots of things online. My doctor suggested B vitamin supplement. My dentist isn't much help. She suggests a sleep study eventhough I never had this until she replaced the 2 fillings. Any suggestions for the constant pain. I'm trying to cutout everything acidic, rinsing with baking soda/water combination, sucking on ice cubes, clonazepam at night. I know I need a newer night guard but my dentist wants me to undergo a sleep study first. Very expensive compared to the night guard.