It's not safe to have anything in your mouth when going into a seizure. In the past people use to stick something in one who is seizing to hold their tongue so one wouldn't bite off tongue. That isn't safe because in narrows airflow of breathing. I was told if one is seizing is turn them to their side so anything in the mouth, including saliva, falls out and prevent choking.

If you have a custom fit mouth guard, then unless your neurologist says "no", then you should wear it. It was my dentist 10 years ago who noted that it appeared as if I was grinding my teeth when I sleep (thus taking the sharpness off of the time), and thus he created the molds to have me the mouth guards that locks on to my teeth because the molds were created by a clay placed on my teeth to give that exact shape. They prevent the grinding and can be an aid if I have a fall from a full seizure. Since, the are fit to your teeth and thus are locked in place, there is no way that they are coming off unless you pull them off thus safe for wearing when sleeping--which is I wear mine because that was determined that I was grinding my teeth, other than potentially during a partial seizure.

Once I had the mouth guard in, the dentist said there was no more sign of any grinding.

I have a mouth guard, but when I was diagnosed with epilepsy my dentist said to stop wearing it. My seizures are primarily nocturnal.🤷🏾‍♀️

I do wear my guard only in the evening but it was just to keep my teeth straightened & plus my sister works for at dentist who its good to stop grinding them at night.

I wear one cause its for one to keep my teeth straight. Not sure if thats what you are asking.