It is partially due to "grinding" of the teeth (or clenching) and partially due to how you place your tongue against the roof of your mouth. Taking an amphetamine type "speed" and not talking leads to your mouth doing things you are unaware of at the time. Its not until you are coming down that you are suddenly aware that you did something because of pain. MY habit was to push my tongue down against the bottom teeth - If I was tweaking alone or silently the next day I would have a pressure blister on the tip of my tongue. The secondary cause is dehydration. Using a speed based drug dries you out in two ways: 1. It speeds up your body causing everything in your body to go faster, heart rate, blood flow - this generates heat - heat is dissipated all the time via water vapor (not to be confused with "sweating". The human body leaks a constant plume of water vapor - even if it is ten below and you are freezing. Speed up the body and the amount of water vapor your release increases. 2. Because most often you ARE sweating on top of that. 3. And because you are not drinking enough fluids. "cures" for this issue would be: 1. Stop using (Duh). 2. Do something oral, like I don't know - talk while high. Yeah I know its insane to talk to yourself, but hey its insane to purposefully ingest known toxins for recreational purposes too. The idea is to keep your tongue moving so you are not pressing it against the roof of your mouth. --> In the Day of Raves pacifiers and "suckable" items in the mouth was common - this was partially to offset the tongue in the roof of the mouth issue. 3. Prior to using hydrate with something along the lines of gaterade (With electrolytes and salts) this will boost your body's H2Olevels and will also give you much needed trace elements which you are sweating away. 4. When on the drug try to drink more fluids - Ah No - no alcohol or coffee, I'm talking about non-caffinated (means no soda too) fluids apple juice, gater ade, weak herbal tea with low sugar content. 5. as your coming down seriously hydrate. Also check what you are doing when you are amped up. Sex (or masturbation) burns a lot more energy with all the grinding and movement. It also burns up more water. Dancing does the same. so do other activities which you would normally stop in a short period of time but when amped up you keep going and going and going. Taking breaks from the session (if you can break away) may help in the long run not only for you mouth but for other things as well.