Never. I don't wear it playing hockey, why the fuck would I wear it for grappling? lol
I personally hate fuckers that wear cups for rolling. Suck it up nancy.
I dont use a mouthpiece, I find them uncomfortable. But I've bitten my tongue a few times for it
I also don't wear a cup, that ruins the "feeling"
I wear one because of a loose front tooth.
When I didn't wear one with the tooth I wouldn't be as explosive or risky because I didn't want to take a blow to the mouth and possibly have my tooth knocked out.
Now with the mouthguard there is no fear/mental block to stop me. 
Always. Every once in awhile I tap from the grind of my teeth alone from some crank or other. With a mouthpiece I can ride it out and escape. Protection and the above is why I always use one.
PR - I personally hate fuckers that wear cups for rolling. Suck it up nancy.
I've heard guys complain because their training partner ISN'T wearing a cup. Saying shit like, "I don't want your balls all over me dude."
FightMeI'mIrish -PR - I personally hate fuckers that wear cups for rolling. Suck it up nancy.
I've heard guys complain because their training partner ISN'T wearing a cup. Saying shit like, "I don't want your balls all over me dude."
Reverse psychology IMO.
I used to wear one more to protect my gums than my teeth. I know they're not designed to protect gums but I felt I didn't get my gums tore up as much while wearing one.
On a side note, you know that little web piece of skin in front and above your front two teeth? I had that split/torn before while defending a rnc. That's why I used to wear a mouth piece. Not sure it would have prevented this but it feels much safer.
Cyril Jeff -
one stray elbow will probably persuade you to wear one, almost got my teeth knocked out during a "flow roll", yeah...
A friend of mine knocked out his own tooth going for a double and ate a knee. Spent hundreds at the dentist along with a brown tooth that died. Had a custom fit mouth guard in his bag, decided not to wear it as it was a light day. Moral of the story wear a mouth guard, and I yours is making you gag invest in a custom one.
stray elbows biting touch etc.
I don't wear a cup or mouth piece for BJJ or Judo because I've never felt the need. I've been hit in the nuts before and when I get choked it's sometimes annoying that my teeth are grinding/pressing together in a way which is extremely uncomfortable. I understand the mouth-piece logic, I just don't wear one because I think people will be all "Oh my God are you wearing a mouthguard dude? Are you fighting in the UFC today or are you just a fag?" but I don't really get the cup thing for grappling. Are you guys grabbing each other's nuts or something? Getting hit in the balls happens but you can walk it off. I don't wear a cup whilst cycling or skareboarding and I've hit my nuts doing both of those.
I went to the dentist before I started BJJ and my teeth were fine. 2 years after starting BJJ my dentist said I had 3 teeth that are cracked. They are sort of split up the middle. It doesn't go to the root though so he said they should be OK. I had a buddy that had one of his molars split while someone was RNC'ing him. He had to have that tooth pulled.
I wear one all the time now. When someone is trying to pass your half guard by using shoulder pressure on your chin/jaw you can feel your teeth smashing together. When you are trying to defend chokes the same happens. Even though you aren't getting hit, your teeth can crack and split from pressure.
Ninja Tea Party - I don't wear a cup or mouth piece for BJJ or Judo because I've never felt the need. I've been hit in the nuts before and when I get choked it's sometimes annoying that my teeth are grinding/pressing together in a way which is extremely uncomfortable. I understand the mouth-piece logic, I just don't wear one because I think people will be all "Oh my God are you wearing a mouthguard dude? Are you fighting in the UFC today or are you just a fag?" but I don't really get the cup thing for grappling. Are you guys grabbing each other's nuts or something? Getting hit in the balls happens but you can walk it off. I don't wear a cup whilst cycling or skareboarding and I've hit my nuts doing both of those.
Wear a mouth piece to protect from knees, elbows, headbutts. Just takes one shot to jack your grill.
Have you never heard of the knee grind on balls guard pass?
why not wear it? it will save your teeth just incase. get a customguard and you won't even know it is in there
I always wear a cup and mouthpiece when rolling. If you fight, you should wear them because you have to when you fight. The cost is minimal compared to dental work or a trip to the urologist, and accidents do happen. 
Josh J - I went to the dentist before I started BJJ and my teeth were fine. 2 years after starting BJJ my dentist said I had 3 teeth that are cracked. They are sort of split up the middle. It doesn't go to the root though so he said they should be OK. I had a buddy that had one of his molars split while someone was RNC'ing him. He had to have that tooth pulled.
I wear one all the time now. When someone is trying to pass your half guard by using shoulder pressure on your chin/jaw you can feel your teeth smashing together. When you are trying to defend chokes the same happens. Even though you aren't getting hit, your teeth can crack and split from pressure.
Mouthguard also helps when you get your head stuck underneath big people.
I've done BJJ since about '96. And have never wore a mouthpiece or a cup, in practice or competition. No fucking lie. I just never could.
I don't wear a cup, even though I've had two nut injuries. One required me to go to the ER. You'd think I'd learn. I wear a mouthpiece religiously, but no cup.
The question is simple :
Do you want to protect your teeth or not ?
Wearing one makes no difference to grappling itself.
i never did but its a good idea. 1 freak accident and u can lose a tooth
I think I should chime in here,
1) a dental injury to your teeth is a permanent injury teeth don't heal
2) more injuries happen during training / practice than game / tournaments.
3)The cost over time of an injured tooth is well into the thousands The Academy Of Sports Dentistry estimates it at 20 thousand per tooth.
4) A custom mouthguard designed for BJJ from us at Gladiator Mouthguards is only $68 with shipping included
5)With a properly designed mouthguard you should experience no discomfort with breathing or speech in fact after a short amount of time you should forget its there.