grinding teeth

Question
my 11wk old bull terrier cross is often grinding her teeth and      while she,s sleeping her legs will start twitching..should i be worried

Answer
I would not be worried about the twitching legs, as that is a sign that the dog is in REM sleep - she's probably dreaming about chasing rabbits or some other doggy pleasure.  The teeth gnashing probably isn't a problem either, but if it makes you feel better, double check with your veterinarian, who can examine your dog individually to make sure.
At 11 weeks, this is a great time to enroll her in puppy kindergarten, too.  She needs to socialize with other dogs and new people every day.  Doing so will make her generally more relaxed, and she may have sweeter dreams;-))  Hope I've reassured you.