No, you won't need a mouthguard. It is bumpy, but there are bars to hold onto so it doesn't throw you around.
It is very very loud though. Granted, not as loud as when it first opened - I heard that they lightened up the ride a little after the move Dinosaur came out since so many kids would want to ride & see the characters from the movie. I agree, it doesn't seem as intense as the first year it opened, but still loud enough that you may instinctivly cover your ears at some portions.