If you chew gum it won't get any worse. If you don't chew, nothing bad will happen. Come to the clinic, go to the toilet, rinse your mouth and that will be enough. tell your dentist that you have bad breath, he will tell you the reasons for this smell. A dentist has seen different teeth during his career and it is very difficult to surprise him with something.
It is better to brush your teeth and tongue before going to the dentist, chewing gum does not remove plaque from the teeth. But if you have bad breath even after brushing your teeth, then, of course, you need chewing gum.
Of course it is. It's no secret that bad breath is not the most attractive thing. And when you are with a stoiatrist, you will have to keep your mouth open most of the time.
This is a sign of respect for the dentist.