As long as it is integrated well and fits a theme. Some games will just use assets taken from all over the place so the experience and immersion is jarring.
Depends on the dentist. If you have a bad dentist, your experience will be bad and you won't want to go again and your trust in them will be broken. A good dentist will make your visit comfortable and try to reduce your discomfort as much as possible, plus they won't try to just sell you on...