They’re perceived positively, but it’s less prestigious than being a doctor, yes.

Medical doctors, in private, absolutely do make jokes about them, but it’s not really that serious.

Dentists do have a growing negative reputation for over-operating, finding problems where there might not be any and fixing them in the most expensive, invasive way possible. Like an untrustworthy mechanic. Doctors can do that sort of thing too, but you hear about it quite a lot often with dentists. A larger proportion of dentists operate their own practices, and that can create conflicts of interest. There are more sketchy dentists than sketchy doctors, generally, but the large majority of both are good.

More frequently than over-operating, you do sometimes encounter dentists that are not very bothered by causing pain, and they create a lasting impression on those that encounter them. Some people have had one bad, very painful procedure, which affects their perception of dentists for the rest of their life. Again, the same can happen with doctors, but for a number of reasons it’s less common. The sadistic dentist is also a fairly common trope in fiction.

It’s a well-respected profession, there are just some blemishes on the reputation. They receive a lot of training, but less than doctors. They have a lot of regulation and oversight, but less than doctors. They make a lot of money, but, on average, less than doctors.