I'll give you a more neutral reason why dentists earn more.
1) When we graduate we require one more year of training to be fully qualified and self sufficient. Medicine is different. A medicine graduate can't practice unsupervised (foundation/core years etc)
2) Dentists are responsible for decontamination of their instruments. This includes the design, purchase, maintenance and operation of their local decontamination unit. Doctors have no responsibility for this (normally everything is single use OR carted away to a central sterilization department)
3) Dentists have a managerial role in that they employ staff from their wage. A dental nurses wage is paid for by the dentist employing her, even as a partner in a practice.
4) Danger money - operating a drill rotating at 500000 rpm for the majority of your day is probably going to be more dangerous than a lot of medical undertakings in your average day. All dental procedures carry a lot of risk for patient and dentist. If you think about it, all dentistry procedures are classed as at least 'semi-critical' in terms of risk of cross infection, so a dentist with a BBV would be out of work, but a doctor could still practice. This reflects both the nature of the work, how high the risk of cross infection is (and thus loss of livelihood). Doctors by nature think more, and dentists 'do' more. As in, get their hands really dirty all day. It's not every day that a general doctor (if we're also talking about general dental practitioners) will have a flap raised, taking a bur to a bone.
5) It's different in England now (not in Scotland) but the NHS pay scheme for a dentist here dictates that if you do a filling you get x amount. It's not
really salaried as such. It depends on how much work you do. NHS dentists normally see around 30-35 patients a day. Not easy.
6) Plus, the NHS really need us! Why else would they have paid me £16k as an undergrad to agree to do NHS work for 5 years
You can charge £1k for a bridge private if you're good enough. You set your fees. Most dentists don't do private, that's a lot of ****. Most dentists do NHS then do private where the NHS restricts them. i.e. a white filling on a back tooth is not allowed.
This is NOT a doctors vs dentists thing. The jobs could not be more different. And that's why they're paid differently, because they aren't different. Any budding young doctors should realise that you need dentists to sign off that patients are ok to go ahead with treatments such as chemo or bisphosphonates. And any young dentists should realise they need doctors to check INRs, liver function etc to go ahead with extractions and many other areas. You're both healthcare professionals, and you both need each other, no one 'works harder' than the other.