Not sure that is the case. The base science and recommended practices seems pretty much as a solid as any other speciality (imperfect as they all are). It really is the case that cavities are bad. We understand what causes them, how they grow, risk factors and how to treat them.

But ... the business model and incentives are different. A general practice MD, doesn't get a cut of revenue when they write a prescription. The incentives are closer to a plastic surgeons. And you can see similar lapses of ethics in that field.

MDs most definitely have incentives to intervene as much as possible.

See https://en.wikipedia.org/wiki/Relative_value_unit

If you ever wonder why some doctors order any test they can possibly, even remotely, justify, this is why.