I’ve heard it said that any field of study that has the word “science” in its name is not actually a science. It seems to be true. Consider: Creation Science, Political Science, Forensic Science, Computer Science…
The question varies by location, among other things because there are locations (such as the US) where dentistry is separate from medicine and others (such as Spain) where it is a medical specialty. Some of the details mentioned in the OP’s cites are US-specific (visiting the dentist twice a year, for example) and directly linked to the for-profit nature of the profession.
In Spain and even though most of our dentistry is private practices, I’d say dentistry is exactly as much of a science as any other branch of medicine. But that applies to places where dentists need to be medical school graduates; it doesn’t follow in places where dentistry is not a branch of medicine. Regarding the for-profit aspect, one reason Spanish dentists with personal practices are better than group clinics is that the individual doctor is looking to make enough to feed his family, not to buy the kind of car that breaks the top of police radars; the group practices are exploitative of both their employees and of their patients (a lot pushier on cosmetic procedures and on more-expensive options) because they are more focused on profit, less on getting and keeping people healthy.