This has not been the case in my experience. Dentists have always told me exactly how much I owe them, and the one time I forgot a payment, they called me and texted me to let me know and I resolved it in a matter of minutes.
Meanwhile a hospital visit sent me a bunch of bills in the mail ranging from $50 to $100, they refused to tell me the total sum even when I visited in person, and when I missed one $50 payment I was sent to collections a year later.
Perhaps they were referring to the idea that dental "insurance" doesn't cover more than a set amount which is far under the price of most dental surgeries. It is only intended to cover preventative maintenance. As far as I am aware, there is no way to get actual insurance for teeth in the US, even via medical insurance.
This has not been the case in my experience. Dentists have always told me exactly how much I owe them, and the one time I forgot a payment, they called me and texted me to let me know and I resolved it in a matter of minutes.
Meanwhile a hospital visit sent me a bunch of bills in the mail ranging from $50 to $100, they refused to tell me the total sum even when I visited in person, and when I missed one $50 payment I was sent to collections a year later.