People are using them here, a friend’s 83 yr old Dad had his first root canal, instead of having his tooth pulled.
This part of the implementation is turning out to be something of a clusterfuck. Dentists aren’t necessarily reluctant to enroll on principle, but apparently many feel that they just don’t have enough information about how the system is supposed to work. I think that UHC had some hiccups in its early stages, too, though AFAIK that was mostly related to late payments by what were then third-party insurance companies acting as payment processors. Today the provincial governments process payments directly and pay electronically.