Dentists in BC take assignment.  It makes A/R a lot easier.  I don't quite get what you're saying about "those controlling the doctor/patient relationship."  Insurance companies have limits, but that's not so much the doctor/patient relationship as the employer/employee relationship.  If employees want better benefits through their employer sponsored dental plan, they need to bring it up with their employer, or be prepared to pay for what's needed but not covered.  There is an issue with extra-billing, and all I can say about that is if your dentist extra-bills, consider switching dentists.  
Dentists need to get paid for the work they do, so if a patient isn't willing or can't go beyond what is covered by insurance, they won't. Dental practices in BC need to be controlled by a dentist.  I'm the spouse of a dentist.  I couldn't open a practice and hire dentists to work there.