From a dentist's perspective: a few decades ago the practice model changed from charging your fee, accepting what insurance paid, and billing the patient for the balance, to agreeing to "participate" (PPO) in the plan and accepting the insurance fee as full payment, regardless of what that fee may be.
Dentists who felt their practices weren't growing as fast as they'd like agreed to participate. Over the years more and more dentists bought in, and now the dentist who is not a participant in some plan or another is a rarity.
As the big INSCOs' (MetLife, Travelers, Delta, United Healthcare come to mind) networks grow, and dental schools keep pumping out more and more desperate young grads with 300K-500K in school loans, they have been able to actually reduce re-imbursements to the providers.
Some plans are so bad, from the dentist's perspective that only the most desperate will accept them. You may draw your own conclusions as to how such desperation, and willingness to accept a re-imbursement that the majority of the profession would not agree to, may effect final outcomes.
More and more plans are approaching that threshold. To the INSCO's benefit however, the dental schools are supplying more and more desperate dentists every year, so the tendency is for these plans to be serviced by younger, desperate, less experienced dentists, with huge loans to pay off. Most often these are large facilities where the emphasis is on volume, rather than successful outcomes.
If you are covered under a plan where the dentist has agreed to accept a negotiated rate, be advised that it is highly likely that the owners of the facility know exactly what procedures are most profitable, least profitable, or simply not profitable at all, and to some extent (maybe a lot, maybe not so much) your treatment is being steered by the fee schedule, as opposed to what may or may not be your best dental options based upon your oral condition.