Network dentist is answer to last question. The dental benefit is not that great but better than nothing. As to the first question, there are a number of Medicare Advantage plans with no "additional" premium. You continue to pay the regular medicare premium of $115/mo. Medicare sends that amount plus a subsidy to the company offering the Advantage plan. Once you sign up for the Advantage plan, you no longer have any ties to Medicare. The Advantage plan takes care of everything. You can reverse that or go to a different Advantage plan every year. I think a post just before "wolf" was asking about an Advantage plan with a supplement. Never heard of anything like that. Why would you want to. Generally speaking, if you have Medicare alone, you would be responsible for deductibles and copays because Medicare does not cover you 100%. Hence, the supplements from some company. When I was first retired, megacorp provided the supplement through Blue Cross/Blue Shield for a premium they took out of my pension check. There are many companies out there offering supplements.
Like I said, Medicare trenafers your $115/mo premium along with a subsidy to whatever insurance company advantage plan you choose. That subsidy allows the insurance company to offer many "advantages" over just plain Medicare. The competition between those insurance companies is fierce and they are banking huge profits. That is why there is a move afoot in this administration to reduce or eliminate those subsidies.
I mentioned earlier that you should go to
www.medicare.gov where you can review all the plans and make comparisons. Select two or three plans and then get into the details of those.
I disagree with TN__INVEST about not getting much coverage for zero premium. All Advantage plans must provide as much coverage as Medicare. They can't short change you there. You have to understand that the subsidy is everything to the company offering the
advantage plan. Under my Advantage plan, I get as much if not better coverage then I got with Medicare and a supplement and it's cheaper.