Since you are dual eligible there are Medicare Advantage plans specifically designed for people on both Medicare and Medicaid and some have dental included. Any premium and co-pay for those plans will be paid for by Medicaid as long as you are QMB and receiving full Medicaid benefits. If you are receiving partial Medicaid benefits you'll have a small premium and/or co-pay. What plans are available to you will depend upon your location and are not available in all counties.

You have an SEP all year because you also have Medicaid and can change plans at any time and as often as you wish.

An Advantage plan will have doctor restrictions. What those restrictions are depends upon the plan option. Those options are HMO, PPO, HMO/POS, PFFS, SNP, MSA, DUAL, Cost, and PACE plans. These plans can be county specific so what is available depends on your county. Some of these plans have drug coverage while others don't. Of those that do not have drug coverage some will allow you to get a separate stand alone drug plan while others won't, and you'll need to know which do and which don't. The premium is generally much less, with many having a $0 premium in many counties.

You and your mom will need to contact a local agent that works with all of the major companies and with both types in her area. The agent can take the time to explain the differences and can find out which plan is best for her budget and situation. There is no charge using an agent.

If you have a Medicare Supplement you can go to any provider that accepts Medicare. With a Supplement the provider first bills Medicare. After Medicare pays most of those providers will bill your Supplement. If the provider chooses not to bill the Supplement you can send the bills off to the insurance company and get payment for what Medicare doesn't pay.

With a Medicare Advantage plan there will be doctor restrictions, and those restrictions will depend upon the type of Medicare plan you have. There are HMO, HMO/POS, PPO, PFFS, SNP, MSA, DUAL, PACE, and Cost plans.

With an HMO you can only go to a doctor in the network.
With and HMO/POS you may go outside of the network with restrictions and approval.
With a PPO there is a doctor network but you can go to a doctor that is not in the network in most cases although your costs will be higher.

PFFS plans come in two flavors – one with a doctor network and one without a doctor network. You can generally go to any doctor that is willing to accept the plan. The doctor can accept the plan today and not accept it tomorrow. They can accept it from you but not accept it from your spouse. Congress really screwed these plans so if you are considering one of these types make sure your agent explains the difficulties fully.

SNP and DUAL plans can be either HMO or PPO.
MSA plans allow you to see any doctor willing to accept the plan and they have a savings account tied to them, similar to the HSA plans except that Medicare funds the account.
PACE and Cost plans are few and far between but do have doctor restrictions.

With an Advantage plan the provider only bills the insurance company.