It's simple, a dentist can accept a horse, cat dog for payment if he wants. Dentacoin is not illegal to use. The US considers it property you can invest in and have to pay taxes for. There is Disney dollars and Kohl's cash (My wife loves these!!) that have been used for years, same thing.
The positives for the Dental office or other medical office is they will have more customers not worried about being in network or not and won't be paying 3% credit card fees. Opens up a whole new demographic for them.