It seems they stumbled over the soluti "If dentists choose not to sign up, the local NHS will use that funding to buy services from other dentists."
At last they have it! Deregulate dentists in the same way they did optitions. Provide some form of funding voucher system so that you can get basic level care from most dentists for free, and you then have the option to add your own money to it if you are able to, and want to, for either more pampering or cosmetic work etc.