I suggest you have a read here and contact NHS direct to query this
http://www.nhs.uk/NHSEngland/AboutNHSservices/Pages/DentistsFAQs.aspx#q08 (http://www.nhs.uk/NHSEngland/AboutNHSservices/Pages/DentistsFAQs.aspx#q0

There are some phone numbers under the section " Am I entitled to free NHS dental treatment? " that may help clear this up
Hope this helps
Jon