Comprises Associate Specialist, Staff Grade, Specialist Registrar, Senior House Officer, Dental Advisor, Hospital Practitioner and GDP (para 107 appointment).4. Some NHS General Dental Services practitioners provide orthodontic treatment only.These dentists are known as NHS General Dental Services orthodontic practitioners.All NHS General Dental Services practitioners, which included NHS General Dental Services orthodontic practitioner, enter into a contract with their local Primary Care Trust (PCT) or Island NHS Board (HB).5.