Specialist dental services are scarce resources and are often oversubscribed. A key element is how these services relate to their referral base, in other words the interface between primary and secondary dental care. Dentistry has several unique qualities when compared with medicine and the nature of the interface between primary and secondary dental care is consequently very different to the medical interface, whilst apparently sharing common features. This paper examines the nature of that interface, the drivers for patient flow between services and outlines the properties of an ideal interface. This model can then be used as a way of describing some of the problems facing specialist dental services and of assessing any proposed solutions.