We  are proud  to present this  first edition of the

International Classification of Orofacial Pain (ICOP). There has, until now, been no comprehensive, inter-

nationally accepted classification that deals with orofacial pain. While, anatomically, the face is clearly part of the head, we have found far too many cases of misdiagnosis and resultant misdirected treatment that a clear diagnostic classification might have helped avoid. Anatomical boundaries, and associated medical specialty demarcations, contribute to the problem. For example, the International Headache Society (IHS) defines facial pain as ‘pain below the orbitomeatal line, anterior to the pinnae and above the neck’. Other definitions of facial pain additionally include the forehead, while the term ‘orofacial pain’ necessarily includes all the structures in the oral cavity. At the same time, headache is often referred to orofacial regions, and vice versa. ‘Headaches’ may be located exclusively within the orofacial region, and cause significant diagnostic difficulties, while orofacial pains that are referred to the head present complex clinical phenotypes.

These were some of the factors that made it clear to us that a classification of orofacial pains (OFPs) was needed. A fundamental principle in this first classifica- tion is that the characteristics of the disorders, not their location (head versus face), should guide the new conceptualization and diagnostic criteria.

While creating this first edition of ICOP, we were cognizant that the International Classification of Headache Disorders, 3rd edition (ICHD-3) thoroughly classifies primary and secondary headaches, and we refer the reader to this for these entities. Moreover, to make ICOP a useful tool for researchers and clinicians accustomed to using ICHD-3, we have adopted the hierarchical design and classification style of ICHD-3. The Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) is a well-tested and established classification that includes regional myalgias and temporomandibular joint (TMJ) pains. We have adopted the DC/TMD criteria, only including the pain- ful TMDs and modifying the presentation style of these criteria to that of ICHD-3. Overall, ICOP is also  aligned to the International Classification of Diseases 11th Revision (ICD-11)/International Association for the Study of Pain (IASP) criteria for orofacial pains and headaches.

The aim is therefore to create a tool that will  enhance the research and clinical management of orofacial pain. Additionally, we are confident that the methodology we have adopted will bring professionals working on head, orofacial, eye, nose, sinus and neck pain closer, and encourage active collaboration.

The members of the ICOP classification committee represent the major associations involved in orofacial and head pain, and are a truly international group, strengthening the future of ICOP. The  road to this first edition began in 2016, when we first met at the World Congress of the International Association for the Study of Pain (IASP) in Yokohama, Japan. In the one-day meeting, we discussed the structure of ICOP and established workgroups. A follow-up meeting in 2017 was held in Rutgers School of Dental Medicine, USA, where we examined the evidence, or lack of it, to establish the individual entities that now make up ICOP. The result is a classification backed in many areas by strong evidence and in others by expert opinion, which will encourage and guide research. It per- mits a period of testing, allowing identification and correction of mistakes and enabling  a broad input into ICOP from researchers and practitioners in the field.

Rafael Benoliel

Arne May Peter Svensson

Facial Pain Classification  Committee