In 2011, the Institute of Medicine published a report documenting that at least 100 million U.S. adults-more than the number afflicted by heart disease, diabetes, and cancer combined-suffer from common chronic pain conditions that persist for ≥3 mo ("Relieving Pain in America: A Blueprint for Transforming Prevention, Care, Education, and Research,"). The national annual costs for this burden was estimated to be in the range of $600 billion in treatment costs and lost work productivity. The report stated that this enormous burden would require a "cultural transformation in the way pain is understood, assessed and treated."
Acute pain is a sensory and emotional experience that is protective by providing a warning signal that there is a threat to our health. It usually can be managed successfully. Chronic pain is more complex. It often persists even after the cause of the pain is identified and remedied. In some cases, it becomes a disease in itself, reflecting dysfunction in the nervous system.
Today, pain is a health problem that requires a broader perspective than in the past. Millions of Americans suffer from overlapping chronic pain conditions that share comorbid behavioral, physiologic, and psychological characteristics as well as genetic determinants. Many of these conditions affect the orofacial region uniquely or have accompanied widespread systemic manifestations. This includes temporomandibular disorders (TMD), headache, arthritis, and fibromyalgia, to name just a few. The majority of patients diagnosed with TMD are women, indicating that there is an important need to provide better understanding and treatment for a major population.
The recognition of the above issues and their importance to students, dental scientists, and practitioners led the Journal of Dental Research to announce the publication of a special issue in 2016 highlighting the latest developments in the field of chronic orofacial pain. This issue interfaced with the November 2015 Eighth AADR Fall Focused Symposium in Washington, DC, titled "Advances in the Biology and Management of Chronic Pain." Original research manuscripts and critical reviews were encouraged for submission and subject to the peer review process in a manner identical to other manuscripts submitted to the journal. Leaders in the field of pain research were chosen as reviewers, and I was pleased to accept the invitation to act as guest editor of this special issue. More than 75 manuscripts relevant to the field of orofacial pain were submitted for publication, and those included in this issue received the highest rankings irrespective of their specific subject matter. They are divided almost equally between reviews and original research reports.
TMDs are the major orofacial chronic pain condition and received considerable interest in manuscript submissions. The advances in this field can be found in review articles and original reports in this issue. They reveal important transformations in our understanding of these conditions that revolve around pain traits rather than localized inflammatory and pathologic changes in the temporomandibular joint or masticatory musculature. TMD is now considered a multidimensional biopsychosocial disorder that shares common features not only with other musculoskeletal conditions, such as fibromyalgia, low back pain, and headache, but with idiopathic inflammatory conditions, such as joint pain, irritable bowel syndrome, vulvodynia, and other somatic and visceral deep tissue injuries. Of interest is the common finding of widespread pain manifested outside the orofacial region and the presence of multiple comorbid persistent disorders in many patients. TMD is a complex systemic disease that has a genetic and immunologic basis. Furthermore, the pain involves changes in the nervous system, resulting in a mismatch between what is perceived and what pathology is actually observed at the peripheral target site. Proper diagnosis and treatment require collaborative efforts by dental and medical specialists. The Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) prospective study (Slade et al. 2016) identified risk factors in TMD-free adults by assessing genotypic and phenotypic measures of biological, psychosocial, clinical, and health status traits. The OPPERA model shown in the Figure displays 2 principal intermediate phenotypes (psychological distress and pain amplification) that contribute to the onset and persistence of TMD. Each phenotype represents a group of more specific risk factors that are subject to genetic regulation that take place in the presence of environmental contributions. As stated by the OPPERA group, "it is a misnomer and no longer appropriate to regard TMD as a localized orofacial pain condition." The Harper et al. (2016) review focuses on 1) TMD pain that is generated and maintained by mechanisms of sensitization in the central nervous system and 2) the need for personalized medicine to provide relief. The Ohrbach and Dworkin (2016) paper reviews the important development of a reliable and valid diagnostic system that has been critical in fostering TMD research over the past 2 decades.
Read complete article at: http://jdr.sagepub.com/content/95/10/1081.full.pdf+html