Late effects of orofacial trauma on the temporomandibular joint

Temporomandibular disorders (TMD) are a set of conditions characterized by pain and dysfunction in the temporomandibular joint and muscles of mastication. These pain conditions are associated with considerable morbidity, societal costs, and reduced quality of life. The prevalence varies between 4% and 10%, with females at higher risk, and a higher prevalence occurs during reproductive years. The increased prevalence of TMD in females and low prevalence in childhood reinforce that sex hormones, like estrogen, play an important, complex role in the pathophysiology of these disorders. The goal of this study was to determine whether women with TMD exhibit a monocytic hyperinflammatory response compared with control women, and to examine associations of monocytic inflammatory responses with clinical pain. Eighteen women, aged 18 to 35 y, were seen during their follicular menstrual phase. A blood sample was collected, a clinical questionnaire about pain history was administered, and a Research Diagnostic Criteria (RDC) exam was performed. Extracted monocytes were stimulated with the toll-like receptor (TLR)-4 ligand, lipopolysaccharide (LPS), in the presence and absence of estrogen, and the levels of IL6 expression evaluated. Women with TMD showed a systemic hyperinflammatory phenotype, 42 manifested by an increased monocytic release of cytokines after an inflammatory insult, and this was further increased by estrogen. In addition, monocytes from participants who self-reported more pain on the VAS scale produced higher levels of IL6 compared with those from participants who self-reported lower pain sensitivity. These data suggest that an estrogen-induced hyperinflammatory phenotype in women with TMD may at least in part contribute to heightened clinical pain, perhaps via central sensitization. J Dent Res.​ 2016 Sep;95(10):1084-92. doi: 10.1177/0022034516653743. Epub 2016 Jun 23. Painful Temporomandibular Disorder: Decade of Discovery from OPPERA Studies. Slade GD​1​, ​Ohrbach R​2​, ​Greenspan JD​3​, ​Fillingim RB​4​, ​Bair E​5​, ​Sanders AE​6​, ​Dubner R​ 7​, ​Diatchenko L​8​, ​Meloto CB​8​, ​Smith S​9​, ​Maixner W​9​. Author information 1 Center for Pain Research and Innovation, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Dental Ecology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA gary_slade@unc.edu. 2 Department of Oral Diagnostic Sciences, University at Buffalo, Buffalo, NY, USA. 3 Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA Brotman Facial Pain Clinic, University of Maryland School of Dentistry, Baltimore, MD, USA. 4 Department of Community Dentistry and Behavioral Science, University of Florida, Gainesville, FL, USA. 5 Center for Pain Research and Innovation, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Endodontics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Biostatistics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. 6 Center for Pain Research and Innovation, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Department of Dental Ecology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. 7 Department of Neural and Pain Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA. 8 The Allan Edwards Centre for Research on Pain, McGill University, Montreal, Canada. 9 Center for Translational Pain Medicine, Duke University, Durham, NC, USA. Abstract In 2006, the OPPERA project (Orofacial Pain: Prospective Evaluation and Risk Assessment) set out to identify risk factors for development of painful temporomandibular disorder (TMD). A decade later, this review summarizes its key findings. At 4 US study sites, OPPERA recruited and examined 3,258 community-based TMD-freeIn 2006, the OPPERA project (Orofacial Pain: Prospective Evaluation and Risk Assessment) set out to identify risk factors for development of painful temporomandibular disorder (TMD). A decade later, this review summarizes its key findings. At 4 US study sites, OPPERA recruited and examined 3,258 community-based TMD-free