Orofacial Pain and Sleep Barry J. Sessle, Kazunori Adachi, Dongyuan Yao, Yoshitaka Suzuki, and Gilles J. Lavigne Abstract This chapter provides an overview of orofacial pain and its underlying mechanisms, as well as sleep and the mechanisms that underlie sleep. It particularly focuses on the clinical features and the processes involved in the interactions between pain and sleep. The chapter outlines the many insights that have been gained from clinical investigations, as well as experimental studies in humans and laboratory animals, of the pathways and processes involved in oro- facial pain and its modulation, as well as the circuits and mechanisms underlying sleep. Some common elements in the pain and sleep processes are highlighted. In addition, the chapter notes that acute pain is part of a protective hypervigilance system that provides an alarm essential in response to injury or potential injury. This chapter also reviews findings indicating that pain, especially when chronic, is commonly associated with dis- turbed sleep, and that there may exist a circular relationship between them that is reflected in mutual deleterious influences producing fur- ther enhancement of both pain and disruption of sleep. The evidence reviewed suggests that therapeutic approaches need to be targeted at both reducing the pain and improving sleep for the effective management of the orofacial pain patient. Such dual targeting will enhance the patient’s quality of life, minimize mood alter- ations or exacerbations of a sleep disorder negatively impacting the patient’s pain, and ultimately optimize healing and the patient’s health. B.J. Sessle (*) Faculty of Dentistry and Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada e-mail: barry.sessle@utoronto.ca; Barry.Sessle@dentistry. utoronto.ca K. Adachi Division of Pharmacology, Meikai University School of Dentistry, Saitama, Japan e-mail: k-adachi@dent.meikai.ac.jp D. Yao Jiangxi Mental Hospital and School of Pharmaceutical Science, Nanchang University, Nanchang, Jiangxi, China e-mail: a.yao@utoronto.ca Y. Suzuki Facultés de médecine dentaire et de médecine, Université de Montréal, Montreal, QC, Canada Department of Stomatognathic Function and Occlusal Reconstruction, Tokushima University Graduate School, Tokushima, Japan e-mail: yosuzuki@tokushima-u.ac.jp G.J. Lavigne Facultés de médecine dentaire et de médecine, Université de Montréal, Montreal, QC, Canada Centre for Advanced Research in Sleep Medicine & Trauma Unit, Surgery Department, Hôpital du Sacré-Cœur de Montréal, Montreal, QC, Canada e-mail: gilles.lavigne@umontreal.ca # Springer International Publishing AG 2017 C.S. Farah et al. (eds.), Contemporary Oral Medicine, DOI 10.1007/978-3-319-28100-1_40-1 1