Idiopathic orofacial pain often develops after dental/surgical treatment. However, there are some cases that develop without nociceptive stimuli. Although most cases show little or no discernable pathology, some patients develop disability and catastrophizing. Traditionally, the mechanisms of such idiopathic pain have been explained as neuropathic pain, dysfunction of the descending pain inhibitory system, or central sensitization. However, recent developments in neuroimaging studies have revealed that sensations of pain can be elicited without nociceptive input or tissue damage. More specifically, studies have shown that diverse non-nociceptive stimuli, such as unpleasant pictures/words or social exclusion, among others, can activate the so-called “pain matrix” and elicit sensations of pain. These findings might provide insights into the mechanisms of idiopathic orofacial pain.
We provide commentary on several theories advocated in the field of brain science, such as augmented central pain processing, neuromatrix, threat matrix, and the saliency hypothesis, and report following two example cases.
Case 1 involved a 74-year-old woman who developed excruciating facial pain after an oral surgeon casually suggested tongue cancer. She became totally disabled from pain; unable to eat or speak, and a gastrostomy tube was eventually placed 3 months after onset.
Case 2 involved an 81-year-old woman who developed severe pain in the left central incisor region just after undergoing implant surgery with 6 implants fixtures in the maxillary molar regions （three in each side）. Due to pain and feelings of general malaise, she became bedridden after 6 months.
Although these were fulminant cases, both patients became rapidly pain-free with administration of tricyclic antidepressants （amitriptyline）.

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Purpose: The trigeminal ganglion branches into three branches – the orbital, maxillary and mandibular nerves – with the peripheral ends distributing widely into the craniocervical region. Within the trigeminal ganglion, predilection in the localization of neurons can be observed, although the relationship between localization of these neurons and the region of innervation is unclear. In the present study, we visualized the neurons with neuronal marker ATF3 antibody (activating transcription factor 3 antibody) and comparatively examined the localization of these neurons.
Method: The rat trigeminal ganglion was extracted seven days after the administration of ATF3 (ATF3 expression is believed to peak after seven days) and the supraorbital, infraorbital, inferior alveolar, and lingual nerves were isolated, along with a control specimen in which no neurons were damaged. The specimens were sliced at a thickness of 100μm. The microscopic slides were stained with ATF3 antibody, NeuN antibody, which discriminately stains the nuclei of neurons, and DAPI antibody, which indiscriminately stains the nuclei of all cells. The stained slides were then observed under an optical microscope and sequential microscopic images were saved onto a hard drive and reconstructed three-dimensionally to recreate a 3D image of the trigeminal ganglion.
Result: The present study revealed that rat trigeminal ganglion consists of two parts; the first and the second branches comprising one, and the third branch sprouting outward from the first two branches comprising the second part. Likewise, the localization of neurons was evident in the rostral and caudal regions. These two regions of innervations were fused in the dorsal area and separated in the abdominal area. Examination of ATF3- and NeuN-positive neurons revealed that following the scission of the supraorbital nerve, the localization of ATF3 neurons were observed medially in the rostral region, whereas the localization of ATF3 neurons were observed throughout the entire rostral region following the scission of the infraorbital nerve. Following the scission of the inferior alveolar nerve, localization of ATF-positive neurons was mainly observed in the dorsal region, and scattered at the rostral-dorsal junction. Scission of the lingual nerve resulted in a similar pattern of localization as observed following the scission of the inferior alveolar nerve. Simultaneous scission of the infraorbital, inferior alveolar, and lingual nerves resulted in intermixed localization of ATF3-positive neurons, making the innervations of these nerves undistinguishable.
Conclusion: Theories exist that damaged neurons within the rat trigeminal ganglion which are adjacent to undamaged neurons transmit a form of neurotransmitter (yet to be identified in the current study) that may be responsible for the onset of ectopic allodynia. We believe that our present study will present an explanation for the mechanisms behind the onset of ectopic allodynia.

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There are several international scientific organizations that work on orofacial pain. Some are societies and some are groups formed in a society. These organizations have functionally cooperated and played important roles. Japanese Society of Orofacial Pain（JSOP）is closely associated with these organizations. International Association for the Study of Pain（IASP）is the largest and the oldest scientific society that deals with pain medicine. Significant Interest Group（SIG）on Orofacial Pain is a specific group consisted of researchers who are members of IASP and are interested in orofacial pain. International Association for Dental Research（IADR）Neuroscience Group（NeuG）is a group of dental researchers who are members of IADR and has formed the Research Diagnostic Criteria of Temporomanidibular Disorders Consortium（RDC/TMD consortium）with a collaboration of the SIG on Orofacial Pain. RDC/TMD consortium has published the Diagnostic Criteria of Temporomandibular Disorders（DC/TMD）in 2014, which is currently the standard of diagnosis of TMD. American Association of Orofacial Pain（AAOP）and Asian Academy of Craniomandibular Disorders（AACMD）constitute International Congress on Orofacial Pain and Temporonadibular Disorders（ICOT）with another sister academies. Scientific meetings of IASP and AACMD are simultaneously scheduled to be held in 2016 in Yokohama and the members of JSOP are strongly recommended to attend these meetings held in Japan to learn about both basic and up-to-date clinical topics of orofacial pain.（223 words）

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Orofacial Pain （OFP） involves dental and medical disorders. OFP disorders range from odontogenic pain, to neurovascular pain such as migraine and cluster headache, musculoskeletal pain such as temporomandibular disorders, neurogenic pain including neuralgias and neuropathies, and pain associated with psychogenic disorders, and the majority of these medical diseases are neurological headache diseases. To diagnose neurological disorders, neurologists perform a proper assessment of patients including history taking and neurological examination, and laboratory and radiological studies. OFP specialists must gain basic methods of neurological diagnosis and current knowledge of the basic and clinical science of major headache disorders, such as migraine, cluster headache and medication overuse headache. Pathophysiological changes of trigeminal nerves and central nervous system are found in patients with migraine and cluster headache. Functional imaging study reveals central sensitization, dysfunction of pain control systems, and pain matrix changes. Chronic pain should be considered a brain disease in which alterations in neural networks affect multiple aspects of brain function, structure and chemistry. Medication overuse headache is associated with reversible functional changes in pain processing structures, but also with persistent orbitofrontal hypofunction after treatment. Pathophysiological changes of central nervous system and persistent hypofunction may occur in chronic OFP. OFP specialists should consider to these pathophysiological changes when to treat patients with intractable OFP. The best way to gain a current medical knowledge of headache disorders for OPF specialists is to join the Japanese Headache Society.

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In order to understand the cognitive aspects of chronic orofacial pain patients, this education lecture describes about poor pharmacotherapeutic prognosis of painful posttraumatic trigeminal neuropathy, meta-analysis of brain imaging studies which revealed functional or structural changes in the brain of the chronic orofacial pain patients, and the recent review in complementary medicine intervention in the emotional and cognitive aspects of chronic pain patients that may be effective for pain relief. By integrating recent scientific advances in chronic pain, future direction of the chronic pain patient management was proposed.
To manage chronic orofacial pain "patients", pain clinician must be familiar with sensory, emotional, and cognitive aspects of pain. Thorough medical interview and the use of questionnaires may be adding insight to understand chronic pain patients. Recent clinical study showed that pharmacotherapeutic prognosis of "patients" with painful posttraumatic trigeminal neuropathy may not be effective, and pointed out the limited number of drugs available, their limited efficacy and side-effect profile. Most chronic pain conditions can be referred to as a “centralization of pain”, which may be explained by functional, structural, or chemical changes of brain. Brain neuroimaging has diagnostic potential to understanding chronic orofacial pain patients. The intervention in the cognitive aspects of chronic pain "patients" of complementary medicine such as cognitive behavioral therapy may be effective; therefore, it is necessary for orofacial pain dentists to consider not only pharmacotherapy in combination with bio-psychosocial approach, also multidisciplinary management with other specialists such as neurologist and/or psychiatrist.

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When examining the patient who feels the pain with the not certain cause, a mental problem will be considered. The grade of the body symptom in which a mental problem participates, the correspondence and the treatment are difficult. It's effective to think which degree pain existence of the body symptom and the view can explain multilaterally to distinguish and investigate. I think it's useful to utilize a case conference and share a gauge. A check name as “Somatic Symptom Disorder” appeared on revised DSM-5 in June, 2013 as a mental disorder related to the pain. Additionally as the spirit disease which should be considered, Schizophrenia Spectrum Disorders, Cenesthopathy and a Depression, it's mentioned. The painful correspondence in which a mental problem participates seems to become little trouble when it's made a judgment with chief complaint and correspondence. A liaison is important to be necessary but not to be made. An assessment of the validity of the operating correspondence, orderly Informed-Consent and the medical treatment which doesn't become one-sided in a press are important about a liaison. The doctor who examines the body symptom first has heavy responsibility about the explanation of an examined result. To influence an after treatment relation, he should pay attention to make the explanation scarce in a basis and the guarantee easy.

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