Atypical Odontalgia (AO) is a condition characterized by tooth pain with no apparent cause. Although psychiatric comorbidity seems to be very common, it has rarely been studied. To clarify the influence of psychiatric comorbidity on the clinical features in patients with AO, we retrospectively evaluated their examination records. Clinical features and psychiatric diagnoses of 383 patients with AO were investigated by reviewing patients' medical records and referral letters. Psychiatric diagnoses were categorized according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). We also analyzed visual analogue scale (VAS), self-rating depression scale (SDS), and the short-form McGill pain questionnaire (SF-MPQ) scores. Of the 383 patients with AO, 177 (46.2%) had comorbid psychiatric disorders. The most common were depressive disorders (15.4%) and anxiety disorders (10.1%). Serious psychotic disorders such as bipolar disorder (3.0%) and schizophrenia (1.8%) were rare. Dental trigger of AO was reported in 217 (56.7%) patients. There were no significant correlations between psychiatric comorbidities and most of the demographic features. Higher VAS and SDS scores, higher frequency of sleep disturbance, and higher ratings of "Fearful" and "Punishing-cruel" descriptors of the SF-MPQ were found in patients with psychiatric comorbidity. About half of AO patients had comorbid psychiatric disorders. Dental procedures are not necessarily causative factors of AO. In AO patients with comorbid psychiatric disorders, pain might have a larger emotional component than a sensory one. VAS, SDS, and SF-MPQ scores might aid in the noticing of underlying comorbid psychiatric disorders in AO patients.

Cenesthopathy is characterized by abnormal and strange bodily sensations and is classified as a ‘delusional disorder, somatic type’ or ‘somatoform disorder’ according to the DSM 5. The oral cavity is one of the frequent sites of cenesthopathy, thus the term ‘oral cenesthopathy.’ Patients with oral cenesthopathy complain of unusual sensations without corresponding abnormal findings in the oral area, such as excessive mucus secretion, a slimy sensation, or a feeling of coils or wires being present within the oral region. They usually visit multiple dentists rather than psychiatrists. Without a proper diagnosis, they repeatedly pursue unnecessary surgical procedures to remove their ‘foreign body’. This sometimes creates a dilemma between the dentists and patients. The nosography of oral cenesthopathy has been discussed in some case reports and reviews but is overlooked in mainstream medicine. This review focuses on the various aspects of oral cenesthopathy. The estimated prevalence of cenesthopathy was 0.2 to 1.9 % in a study done at a Japanese university psychiatry clinic and 27 % in a study done at a Japanese psychosomatic dentistry clinic. Oral cenesthopathy do not have clear disposition, while some studies reported that elderly women were most commonly affected. Its pathophysiology has not been fully elucidated. However, recent studies have suggested a right > left asymmetrical pattern of the cerebral blood flow of patients with oral cenesthopathy. Antidepressants, antipsychotic drugs, electroconvulsive therapy, and psychotherapy might be effective in some cases, though it is known to be intractable. To date, the epidemiology, pathophysiology, etiology, classification and treatment of oral cenesthopathy are unknown due to the few reports on the disorder, though there are a few case reports. To overcome this difficult medical condition, clinico-statistical and case–control studies done under rigorous criteria and with a large sample size are required.

Phantom bite syndrome (PBS) is characterized by a persistent uncomfortable sensation of occlusion without an evident occlusal discrepancy. The aims of this retrospective cross-sectional study were to assess psychiatric comorbidities and evaluate psychopharmacological outcomes of PBS. The database of the Psychosomatic Dentistry Clinic of Tokyo Medical and Dental University Dental Hospital was reviewed for cases of PBS diagnosed between April 2009 and March 2012. Clinical Global Impression indices were used to assess psychopharmacological outcomes. The review revealed 130 patients (107 women, 23 men) with a mean age of 53.0 ±13.1 years. They previously visited 4.4 ±3.4 dental clinicsand had a mean symptom duration of 5.3 ±5.4 years. Only 24 (18.5%) of 63 (48.5%) patients with psychiatric comorbidities had schizophrenia, major depressive disorder, or bipolar disorder. The frequency of psychiatric comorbidities was significantly lower in PBS with a dental trigger than that without a specific trigger. Moreover, patients without a psychiatric comorbidity showed significantly better outcomes than those with a psychiatric comorbidity. Forty patients (30.8%) showed remarkable clinical improvement after receiving amitriptyline, mirtazapine, or aripiprazole. PBS is generally not associated with severe psychiatric disorders. Absence of a dental trigger predicts a psychiatric comorbidity, which affects the psychopharmacological outcome. Antidepressant or antipsychotic therapy may be effective for symptom management in PBS.

Objective: Oral cenesthopathy is characterized by foreign body sensations without medical and dental evidence for them. It is thought to be a rare disease in psychiatry, but many patients are visiting dental clinics seeking treatment to remove a foreign body. Even though the features of oral cenesthopathy might be different between a psychiatric clinic and a dental clinic, there has been no clinico-statistical study from dentists. In this study, we report a clinico-statistical study of patients with oral cenesthopathy in dentistry. Methods: This is a retrospective chart review of 606 outpatients with oral cenesthopathy in Tokyo Medical and Dental University from April 2010 through to March 2015. Results: A total of 159 male and 447 female patients were included in this study. The mean age was 62.08 years, and female patients were older than male patients. The trigger of the dental treatment and the acute phase of depression at the onset were significantly related (p=0.037). Only 128 patients (36%) had clinically significant improvement after 6 months of pharmacotherapy. No history of psychiatric disorders (odds ratio [OR] 0.479 [95% confidence interval {CI}: 0.262–0.875], p=0.017) and longer duration of illness (>18 months) (OR 2.626 [95% CI: 1.437–4.799], p=0.002) were significant factors for clinical outcomes. Conclusion: Patients with oral cenesthopathy in our clinic were predominantly elderly female patients. Dental treatment in the acute phase of depression might be a risk factor for oral cenesthopathy. Therefore, comprehending the situation of psychiatric disorder and obtaining adequate informed consent might be required to prevent the trouble concerning oral cenesthopathy.

The concept of cenesthopathy was first introduced by Dupré and Camus in 1907 to describe clinically unexplainable bodily sensations mainly attributed to psychiatric pathology. If it occurs in oral regions, it is termed oral cenesthopathy and it has been of special interest to psychiatrists and dentists. While there is no independently defined criteria for this condition, which is classified as either a delusional or a somatoform disorder, clinical practice and research require a standard scale to measure and rate its symptoms. In this study, we included any types of psychosomatic symptoms in oral regions as oral dysesthesia, and developed an Oral Dysesthesia Rating Scale (Oral DRS) and evaluated its validity and reliability as an assessment tool. The scale was developed based on literature review and extensive clinical experience. Twelve reviewers assessed relevancy of each item to oral dysesthesia symptoms by 1–4 scoring scale and item content validity index was computed. To evaluate the inter-rater reliability of Oral DRS, pairs of raters administered the scale to 40 randomly selected patients with complaints of oral dysesthesia symptoms and Cohen’s weighted kappa coefficient was determined for each item. The scale assesses the severity of feelings of foreign body [A1], exudation [A2], squeezing-pulling [A3], movement [A4], misalignment [A5], pain [A6], and spontaneous thermal sensation or tastes [A7], and the degree of impairment in eating [B1], articulation [B2], work [B3], and social activities [B4] on a scale of 0–5. Items A1, A2, A3, A4, B3, and B4 demonstrated acceptable content validity. Inter-rater reliabilities were good or excellent for all items evaluated. The Oral DRS can help define the nosography of clinically unexplainable oral dysesthesia through further case evaluation and clinical research and facilitate devising of treatment modalities.

Oral cenesthopathy is a somatic delusion or hallucination involving the oral area and is categorized as a delusional disorder, somatic type. The pathophysiology of this intractable condition remains obscure. In this study, we clarified the pathophysiology of oral cenesthopathy by evaluating regional brain perfusion. We performed single photon emission computed tomography (SPECT) using ^99mTc-ethylcysteinate dimer in 16 subjects (cenesthopathy:control = 8:8). The SPECT images were visually assessed qualitatively, and quantitative analyses were also performed using a three-dimensional stereotactic region-of-interest template. The visual assessment revealed a right > left perfusion asymmetry in broad areas of the brain among the patients. The quantitative analysis confirmed that the regional cerebral blood flow values on the right side were significantly larger than those on the left side for most areas of the brain in the patients. A comparison of the R/(R + L) ratios in both groups confirmed the significant brain perfusion asymmetry between the two sides in the callosomarginal, precentral, and temporal regions in the patients. Qualitative evaluation of the SPECT images revealed right > left brain perfusion asymmetry in broad regions of the brain. Moreover, the quantitative analyses confirmed the perfusion asymmetry between the two sides in the frontal and temporal areas. Those may provide the key for elucidation of the pathophysiology of oral cenesthopathy.