The tooth has an unusual sensory system that converts external stimuli predominantly into pain, yet its sensory afferents in teeth demonstrate cytochemical properties of non-nociceptive neurons. This review summarizes the recent knowledge underlying this paradoxical nociception, with a focus on the ion channels involved in tooth pain. The expression of temperature-sensitive ion channels has been extensively investigated because thermal stimulation often evokes tooth pain. However, temperature-sensitive ion channels cannot explain the sudden intense tooth pain evoked by innocuous temperatures or light air puffs, leading to the hydrodynamic theory emphasizing the microfluidic movement within the dentinal tubules for detection by mechanosensitive ion channels. Several mechanosensitive ion channels expressed in dental sensory systems have been suggested as key players in the hydrodynamic theory, and TRPM7, which is abundant in the odontoblasts, and recently discovered PIEZO receptors are promising candidates. Several ligand-gated ion channels and voltage-gated ion channels expressed in dental primary afferent neurons have been discussed in relation to their potential contribution to tooth pain. In addition, in recent years, there has been growing interest in the potential sensory role of odontoblasts; thus, the expression of ion channels in odontoblasts and their potential relation to tooth pain is also reviewed.

Burning mouth syndrome (BMS) is a chronic pain condition accompanied by unpleasant burning sensations of the oral mucosa. While multiple factors were proposed for the etiology, evidence suggested a neuropathic pain origin while others suspected the use of antibiotics as the underlying cause. Interestingly, several reports demonstrated the intimate interaction of the nervous system and the microbiome. The current study aims to elucidate the correlation of the oral microbiome with the pathophysiology of the primary BMS. Microbiome samples obtained from the unstimulated whole saliva of 19 primary BMS patients and 22 healthy controls were sequenced and analyzed of the V3-V4 region of 16S rRNA gene. There was a distinct difference in the microbial composition between the BMS and the control groups at all taxonomic levels. Alpha diversity indexes of the oral microbiome were significantly lower in the BMS group. The samples were readily distinguished by multidimensional scaling analysis and linear discriminant analysis effect size. Streptococcus , Rothia , Bergeyella , and Granulicatella genus were dominant in the BMS group, while Prevotella , Haemophilus , Fusobacterium , Campylobacter , and Allorevotella genus were more abundant in the healthy group. Distinct microbiome signatures of BMS patients suggested a diagnostic value and a potential role in the pathogenesis of BMS.

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Background Despite its major existential, societal, and health impacts, research concerning the COVID-19 pandemic and Temporomandibular disorders (TMDs) is still limited. This study examined the effect of the pandemic on TMD subtypes and elucidated the influence of the pandemic, sex, and age on the prospect of pain-related (PT) and/or intra-articular (IT) TMDs in East Asian patients. Methods Data were accrued from consecutive new patients attending two university-based TMD/orofacial pain clinics in China and South Korea, 12 months before (BC; Mar 2019-Feb 2020) and during (DC; Mar 2020-Feb 2021) the COVID-19 pandemic. TMD diagnoses were derived from pertinent symptoms, signs, and radiographic findings according to the Diagnostic Criteria for TMDs (DC/TMD) methodology. Patients were subsequently categorized into those with PT, IT, and combined TMDs (CT) and also stratified by attendance period, sex, and age groups (adolescents/young adults [AY] and middle-aged/older adults [MO]) for statistical analyses using Chi-square/Mann-Whitney U tests and logistic regression analyses (α = 0.05). Results The BC and DC groups comprised 367 (75.2% females; 82.8% AY) and 471 (74.3% females; 78.3% AY) patients correspondingly. No significant differences in sex and age group distributions were observed. The DC group had significantly more PT/IT conditions with higher prevalence of myalgia, headache, and degenerative joint disease than the BC group. Univariate analyses showed that PT/CT was associated with sex and age, whereas IT was related to the pandemic and age. However, multivariate analyses indicated that the odds of PT were affected by sex (OR = 2.52) and age (OR = 1.04) while the odds of IT (OR = 0.95) and CT (OR = 1.02) were influenced by age only. Conclusions The COVID-19 pandemic, as an impact event, did not influence the prospect of PT and/or IT. Sex and age appeared to play more crucial roles in the development of PT and IT/CT respectively.