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Background: Symptomatic irreversible pulpitis often results in heightened reactions to thermal stimuli such as pain evoked by a cold stimulus, and spontaneous odontogenic pain (unprovoked pain)., Objective: This study primarily compared the clinical manifestations of odontogenic spontaneous pain and pain provoked by cold stimulus specifically focusing on their sensory discriminative characteristics (intensity, duration and quality) between symptomatic irreversible pulpitis patients with and without referred pain., Methods: Twenty-three patients with symptomatic irreversible pulpitis with referred pain and 12 patients without referred pain were included in this cross-sectional study. The following outcomes were assessed: odontogenic spontaneous pain and its descriptors; pain evoked by cold stimulus and qualitative sensory testing before and after local anaesthesia; referred pain location; use of analgesic medication; complementary anaesthesia efficacy. T-test, chi-squared and McNemar tests were applied to the data (p < .50)., Results: Patients with referred pain presented a greater odontogenic pain intensity (p < .05) when considered the average of the last 24 h. These patients also showed higher pain rating and pain descriptors (p < .05). Intensity and duration of the pain evoked by cold stimulus in the non-affected contralateral tooth at baseline were higher for patients with referred pain (p < .05)., Conclusion: Symptomatic irreversible pulpitis patients with referred pain present greater odontogenic spontaneous pain and a heightened pain sensitivity. Therefore, patients with referred pain seem more complex from a pain severity perspective, supporting the clinical utility of discriminating symptomatic irreversible pulpitis with and without referred pain., (© 2024 John Wiley & Sons Ltd.)

Objective: Low-intensity pulsed ultrasound (LIPUS) is a noninvasive modality to stimulate bone remodeling (BR) and the healing of hard and soft tissues. This research evaluates the biostimulatory effect of LIPUS on the rate of orthodontic tooth movement (OTM) and associated pain, when applied at 3-week intervals., Methods: Twenty-two patients (11 males and 11 females; mean age 19.18 ± 2.00 years) having Angle's Class II division 1 malocclusion needing bilateral extractions of maxillary first bicuspids were recruited for this split-mouth randomized clinical trial. After the initial stage of alignment and leveling with contemporary edgewise MBT (McLaughlin-Bennett-Trevisi) prescription brackets (Ortho Organizers, Carlsbad, Calif) of 22 mil, followed by extractions of premolars bilaterally, 6 mm nickel-titanium spring was used to retract the canines separately by applying 150 g force on 0.019 × 0.025-in stainless steel working archwires. LIPUS (1.1 MHz frequency and 30 mW/cm 2 intensity output) was applied for 20 minutes extraorally and reapplied after 3 weeks for 2 more successive visits over the root of maxillary canine on the experimental side whereas the other side was placebo. A numerical rating scale- (NRS-) based questionnaire was given to the patients on each visit to record their weekly pain experience. Impressions were also made at each visit before the application of LIPUS (T1, T2, and T3). Models were scanned with a CAD/CAM scanner (Planmeca, Helsinki, Finland). Mann-Whitney U test was applied for comparison of canine movement and pain intensity between both the groups., Results: No significant difference in the rate of canine movement was found among the experimental (0.90 mm ± 0.33 mm) and placebo groups (0.81 mm ± 0.32 mm). There was no difference in pain reduction between experimental and placebo groups ( p > 0.05)., Conclusion: Single-dose application of LIPUS at 3-week intervals is ineffective in stimulating the OTM and reducing associated treatment pain., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2021 Irfan Qamruddin et al.)

The continuously growing mouse incisor provides a fascinating model for studying stem cell regulation and organ renewal. In the incisor, epithelial and mesenchymal stem cells assure lifelong tooth growth. The epithelial stem cells reside in a niche known as the cervical loop. Mesenchymal stem cells are located in the nearby apical neurovascular bundle and in the neural plexus. So far, little is known about extracellular cues that are controlling incisor stem cell renewal and guidance. The extracellular matrix protein tenascin-W, also known as tenascin-N (TNN), is expressed in the mesenchyme of the pulp and of the periodontal ligament of the incisor, and is closely associated with collagen 3 fibers. Here, we report for the first time the phenotype of tenascin-W/TNN deficient mice, which in a C57BL/6N background exhibit a reduced body weight and lifespan. We found major defects in the alveolar bone and periodontal ligament of the growing rodent incisors, whereas molars were not affected. The alveolar bone around the incisor was replaced by a dense scar-like connective tissue, enriched with newly formed nerve fibers likely leading to periodontal pain, less food intake and reduced body weight. Using soft food to reduce mechanical load on the incisor partially rescued the phenotype. In situ hybridization and Gli1 reporter mouse experiments revealed decreased hedgehog signaling in the incisor mesenchymal stem cell compartment, which coordinates the development of mesenchymal stem cell niche. These results indicate that TNN deficiency in mice affects periodontal remodeling and increases nerve fiber branching. Through periodontal pain the food intake is reduced and the incisor renewal and the neurovascular sonic hedgehog secretion rate are reduced. In conclusion, tenascin-W/TNN seems to have a primary function in rapid periodontal tissue remodeling and a secondary function in mechanosensation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Imhof, Balic, Heilig, Chiquet-Ehrismann, Chiquet, Niehoff, Brachvogel, Thesleff and Koch.)

Objective: In order to further study the changes of cerebral functional connectivity in patients with toothache (TA), this study used the resting-state functional magnetic resonance imaging (rs-fMRI) technique and degree centrality (DC) analysis method., Methods: Eighteen TA patients (8 males, 10 females) and 18 healthy individuals of similar age, sex, and educational levels were recruited as healthy controls (HCs) to take part in the study, and all underwent rs-fMRI examination. And DC technology was used to compare the state of their cerebral spontaneous functional activity. In order to compare the average DC values of the TA group and HC group, we used independent two-sample t -test and receiver operating characteristic (ROC) curve to compare the difference of DC values between the two groups, so as to distinguish the accuracy of TA diagnosis. Finally, we also carry out Pearson's linear regression analysis., Results: The TA group showed higher DC values in the right lingual gyrus (RLG), right precentral gyrus, and left middle temporal gyrus (LMTG) than HCs. Moreover, ROC curve analysis indicated that the area under the curve (AUC) of each cerebral region studied had high accuracy. In addition, linear analysis indicated that the DC values of the RLG were positively correlated with the Hospital Anxiety and Depression Scale (HADS) ( r = 0.844, p < 0.001), and the DC values of the LMTG were positively correlated with the visual analogue scale (VAS) ( r = 0.723, p < 0.001)., Conclusion: TA generates abnormal changes in the intrinsic activity patterns of pain-related and vision-related areas of the cerebral cortex, which will be beneficial to reveal the underlying neuropathic mechanisms., Competing Interests: The authors declare no potential conflicts of interest., (Copyright © 2020 Shi-Nan Wu et al.)

This study examined the effects of delivery mode on the response to inflammatory pulpal pain and pain-induced changes in cognitive performance in adult rats. Experiments were done on rats born by vaginal or caesarean section (C-section) delivery. Dental pulp was irritated by intradental capsaicin (100 μg) application and then nociceptive scores were recorded for 40 min. Spatial and passive avoidance learning and memory were assessed using the Morris water maze (MWM) and shuttle box tools, respectively. Additionally, in vivo recording of field excitatory postsynaptic potential (fEPSP) in the CA1 of the hippocampus was used to verify synaptic plasticity. Capsaicin produced more significant nociceptive behavior in vaginally delivered rats compared to C-section rats ( P < 0.01). C-section-delivered rats show better performance in both MWM and shuttle box tests. Likewise, C-section rats had greater fEPSP slopes compared to the vaginally delivered group ( P < 0.05). Capsaicin impairs cognitive performance in rats born by each delivery route. However, capsaicin effects were more significant in rats delivered vaginally than by C-section. Overall, C-section-delivered rats show lower sensitivity to capsaicin-evoked pulpal nociception and better cognitive performance than vaginally delivered rats. These effects are in part mediated by reduced neuroinflammation and enhanced neuronal synaptic plasticity following C-section delivery.

Background: Persistent idiopathic facial pain (PIFP) is the unexplained pain along the territory of the trigeminal nerve, including nonorganic tooth pain called atypical odontalgia (AO). Though PIFP is debilitating to patients' livelihood and well-being, its pathophysiology remains poorly understood. Although neurovascular compression (NVC) of the trigeminal nerve is known to be associated with trigeminal neuralgia (TN), the relationship between NVC and other orofacial pains has not been fully elucidated., Methods: In this study, we investigated the differences in the characteristics of PIFP (primarily AO) patients in the presence or absence of NVC. A retrospective analysis was performed on data from 121 consecutive patients who had been diagnosed with unilateral PIFP according to the criteria of the International Classification of Headache Disorders (ICHD)-3 and underwent magnetic resonance imaging scans of the head., Results: In the group without NVC, characteristic findings were significant for psychiatric morbidity, somatization, and pain disability, when compared with the group with NVC. Furthermore, the group without NVC exhibited significant headache, noncardiac chest pain, shortness of breath, and pain catastrophizing., Conclusions: These results suggest that PIFP patients can be divided into two groups: one consistent with a neuropathic pain phenotype when NVC is present and a functional somatic symptom phenotype when presenting without NVC. Our findings may enable a more precise understanding of pathophysiology of PIFP and lead to better treatment strategies., (© 2020 American Academy of Pain Medicine.)

Introduction: Orthodontic pain is the most common adverse side effect reported in the context of tooth movement. Given its central role in processing pain and negative emotion, the central nucleus of the amygdala (CeA) is thought to be a key site involved in orthodontic pain sensation., Methods: In the present study, we therefore explored whether the CeA is involved in contributing to orthodontic pain in a rat model of tooth movement. For this study, we utilized adult male rats with bilateral sham or electrolytic CeA lesions (400 μA; 25 s), and then we analyzed face grooming behavior as a measure of pain sensation., Results: Through this approach, we found that there were time- and force-dependent factors influencing pain levels in these rats. We further found that bilateral CeA lesions markedly reduced tooth movement-induced orofacial pain and that unilateral CeA lesions did so to a lesser extent., Conclusions: As such, these results suggest the CeA is a key area of orthodontic pain, with the results of this study highlighting potential avenues for achieving pain relief in those suffering from orthodontic pain., (© 2019 The Authors. Brain and Behavior published by Wiley Periodicals, Inc.)

Objective: To investigate the relationship between subjective symptoms of orofacial pain and oral health-related quality of life (OHRQoL), as well as psychological distress in population-based middle-aged women. Material and methods: The two study samples comprised 1059 women, 38 and 50 years old, in representative cross-sectional studies. Women with long-lasting, frequent pain or headaches, related to temporomandibular disorders (TMD), with moderate-to-high estimates were analysed in relation to the non-case group. OHRQoL was measured using the Oral Health Impact Profile (OHIP-5). Psychological distress was measured using the Hospital Anxiety and Depression Scale (HADS) and Sense of Coherence (SOC-13). Results: Women with orofacial pain ( n  = 82, 7.7%) had a significantly higher mean score on the OHIP-5, HADS-A and HADS-D and a lower mean score for SOC-13. In a multivariable logistic regression, orofacial pain was statistically significantly associated with poorer OHRQoL (OR = 1.2) and signs of depression (HADS-D) (OR = 2.0). A higher score for SOC-13 protected from the experience of orofacial pain (OR = 0.95). Conclusion: Orofacial pain was associated with poorer OHRQoL and signs of psychological distress. In interpreting the value of SOC, women with orofacial pain also appear to have a poorer adaptive capacity.

We report a case that illustrates how chronic migraine headaches and multiple dental pathologies caused severe and long-standing cranial pain that affected the quality of life of a man for more than 35 years. His case was investigated at several settings including the neurology outpatient clinic of the hospital without a definitive diagnosis or resolution. After investigations, multiple oral pathologies including two occult dental abscesses were diagnosed. Once both affected teeth and associated abscesses were surgically removed, with subsequent antibiotic therapy the headaches resolved., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Ancillary factors, not directly related to treatment, often play a significant role by affecting therapeutic outcome. A search of the literature was conducted including words related to the placebo phenomenon and orofacial diseases. Therefore, critical factors have been grouped into three major categories: (a) the natural course of the diseases; (b) the regression of the symptoms to their mean intensity; and (c) placebo response. This topical narrative review describes the elements mentioned above, provides an up-to-date overview of the hot topics and gaps in the field and indicates developing and future research direction of the orofacial pain field. Such a knowledge might be positively used during daily clinical practice to optimise the management of orofacial pain diseases, as well as in conducting future clinical trials for validating new interventions., (© 2018 John Wiley & Sons Ltd.)

This study further investigated the mechanisms underlying the rat model of tooth pulp inflammatory pain elicited by complete Freund's adjuvant (CFA), in comparison to other pulpitis models. Pulps of the left maxillary first molars were accessed. In the CFA group, the pulps were exposed, and CFA application was followed by dental sealing. In the open group, the pulps were left exposed to the oral cavity. For the closed group, the pulps were exposed, and the teeth were immediately sealed. Naïve rats were used as negative controls. Several parameters were evaluated at 1, 2, 3 and 8 days. There was no statistical significant difference among the groups when body weight variation, food or water consumption were compared. Analysis of serum cytokines (IL-1β, TNF or IL-6) or differential blood cell counts did not reveal any evidence of systemic inflammation. The CFA group displayed a significant reduction in the locomotor activity (at 1 and 3 days), associated with an increased activation of satellite glial cells in the ipsilateral trigeminal ganglion (TG; for up to 8 days). Amygdala astrocyte activation was unaffected in any experimental groups. We provide novel evidence indicating that CFA-induced pulp inflammation impaired the locomotor activity, with persistent activation of ipsilateral TG satellite cells surrounding sensory neurons, without any evidence of systemic inflammation or amygdala astrogliosis., Competing Interests: The authors have declared that no competing interests exist.

Introduction: Persistent dentoalveolar pain of idiopathic origin represents a diagnostic challenge for the dentist and physician alike. Disagreement on taxonomy and diagnostic criteria presents a significant limit to the advancement of research in the field. Patients struggle with a lack of knowledge by dental and medical professionals, diagnostic delays, and unnecessary treatments., Methods: A PubMed search was performed as of January 1, 2017 by using the terms atypical odontalgia, phantom tooth pain, persistent idiopathic facial pain, painful posttraumatic trigeminal neuropathy, idiopathic toothache, persistent dentoalveolar pain disorder, nonodontogenic tooth pain, and continuous neuropathic orofacial pain. Three hundred forty-five abstracts were screened, and 128 articles that were pertinent to the topic went through full-text reading., Results: Case reports and narrative reviews constitute the majority of available literature. Several retrospective case-control studies investigated the clinical characteristics, pathophysiology, and diagnostic processes. Treatment strategies were evaluated in only 7 open-label and 2 randomized controlled trials., Conclusions: Persistent dentoalveolar pain disorder is likely neuropathic in origin, but pathophysiological mechanisms to explain the onset and persistence of the pain are still far from understood. A correct diagnosis should be established before treatments are performed. Researchers should reach an agreement on the diagnostic criteria to enable a coherent research path to better understand the condition and reduce patient suffering., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: Irreversible pulpitis is a highly painful inflammatory condition of the dental pulp which represents a common dental emergency. Recommended care is partial endodontic treatment. The dental literature reports major difficulties in achieving adequate analgesia to perform this emergency treatment, especially in the case of mandibular molars. In current practice, short-course, orally administered corticotherapy is used for the management of oral pain of inflammatory origin. The efficacy of intraosseous local steroid injections for irreversible pulpitis in mandibular molars has already been demonstrated but resulted in local comorbidities. Oral administration of short-course prednisolone is simple and safe but its efficacy to manage pain caused by irreversible pulpitis has not yet been demonstrated. This trial aims to evaluate the noninferiority of short-course, orally administered corticotherapy versus partial endodontic treatment for the emergency care of irreversible pulpitis in mandibular molars., Methods/design: This study is a noninferiority, open-label, randomized controlled clinical trial conducted at the Bordeaux University Hospital. One hundred and twenty subjects will be randomized in two 1:1 parallel arms: the intervention arm will receive one oral dose of prednisolone (1 mg/kg) during the emergency visit, followed by one morning dose each day for 3 days and the reference arm will receive partial endodontic treatment. Both groups will receive planned complete endodontic treatment 72 h after enrollment. The primary outcome is the proportion of patients with pain intensity below 5 on a Numeric Scale 24 h after the emergency visit. Secondary outcomes include comfort during care, the number of injected anesthetic cartridges when performing complete endodontic treatment, the number of antalgic drugs and the number of patients coming back for consultation after 72 h., Discussion: This randomized trial will assess the ability of short-term corticotherapy to reduce pain in irreversible pulpitis as a simple and rapid alternative to partial endodontic treatment and to enable planning of endodontic treatment in optimal analgesic conditions., Trial Registration: ClinicalTrials.gov, identifier: NCT02629042 . Registered on 7 December 2015. (Version n°1.1 28 July 2015).

To ascertain whether steroid therapy evokes dentin hypersensitivity (DH)-like tooth pain, we performed a study based on compelling evidence from patients receiving steroid therapy. An exploratory study was conducted using a questionnaire for 220 patients prescribed steroids who attended the Department of Hematology and Rheumatology of Tohoku University Hospital. Group comparisons between patients with and without steroid pulse therapy were analysed by statistical means. In this study, any DH-like tooth pain that commenced subsequent to steroid treatment was defined as steroid-derived (SD) tooth pain. The prevalence of SD tooth pain was 17.7% (39/220 patients). SD tooth pain was triggered in many vital teeth by cold and/or hot water (84.2% and 23.7%, respectively) with the pain characterised as continuous, in contrast to typical DH tooth pain. SD tooth pain was significantly more frequent in pulse therapy patients than in non-pulse therapy patients (p < 0.05). Logistic regression analysis adjusted for age and sex showed similar results (odds ratio = 3.74, p = 0.013). Moreover, a positive correlation was observed between the steroid dose and pain score (ρ = 0.642). Dose reduction or discontinuation of steroid therapy relieved SD tooth pain in all cases. Thus, steroid therapy can evoke DH-like tooth pain during treatment., (Copyright © 2016 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

Objective: To observe the clinical efficacy of transcutanclus electrical acupoint stimulation (TEAS) on prevention and treatment of orthodontic toothache and oral dysfunction., Methods: A total of 85 patients of malocclusions in the preliminary diagnosis were randomly divided into a control group (20 cases), a psychological intervention group (22 cases), a medication group (20 cases) and a TEAS group (23 cases). Orthodontics treatment was given in all the groups. Patients in the control group received no further treatment; patients in the psychological intervention group received comprehensive psychological intervention, including cognitive education and music therapy; patients in the medication group received oral administration of ibuprofen; patients in the TEAS group received TEAS at Juliao (ST 3), Jiachengjiang (Extra) and auricular point Ya (LO1). The treatment was given twice a day, one in morning and one at night, for 7 days. The pain scores of orthodontic toothache and changes of oral dysfunction were observed in all groups., Results: (1) At 5 time points from the 12th hour to the 4th day, the scores of spontaneous pain in TEAS group were lower than those in the control group (all P < 0.01); during the time points, the scores in TEAS group were lower than those in the psychological intervention group (P < 0.05, P < 0.01), which were similar to those in the medication group (all P > 0.05). (2) During the peak cycle of spontaneous toothache, the scores of irritation pain in TEAS group were significantly lower than those in the control group (all P < O.01), regardless of time-point statistics or general statistics; the scores of irritation pain in the TEAS group were also significantly lower than those in the psychological intervention group (all P < 0.01), which were similar to those in the medication group (all P > 0. 05). (3) Compared with control group, the grading of talking disorder in the remaining groups did not change significantly (P > 0.05). (4) Compared with control group, the grading of moderate-severe eating disorder in TEAS group was significantly reduced (P < O.05), which was not different from that in the medication group (P > 0.05). The differences of the grading of moderate-severe eating disorder were not significantly different between the psychological intervention group and control group (P > 0.05). (5) There were 3 cases of digestive system adverse reactions in the medication group., Conclusion: TEAS can efficiently prevent orthodontic toothache and oral dysfunction, which is superior to psychological intervention and similar to medication. In addition, it can avoid possible side-effect of medication.

Objective: Divers are vulnerable to barodontalgia (atmospheric pressure change related dental pain), which may jeopardize diving safety and mission completion. Our aim was to investigate the experience of barodontalgia among western military divers., Methods: French Armed Forces diving personnel were asked to answer a structured questionnaire including questions regarding their oral health, diving and career features, and barodontalgia while diving. For analysis, the participants were divided into commando/clearance divers (Group A) and ship divers (Group B)., Results: All the requested 1389 divers agreed to participate in the study (100%) and 1317 divers (94.8%) who fully completed the questionnaire were included in the analysis. Of these 1317 individuals, 96 (7.3%) suffered from at least 1 episode of barodontalgia while diving, with a total of 119 episodes of barodontalgia. Barodontalgia was more frequent in the upper (62.2%) than the lower dentition (37.8%) (OR = 2.7; 95% CI, 1.6-4.5) and appeared more common during descent (77.3%) than ascent (22.7%) (OR = 11.6; 95% CI, 6.3-31.3). Barodontalgia experience was higher in divers who have an examination less than once per year (14.5%) in comparison to divers who usually have a dental examination once a year or more (6.3%) (OR = 2.5; 95% CI, 1.5-4.2)., Discussion: Barodontalgia mostly appeared in the maxilla and during descent; therefore, a great role for barosinusitis in the etiology of oral pain while diving may be suggested. The infrequent experience of barodontalgia in divers who routinely visit the dentist once a year or more suggests that the risk of barodontalgia might decrease with the maintenance of a good oral status.

Objective: The aim of this study was to identify the facial areas defined by thermal gradient, in individuals compatible with the pattern of normality, and to quantify and describe them anatomically., Methods: The sample consisted of 161 volunteers, of both genders, aged between 26 and 84 years (63 ± 15 years)., Results: The results demonstrated that the thermal gradient areas suggested for the study were present in at least 95% of the thermograms evaluated and that there is significant difference in temperature between the genders, racial group and variables "odontalgia", "dental prothesis" and "history of migraine" (p < 0.05). Moreover, there was no statistically significant difference in the absolute temperatures between ages, and right and left sides of the face, in individuals compatible with the pattern of normality (ΔT = 0.11°C)., Conclusions: The authors concluded that according to the suggested areas of thermal gradients, these were present in at least 95% of all the thermograms evaluated, and the areas of high intensity found in the face were medial palpebral commissure, labial commissure, temporal, supratrochlear and external acoustic meatus, whereas the points of low intensity were inferior labial, lateral palpebral commissure and nasolabial.

The present study tested the hypothesis that the amount and severity of preoperative pain will affect the anesthetic efficacy of inferior alveolar nerve block (IANB) in patients with symptomatic irreversible pulpitis. One-hundred seventy-seven adult volunteer subjects, actively experiencing pain in a mandibular molar, participated in this prospective double-blind study carried out at 2 different centers. The patients were classified into 3 groups on the basis of severity of preoperative pain: mild, 1-54 mm on the Heft-Parker visual analog scale (HP VAS); moderate, 55-114 mm; and severe, greater than 114 mm. After IANB with 1.8 mL of 2% lidocaine, endodontic access preparation was initiated. Pain during treatment was recorded using the HP VAS. The primary outcome measure was the ability to undertake pulp access and canal instrumentation with no or mild pain. The success rates were statistically analyzed by multiple logistic regression test. There was a significant difference between the mild and severe preoperative pain group (P = .03). There was a positive correlation between the values of preoperative and intraoperative pain (r = .2 and .4 at 2 centers). The amount of preoperative pain can affect the anesthetic success rates of IANB in patients with symptomatic irreversible pulpitis.

Achieving profound pulpal anaesthesia in a mandibular molar diagnosed with irreversible pulpitis can be argued to be the most testing of dental anaesthetic challenges. This can be attributed to the technical complexities of conventional techniques and the presence of pulp pathosis. Reasons for why the latter influences the ability to attain pulpal anaesthesia is not yet fully understood, but its frequent occurrence is well documented. In light of overcoming this it has become common practice to prescribe antibiotics, refer onto secondary care or to even commence treatment without appropriately anaesthetising the tooth. Therefore, this two part series aims to help practitioners attain clinically acceptable pulpal anaesthesia in the most testing of scenarios; the acutely inflamed mandibular molar. They should then be able to apply these same principles to other teeth presenting with similar symptoms. This section outlines the clinical presentation and pathophysiology associated with an acutely inflamed pulp, defines what it is to attain pulpal anaesthesia and critically analyses theories as to why these teeth are up to eight times more difficult to anaesthetise than their healthy counterparts.

Objectives: Orofacial pain (OFP) is thought to substantially reduce oral health-related quality of life (OHRQoL). Little has been reported about the impact of acute dental pain and persistent (chronic) orofacial pain conditions, other than temporomandibular disorders (TMD), on OHRQoL. The aim of this study was to examine and compare OHRQoL impairment among four OFP conditions: TMD, acute dental pain (ADP), trigeminal neuralgia (TN) and persistent dentoalveolar pain disorder (PDAP)., Methods: OHRQoL was measured using the OHIP-49 in a convenience sample of subjects with four OFP conditions (TMD (n=41), ADP (n=41), TN (n=21), PDAP (n=22) and a pain-free control group (n=21)). The mean OHIP-49 summary score described the level of impact and inferential and descriptive statistics were used to examine any differences inter-condition. The mean of the OHIP-14 and 5 were also measured by extracting the corresponding items from the OHIP-49., Results: All pain conditions presented with statistically significant (P<0.001) and clinically relevant (measured by effect sizes and the OHIP's minimal important difference) impairment when compared to the control group (P<0.001). The OHRQoL for the four OFP conditions had similar levels of impairment (TMD=62.3, ADP=55.5, TN=58.1 and PDAP=69.8)., Conclusion: TMD, ADP, TN and PDAP have substantial impact on OHRQoL as measured by the OHIP-49 and the extracted items for the OHIP-14 and 5. Differences among the four groups of orofacial pain conditions are likely not to be substantial., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Aims: (1) To determine the brain regions activated by dentoalveolar pressure stimulation in persistent dentoalveolar pain disorder (PDAP) patients, and (2) to compare these activation patterns to those seen in pain-free control subjects., Methods: A total of 13 PDAP patients and 13 matched controls completed the study. Clinical pain characteristics and psychosocial data were collected. Dentoalveolar mechanical pain thresholds were determined with a custom-made device over the painful area for patients and were used as the stimulation level during functional magnetic resonance imaging (fMRI) data acquisition. Control subjects received two stimulation levels over matched locations during fMRI scanning: one determined (as above) that evoked equally subjective pain ratings matching those of patients (subjective-pain match) and another nonpainful stimulation level matching the average stimulus intensity provided to patients (stimulus-intensity match). Clinical and psychosocial data were analyzed using independent samples t tests, Mann-Whitney U test, and Spearman rank-order correlation coefficient. fMRI data were analyzed using validated neuroimaging software and tested using a general linear model., Results: PDAP patients had greater anxiety (P<.0001) and depression scores (P=.001), more jaw function impairment (P<.0001), and greater social impact (P<.0001) than controls. No significant differences were found for brain activation spatial extent (PDAP X Controls subjective pain: P=.48; PDAP X Controls stimulus intensity: P=.12). Brain activations were significantly increased for PDAP patients compared to control subjects when matched to stimulus intensity in several regions related to the sensory-discriminative and cognitive components of pain perception, including the primary and secondary somatosensory cortices, inferior parietal lobule, insula, premotor cortex, prefrontal cortex, and thalamus. When matched to subjective pain ratings, increased brain activations were still present for PDAP patients compared to controls, although to a lesser extent., Conclusion: The present results suggest that dentoalveolar pressure is processed differently in the brain of PDAP patients, and the increased activation in several brain areas is consistent with amplified pain processing.

Local anesthesia has made dental treatment more comfortable since 1884, but little is known about associated brain mechanisms. Functional magnetic resonance imaging is a modern neuroimaging tool widely used for investigating human brain activity related to sensory perceptions, including pain. Most brain regions that respond to experimental noxious stimuli have recently been found to react not only to nociception alone, but also to visual, auditory, and other stimuli. Thus, presumed functional attributions have come under scrutiny regarding selective pain processing in the brain. Evidently, innovative approaches are warranted to identify cerebral regions that are nociceptive specific. In this study, we aimed at circumventing known methodological confounders by applying a novel paradigm in 14 volunteers: rather than varying the intensity and thus the salience of painful stimuli, we applied repetitive noxious dental stimuli at constant intensity to the left mandibular canine. During the functional magnetic resonance imaging paradigm, we suppressed the nociceptive barrage by a mental nerve block. Brain activity before and after injection of 4% articaine was compared intraindividually on a group level. Dental pain extinction was observed to correspond to activity reduction in a discrete region of the left posterior insular cortex. These results confirm previous reports demonstrating that direct electrical stimulation of this brain region-but not of others-evokes bodily pain sensations. Hence, our investigation adds further evidence to the notion that the posterior insula plays a unique role in nociceptive processing., (© International & American Associations for Dental Research 2015.)

Orexin 1 receptor signaling plays a significant role in pain as well as learning and memory processes. This study was conducted to assess the changes in orexin 1 receptor expression levels in hippocampus following learning and memory impairment induced by tooth inflammatory pulpal pain. Adult male Wistar rats received intradental injection of 100 µg capsaicin to induce pulpal pain. After recording the pain scores, spatial learning and memory were assessed using Morris Water Maze test. The hippocampal levels of orexin 1 receptor mRNA and protein were determined by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) and immunoblotting respectively. The data showed that capsaicin-induced tooth inflammatory pulpal pain was correlated with learning and memory impairment. Intra-hippocampal injection of orexin A inhibited pain-induced learning and memory impairment. However, orexin 1 receptor antagonist, SB-334867, had no effect on learning and memory impairment. Moreover, capsaicin-induced pain significantly decreased hippocampal orexin 1 receptor mRNA and protein levels. Meanwhile, reversed changes took place in the ibuprofen-pretreated group (p < 0.05). It seems that decrease in orexin 1 receptor density and signaling could be involved in tooth pain-induced learning and memory impairment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Chronic oro-facial pain conditions such as persistent idiopathic facial pain (PIFP), atypical odontalgia (AO) and burning mouth syndrome (BMS), usually grouped together under the concept of idiopathic oro-facial pain, remain a diagnostic and therapeutic challenge. Lack of understanding of the underlying pathophysiological mechanisms of these pain conditions is one of the important reasons behind the problems in diagnostic and management. During the last two decades, neurophysiological, psychophysical, brain imaging and neuropathological methods have been systematically applied to study the trigeminal system in idiopathic oro-facial pain. The findings in these studies have provided evidence for neuropathic involvement in the pathophysiology of PIFP, AO and BMS. The present qualitative review is a joint effort of a group of oro-facial pain specialists and researchers to appraise the literature on idiopathic oro-facial pain with special focus on the currently available studies on their pathophysiological mechanisms. The implications of the findings of these studies for the clinical diagnosis and treatment of idiopathic oro-facial pain conditions are discussed., (© 2014 John Wiley & Sons Ltd.)

Dento-alveolar pain is common in the orofacial area. Persistent dento-alveolar pain could be experienced without an identifiable etiology with poor response to existing treatments. Confusion about the diagnosis and classification of persistent dento-alveolar pain (PDAP) disorders could explain the difficulties in treatment and unfavorable prognosis. Recently, initial steps were made to improve the taxonomy and diagnostic criteria for PDAP in order to improve clinical research and care.

The reliability of comprehensive intra-oral quantitative sensory testing (QST) protocol has not been examined systematically in patients with chronic oro-facial pain. The aim of the present multicentre study was to examine test-retest and interexaminer reliability of intra-oral QST measures in terms of absolute values and z-scores as well as within-session coefficients of variation (CV) values in patients with atypical odontalgia (AO) and healthy pain-free controls. Forty-five patients with AO and 68 healthy controls were subjected to bilateral intra-oral gingival QST and unilateral extratrigeminal QST (thenar) on three occasions (twice on 1 day by two different examiners and once approximately 1 week later by one of the examiners). Intra-class correlation coefficients and kappa values for interexaminer and test-retest reliability were computed. Most of the standardised intra-oral QST measures showed fair to excellent interexaminer (9-12 of 13 measures) and test-retest (7-11 of 13 measures) reliability. Furthermore, no robust differences in reliability measures or within-session variability (CV) were detected between patients with AO and the healthy reference group. These reliability results in chronic orofacial pain patients support earlier suggestions based on data from healthy subjects that intra-oral QST is sufficiently reliable for use as a part of a comprehensive evaluation of patients with somatosensory disturbances or neuropathic pain in the trigeminal region., (© 2014 John Wiley & Sons Ltd.)

A systematic review was conducted to identify reliable somatosensory evaluation methods for atypical odontalgia (AO) patients. The computerized search included the main databases (MEDLINE, EMBASE, and Cochrane Library). The studies included used the following quantitative sensory testing (QST) methods: mechanical detection threshold (MDT), mechanical pain threshold (MPT) (pinprick), pressure pain threshold (PPT), dynamic mechanical allodynia with a cotton swab (DMA1) or a brush (DMA2), warm detection threshold (WDT), cold detection threshold (CDT), heat pain threshold (HPT), cold pain detection (CPT), and/or wind-up ratio (WUR). The publications meeting the inclusion criteria revealed that only mechanical allodynia tests (DMA1, DMA2, and WUR) were significantly higher and pain threshold tests to heat stimulation (HPT) were significantly lower in the affected side, compared with the contralateral side, in AO patients; however, for MDT, MPT, PPT, CDT, and WDT, the results were not significant. These data support the presence of central sensitization features, such as allodynia and temporal summation. In contrast, considerable inconsistencies between studies were found when AO patients were compared with healthy subjects. In clinical settings, the most reliable evaluation method for AO in patients with persistent idiopathic facial pain would be intraindividual assessments using HPT or mechanical allodynia tests.

Introduction: The purpose of this prospective randomized, double-blind, placebo-controlled study was to determine the effects of a combination dose of 1000 mg acetaminophen/10 mg hydrocodone on cold pulpal testing in patients experiencing symptomatic irreversible pulpitis., Methods: One hundred emergency patients in moderate to severe pain diagnosed with symptomatic irreversible pulpitis of a mandibular posterior tooth randomly received, in a double-blind manner, identical capsules of either a combination of 1000 mg acetaminophen/10 hydrocodone or placebo. Cold testing with Endo-Ice (1,1,1,2 tetrafluoroethane; Hygenic Corp, Akron, OH) was performed at baseline and every 10 minutes for 60 minutes. Pain to cold testing was recorded by the patient using a Heft-Parker visual analog scale. Patients' reaction to the cold application was also rated., Results: Cold testing at baseline and at 10 minutes resulted in severe pain for both the acetaminophen/hydrocodone and placebo groups. Although pain ratings decreased from 20-60 minutes, the ratings still resulted in moderate pain. Patient reaction to cold testing showed that 56%-62% had a severe reaction. Although the reactions decreased in severity over the 60 minutes, 20%-34% still had severe reactions at 60 minutes. Regarding pain and patients' reactions to cold testing, there were no significant differences between the combination acetaminophen/hydrocodone and placebo groups at any time period., Conclusions: A combination dose of 1000 mg of acetaminophen/10 mg of hydrocodone did not statistically affect cold pulpal testing in patients presenting with symptomatic irreversible pulpitis. Patients experienced moderate to severe pain and reactions to cold testing., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Aims: To test the role of fatigue and its subtypes (general, physical, emotional, mental, and vigor) in mediating the relationship between psychological distress and pain interference., Methods: Retrospective, de-identified records were examined for 431 patients seeking treatment for persistent orofacial pain. Primary diagnoses of participants were muscle pain (29.8%), joint pain (26.0%), neuropathic pain (19.5%), and other (ie, fibromyalgia, centrally mediated myalgia, tendonitis, dental pain, cervical spine displacement, and no diagnosis; 24.7%). Mediation models were tested with distress as the independent variable, interference as the dependent variable, and fatigue or its subtypes as the mediators., Results: After controlling for pain duration and average levels of pain, total fatigue mediated the relationship between distress and interference. Fatigue subtypes partially mediated the relationship between distress and interference, but mediation was strongest with the composite fatigue variable. The results, however, should be interpreted cautiously, as data were collected at a single time point and do not imply causality., Conclusion: These results suggest that interventions targeted specifically at fatigue symptoms may be helpful for reducing interference and improving quality of life in patients with persistent orofacial pain.

Introduction: Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism., Methods: Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation., Results: Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings., Conclusions: The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: The authors conducted a study of tweets posted on Twitter to compare self-reported toothache experiences with those of backache, earache and headache in regard to pain intensity, action taken, perceived cause and effect of pain., Methods: From a total of 508,591 relevant tweets collected on seven nonconsecutive days, the authors randomly selected 1,204 tweets (301 per pain type) and conducted content analyses of each tweet., Results: Toothaches were described as having higher pain intensity than were earaches or headaches but pain intensity comparable with that of backaches. Despite people who experience toothache being more likely to seek health care than those experiencing backaches (odds ratio [OR], 3.91; 95 percent confidence interval [CI], 1.57-9.71) or headaches (OR, 6.11; 95 percent CI, 2.16-17.25), only one in 10 people with toothaches mentioned seeking health care for their pain. People with toothaches were less likely to report an effect on daily functioning compared with those with backaches (OR, 0.13; 95 percent CI, 0.03-0.56) or earaches (OR, 0.19; 95 percent CI, 0.05-0.77)., Conclusions: Using unsolicited self-reported data from Twitter, the authors found similarities and differences in the experiences of people with toothaches compared with those of people with other common pains. These findings offer insights into understanding dental pain and dental care utilization., Practical Implications: The use of social media, such as Twitter, to discuss health issues provides opportunities for dental professionals to better understand dental care experiences from the patients' perspective. Furthermore, social media such as Twitter offer providers the opportunity to share information with the public and to facilitate provider-patient communication.

Aims: To better quantify oral pre-trigeminal neuralgia (PTN) symptoms, attempt to identify PTN symptoms that could reliably differentiate between PTN and odontogenic tooth pain, and determine whether an anesthetic test would reliably differentiate these disorders., Methodology: This was accomplished through a survey of symptom recall for 49 trigeminal neuralgia patients who had PTN tooth and/or gum pain., Results: The variability of oral PTN symptoms, factors that worsened or improved them, and how dental anesthesia affected them, explain the reason for variations found in the literature. A throbbing pain quality is not in the literature, but present for 63% of respondents., Conclusions: No specific PTN symptom would reliably differentiate PTN from odontogenic tooth pain. The results also suggest that an anesthetic test would not be totally reliable for differentiating these disorders. A protocol is provided that should help practitioners identify the tooth pain source when there is no dental pathology.

Comprehending orofacial referred pain requires an understanding of the neuroanatomy of the trigeminal nerve and associated cranial nerves. It also requires knowledge of the concept of neuronal convergence as well as the recognition that the caudalis is laminated and is therefore responsible for sensory receptive fields-that one interneuron may receive multiple sensory inputs and that structures within a lamina have sensory neurons which project into the caudalis and may share the same interneuron.

Functional magnetic resonance imaging (fMRI) has been widely used for investigating the brain representation associated with dental pain evoked by pulpal electrical stimulation. However, because of the heterogeneity of experimental designs and the small sample size of individual studies, the common brain representation regarding dental pain has remained elusive. We used imaging meta-analysis to investigate six dental pain-related fMRI studies (n = 87) and tested 3 hypotheses: (1) Dental pain is associated with the 'core' pain-related network; (2) pain-related brain activation is somatotopically organized in the somatosensory cortex; and (3) dental pain is associated with the cognitive-affective network related to pain. Qualitative and quantitative meta-analyses revealed: (1) common activation of the core pain-related network, including the somatosensory cortex, the insula, and the cingulate cortex; (2) inconsistency in somatotopically organized activation of the primary somatosensory cortex; and (3) common activation in the dorsolateral prefrontal cortex, suggesting a role of re-appraisal and coping in the experience of dental pain. In conclusion, fMRI combined with pulpal stimulation can effectively evoke activity in the pain-related network. The dental pain-related brain representation disclosed the mechanisms of how sensory and cognitive-affective factors shape dental pain, which will help in the development of more effective customized methods for central pain control.

Due, in part, to the unique structure of the tooth, dental pain is initiated via distinct mechanisms. Here we review recent advances in our understanding of inflammatory tooth pain and discuss 3 hypotheses proposed to explain dentinal hypersensitivity: The first hypothesis, supported by functional expression of temperature-sensitive transient receptor potential channels, emphasizes the direct transduction of noxious temperatures by dental primary afferent neurons. The second hypothesis, known as hydrodynamic theory, attributes dental pain to fluid movement within dentinal tubules, and we discuss several candidate cellular mechanical transducers for the detection of fluid movement. The third hypothesis focuses on the potential sensory function of odontoblasts in the detection of thermal or mechanical stimuli, and we discuss the accumulating evidence that supports their excitability. We also briefly update on a novel strategy for local nociceptive anesthesia via nociceptive transducer molecules in dental primary afferents with the potential to specifically silence pain fibers during dental treatment. Further understanding of the molecular mechanisms of dental pain would greatly enhance the development of therapeutics that target dental pain.

Objectives: The objective of this study is to assess prevalence and extent of school absence due to toothache, dental caries, and Oral Health-Related Quality of Life (OHRQoL) in a subsample of the Thailand national oral health survey. In addition, associations of school absence as the outcome variable with explanatory behavioral and sociodemographic variables, dental caries, and OHRQoL were investigated., Methods: Study sample was half of the Sixth Thailand National Oral Health Survey sample (1,063 12-year-old and 811 15-year-old children). Children were orally examined and interviewed about OHRQoL using the Child Oral Impacts on Daily Performances or the Oral Impacts on Daily Performances indices. Children completed a sociodemographic and behavioral questionnaire on school absence due to toothache in current semester., Results: Over a 3-month period, 5.1 percent of 12- and 4.4 percent of 15-year-olds absented themselves from school due to toothache. The number of days absent in 12-year-olds was significantly higher than in 15-year-olds. For 12-year-olds, OHRQoL and toothache were significantly associated with school absence. Severe dental decay was the main dental factor related to school absence but not significantly associated with school absence in the adjusted analyses. Children in lower school grades and those who received dental treatment in current semester were more likely to miss school compared with their counterparts., Conclusions: About one in 20 of Thai school-aged children reported missing school due to toothache. School absence due to toothache was inversely associated with the current year of study and positively with recently receiving dental treatment and with OHRQoL and toothache in 12-year-olds., (© 2013 American Association of Public Health Dentistry.)

Objectives: This study uses a fluid-structure interaction (FSI) simulation to evaluate the fluid flow in a dental intrapulpal chamber induced by the deformation of the tooth structure during loading in various directions., Methods: The FSI is used for the biomechanics simulation of dental intrapulpal responses with the force loading gradually increasing from 0 to 100N at 0°, 30°, 45°, 60°, and 90° on the tooth surface in 1s, respectively. The effect of stress or deformation on tooth and fluid flow changes in the pulp chamber are evaluated., Results: A horizontal loading force on a tooth may induce tooth structure deformation, which increases fluid flow velocity in the coronal pulp. Thus, horizontal loading on a tooth may easily induce tooth pain., Conclusion: This study suggests that experiments to investigate the relationship between loading in various directions and dental pain should avoid measuring the bulk pulpal fluid flow from radicular pulp, but rather should measure the dentinal fluid flow in the dentinal tubules or coronal pulp. The FSI analysis used here could provide a powerful tool for investigating problems with coupled solid and fluid structures in dental biomechanics., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Atypical odontalgia (AO) is a little known chronic pain condition. It usually presents as pain in a site where a tooth was endodontically treated or extracted, in the absence of clinical or radiographic evidence of tooth pathology. It is a rare clinical challenge for most clinicians, which leads to the patients being referred to several specialists and sometimes undergoing unnecessary surgical procedures. The pain mechanisms involved in AO are far from clear, and numerous potential mechanisms have been suggested. Currently, the most accredited hypothesis is that AO is a neuropathic pain condition caused by deafferentation. The differential diagnosis of AO remains difficult, because it shares symptoms with many others pathologies affecting this area. Patients have difficulties accepting the AO diagnosis and treatment. As a result, they frequently change physicians, and may potentially also receive several invasive treatments, usually resulting in an aggravation of the pain. Although some patients do get complete pain relief following treatment, for most patients the goal should be to achieve adequate pain management. Currently, most management is based on expert opinion and case reports. More research and high quality randomized controlled trials are needed in order to develop evidence-based treatments, currently based on expert opinion or carried over from other neuropathic pain conditions in the orofacial region.

Aims: To examine the long-term prognosis of 46 previously examined atypical odontalgia (AO) patients., Methods: In 2002 and 2009, AO patients completed validated instruments measuring pain characteristics (pain frequency and intensity), physical functioning (Graded Chronic Pain Severity, GCPS) and emotional functioning (Symptoms Checklist, SCL-90R). The main outcome was global improvement. Baseline data on quantitative somatosensory testing and responsiveness to lidocaine injection were available for a subgroup of patients. Paired tests compared baseline and follow-up data, and logistic regression explored the possible prognostic value of baseline data., Results: Data from 37 patients (80%) were obtained. Thirteen patients (35%; 95% confidence intervals [CI] 20.2%-52.5%) rated their overall pain status as significantly improved, 22 (60%; 95% CI 42.1%-75.3%) as a little improved or unchanged, and two patients (5%; 95% CI 0.7%-18.2%) as worse. Five patients (14%; 95% CI 4.5%-28.8%) were pain-free, indicated by a characteristic pain intensity score of 0. Average pain intensity decreased (from 5.7 ± 2.0 to 3.5 ± 2.4; P < .001). Pain frequency (P < .001) and GCPS (P < .001) also decreased, whereas SCL-90R scores remained unchanged and 26 of the 37 patients reported ongoing treatment. Low baseline pain intensity was the only factor predictive of favorable outcome., Conclusion: A third of the AO patients improved considerably over time, but for many of the patients, AO was a persistent and treatment-resistant condition.

Aims: To assess intraoral inter- and intraexaminer reliability of three qualitative measures of intraoral somatosensory function and to compare these measures between patients with atypical odontalgia (AO) and healthy controls., Methods: Thirty-one AO patients and 47 healthy controls participated. Inter- and intraexaminer reliability was tested on a subgroup of 46 subjects (25 AO; 21 healthy). Sensitivity to touch, cold, and pinprick stimuli was evaluated on the painful gingival site and the corresponding contralateral site in AO patients, and bilaterally on the gingiva of the first maxillary premolars in controls. Patients were asked to report hypersensitivity, hyposensitivity, or normal sensitivity to stimuli on the painful site compared with the nonpainful site. Kappa values were calculated, and chi-square and Fisher's exact tests were used to compare frequencies between groups., Results: Kappa values ranged between 0.63 and 0.75. The frequency of hypersensitivity to either modality was significantly higher in patients (29% to 61%) than in controls (9% to 17%) (P < .015), whereas reports of hyposensitivity were similar between groups (2% to 16%) (P > .057). Only 3.2% of the AO patients had no reports of abnormal sensitivity on any of the tests, compared with 59.6% of the healthy subjects (P < .001)., Conclusion: Intraoral qualitative somatosensory testing can detect intraoral sensory disturbances in AO patients, and the reliability is sufficient for initial screening of orofacial somatosensory function.

There are few review articles in the area of human research that focus on the interactions between occlusion and brain function. This systematic review discusses the effect of occlusion on the health of the entire body with a focus on brain function. Available relevant articles in English from 1999 to 2011 were assessed in an online database and as hard copies in libraries. The selected 19 articles were classified into the following five categories: chewing and tongue movements, clenching and grinding, occlusal splints and occlusal interference, prosthetic rehabilitation, and pain and stimulation. The relationships between the brain activity observed in the motor and sensory cortices and movements of the oral and maxillofacial area, such as those produced by gum chewing, tapping and clenching, were investigated. It was found that the sensorimotor cortex was also affected by the placement of the occlusal interference devices, splints and implant prostheses. Brain activity may change depending on the strength of the movements in the oral and maxillofacial area. Therefore, mastication and other movements stimulate the activity in the cerebral cortex and may be helpful in preventing degradation of a brain function. However, these findings must be verified by evidence gathered from more subjects., (© 2012 Blackwell Publishing Ltd.)

Background: This study evaluates associations between oral health-related factors and chewing ability, and quantifies the risk contributed by each factor., Materials and Methods: Chewing ability and information on number of teeth, dentures and dental problems over the last 12 months were collected by mailing questionnaires to a random sample of 60- to 71-year-olds from Adelaide, South Australia. Logistic regression was used to model oral status and oral symptoms as predictors of chewing disability, and to estimate the population-attributable fraction., Results: A total of 444 persons responded (response rate = 68.8%). Among dentate subjects, 10.3% were chewing-deficient, with chewing disability more prevalent (p < 0.05) among those with <21 teeth (26.4%), dentures (20.4%), painful aching in the mouth (25.4%), pain in the face (16.7%), broken/chipped teeth (15.6%), sensitive teeth (14.1%), loose teeth (37.1%), and sore gums (18.0%). Adjusted Odds ratios (OR) showed inadequate dentition (OR = 4.20), painful aching in the mouth (OR = 4.88), and presence of loose teeth (OR = 4.70) were associated with chewing disability (p < 0.01), and their population attributable fractions were 18.5%, 15.1% and 7.8% respectively., Conclusions: Loose teeth, number of teeth and pain in the mouth were associated with chewing disability, with an inadequate dentition and pain in the mouth contributing most to chewing disability in this population., (© 2012 The Gerodontology Society and John Wiley & Sons A/S.)

Identification of brain regions that differentially respond to pain intensity may improve our understanding of trigeminally mediated nociception. This report analyzed cortical responses to painless and painful electrical stimulation of a right human maxillary canine tooth. Functional magnetic resonance images were obtained during the application of five graded stimulus strengths, from below, at, and above the individually determined pain thresholds. Study participants reported each stimulus on a visual rating scale with respect to evoked sensation. Based on hemodynamic responses of all pooled stimuli, a cerebral network was identified that largely corresponds to the known lateral and medial nociceptive system. Further analysis of the five graded stimulus strengths revealed positive linear correlations for the anterior insula bilaterally, the contralateral (left) anterior mid-cingulate, as well as contralateral (left) pregenual cingulate cortices. Cerebral toothache intensity coding on a group level can thus be attributed to specific subregions within the cortical pain network.

A dual thermal and electrical stimulator was developed to examine the central pathways that transmit noxious stimuli for intact dentition. This system allows computer-controlled stimulation of the canines of ferrets with either noxious heat or electrical stimuli. A set of in vitro studies demonstrated that the application of thermal stimuli to an intact tooth can produce pulpal temperatures above 43 °C, which is perceived as a painful stimulus in humans. In a set of in vivo studies, it was demonstrated that heating an intact tooth at temperatures of at least 40 °C, excited trigeminal brainstem neurons. Only 15% of the neurons activated by electrical stimulation responded to noxious heat applied to the canine. Eight of the 23 neurons were classified as nociceptive specific neurons and responded only to noxious stimulation of their cutaneous receptive fields. Fifteen of the 23 neurons were classified as wide dynamic range neurons and responded to both noxious and non-noxious stimulation applied to their cutaneous receptive fields. This new device can accurately deliver both thermal and electrical stimuli to an intact tooth, which allows an evaluation of the central neural circuits that respond to noxious stimulation of the dentition., (Copyright © 2011 Elsevier B.V. All rights reserved.)