Insight into orthodontic appliance induced pain:Mechanism,duration and management

Most of the orthodontic patients experience pain during treatment and this significantly influences their attitudes and the approach towards treatment. A number of factors that influence pain response include age, gender, personal pain threshold, mood and stress level of the person, cultural differences and types of orthodontic treatment. Pain is a often overlooked subject by orthodontists, it is nevertheless important to understand the source and mechanism of the pain that occurs during treatment, as well as the methods for managing and controlling this pain. This review attempts to overview the mechanism, duration and current management strategies of orthodontic treatment.

Newborn with Giant Non-Involuting Congenital Hemangioma: Mechanisms of Allodynia, Hyperalgesia and Treatment

In a newborn affected by a non involuting congenital hemangioma we measured allodynia through the application of a standard tactile stimulus and hyperalgesia through the regular administration of the Comfort scale which rates pain intensity. The baby presented signs of these pathological events over long periods of the disease. They may be attributed to the high amount of the nociceptive ligands in the hemangioma microenviroment and to the elevated concentration of TNF-alpha and IL-6 in the blood. For a long time, the pain was relieved by a combination of opioids, adjuvants and paracetamol, but also by thalidomide and unexpectedly by interferon alpha. A mechanism-based pain treatment needs to take into account the processes underlying pain and also the ongoing pathology.

Lumbar interspinous pressure pain threshold values for healthy young men and women and the effect of prolonged fully flexed lumbar sitting posture:An observational study

BACKGROUND Low back pain(LBP)is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBP.No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain,despite this being a suggested risk factor for LBP.AIM To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBP.METHODS This is a an observational before and after study of 26 participants(13 men,13 women)between 20-35 years old.Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5.Pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back(Borg CR10=7/10).Wilcoxon signed-rank test was used for analyze values from the before and after test conditions.Mann-Whitney U test was used to investigate potential gender difference.RESULTS Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%.For all pain pressure threshold locations tested,there was a significant difference for the study population with moderate-large decreased(r=-0.56)pressure pain threshold after exposure to prolonged flexed sitting posture(P<0.01).Comparisons between gender did not show any significant difference.CONCLUSION The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBP and significantly reduced lumbar interspinous pressure pain thresholds.No gender-based differences were observed.

Puerarin ameliorates allodynia and hyperalgesia in rats with peripheral nerve injury

Puerarin is a major active ingredient of the traditional Chinese plant medicine,Radix Puerariae,and commonly used in the treatment of myocardial and cerebral ischemia.However,the effects of puerarin on neuropathic pain are still unclear.In this study,a neuropathic pain animal model was created by partial sciatic nerve ligation.Puerarin（30 or 60 mg/kg） was intraperitoneally injected once a day for 7 days.Mechanical allodynia and thermal hyperalgesia were examined at 1 day after model establishment.Mechanical threshold and paw withdrawal latency markedly increased in a dose-dependent manner in puerarin-treated rats,especially at 7 days after model establishment.At 7 days after model establishment,quantitative real-time reverse transcriptase-polymerase chain reaction results showed that puerarin administration reversed m RNA expression of transient receptor potential vanilloid 1（Trpv1） and transient receptor potential ankyrin 1（Trpa1） in a dose-dependent manner in dorsal root ganglion neurons after peripheral nerve injury.These results suggest that puerarin dose-dependently ameliorates neuropathic pain by suppressing Trpv1 and Trpa1 up-regulation in dorsal root ganglion of neuropathic pain rats.

Recent Progress in Understanding the Mechanisms of Pain and Itch:the Second Special Issue

In 2012, we published the first special issue on mechanisms of pain and itch in Neuroscience Bulletin, which covered the peripheral, central, and glial mechanisms of pain and itch [1-5]. In the last 5 years, the field has seen tremendous progress in the molecular and functional characterization of primary sensory neurons [6, 7], neurocircuits of pain and itch [8-10], immune and glial modulation of pain and itch [11-15], molecular mechanisms of pain [16, 17], and identification of brain signatures of pain [18]. Thus, it is timely to highlight the recent progress in a second special issue. I invited the previous authors and new authors from China, the USA, and Japan, and they have contributed 20 mini-reviews and original articles to this special issue.

Post-stroke pain hypersensitivity induced by experimental thalamic hemorrhage in rats is region-specific and demonstrates limited efficacy of gabapentin

Intractable central post-stroke pain（CPSP） is one of the most common sequelae of stroke, but has been inadequately studied to date. In this study, we first determined the relationship between the lesion site and changes in mechanical or thermal pain sensitivity in a rat CPSP model with experimental thalamic hemorrhage produced by unilateral intra-thalamic collagenase IV（ITC） injection. Then, we evaluated the efficacy of gabapentin（GBP）, an anticonvulsant that binds the voltage-gated Ca2＋ channel α2δ and a commonly used anti-neuropathic pain medication. Histological case-by-case analysis showed that only lesions confined to the medial lemniscus and the ventroposterior lateral/medial nuclei of the thalamus and/or the posterior thalamic nucleus resulted in bilateral mechanical pain hypersensitivity. All of the animals displaying CPSP also had impaired motor coordination, while control rats with intra-thalamic saline developed no central pain or motor deficits. GBP had a dose-related anti-allodynic effect after a single administration（1, 10, or 100 mg/kg） on day 7 post-ITC, with significant effects lasting at least 5 hfor the higher doses. However, repeated treatment, once a day for two weeks, resulted in complete loss of effectiveness（drug tolerance） at 10 mg/kg, while effectiveness remained at 100 mg/kg, although the time period of efficacious analgesia was reduced. In addition, GBP did not change the basal pain sensitivity and the motor impairment caused by the ITC lesion, suggesting selective action of GBP on the somatosensory system.

Insular Cortex is Critical for the Perception, Modulation,and Chronification of Pain

An increasing body of neuroimaging and electrophysiological studies of the brain suggest that the insular cortex（IC） integrates multimodal salient information ranging from sensation to cognitive-affective events to create conscious interoception. Especially with regard to pain experience, the IC has been supposed to participate in both sensory-discriminative and affective-motivational aspects of pain. In this review, we discuss the latest data proposing that subregions of the IC are involved in isolated pain networks： the posterior sensory circuit and the anterior emotional network. Due to abundant connections with other brain areas, the IC is likely to serve as an interface where cross-modal shaping of pain occurs. In chronic pain,however, this mode of emotional awareness and the modulation of pain are disrupted. We highlight some of the molecular mechanisms underlying the changes of the pain modulation system that contribute to the transition from acute to chronic pain in the IC.