Chronic jaw pain attenuates neural oscillations during motor-evoked pain.

Motor- and pain-related processes separately induce a reduction in alpha and beta power. When movement and pain occur simultaneously but are independent of each other, the effects on alpha and beta power are additive. It is not clear whether this additive effect is evident during motor-evoked pain in individuals with chronic pain. We combined highdensity electroencephalography (EEG) with a paradigm in which motor-evoked pain was induced during a jaw force task. Participants with chronic jaw pain and pain-free controls produced jaw force at 2% and 15% of their maximum voluntary contraction. The chronic jaw pain group showed exacerbated motor-evoked pain as force amplitude increased and showed increased motor variability and motor error irrespective of force amplitude. The chronic jaw pain group had an attenuated decrease in power in alpha and lower-beta frequencies in the occipital cortex during the anticipation and experience of motor-evoked pain. Rather than being additive, motor-evoked pain attenuated the modulation of alpha and beta power, and this was most evident in occipital cortex. Our findings provide the first evidence of changes in neural oscillations in the cortex during motor-evoked jaw pain.

Altered neural oscillations within and between sensorimotor cortex and parietal cortex in chronic jaw pain.

Pain perception is associated with priming of the motor system and the orienting of attention in healthy adults. These processes correspond with decreases in alpha and beta power in the sensorimotor and parietal cortices. The goal of the present study was to determine whether these findings extend to individuals with chronic pain. Individuals with chronic jaw pain and pain-free controls anticipated and experienced a low pain or a moderate pain-eliciting heat stimulus. Although stimuli were calibrated for each subject, stimulus temperature was not different between groups. High-density EEG data were collected during the anticipation and heat stimulation periods and were analyzed using independent component analyses, EEG source localization, and measure projection analyses. Direct directed transfer function was also estimated to identify frequency specific effective connectivity between regions. Between group differences were most evident during the heat stimulation period. We report three novel findings. First, the chronic jaw pain group had a relative increase in alpha and beta power and a relative decrease in theta and gamma power in sensorimotor cortex. Second, the chronic jaw pain group had a relative increase in power in the alpha and beta bands in parietal cortex. Third, the chronic jaw pain group had less connectivity strength in the beta and gamma bands between sensorimotor cortex and parietal cortex. Our findings show that the effect of chronic pain attenuates rather than magnifies neural responses to heat stimuli. We interpret these findings in the context of system-level changes in intrinsic sensorimotor and attentional circuits in chronic pain.

Genome-wide association reveals contribution of MRAS to painful temporomandibular disorder in males.

Painful temporomandibular disorders (TMDs) are the leading cause of chronic orofacial pain, but its underlying molecular mechanisms remain obscure. Although many environmental factors have been associated with higher risk of developing painful TMD, family and twin studies support a heritable genetic component as well. We performed a genome-wide association study assuming an additive genetic model of TMD in a discovery cohort of 999 cases and 2031 TMD-free controls from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) study. Using logistic models adjusted for sex, age, enrollment site, and race, we identified 3 distinct loci that were significant in combined or sex-segregated analyses. A single-nucleotide polymorphism on chromosome 3 (rs13078961) was significantly associated with TMD in males only (odds ratio = 2.9, 95% confidence interval: 2.02-4.27, P = 2.2 × 10). This association was nominally replicated in a meta-analysis of 7 independent orofacial pain cohorts including 160,194 participants (odds ratio = 1.16, 95% confidence interval: 1.0-1.35, P = 2.3 × 10). Functional analysis in human dorsal root ganglia and blood indicated this variant is an expression quantitative trait locus, with the minor allele associated with decreased expression of the nearby muscle RAS oncogene homolog (MRAS) gene (beta = -0.51, P = 2.43 × 10). Male mice, but not female mice, with a null mutation of Mras displayed persistent mechanical allodynia in a model of inflammatory pain. Genetic and behavioral evidence support a novel mechanism by which genetically determined MRAS expression moderates the resiliency to chronic pain. This effect is male-specific and may contribute to the lower rates of painful TMD in men.

Functional brain activity during motor control and pain processing in chronic jaw pain.

Changes in brain function in chronic pain have been studied using paradigms that deliver acute pain-eliciting stimuli or assess the brain at rest. Although motor disability accompanies many chronic pain conditions, few studies have directly assessed brain activity during motor function in individuals with chronic pain. Using chronic jaw pain as a model, we assessed brain activity during a precisely controlled grip force task and during a precisely controlled pain-eliciting stimulus on the forearm. We used multivariate analyses to identify regions across the brain whose activity together best separated the groups. We report 2 novel findings. First, although the parameters of grip force production were similar between the groups, the functional activity in regions including the prefrontal cortex, insula, and thalamus best separated the groups. Second, although stimulus intensity and pain perception were similar between the groups, functional activity in brain regions including the dorsal lateral prefrontal cortex, rostral ventral premotor cortex, and inferior parietal lobule best separated the groups. Our observations suggest that chronic jaw pain is associated with changes in how the brain processes motor and pain-related information even when the effector producing the force or experiencing the pain-eliciting stimulus is distant from the jaw. We also demonstrate that motor tasks and multivariate analyses offer alternative approaches for studying brain function in chronic jaw pain.

Associação entre o tipo de aleitamento na alta hospitalar do recém-nascido e aos seis meses de vida / Association between type of breastfeeding of newborns at hospital discharge and at six months of age

Resumo Introdução Os índices de aleitamento materno no Brasil permanecem muito abaixo dos considerados ideais, fazendo-se necessário o entendimento das variáveis envolvidas na fragmentação do aleitamento ao longo dos meses de vida da criança. Objetivo Objetivou-se, neste estudo, verificar a associação entre o tipo de aleitamento no momento da alta hospitalar do recém-nascido e a prática da amamentação aos seis meses de vida. Método Estudo transversal, com dados coletados do prontuário clínico de 301 crianças participantes de um programa de incentivo ao aleitamento materno. Foram considerados os fatores de risco e de proteção ao aleitamento, tais como: idade dos pais, presença do companheiro, paridade, renda familiar, permanência em alojamento conjunto, tempo decorrido do nascimento até a primeira mamada, tempo de hospitalização, tipo de amamentação na alta hospitalar e uso de chupeta ao longo dos seis meses de vida. Resultados Os resultados mostraram haver associação significativa entre aleitamento materno exclusivo na alta hospitalar e aos seis meses de idade (p=0,0205). Conclusão A observação desses dados permite concluir que é importante que, ao deixar a maternidade, o bebê esteja em amamentação exclusiva, pois, dessa forma, terá 2,5 vezes mais chances de manter esse tipo de aleitamento até os seis meses de vida.

Abstract Introduction Breastfeeding rates in Brazil remain far below those considered ideal, making it necessary understanding the variables involved in the fragmentation of this process over the months of a child's life. Objective The objective of this study was to investigate the association between type of breastfeeding of newborns at hospital discharge and at six months of age. Method A cross-sectional study with data collected from the medical records of 301 children participating in a program to encourage exclusive breastfeeding. The study considered risk and protection factors to breastfeeding such as age of parents, presence of mate, parity, family income, stay in room, time elapsed from birth to first breastfeeding, hospitalization time, type of breastfeeding at hospital discharge, and use of pacifier until the age of six months. Results The results revealed significant correlation between exclusive breastfeeding at hospital discharge and at six months of age (p=0.0205). Conclusion Observation of data enabled the following conclusion: it is important that newborns undergo exclusive breastfeeding after hospital discharge because, this way, they will be 2.5 times more likely to maintain this type of feeding until the age of six months.

Motor-Evoked Pain Increases Force Variability in Chronic Jaw Pain.

Musculoskeletal pain changes how people move. Although experimental pain is associated with increases in the variability of motor output, it is not clear whether motor-evoked pain in clinical conditions is also associated with increases in variability. In the current study, we measured jaw force production during a visually guided force paradigm in which individuals with chronic jaw pain and control subjects produced force at 2% of their maximum voluntary contraction (low target force level) and at 15% of their maximum voluntary contraction (high target force level). State measures of pain were collected before and after each trial. Trait measures of pain intensity and pain interference, self-report measures of jaw function, and measures of depression, anxiety, and fatigue were also collected. We showed that the chronic jaw pain group exhibited greater force variability compared with controls irrespective of the force level, whereas the accuracy of force production did not differ between groups. Furthermore, predictors of force variability shifted from trait measures of pain intensity and pain interference at the low force level to state measures of pain intensity at the high force level. Our observations show that motor-evoked jaw pain is associated with increases in force variability that are predicted by a combination of trait measures and state measures of pain intensity and pain interference. PERSPECTIVE: Chronic jaw pain is characterized by increases in variability during force production, which can be predicted by pain intensity and pain interference. This report could help clinicians better understand the long-term consequences of chronic jaw pain on the motor system.

Salivary cortisol level and uncooperative behavior in pediatric dental practice

Aim: To investigate the relation between uncooperative behavior and salivary cortisol level in childrenwho underwent preventive dental care. Methods: The sample was composed by 10 children of bothsexes aged 40 to 52 months, presenting uncooperative behavior during dental preventive treatments.The saliva collection was performed using a cotton wheel and an Eppendorf tube (Sarstedt Salivete®)in 3 different moments: a) at home, on a day without dental treatment and at the same time on theday of the sessions treatment; b) 30 min after the end of the session, when there was manifestationof uncooperative behavior; c) 30 min after the end of the session, when there was a cooperativebehavior of the child. A sample of saliva was centrifuged for 5 minutes at 2400 rpm, 1 of mL of salivawas pipetted in an Eppendorf tube and stored in a freezer at -20 ° C. For the determination of thelevels of salivary cortisol was used an Active® kit for cortisol enzyme immunoassay (EIA) DSL-10-67100, composed of specific rabbit antibody anti-cortisol. Data were analyzed statistically for theuncooperative behavior issued in the beginning and at the end of sessions, using the paired t test(p<0.05) and for cortisol levels in saliva samples at home, after the beginning and at the end ofsessions, using repeated-measures ANOVA and Tukey’s test (p<0.05). Results: During expression ofuncooperative behavior in preventive dental care sessions the salivary cortisol level was significantlyhigher (0.65 ± 0.25 µg/dL) compared with expression of collaborative behavior (0.24 ± 0.10 µg/dL).Conclusions: It is possible to conclude that, even under preventive intervention, the stress must becontrolled in order to reduce dental anxiety and fear.

Genomics and the new perspectives for temporomandibular disorders.

The field of temporomandibular disorders (TMD) is experiencing significant changes in terms of aetiology and treatment. Researchers and clinicians are becoming increasingly aware of the possibility that genetic variations may play a role in pain perception and onset of TMD. In this review, we purpose to briefly describe these allelic variants, how they may be involved in TMD pathophysiology and how they may affect TMD treatment. Studies have already pointed the association between TMD and genetic polymorphisms in the oestrogen receptor alpha, adrenergic receptor beta 2, serotonin receptor, serotonin transporter and catechol-O-methyltransferase genes, and other candidate genes continue to emerge. The main implication of these findings refers to the promising possibilities of "genome/omics-based personalised care", which consists of tailoring individual treatment based on personalised medication, depending on the individual genetic differences and early diagnosis and prognosis of the disorder, preventing acute pain conditions from becoming chronic. The following years of research shall focus on collecting and endorsing these findings if we are to provide patients in pain with efficient and successful TMD treatments.

Influence of double flask investing and microwave heating on the superficial porosity, surface roughness, and knoop hardness of acrylic resin.

PURPOSE: Simultaneous polymerization of maxillary and mandibular complete dentures with teeth in occlusion through investing in a double special flask has been described as a more rapid and efficient method to polymerize prostheses than the conventional method; however, no study has been done to verify important properties of resin, including superficial porosity, surface roughness, and hardness, when processed by this technique. The purpose of this study was to verify if the simultaneous polymerization associated with microwave heating may alter the superficial porosity, surface roughness, and Knoop hardness of acrylic resin. MATERIALS AND METHODS: Resin specimens processed in single and double dental flasks were compared using microwave energy and warm water methods. Four groups were tested according to the investing flask and the method of resin cure: Group I control specimens (n = 15) were invested in single metal flasks and cured by warm water at 74 degrees C for 9 hours. Group II (n = 15) specimens were invested in single polyvinyl chloride flasks and cured by microwave energy at 90 W for 20 minutes plus 450 W for 5 minutes. Group III (n = 30) and Group IV (n = 30) specimens were processed by simultaneous polymerization in double flasks and cured by the same warm water and microwave energy protocols, respectively. RESULTS: No significant differences were found in mean superficial porosity (8.06 +/- 2.28 pore/cm(2)), surface roughness (0.14 +/- 0.03 mum), or Knoop hardness (19.66 +/- 2.25 kgf/mm(2)) between the control group (GI), and the other three experimental groups (p > 0.05). CONCLUSION: Processing acrylic resin in a double flask heated by either warm water or microwave energy does not alter the resin's superficial porosity, surface roughness, or Knoop hardness; however, other properties of resin should be analyzed using this denture processing technique.

Sex, gender, and pain: a review of recent clinical and experimental findings.

UNLABELLED: Sex-related influences on pain and analgesia have become a topic of tremendous scientific and clinical interest, especially in the last 10 to 15 years. Members of our research group published reviews of this literature more than a decade ago, and the intervening time period has witnessed robust growth in research regarding sex, gender, and pain. Therefore, it seems timely to revisit this literature. Abundant evidence from recent epidemiologic studies clearly demonstrates that women are at substantially greater risk for many clinical pain conditions, and there is some suggestion that postoperative and procedural pain may be more severe among women than men. Consistent with our previous reviews, current human findings regarding sex differences in experimental pain indicate greater pain sensitivity among females compared with males for most pain modalities, including more recently implemented clinically relevant pain models such as temporal summation of pain and intramuscular injection of algesic substances. The evidence regarding sex differences in laboratory measures of endogenous pain modulation is mixed, as are findings from studies using functional brain imaging to ascertain sex differences in pain-related cerebral activation. Also inconsistent are findings regarding sex differences in responses to pharmacologic and non-pharmacologic pain treatments. The article concludes with a discussion of potential biopsychosocial mechanisms that may underlie sex differences in pain, and considerations for future research are discussed. PERSPECTIVE: This article reviews the recent literature regarding sex, gender, and pain. The growing body of evidence that has accumulated in the past 10 to 15 years continues to indicate substantial sex differences in clinical and experimental pain responses, and some evidence suggests that pain treatment responses may differ for women versus men.