A comparative evaluation of the efficiency of warm local anesthetic solution delivered on precooled injection sites with the conventional local anesthetic technique in 7-9-year-old children: A randomized split-mouth cross-over trial.

BACKGROUND: Both precooling the site and injecting a warm anesthetic solution have proven to be efficient in reducing pain individually. However, there is insufficient data on evaluating the efficiency of precooling the site of injection along with the simultaneous administration of a warm local anesthetic solution on the same site in a single patient. AIM: The aim of this study was to evaluate and compare the efficacy, pain perception, hemodynamic changes, and adverse effects of a warm local anesthetic solution injected on precooled injection sites using 2% lignocaine with the conventional local anesthetic technique during inferior alveolar nerve block in 7-9-year-old children. METHODS: A split-mouth, double-blinded, randomized clinical trial was conducted on 70 children who received 2% lignocaine with either technique A or B during the first or second appointment of the treatment procedure. The pain perception, anesthetic efficacy, pulse rate, oxygen saturation levels, and adverse events were evaluated. RESULTS: Pain during injection and treatment after administration of the warm local anesthesia (LA) technique was less as compared to the conventional block technique. Anesthetic success was observed with a faster onset of action (212.57 ± 32.51 s) and shorter duration of LA (165.16 ± 33.09 min) in the warm local technique as compared to the conventional technique. No significant differences were found with regard to heart rate and oxygen saturation levels between the two techniques. Administrating warm LA solutions at precooled injection sites revealed fewer adverse events. CONCLUSION: Injecting warm LA solution on precooled injection sites causes less discomfort and anxiety in children, which makes it more suitable for the child as well as the pediatric dentist.

Inferior alveolar nerve block anesthesia in children: The effect of ibuprofen and phentolamine mesylate on pain perception.

CONTEXT: For successfully managing pediatric dental patients, local anesthesia is essential to eliminate pain during or after the operative period. An early recovery from soft-tissue anesthesia after an inferior alveolar nerve block (IANB) should benefit a young child patient by avoiding the risk of inadvertently biting the soft tissues. AIMS: Hence, the purpose of the study was to (1) evaluate and compare the efficacy of pre- and postoperative ibuprofen on pain perception in children who undergo IANB anesthesia with or without the use of PM and (2) evaluate the average time required for reversal of anesthesia symptoms using phentolamine mesylate. METHODS: The present study was a randomized, clinical trial performed among 60 children between 6 and 8 years of age using a convenient sampling method. The children were randomly assigned into four equal groups of 15 each using the computer-generated randomization sequence. IANB anesthesia was performed using 2% lignocaine with 1:100,000 epinephrine, and a mandibular primary molar pulpotomy was performed on each group. Group 1: the ibuprofen tablet was taken 1 h before the onset of the procedure. Group 2: ibuprofen tablet 30 min after the pulpotomy procedure. Group 3: the ibuprofen tablet was taken 1 h before the onset of the procedure, and the Phentolamine mesylate (PM) injection was administered. Group 4: immediately after the pulpotomy, the PM injection was administered, and an ibuprofen tablet was taken 30 min after the pulpotomy procedure. All children were assessed for the duration of soft-tissue anesthesia, their behavior scores and pain rating, as well as the incidence of postoperative self-inflicted injuries. STATISTICAL ANALYSIS USED: A one-way ANOVA was used to compare the average time needed for the reversal of anesthetic symptoms between groups. The effects of phentolamine, local anesthetics, and ibuprofen on the child's behavior and pain scores were compared using the Student's t-test. For the study, P < 0.05 was accepted as statistically significant. RESULTS: The time needed for the full reversal of anesthetic symptoms to manifest on the tongue and lip was substantially reduced by the injection of phentolamine (P < 0.001). The use of phentolamine for reversal or the intake of ibuprofen pre- or postoperatively did not exhibit any significant variation in the behavior, pain experience, or incidence of self-inflicted injuries in the child. CONCLUSION: It is evident that although phentolamine injections shorten the duration of anesthesia, the adjunctive use of pre- or postoperative ibuprofen did not significantly alter pain scores.

Posttraumatic headache: pain related evoked potentials (PREP) and conditioned pain modulation (CPM) to assess the pain modulatory function.

Posttraumatic headache (PTH) is common following traumatic brain injury and impacts quality of life. We investigated descending pain modulation as one possible mechanism for PTH and correlated it to clinical measures. Pain-related evoked potentials (PREP) were recorded in 26 PTH-patients and 20 controls after electrical stimulation at the right hand and forehead with concentric surface electrodes. Conditioned pain modulation (CPM) was assessed using painful cutaneous electric stimulation (PCES) on the right hand as test stimulus and immersion of the left hand into 10 °C-cold water bath as conditioning stimulus based on changes in pain intensity and in amplitudes of PCES-evoked potentials. All participants completed questionnaires assessing depression, anxiety, and pain catastrophising. PTH-patients reported significantly higher pain ratings during PREP-recording in both areas despite similar stimulus intensity at pain threshold. N1P1-amplitudes during PREP and CPM-assessment were lower in patients in both areas, but statistically significant only on the hand. Both, PREP-N1-latencies and CPM-effects (based on the N1P1-amplitudes and pain ratings) were similar in both groups. Patients showed significantly higher ratings for anxiety and depression, which did not correlate with the CPM-effect. Our results indicate generalized hyperalgesia for electrical stimuli in both hand and face in PTH. The lacking correlation between pain ratings and EEG parameters indicates different mechanisms of pain perception and nociception.

Unpacking the relationship between Big Five personality traits and experimental pain: A systematic review and meta-analysis.

Pain is essential for survival, but individual responses to painful stimuli vary, representing a complex interplay between sensory, cognitive, and affective factors. Individual differences in personality traits and in pain perception covary but it is unclear which traits play the most significant role in understanding the pain experience and whether this depends on pain modality. A systematic search identified 1534 records (CINAHL, MEDLINE, PsycInfo, PubMed and Web of Science), of which 22 were retained and included in a systematic review. Only studies from the pressure pain domain (n=6) could be compared in a formal meta-analysis to evaluate the relationship between Big Five traits and experimental pain. Pressure pain tolerance correlated positively with Extraversion and negatively with Neuroticism with a trivial effect size (<0.1). While these findings suggest personality might be only weakly related to pain in healthy individuals, we emphasize the need to consider standardization, biases, and adequate sample sizes in future research, as well as additional factors that might affect experimental pain sensitivity.

Statistical learning shapes pain perception and prediction independently of external cues.

The placebo and nocebo effects highlight the importance of expectations in modulating pain perception, but in everyday life we don't need an external source of information to form expectations about pain. The brain can learn to predict pain in a more fundamental way, simply by experiencing fluctuating, non-random streams of noxious inputs, and extracting their temporal regularities. This process is called statistical learning. Here, we address a key open question: does statistical learning modulate pain perception? We asked 27 participants to both rate and predict pain intensity levels in sequences of fluctuating heat pain. Using a computational approach, we show that probabilistic expectations and confidence were used to weigh pain perception and prediction. As such, this study goes beyond well-established conditioning paradigms associating non-pain cues with pain outcomes, and shows that statistical learning itself shapes pain experience. This finding opens a new path of research into the brain mechanisms of pain regulation, with relevance to chronic pain where it may be dysfunctional.

Pain perception as hierarchical Bayesian inference: A test case for the theory of constructed emotion.

An intriguing perspective about human emotion, the theory of constructed emotion considers emotions as generative models according to the Bayesian brain hypothesis. This theory brings fresh insight to existing findings, but its complexity renders it challenging to test experimentally. We argue that laboratory studies of pain could support the theory because although some may not consider pain to be a genuine emotion, the theory must at minimum be able to explain pain perception and its dysfunction in pathology. We review emerging evidence that bear on this question. We cover behavioral and neural laboratory findings, computational models, placebo hyperalgesia, and chronic pain. We conclude that there is substantial evidence for a predictive processing account of painful experience, paving the way for a better understanding of neuronal and computational mechanisms of other emotions.

An evaluation of the behavioural inhibition system and behavioural activation system (BIS-BAS) model of pain in athletes.

This study examined coping and pain responses using a behavioural inhibition (BIS) - behavioural activation (BAS) framework in 489 student athletes (M(age) = 20, SD = 4; 69% female). Two samples of athletes (226 pain-free athletes and 232 athletes with current pain) completed surveys assessing BIS- and BAS-related cognitions, emotions, and behaviours. Distinct groupings of BAS-related variables were identified in both samples, evidenced by significant positive correlations within BAS-related variables (positive affect, pain openness, approach thoughts and behaviours). Most BIS-related variables (depression, anxiety, harm beliefs, pain catastrophizing and avoidance behaviours) were also correlated in the sample of athletes with pain; however, this was not observed in pain-free athletes. In athletes with pain, BIS-related variables were significantly associated with pain variables, with this association stronger than that found for BAS-related variables. Regression analyses highlighted the pivotal role of pain catastrophizing as a predictor of pain unpleasantness and intensity. Findings shed light on the factors shaping athletes' coping, pain perception and decisions as to whether to pause or push through. Future investigations to explore these dynamics in more depth may aid in the development of targeted interventions that enhance athletes' ability to cope and to manage pain more effectively.

Dissecting shared pain representations to understand their behavioral and clinical relevance.

Accounts of shared representations posit that the experience of pain and pain empathy rely on similar neural mechanisms. Experimental research employing novel analytical and methodological approaches has made significant advances in both the identification and targeted manipulation of such shared experiences and their neural underpinnings. This revealed that painful experiences can be shared on different representational levels, from pain-specific to domain-general features, such as negative affect and its regulation. In view of direct links between such representations and social behaviors such as prosocial behavior, conditions characterized by aberrant pain processing may come along with heavy impairments in the social domain, depending on the affected representational level. This has wide potential implications in light of the high prevalence of pain-related clinical conditions, their management, and the overuse of pain medication. In this review and opinion paper, we aim to chart the path toward a better understanding of the link between shared affect and prosocial behavior.

Endogenous Opioids and Exercise-Related Hypoalgesia: Modern Models, Measurement, and Mechanisms of Action.

This chapter will focus on the role exercise appears to have on activation and modulating factors within the central nervous system related to endogenous like opioids and its possible contribution to exercise-induced hypoalgesia. The implications for the exercise-mediated alterations of CNS activation factors related to opioids, specifically endorphins and enkephalins, will be presented. In this update, we discuss utilization of new technology and methods to monitor mechanisms of opioid involvement to suggest their contribution with exercise mediated hypoalgesia as well as their relationships to alterations of perceptions of pain and mood. Several special populations were included to suggest that not all individuals will respond to the exercise by mediating hypoalgesia. Factors that may confound the current understanding and suggestions from the recent literature will be presented as well as suggestions for future investigations.

The independence and predictivity of resting pain-free slow alpha frequency as a biomarker of pain: A reply to Mazaheri et al.

In response to Mazaheri et al.'s critique, we revisited our study (Valentini et al., 2022) on the relationship between peak alpha frequency (PAF) and pain. Their commentary prompted us to reassess our data to address the independence between slow and slowing alpha brain oscillations, as well as the predictivity of slow alpha oscillations in pain perception. Bayesian correlation analyses revealed mixed support for independence. Investigating predictivity, we found inconsistent associations between pre-PAF and unpleasantness ratings. We critically reflected on methodological and theoretical issues on the path to PAF validation as a pain biomarker. We emphasized the need for diversified methodology and analytical approaches as well as robust findings across research groups.

Intracranial EEG signals disentangle multi-areal neural dynamics of vicarious pain perception.

Empathy enables understanding and sharing of others' feelings. Human neuroimaging studies have identified critical brain regions supporting empathy for pain, including the anterior insula (AI), anterior cingulate (ACC), amygdala, and inferior frontal gyrus (IFG). However, to date, the precise spatio-temporal profiles of empathic neural responses and inter-regional communications remain elusive. Here, using intracranial electroencephalography, we investigated electrophysiological signatures of vicarious pain perception. Others' pain perception induced early increases in high-gamma activity in IFG, beta power increases in ACC, but decreased beta power in AI and amygdala. Vicarious pain perception also altered the beta-band-coordinated coupling between ACC, AI, and amygdala, as well as increased modulation of IFG high-gamma amplitudes by beta phases of amygdala/AI/ACC. We identified a necessary combination of neural features for decoding vicarious pain perception. These spatio-temporally specific regional activities and inter-regional interactions within the empathy network suggest a neurodynamic model of human pain empathy.

Donor site wound healing following free gingival graft surgery using platelet rich fibrin: A randomized controlled trial.

BACKGROUND: The primary purpose of this two-arm, parallel design, randomized controlled study is to compare healing of the palatal tissue donor site when platelet-rich fibrin (PRF) is used as a wound dressing compared to the use of a hemostatic agent. Secondary outcomes of patient pain perception and analgesic intake were also evaluated. METHODS: Seventy-four patients receiving free gingival grafts were randomized to receive either PRF (test) or hemostatic agent (control) as a palatal wound dressing by patients selecting a sealed envelope containing their group assignment (initially 37 envelopes for PRF group and 37 for hemostatic agent group). Patient pain assessment and analgesic consumption were documented using a 21-point numerical scale (NMRS-21) at 24, 48, and 72 hours post-surgery. At 1-, 2-, 3-, and 4-week follow-up appointments palatal early healing index (PEHI) scores including wound color, epithelialization, presence or absence of swelling, granulation tissue, and bleeding on gentle palpation were generated by direct intraoral examination by a blinded examiner unaware of the patients' treatment group. RESULTS: NMRS-21 pain scores showed a significant reduction in pain over time in both groups, with no significant difference between groups at any time point. No significant between-group difference was found in the amount of analgesics taken by patients at 24, 48, and 72 hours. There was significant improvement in PEHI scores over the 4-week time period in both groups, but there was no significant difference in PEHI score at each time point (1, 2, 3, 4 weeks) between groups.  CONCLUSIONS: Study findings suggest that there is no difference in early palatal wound healing, patient pain perception, or analgesic consumption between use of PRF or a hemostatic agent as donor-site wound dressings.

Assessment of Perception of Pain with E-Speed Film, CCD Sensor and Photostimulable Phosphor Plates for Intraoral Radiographs in Children using Three Pain Rating Scales.

BACKGROUND: Dental radiography is an integral part of intraoral evaluation. Children are often uncomfortable during the placement of film or sensor due to the impingement of the soft tissues. Thus, the perception of pain with three intraoral radiographic methods in children was evaluated using three subjective pain rating scales. AIM: To evaluate the discomfort with three different techniques, that is, intraoral periapical (IOPA) radiograph, charge-coupled device (CCD), and photostimulable phosphor (PSP) luminescence (PSPL), using the Wong-Baker Faces Pain Rating Scale (WBFPRS), numerical rating scale, and visual analog scale (VAS). MATERIALS AND METHODS: A sample of 35 children aged 6-12 years were divided into two groups: group 1 (6-8 years) and group 2 (9-12 years). For each child, simulations of the three radiological methods (IOPA, CCD, and PSPL) were performed. The meaning of each facial expression on the WBFPRS, VAS, and the numbers on the numerical rating scale was explained to each child before the procedure. STATISTICAL ANALYSIS USED: A one-way analysis of variance (ANOVA) test and paired-samples t-test are used. RESULTS: The results revealed that the CCD sensors elicited higher pain scores than those obtained with IOPA and PSPL, whereas the IOPA film showed the least pain score. Higher score values were obtained in group 1 than in group 2, indicating that children aged 6-8 years felt higher discomfort than the 9- to 12-year age group for the same procedure. This difference was statistically significant (P < 0.001). CONCLUSION: It was concluded that conventional IOPA films were tolerated better by children when compared to PSP plates and CCD sensors.

A Suspended, 3D Morphing Sensory System for Robots to Feel and Protect.

Artificial sensory systems with synergistic touch and pain perception hold substantial promise for environment interaction and human-robot communication. However, the realization of biological skin-like functional integration of sensors with sensitive touch and pain perception still remains a challenge. Here, a concept is proposed of suspended electronic skins enabling 3D deformation-mechanical contact interactions for achieving synergetic ultrasensitive touch and adjustable pain perception. The suspended sensory system can sensitively capture tiny touch stimuli as low as 0.02 Pa and actively perceive pain response with reliable 5200 cycles via 3D deformation and mechanical contact mechanism, respectively. Based on the touch-pain effect, a visualized feedback demo with miniaturized sensor arrays on artificial fingers is rationally designed to give a pain perception mapping on sharp surfaces. Furthermore, the capability is shown of the suspended electronic skin serving as a safe human-robot communication interface from active and passive view through a feedback control system, demonstrating potential in bionic electronics and intelligent robotics.

Age-associated changes in multimodal pain perception.

BACKGROUND: Pain sensitivity varies across multimodal somatosensory stimuli that can rely on different conductive fibres, which, when damaged, will lead to neuropathies. However, there is limited research examining the characteristics of perceived pain, particularly as affected by the ageing process, as induced by various somatosensory stimuli that may rely on small or large fibres. METHODS: Using heat and pressure stimuli on small and large fibres separately on both younger and older adults, this study examined age-associated changes in pain perception by measuring self-reported pain sensitivity, pain threshold and pain discriminability. RESULTS: Heat pain threshold was significantly positively correlated with age, but not pressure pain threshold. Pain threshold increased and pain discriminability decreased in response to heat stimuli in the older participants compared with the younger ones. CONCLUSION: An age-associated decline in heat pain perception was observed, suggesting an earlier degradation of heat perception. These findings provide new insight into understanding and assessing somatosensory disorders, which can help ageing populations better maintain healthy sensory functioning.

Enhanced EEG power density during painful stretching in individuals with cerebral palsy.

BACKGROUND: Pain perception mechanisms in cerebral palsy remain largely unclear. AIMS: This study investigates brain activity in adults with cerebral palsy during painful and non-painful stretching to elucidate their pain processing characteristics. METHODS AND PROCEDURES: Twenty adults with cerebral palsy and 20 controls underwent EEG in three conditions: rest, non-painful stretching, and painful stretching. Time-frequency power density of theta, alpha, and beta waves in somatosensory and frontal cortices was analyzed, alongside baseline pressure pain thresholds. OUTCOMES AND RESULTS: Cerebral palsy individuals exhibited higher theta, alpha, and beta power density in both cortices during painful stretching compared to rest, and lower during non-painful stretching. Controls showed higher power density during non-painful stretching but lower during painful stretching. Cerebral palsy individuals had higher pain sensitivity, with those more sensitive experiencing greater alpha power density. CONCLUSIONS AND IMPLICATIONS: These findings confirm alterations in the cerebral processing of pain in individuals with cerebral palsy. This knowledge could enhance future approaches to the diagnosis and treatment of pain in this vulnerable population.

The effect of olanzapine on spatial memory impairment, depressive-like behavior, pain perception, and BDNF and synaptophysin expression following childhood chronic unpredictable mild stress in adult male and female rats.

Chronic unpredictable mild stress (CUMS) method has been introduced as a rodent model of depression. On the other hand, olanzapine, as an antipsychotic, can induce antidepressant and antipsychotic effects. Also, olanzapine may improve cognitive functions. Both CUMS and olanzapine can also affect the expression level of brain-derived neurotrophic factor (BDNF) and synaptophysin, the molecular factors involved in synaptic function, and learning and memory. In this study, we investigated the effect of olanzapine on locomotor activity (using open field test), pain threshold (using hot plate), depressive-like behavior (using forced swim test), spatial learning and memory (using Morris water maze), and BDNF and synaptophysin hippocampal expression (using real-time PCR) in both male and female CUMS rats. CUMS was performed for three consecutive weeks. Olanzapine was also injected intraperitoneally at the dose of 5 mg/kg. Our data showed that olanzapine can reverse the effects of CUMS on behavioral functions and BDNF and synaptophysin expression levels in the hippocampus of both males and females. It was also shown that olanzapine effects on spatial memory, pain perception, and BDNF and synaptophysin level were stronger in females than males. In conclusion, we suggested that the therapeutic effects of olanzapine in CUMS rats may be closely related to the function of BDNF and synaptophysin. Also, the therapeutic effects of olanzapine may be stronger in females. Therefore, and for the first time, we showed that there may be a sex difference in the effects of olanzapine on behavioral and molecular changes following CUMS.

Discussing Conflicting Explanatory Approaches in Flexibility Training Under Consideration of Physiology: A Narrative Review.

The mechanisms underlying range of motion enhancements via flexibility training discussed in the literature show high heterogeneity in research methodology and study findings. In addition, scientific conclusions are mostly based on functional observations while studies considering the underlying physiology are less common. However, understanding the underlying mechanisms that contribute to an improved range of motion through stretching is crucial for conducting comparable studies with sound designs, optimising training routines and accurately interpreting resulting outcomes. While there seems to be no evidence to attribute acute range of motion increases as well as changes in muscle and tendon stiffness and pain perception specifically to stretching or foam rolling, the role of general warm-up effects is discussed in this paper. Additionally, the role of mechanical tension applied to greater muscle lengths for range of motion improvement will be discussed. Thus, it is suggested that physical training stressors can be seen as external stimuli that control gene expression via the targeted stimulation of transcription factors, leading to structural adaptations due to enhanced protein synthesis. Hence, the possible role of serial sarcomerogenesis in altering pain perception, reducing muscle stiffness and passive torque, or changes in the optimal joint angle for force development is considered as well as alternative interventions with a potential impact on anabolic pathways. As there are limited possibilities to directly measure serial sarcomere number, longitudinal muscle hypertrophy remains without direct evidence. The available literature does not demonstrate the necessity of only using specific flexibility training routines such as stretching to enhance acute or chronic range of motion.