Effect of low-level laser therapy in wound healing of primary molar teeth extraction

INTRODUCTION

Tooth extraction in children requires attention to wound healing and pain management, which are influenced by patient-related factors and behavioral guidance.

AIM OF THE STUDY

The study aimed to evaluate the effect of LLLT on healing sockets in pediatric patients with bilateral primary molar teeth extraction and determine its impact on pain management.

METHODS

6-10 years of age, systemically healthy, and with atraumatic extraction indications of bilateral primary molar teeth were included in the study (n = 40). In the first session, randomly selected teeth were extracted under local anesthesia. In the control group, only clot formation in the socket was observed and photographed. The other group extractions were performed 2 weeks later. The low-level laser therapy (LLLT) group was treated with a 980 nm wavelength, in a continuous emission mode, 0.5 W power, 300 J of energy, 400 µm tip, 60 s diode laser and photographed. Nonepithelialized surface measurements were performed using ImageJ. Pain assessment was performed using the Wong-Baker Pain Scale. Statistical analyses were performed using SPSS software.

RESULTS

There was a statistically significant difference between the groups in the Wong-Baker values in 3rd day (p < 0.05). In soft tissue healing on the 3rd and 7th day, the nonepithelialized surface of the laser socket was smaller than that of the control group, and the measurement results were found to be statistically significant (p < 0.05).

CONCLUSION

Although LLLT was not found to be very effective in reducing postoperative discomfort after extraction of primary molars, it provided better wound healing in extraction sockets.

Role of proprioceptors in chronic musculoskeletal pain

Proprioceptors are non-nociceptive low-threshold mechanoreceptors. However, recent studies have shown that proprioceptors are acid-sensitive and express a variety of proton-sensing ion channels and receptors. Accordingly, although proprioceptors are commonly known as mechanosensing neurons that monitor muscle contraction status and body position, they may have a role in the development of pain associated with tissue acidosis. In clinical practice, proprioception training is beneficial for pain relief. Here we summarize the current evidence to sketch a different role of proprioceptors in 'non-nociceptive pain' with a focus on their acid-sensing properties.

Electroacupuncture exerts prolonged analgesic and neuroprotective effects in a persistent dental pain model induced by multiple dental pulp injuries: GABAergic interneurons-astrocytes interaction

Pain within the trigeminal system, particularly dental pain, is poorly understood. This study aimed to determine whether single or multiple dental pulp injuries induce persistent pain, its association with trigeminal central nociceptive pathways and whether electroacupuncture (EA) provides prolonged analgesic and neuroprotective effects in a persistent dental pain model. Models of single dental pulp injury (SDPI) and multiple dental pulp injuries (MDPI) were used to induce trigeminal neuropathic pain. The signs of dental pain-related behavior were assessed using the mechanical head withdrawal threshold (HWT). Immunofluorescence and western blot protocols were used to monitor astrocyte activation, changes in apoptosis-related proteins, and GABAergic interneuron plasticity. SDPI mice exhibited an initial marked decrease in HWT from days one to 14, followed by progressive recovery from days 21 to 42. From days 49 to 70, the HWT increased and returned to the control values. In contrast, MDPI mice showed a persistent decrease in HWT from days one to 70. MDPI increased glial fibrillary acidic protein (GFAP) and decreased glutamine synthetase (GS) and glutamate transporter-1 (GLT1) expression in the Vi/Vc transition zone of the brainstem on day 70, whereas no changes in astrocytic markers were observed on day 70 after SDPI. Increased expression of cleaved cysteine-aspartic protease-3 (cleaved caspase-3) and Bcl-2-associated X protein (Bax), along with decreased B-cell lymphoma/leukemia 2 (Bcl-2), were observed at day 70 after MDPI but not after SDPI. The downregulation of glutamic acid decarboxylase (GAD65) expression was observed on day 70 only after MDPI. The effects of MDPI-induced lower HWT from days one to 70 were attenuated by 12 sessions of EA treatment (days one to 21 after MDPI). Changes in astrocytic GFAP, GS, and GLT-1, along with cleaved caspase-3, Bax, Bcl-2, and GAD65 expression observed 70 days after MDPI, were reversed by EA treatment. The results suggest that persistent dental pain in mice was induced by MDPI but not by SDPI. This effect was associated with trigeminal GABAergic interneuron plasticity along with morphological and functional changes in astrocytes. EA exerts prolonged analgesic and neuroprotective effects that might be associated with the modulation of neuron-glia crosstalk mechanisms.

Photobiomodulation and vitamin B treatment alleviate both thermal and mechanical orofacial pain in rats

PURPOSE

The present study investigates the efficacy of Photobiomodulation (PBM) and Vitamin B Complex (VBC) to relieve pain, both in separately and combined (PBM and VBC).

METHODS

Rats with chronic constriction injury of the right infraorbital nerve (CCI-IoN) or Sham surgery were used. PBM was administered at a wavelength of 904 nm and energy density of 6.23 J/cm2 and VBC (containing B1, B6 and B12) subcutaneously, both separately and combined. Behavioral tests were performed to assess mechanical and thermal hypersensitivity before and after CCI and after PBM, VBC, or PBM + VBC. The expression of inflammatory proteins in the trigeminal ganglion and the immunohistochemical alterations of Periaqueductal Gray (PAG) astrocytes and microglia were examined following CCI and treatments.

RESULTS

All testeds treatments reversed the painful behavior. The decrease in pain was accompanied by a decrease of Glial Fibrillary Acidic Protein (GFAP), a specific astrocytic marker, and Ionized calcium-binding adaptor molecule 1 (Iba-1), a marker of microglia, and decreased expression of Transient Receptor Potential Vanilloid 1 (TRPV1), Substance P, and Calcitonin Gene-Related Peptide (CGRP) induced by CCI-IoN in PAG and Trigeminal ganglion. Furthermore, both treatments showed a higher expression of Cannabinoid-type 1 (CB1) receptor in the trigeminal ganglion compared to CCI-IoN rats. Our results show that no difference was observed between groups.

CONCLUSION

We showed that PBM or VBC regulates neuroinflammation and reduces inflammatory protein expression. However, the combination of PBM and VBC did not enhance the effectiveness of both therapies alone.

Involvement of ASIC3 and Substance P in Therapeutic Ultrasound-Mediated Analgesia in Mouse Models of Fibromyalgia

Therapeutic ultrasound (tUS) is widely used in chronic muscle pain control. However, its analgesic molecular mechanism is still not known. Our objective is to reveal the mechanism of the tUS-induced analgesia in mouse models of fibromyalgia. We applied tUS in mice that have developed chronic hyperalgesia induced by intramuscular acidification and determined the tUS frequency at 3 MHz, dosage at 1 W/cm2 (measured output as 6.3 mW/cm2) and 100% duty cycle for 3 minutes having the best analgesic effect. Pharmacological and genetic approaches were used to probe the molecular determinants involved in tUS-mediated analgesia. A second mouse model of fibromyalgia induced by intermittent cold stress was further used to validate the mechanism underlying the tUS-mediated analgesia. The tUS-mediated analgesia was abolished by a pretreatment of NK1 receptor antagonist-RP-67580 or knockout of substance P (Tac1-/-). Besides, the tUS-mediated analgesia was abolished by ASIC3-selective antagonist APETx2 but not TRPV1-selective antagonist capsazepine, suggesting a role for ASIC3. Moreover, the tUS-mediated analgesia was attenuated by ASIC3-selective nonsteroid anti-inflammation drugs (NSAIDs)-aspirin and diclofenac but not by ASIC1a-selective ibuprofen. We next validated the antinociceptive role of substance P signaling in the model induced by intermittent cold stress, in which tUS-mediated analgesia was abolished in mice lacking substance P, NK1R, Asic1a, Asic2b, or Asic3 gene. tUS treatment could activate ASIC3-containing channels in muscle afferents to release substance P intramuscularly and exert an analgesic effect in mouse models of fibromyalgia. NSAIDs should be cautiously used or avoided in the tUS treatment. PERSPECTIVE: Therapeutic ultrasound showed analgesic effects against chronic mechanical hyperalgesia in the mouse model of fibromyalgia through the signaling pathways involving substance P and ASIC3-containing ion channels in muscle afferents. NSAIDs should be cautiously used during tUS treatment.

Efficiency of diode laser in control of post-endodontic pain: a randomized controlled trial

OBJECTIVES

As post-endodontic pain control is one of the main targeted addressed in endodontics, our aim was delignated to compare two different methods for low-level laser application utilizing diode laser: low-level laser therapy (LLLT) and laser-activated irrigation (LAI) in the control of post-endodontic pain.

MATERIALS AND SUBJECTS

A total of 180 patients received single-visit root canal treatment; they were randomly allocated into 3 equal groups. Group I received LAI, group II received LLLT, and group III served as control with normal root canal treatment and mock laser intervention (ML group). Postoperative pain was recorded using visual analogue scale (VAS) after 24, 48, and 72 h. Data were tabulated and statistically analyzed.

RESULTS

At 24 h, there was a statistically significant difference between median pain scores in the three groups (P value < 0.001) with ML group scored highest score followed by LAI and then LLLT group. At 48 h, there was a statistically significant difference between the three groups (P value < 0.001), with ML group scoring highest median pain scores while LLLT and LAI showed statistical insignificant scores. At 72 h, there was no statistically significant difference between the 3 groups (P value = 0.179).

CONCLUSION

LLLT is superior to LAI and ML group in the control of immediate postoperative pain after 24 h while after 48 h both LAI and LLLT were equally effective, but they still showed significant differences when compared to ML group.

CLINICAL RELEVANCE

Diode laser can be used by clinicians as it decreases the post-endodontic pain in patients with symptomatic apical periodontitis undergoing endodontic treatment.

Acidosis-related pain and its receptors as targets for chronic pain

Sensing acidosis is an important somatosensory function in responses to ischemia, inflammation, and metabolic alteration. Accumulating evidence has shown that acidosis is an effective factor for pain induction and that many intractable chronic pain diseases are associated with acidosis signaling. Various receptors have been known to detect extracellular acidosis and all express in the somatosensory neurons, such as acid sensing ion channels (ASIC), transient receptor potential (TRP) channels and proton-sensing G-protein coupled receptors. In addition to sense noxious acidic stimulation, these proton-sensing receptors also play a vital role in pain processing. For example, ASICs and TRPs are involved in not only nociceptive activation but also anti-nociceptive effects as well as some other non-nociceptive pathways. Herein, we review recent progress in probing the roles of proton-sensing receptors in preclinical pain research and their clinical relevance. We also propose a new concept of sngception to address the specific somatosensory function of acid sensation. This review aims to connect these acid-sensing receptors with basic pain research and clinical pain diseases, thus helping with better understanding the acid-related pain pathogenesis and their potential therapeutic roles via the mechanism of acid-mediated antinociception.

Comparison of the Penetration Depth of 905 nm and 1064 nm Laser Light in Surface Layers of Biological Tissue Ex Vivo

The choice of parameters for laser beams used in the treatment of musculoskeletal diseases is of great importance. First, to reach high penetration depths into biological tissue and, secondly, to achieve the required effects on a molecular level. The penetration depth depends on the wavelength since there are multiple light-absorbing and scattering molecules in tissue with different absorption spectra. The present study is the first comparing the penetration depth of 1064 nm laser light with light of a smaller wavelength (905 nm) using high-fidelity laser measurement technology. Penetration depths in two types of tissue ex vivo (porcine skin and bovine muscle) were investigated. The transmittance of 1064 nm light through both tissue types was consistently higher than of 905 nm light. The largest differences (up to 5.9%) were seen in the upper 10 mm of tissue, while the difference vanished with increasing tissue thickness. Overall, the differences in penetration depth were comparably small. These results may be of relevance in the selection of a certain wavelength in the treatment of musculoskeletal diseases with laser therapy.

Anxiety and Depression: What Do We Know of Neuropeptides?

In modern society, there has been a rising trend of depression and anxiety. This trend heavily impacts the population’s mental health and thus contributes significantly to morbidity and, in the worst case, to suicides. Modern medicine, with many antidepressants and anxiolytics at hand, is still unable to achieve remission in many patients. The pathophysiology of depression and anxiety is still only marginally understood, which encouraged researchers to focus on neuropeptides, as they are a vast group of signaling molecules in the nervous system. Neuropeptides are involved in the regulation of many physiological functions. Some act as neuromodulators and are often co-released with neurotransmitters that allow for reciprocal communication between the brain and the body. Most studied in the past were the antidepressant and anxiolytic effects of oxytocin, vasopressin or neuropeptide Y and S, or Substance P. However, in recent years, more and more novel neuropeptides have been added to the list, with implications for the research and development of new targets, diagnostic elements, and even therapies to treat anxiety and depressive disorders. In this review, we take a close look at all currently studied neuropeptides, their related pathways, their roles in stress adaptation, and the etiology of anxiety and depression in humans and animal models. We will focus on the latest research and information regarding these associated neuropeptides and thus picture their potential uses in the future.

Neurokinin-1 Receptor as a potential drug target for COVID-19 treatment

Novel Coronavirus infection (COVID-19) has become a pandemic in these days. It is an acute respiratory and infectious disease with no known etiology and treatment. It is continuously causing losses of precious lives and economy at a global scale on daily basis. It is the need of the hour to find more treatment strategies by either developing a drug or to boost the immune system. This opinion article aims to provide Substance P (SP) as a possible cause of the initiation of cytokine storm developed in COVID-19 infection and to suggest Neurokinin-1 Receptor (NK-1R) antagonist, Aprepitant, as a drug to be used for its treatment. This perspective will provide directions to the Biomedical scientists to explore SP and NK-1R and prepare a drug to alleviate the symptoms and cure the disease. It is very important to work on this perspective at earliest to reach to some conclusion regarding the therapeutic intervention. Clinical studies may also be conducted if proven successful. SP is a neurotransmitter and neuromodulator, released from the trigeminal nerve of brainstem as a result of nociception. It is directly related to the respiratory illness as in COVID-19 infection. It is responsible for the increased inflammation and the signature symptoms associated with this disease. It is the main switch that needs to be switched off by administering Aprepitant along with glucocorticosteroid, dexamethasone.

A role for substance P and acid-sensing ion channel 1a in prolotherapy with dextrose-mediated analgesia in a mouse model of chronic muscle pain

ABSTRACT

Prolotherapy is widely used in pain control and tissue repair in pain medicine. The classical mode is injection with hypertonic dextrose in muscle or perimysium. However, the analgesic mechanism is still not known. Here we successfully established dextrose-mediated antinociception in a mouse model of fibromyalgia. The antinociceptive effects of dextrose injections were evaluated in a mouse model of fibromyalgia, in which bilateral chronic mechanical hyperalgesia was induced by unilateral intramuscular acid injection. The injectant (dextrose), dose (≥ 5%) and volume (>10 μL) but not osmolarity were essential for the prolotherapy. Further studies showed that activation of acid-sensing ion channel 1a (ASIC1a), neural activation, and the release of substance P from muscle afferents were required in the dextrose-induced reduction of mechanical hypersensitivity. Both pharmacological blockade and genetic deletion of ASIC1a or substance P as well as lidocaine abolished the dextrose-induced antinociception in mice with chronic hyperalgesia. Moreover, intramuscular dextrose injection induced phosphorylated extracellular signal-regulated kinase (pERK) expression in dorsal root ganglia neurons expressing substance P; the pERK expression was inhibited by the ASIC1a antagonist PcTx1. The optimal settings for prolotherapy in fibromyalgia-like pain are dextrose- and volume-dependent, and the peripheral antinociception involves ASIC1a and substance P signaling in muscle afferents. This study suggests a possible mechanism of action of dextrose prolotherapy in non-inflammatory muscle pain such as fibromyalgia and provides insights for treating other types of chronic pain.

Animal models of fibromyalgia: What is the best choice?

Fibromyalgia (FM) is a complex syndrome, with an indefinite aetiology and intricate pathophysiology that affects 2 - 3% of the world population. From the beginning of the 2000s, experimental animal models have been developed to mimic clinical FM and help obtain a better understanding of the relevant neurobiology. These animal models have enabled a broad study of FM symptoms and mechanisms, as well as new treatment strategies. Current experimental FM models include the reserpine-induced systemic depletion of biogenic amines, muscle application of acid saline, and stress-based (cold, sound, or swim) approaches, among other emerging models. FM models should: (i) mimic the cardinal symptoms and complaints reported by FM patients (e.g., spontaneous nociception, muscle pain, hypersensitivity); (ii) mimic primary comorbidities that can aggravate quality of life and lead to worse outcomes (e.g., fatigue, sleep disturbance, depression, anxiety); (iii) mimic the prevalent pathological mechanisms (e.g., peripheral and central sensitization, inflammation/neuroinflammation, change in the levels of the excitatory and inhibitory neurotransmitters); and (iv) demonstrate a pharmacological profile similar to the clinical treatment of FM. However, it is difficult for any one of these models to include the entire spectrum of clinical FM features once even FM patients are highly heterogeneous. In the past six years (2015 - 2020), a wide range of experimental FM studies has amounted to the literature reinforcing the need for an updated review. Here we have described, in detail, several approaches used to experimentally study FM, with a focus on recent studies in the field and in previously less discussed mechanisms. We highlight each model's challenges, limitations, and future directions, intending to help preclinical researchers establish the correct experimental FM model to use depending on their goals.

Ion Channels Involved in Substance P-Mediated Nociception and Antinociception

Substance P (SP), an 11-amino-acid neuropeptide, has long been considered an effector of pain. However, accumulating studies have proposed a paradoxical role of SP in anti-nociception. Here, we review studies of SP-mediated nociception and anti-nociception in terms of peptide features, SP-modulated ion channels, and differential effector systems underlying neurokinin 1 receptors (NK1Rs) in differential cell types to elucidate the effect of SP and further our understanding of SP in anti-nociception. Most importantly, understanding the anti-nociceptive SP-NK1R pathway would provide new insights for analgesic drug development.