Optogenetic Approach in Trigeminal Neuralgia and Potential Concerns: Preclinical Insights

The integration of optogenetics in the trigeminal pain circuitry broadens and reinforces existing pain investigations. Similar to research on spinal neuropathic pain, the exploration of the underlying determinants of orofacial pain is expanding. Optogenetics facilitates more direct, specific, and subtle investigations of the neuronal circuits involved in orofacial pain. One of the most significant concerns of both dentistry and medicine is trigeminal neuralgia (TN) management due to its substantial impact on a patient's quality of life. Our objective is to gather insights from preclinical studies conducted in TN employing an optogenetic paradigm, thereby extending the prospects for in-depth neurobiological research. This review highlights optogenetic research in trigeminal pain circuitry involving TN. We outline the central and peripheral regions associated with pain-that have been investigated using optogenetics in the trigeminal pain circuitry. The study further reports its scope and limitations as well as its potential for future applications from bench to bedside.

Craniofacial disorders and dysplasias: Molecular, clinical, and management perspectives

There is a wide spectrum of craniofacial bone disorders and dysplasias because embryological development of the craniofacial region is complex. Classification of craniofacial bone disorders and dysplasias is also complex because they exhibit complex clinical, pathological, and molecular heterogeneity. Most craniofacial disorders and dysplasias are rare but they present an array of phenotypes that functionally impact the orofacial complex. Management of craniofacial disorders is a multidisciplinary approach that involves the collaborative efforts of multiple professionals. This review provides an overview of the complexity of craniofacial disorders and dysplasias from molecular, clinical, and management perspectives.

Imaging findings of orofacial cysticercosis: report of 5 cases with review of literature

Cysticercosis, a fatal disease of parasitic aetiology seen in humans, is caused by ingestion of larvae of Taenia solium in form of raw or poorly cooked pork. Commonly seen in developing countries, it affects the brain, muscle, lungs, heart and liver and is rarely found in the maxillofacial region. Sometimes, the only evidence of cysticercosis could be the cystic swellings or nodules in the maxillofacial region. Such solitary clinical presentation can be diagnosed early with the aid of ultrasound (USG) and Magnetic resonance imaging (MRI). Here, we present 5 cases of intramuscular cysticercosis of Orofacial region which were initially diagnosed on ultrasonography and later confirmed by MRI and aspiration cytology. We have conducted a systematic review of PubMed Literature for Intramuscular cysticercosis of orofacial region and highlighted key imaging findings from 18 cases retrieved. Through this case series, we highlight the USG and MRI imaging features of intramuscular cysticercosis which are characteristic and diagnostic of the condition.

Mechanism and clinical use of botulinum neurotoxin in head and facial region

PURPOSE

Botulinum neurotoxin (BoNT) is a biological toxin produced by Clostridium botulinum. BoNT is a potent toxin extensively used in therapeutic interventions. This review provides an updated overview of the mechanisms of action and clinical applications of BoNT in head and facial region.

STUDY SELECTION

MEDLINE/PubMed searches were conducted using the terms "botulinum neurotoxin" and "dentistry" along with a combination of other related terms. In addition, studies were manually selected from reference lists of the selected articles.

RESULTS

The Food and Drug Administration in the United States initially approved BoNT to treat strabismus, blepharospasm, and hemifacial spasms. The use of BoNT in dermatology and cosmetics has been widely established and has created a revolution in these fields. Over the years, its applications in various medical specialties have expanded widely. Owing to its safety, efficacy, and long duration of action, it is well-accepted by patients. BoNT/A and BoNT/B are widely used in clinical practice. Several off-label uses of BoNT in the dental fraternity have yielded promising results. We have elaborated on the speculated mechanism of action, dosage, effective sites of injection, and adverse effects of each therapeutic application. The various clinical indications for BoNT include bruxism, myofascial pain, temporomandibular joint dislocation, hemifacial pain, orofacial dystonia, facial paralysis, chronic migraine, and trigeminal neuralgia.

CONCLUSIONS

BoNT is a safe treatment that can be used effectively, provided that the clinician has adequate knowledge regarding the mechanism, injection techniques, and local and systemic side effects and that it is administered cautiously and purposefully.

Fifty years of development of neuroscientific insights into orofacial pain and its control

When the Journal of Oral Rehabilitation was established in 1973, there was very limited understanding of the mechanisms underlying neurally based functions, including those unique to the face, mouth, and jaws (e.g. dental pain, taste, chewing, swallowing, and salivation). Since that time, technological and other advances have led to new insights into the structure, connectivity and function of cranial nerves and areas of the central nervous system (CNS) involved in orofacial functions and disorders or related functions (e.g. cognition, emotion, stress, consciousness, sleep, learning and memory). This review focusses on the advances in understanding of the neural basis of orofacial pain and its control over the past five decades. The review first briefly considers how orofacial pain conditions are now classified, diagnosed and managed. It then outlines novel insights that have been gained over this period through neuroscience research into the neural basis of these orofacial pain conditions and the clinical relevance to these insights to the diagnosis and management of these conditions. The review also identifies promising research directions and gaps in knowledge that still need to be addressed to improve the understanding, diagnosis and management of orofacial pain conditions.

Post-Covid Orofacial Mucormycosis: A Clinico-Radiological Classification System and Management Protocol

Background

In the wake of the second wave of the COVID-19 pandemic, a substantial number of individuals were afflicted by orofacial mucormycosis post-COVID. The immunocompromised state rendered by the SARS-COV2 (Severe Acute Respiratory Syndrome Corona Virus 2) infection provides a breeding ground for the opportunistic mucor invasion. Corticosteroid and COVID-induced hyperglycemia contribute to the unhindered progress of the mucor infection in these patients. The sino-nasal region serves as the entry point and rapid progress of the disease to the oral cavity, mid-face, orbits, and ultimately the brain proves fatal.

Aim and Objectives

The aim of this study was to present a definitive clinico-radiological staging/classification system for patients of post-covid mid-face mucormycosis based on combined radiographic and clinical features for subsequent convenient staging of maxillofacial mucormycosis. The objectives are being to lay down a comprehensive management protocol for these patients.

Methods

This retrospective study consisted of a cohort of 31 patients presenting to a tertiary care center over a 12-month period and diagnosed as post-covid mucormycosis. Their clinical features at the time of presentation along with radiographic presentation/extent of anatomical destruction were combined to create a clinico-radiological staging system. Further, a comprehensive management protocol including cultures, surgery and chemotherapy has been laid down.

Results

This included 18 males and 13 females. Average age of the patients was 53.5 years. As per the clinico-radiological system formulated by the authors, 2 patients (1 males and 1 females) displayed features of Stage 0, 12 patients (7 males and 5 females) of Stage 1-A, 8 patients (5 males and 3 females) of Stage 1-B, 6 patients (4 males and 2 females) and 3 patients (1 male and 2 females) of Stage 3.

Conclusion

The lacuna of a comprehensive staging/classification system for patients of maxillofacial mucormycosis was felt by the authors while treating those affected by post-covid mucormycosis along with a detailed algorithm for management of the study population. It is to this effect that this clinic-radiological classification system has been suggested by the authors along with a management protocol.

CIVILIAN GUNSHOT OROFACIAL INJURY IN A NIGERIAN TERTIARY HOSPITAL: A 10-YEAR RETROSPECTIVE REVIEW

Background

Gunshot related injuries to the face are relatively rare in peacetime. This study reported the pattern of presentation and management of orofacial civilian gunshot injuries at a Nigerian tertiary hospital.

Methodology

Medical records of 25 patients who sustained gunshot injuries to the face and were managed at the Obafemi Awolowo University Teaching Hospitals Complex, Ile Ife between 2010 and 2019 were reviewed. Patients' demographics, wounding mechanisms, clinical presentations and treatment administered were retrieved from the patients' case record. Patient records with incomplete information were excluded. Data generated were inputed into IBM-SPSS version 26 and analysed.

Results

A total of 2,847 patients were admitted through our department over the study period and 28 of them sustained orofacial gunshot injuries, giving a prevalence of 0.98%. Twenty-five out of the 28 retrieved case files met the inclusion criteria. There were 22 males and 3 females; with a male to female ratio of 7.3:1. The mean age was 37.60 ± 11.86 years with highest prevalence at fourth decade of life. About two-thirds of these injuries were intentionally inflicted by others with the use of Dane guns on highways. Majority (64%) of these injuries involved the middle third of the face. Definitive treatments ranged from simple to complex reconstructive procedures to restore pre-injury form and functions.

Conclusion

Gunshot injury involving the maxillofacial region is uncommon during peace time. The male gender was predominantly affected and the middle third facial skeleton was the most involved anatomic site. Most of the injuries were intentionally inflicted by others using Dane gun.

Interplay of Oral, Mandibular, and Facial Disorders and Migraine

PURPOSE OF THE REVIEW

Migraine and other primary headache disorders can be localized in the face resembling facial or dental pain, indicating the influence of the trigeminovascular system in the structures innervated by the maxillary (V2) and mandibulary (V3) branches of the trigeminal nerve. Disorders of oral and craniofacial structures may influence primary headache disorders. In the current article, we review the potential links of this interplay.

RECENT FINDINGS

This interplay may be related to anatomy, with the trigeminal pathway and the involvement of both peripheral and central mechanisms, and the presence of calcitonin gene-related peptide (CGRP), a key mediator in migraine pathophysiology. CGRP is also involved in the pathophysiology of temporomandibular disorders (TMD) and their comorbidity with migraine and is also implicated in dental and periodontal pathology. Inflammatory and pathological processes of these structures and their trigeminal nociceptive pathways may influence the trigeminovascular system and consequently may exacerbate or even potentially trigger migraine.

Orofacial injuries in child family homicide: a population study

Child family violence homicide (FVH) is a significant public health problem in Australia and globally. Population-wide studies of orofacial injuries in child FVH are uncommon despite their recognized importance. This whole population descriptive study of orofacial injuries in child FVH in Victoria, Australia aims to implement a novel methodological approach to provide an overview of child FVH and describe frequency and patterns of abusive orofacial injuries. Closed cases of child FVH aged 0-17 years, January 2000-December 2018, were identified from screening all Victorian assault deaths for eligible offender relationships. Significant associations of clinical/demographic characteristics were explored using two-step clustering and the Spearman correlation coefficient. Of 895 closed homicide cases, 358 were FV-related. Of the 53 child FVH, 40 were eligible for injury analysis with 36 of these cases (90%) having orofacial injuries. Among these 36 cases, 72% were aged 0-4 years, males predominated (64%) and the injury mechanism was blunt force for 56%. The discrete orofacial injury frequency was associated with the non-orofacial injury frequency (rho: 0.362, 2-tailed p < 0.03). A three-cluster statistical solution was identified, each represented by an injury mechanism. The largest cluster identified a pattern of blunt force trauma in 0-4 years with drug presence, high average non-orofacial injury numbers and parent-offenders. A novel methodological approach was implemented to comprehensively describe the frequency, nature, patterns and risk indicators of orofacial injuries in child FVH. It explored associations between a wide range of clinical and demographic characteristics, which might have otherwise been missed in summary description. These methods will potentially underpin future comparative studies of intentional-unintentional child injuries and fatal-nonfatal child abuse. The study narrows a significant research gap regarding patterns of inflicted injuries, and demographic and clinical indicators in child FVH potentially informing future systematic classification processes, risk assessment tools and pathways to FV intervention.

Efficacy of Computed Tomography and Ultrasonography in Diagnosis of Metastatic Cervical Lymph Nodes in Orofacial Cancer

INTRODUCTION

There is no consensus on which imaging modality is better for the detection of metastatic cervical lymph nodes in orofacial malignancies. This study evaluates the efficacy of computed tomography (CT) and ultrasonography (US) in diagnosis of metastatic cervical lymph nodes in orofacial cancer.

MATERIALS AND METHODS

Sixty patients with various histologically diagnosed orofacial malignant lesions and clinical evidence of cervical lymph node metastasis were examined using US and CT. Further, the affected lymph nodes were biopsied and examined histologically. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the techniques were calculated. The data was analyzed using Statistical Package for Social Sciences (SPSS) version 19 (SPSS Inc., Chicago, IL, USA) and Microsoft Excel 2010 (Microsoft, Redmond, WA, USA). Test of statistical significance was set at 0.05.

RESULTS

US recorded a sensitivity, specificity, PPV, NPV, and accuracy of 80.0%, 57.1%, 77.5%, 60.0%, and 71.7%, respectively (P = 0.004), while CT recorded a sensitivity, specificity, PPV, NPV, and accuracy of 87.1%, 71.4%, 85.0%, 75.0%, and 81.7%, respectively (P< 0.0001). Lymph node size was the commonest criterion in the diagnoses of metastases in cases with cervical lymph nodes.

CONCLUSION

Although we obtained great results using US, our results indicated CT to be a better imaging modality for detecting metastatic cervical lymph nodes in orofacial malignancies.

Orofacial pain in 1916 patients with early or moderate Parkinson disease

This article reports the largest epidemiological study of orofacial pain prevalence in patients with Parkinson disease to date.

Introduction:

Several studies have reported that some types of orofacial pain are more common in patients with Parkinson disease (PD) than the general population.

Objectives:

In this study, we aimed to investigate the prevalence of self-reported orofacial pain in a larger group of patients with PD than has been previously studied.

Methods:

We analysed data from 1916 participants with PD in a cross-sectional study recruited to the UK Parkinson's Pain Study who had detailed assessments of pain, motor, and nonmotor symptoms. The King's Parkinson's Pain scale was used to quantify different subtypes of pain.

Results:

A total of 139 (7.3%) patients reported the presence of some form of orofacial pain. Burning mouth syndrome was reported in 32 (1.7%), whereas chewing pain was found in 38 (2.0%) and grinding pain in 78 (4.0%). Orofacial pain was significantly more common in females (10.4%) than males (5.9%). Multiple logistic regression analysis showed a significant association between orofacial pain and pain severity, neuropathic pain, and oral motor and nonmotor dysfunction.

Conclusion:

In our study, population cohort of early patients with PD found prevalence of orofacial pain conditions similar to that in the general population.

Reduced activity of GAD67 expressing cells in the reticular thalamus enhance thalamic excitatory activity and varicella zoster virus associated pain

Within the reticular thalamic nucleus neurons express gamma aminobutyric acid (GABA) and these cells project to the ventral posteromedial thalamic nucleus. When GABA activity decreases the activity of excitatory cells in the ventral posteromedial nucleus would be expected to increase. In this study, we addressed the hypothesis that attenuating GABAergic cells in the reticular thalamic nucleus increases excitatory activity in the ventral posteromedial nucleus increasing varicella zoster virus (VZV) associated pain in the orofacial region. Adeno-associated virus (AAV) was infused in the reticular thalamic nucleus of Gad1-Cre rats. This virus transduced a G inhibitory designer receptor exclusively activated by designer drugs (DREADD) gene that was Cre dependent. A dose of estradiol that was previously shown to reduce VZV pain and increase GABAergic activity was administered to castrated and ovariectomized rats. Previous studies suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons and decreasing the activity of excitatory cells within the lateral thalamic region. The ventral posteromedial nucleus was infused with AAV containing a GCaMP6f expression construct. A glass lens was implanted for miniscope imaging. Our results show that the activity of GABA cells within the reticular thalamic region decreased with clozapine N-oxide treatment concomitant with increased calcium activity of excitatory cells in the ventral posteromedial nucleus and an increased orofacial pain response. The results suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons within the reticular thalamus that then inhibit excitatory activity in ventral posteromedial nucleus causing a reduction in orofacial pain.

Topical application in burning mouth syndrome

Background/purpose

Intraoral and perioral burning sensations may be sequelae of burning mouth syndrome (BMSD) or burning mouth symptoms (BMSP), which present a diagnostic challenge. The aims of the study were to evaluate the efficacy of a topical anesthetic as a diagnostic test to differentiate BMSD from BMSP and to assess the comorbidities and responses to various pharmacologic treatments in BMSD and BMSP patients.

Materials and methods

A total of forty-four charts of patients with burning mouth that visited the Rutgers School of Dental Medicine Orofacial Pain Clinic between January 1st, 2000 and November 1st, 2014 were retrospectively reviewed. Twenty patients were diagnosed with BMSD, and 24 patients were diagnosed with BMSP attributed to local and systemic causes. The diagnosis was determined per the guidelines of the International Association for the Study of Pain and American Academy of Orofacial Pain. The main goal of this study was to evaluate the effect of topical anesthetic medication applied to the burning site.

Results

The percentage of change in pain reduction following topical anesthetic application in the BMSP group was significantly higher than that of the BMSD group (p < 0.05). In the BMSD group, 77% of females and 27% of males responded to clonazepam. One third of the females in the BMSP group also suffered from hypertension.

Conclusion

Topical anesthetics can be used as a simple, swift and efficient chair-side diagnostic tool to differentiate BMSD and BMSP. Females have a better response to clonazepam in BMSD.

Methods in population study of orofacial injuries in Victorian family violence homicides

This study standardized the methods used in the determination of orofacial injuries in Victorian family violence homicides and informed potential control selection for an analytic study. Dental service contacts with family violence victims may be intervention avenues due to the presence of abusive injuries in the orofacial region. All Victorian family homicides from January 2000-September 2018 were identified by determining the kinship/relationship and grouped by age. A 20% random sample of adult cases, aged 18-64 years was selected. The median number of orofacial injuries in categories of injury mechanisms/age/gender and the nature of abusive orofacial injuries was reported for the sample. Of 357 closed cases of family homicide, 261 were adults aged 18-64 years. Offender information and injury mechanism data was available for all closed cases, enabling case selection. Of a random sample of 50 adults, 8 cases were excluded. After 2006, CT scans and photos were present in 20 (91%) and 19 (86.4%) of 22 cases, respectively. The nature and median number of orofacial injuries showed correlation to the reported injury mechanism. Strengths and limitations of the used methods were assessed. Not all cases were compatible for assessment of orofacial injuries, thus serving as an additional criterion for exclusion in our methodology. Further detailed study of the whole population of adults should be limited to the period 2006-2018 where the data is more complete. The mechanism of injury may influence control selection for analytic studies. We present preliminary evidence of the frequent occurrence of orofacial injuries in family violence homicides.

The orotrigeminal system

The trigeminal sensory nerve fiber branches supply afferent information from the skin and mucous membranes of the face and head and the oral cavity regarding information on temperature, touch, and pain. Under normal conditions, the trigeminal nerve serves to provide important information from nerve fibers and tissues using specialized receptors sensitive for irritant and painful stimuli. The current scientific consensus indicates that nerve endings responsible for chemical and thermal sensitivity of the skin and mucous membranes are the same nerves responsible for nociception. This "chemesthetic sense" allows many vertebrates to detect chemical agonists that induce sensations such as touch, burning, stinging, tingling, or changes in temperature. Research has been under way for many years to determine how exposure of the oral and/or nasal cavity to compounds that elicit pungent or irritant sensations can produce these sensations. In addition, these chemicals can alter other sensory information such as taste and smell to affect the flavor of foods and beverages. We now know that these 'chemesthetic molecules' are agonists of molecular receptors, which exist on primary afferent nerve fibers that innervate the orofacial area. However, under pathophysiologic conditions, over- or underexpression or activity of these receptors may lead to painful orotrigeminal syndromes. Some of these individual receptors are discussed in detail, including transient receptor potential channels and acid sensing ion channels, among others.

Reconstruction with submental flap for aggressive orofacial cancer- an updated series

PURPOSE

Submental flap is gaining popularity for head and neck reconstruction. We have reported in 2007 our early experience of using submental flap for aggressive orofacial malignancy. Novel flap design and application is described in this updated series.

MATERIALS AND METHODS

15 patients who had received submental flap reconstruction after extirpation of newly diagnosed aggressive orofacial lesions were retrieved. The details of the flap harvest was studied for flap size, inclusion of mylohyoid muscle, antegrade versus retrograde blood supply, and compared with our previous series.

RESULTS

The dimension of flap skin paddle was 30cm² (range 20-72). Retrograde pedicle flow was used in 2(13.3%) patients. Mylohyoid muscle was included in the flap in 6(40%) patients. There was no total flap necrosis while partial flap necrosis occurred in 1 patient(6.7%). There was a significant increase of inclusion of mylohyoid muscle to the flap in this series (p = 0.02). Novel techniques including double-paddled flap skin to resurface full-thickness defect and chimeric osteocutaneous mandible submental flap for maxillary defect were successfully performed.

CONCLUSIONS

Submental flap is a viable reconstructive option in selected patients with aggressive orofacial malignancy. The indications are expanding and its technical modification is evolving and resulting in more innovative applications.

Tongue necrosis secondary to mucormycosis in a diabetic patient: A first case report in Malaysia

Mucormycosis is a rare fungal infection and high mortality that commonly affects patients with the weakened immune system. We present an unusual case of tongue necrosis probably due to the healthcare-associated mucormycosis (HCM) in a diabetic patient. Although cannot be proved with certainty, we surmise that intubation as a risk factor in our case. The diagnosis was confirmed by histopathological examination (HPE) of the necrotic tissue specimen. The patient was responded well to lipid complex amphotericin B (250mg) regime after surgery. Subsequent follow up revealed that no signs of recurrence. Early, recognition, diagnosis, prompt treatment and awareness among clinician are representing the most effective way of managing the disease.

Gi protein functions in thalamic neurons to decrease orofacial nociceptive response

Orofacial pain includes neuronal pathways that project from the trigeminal nucleus to and through the thalamus. What role the ventroposterior thalamic complex (VP) has on orofacial pain transmission is not understood. To begin to address this question an inhibitory G protein (Gi) designer receptor exclusively activated by a designer drug (DREADD) was transfected in cells of the VP using adeno-associated virus isotype 8. Virus infected cells were identified by a fluorescent tag and immunostaining. Cells were silenced after injecting the designer drug clozapine-n-oxide, which binds the designer receptor activating Gi. Facial rubbing and local field potentials (LFP) in the VP were then recorded in awake, free moving Sprague Dawley rats after formalin injection of the masseter muscle to induce nociception. Formalin injection significantly increased LFP and the nociceptive behavioral response. Activation of DREADD Gi with clozapine-n-oxide significantly reduced LFP in the VP and reduced the orofacial nociceptive response. Because DREADD silencing can result from Gi-coupled inwardly-rectifying potassium channels (GIRK), the GIRK channel blocker tertiapin-Q was injected. Injection of GIRK blocker resulted in an increase in the nociceptive response and increased LFP activity. Immunostaining of the VP for glutamate vesicular transporter (VGLUT2) and gamma-aminobutyric acid vesicular transporter (VGAT) indicated a majority of the virally transfected cells were excitatory (VGLUT2 positive) and a minority were inhibitory (VGAT positive). We conclude first, that inhibition of the excitatory neurons within the VP reduced electrical activity and the orofacial nociceptive response and that the effect on excitatory neurons overwhelmed any change resulting from inhibitor neurons. Second, inhibition of LFP and nociception was due, in part, to GIRK activation.

Occurrence of Malocclusion in Patients with Orofacial Pain and Temporomandibular Disorders

AIM

This study aims to investigate the occurrence of malocclusion in patients with orofacial pain and temporomandibular disorders (TMDs).

MATERIALS AND METHODS

A total of 437 standard orthodontic screening forms at a craniofacial pain TMD center were utilized to collect the data for this retrospective study. In addition to patient's demographics and Angle's molar classification, the following data were collected: Overjet (OJ), overbite (OB), mandibular range of motion, and whether or not there was a posterior crossbite or prior history of orthodontic therapy. Analysis of variance (ANOVA) and chi-square tests were then used to detect any statistical significant difference of the secondary variables' distribution among the three malocclusion groups.

RESULTS

The majority of the studied population sample had a class I molar relationship (70.9%), followed by class II (21.1%) and class III molar relationship (8%). Overjet and OB were significantly increased for class II molar relationship group (p < 0.001), where no statistical differences could be identified for the mandibular range of motion between the groups. The prevalence of right and left posterior crossbite was about 12% for both, and most of the crossbites presented within class I molar group.

CONCLUSION

Class I followed by class II molar relationships were found to be the most occurring relationship in the studied population. Posterior crossbite presented in 12% of cases and mostly affected subjects with class I molar relationship.

CLINICAL SIGNIFICANCE

These findings would aid in recognizing the studied population's orthodontic presentation and support the assessment of their transverse interventional needs.

Behavioral characteristics of capsaicin mediated cutaneous, myogenic, and arthrogenic orofacial nociception in rats

OBJECTIVE

To assess changes in orofacial tactile sensitivity and gnawing related to capsaicin-mediated cutaneous, myogenic, and arthrogenic nociception in the rat.

DESIGN

After recovery from anesthesia, orofacial tactile sensitivity and gnawing were assessed using operant testing methods following capsaicin application. Twenty female CD-Hairless rats were tested with bilateral capsaicin cream application to the cheek or with isoflurane anesthesia alone. Following several weeks of recovery, animals (n = 20) received either 10 μL unilateral masseter injections of vehicle, or phosphate buffered saline (PBS) to assess injection sensitization. After several weeks, masseter capsaicin (1.0%) injections (10 μL) were assessed compared to vehicle and PBS (n = 13). Weeks later capsaicin TMJ injections were evaluated. Animals (n = 11) received either 10 μL unilateral TMJ injections of capsaicin solution (1%) or vehicle.

RESULTS

Capsaicin cream to the skin significantly altered gnawing activity (increased puncture time by 248 s (p = 0.0002)) and tactile sensitivity (decreased tolerated bottle distance by 0.980 cm compared to isoflurane only (p = 0.0001)). Similarly, capsaicin masseter injection increased puncture time (339.6 s, p = 0.07) and decreased tolerated bottle distance (1.04 cm, p = 0.005) compared to vehicle. However, intra-articular capsaicin in the TMJ only modified gnawing (increased puncture time by 133 s), with no changes found in tactile sensitivity compared to vehicle.

CONCLUSION

Application of capsaicin to the skin and masseter had similar behavioral effects; however, intra-articular injections to the TMJ only affected gnawing. These data indicate the behavioral changes in rodent models of myogenic and cutaneous pain may be markedly different than models of arthrogenic pain originating from the TMJ.

Assessment of orofacial pain management in a pediatric emergency department and at home after discharge

INTRODUCTION

An inadequate pain management is common in the emergency department. Our objective was to analyze pain management among children with an orofacial infection or trauma in the emergency department and to assess compliance and satisfaction with analgesia prescribed at discharge.

POPULATION AND METHODS

Cross-sectional, observational and analytical study in children attending the emergency department for an orofacial infection or trauma over 2 months. Pain management in the emergency department, analgesia prescribed at home and, following a call to parents, treatment provided and its adequacy to control pain were registered.

RESULTS

In total, 252patients (mean age: 4.5 years, SD: 3.89) were included. Pain assessment was recorded at the triage for 8.7%, and in the medical report, for 3.6%. Analgesia was administered to 41.3% in the emergency room. At discharge, no analgesia was prescribed to 13.9%; scheduled analgesia, to 25.4%; and as needed, to 60.3%. Pediatricians prescribed scheduled analgesia more frequently than surgeons (34.4% versus 16.5%, p < 0.01). At home, no analgesia was administered to 39.3%; scheduled analgesia, to 36.1%; and as needed, to 23%. There is little correlation between prescription at discharge and at home (Kappa: 0.178). Analgesia was considered adequate in 84% of cases, and was more frequent in trauma injuries than in infections (85.7% versus 14.3%, p < 0.01).

CONCLUSIONS

Pain assessment and management was scarce in the emergency department. The most common prescription was as needed, contrary to what is recommended in the guidelines. Analgesic control worked better for trauma injuries than for infections.

Oxytocin inhibits the rat medullary dorsal horn Sp5c/C1 nociceptive transmission through OT but not V1A receptors

The medullary dorsal horn (MDH or Sp5c/C1 region) plays a key role modulating the nociceptive input arriving from craniofacial structures. Some reports suggest that oxytocin could play a role modulating the nociceptive input at the MDH level, but no study has properly tested this hypothesis. Using an electrophysiological and pharmacological approach, the present study aimed to determine the effect of oxytocin on the nociceptive signaling in the MDH and the receptor involved. In sevoflurane, anesthetized rats, we performed electrophysiological unitary recordings of second order neurons at the MDH region responding to peripheral nociceptive-evoked responses of the first branch (V1; ophthalmic) of the trigeminal nerve. Under this condition, we constructed dose-response curves analyzing the effect of local spinal oxytocin (0.2-20 nmol) on MDH nociceptive neuronal firing. Furthermore, we tested the role of oxytocin receptors (OTR) or vasopressin V_1A receptors (V_1AR) involved in the oxytocin effects. Oxytocin dose-dependently inhibits the peripheral-evoked activity in nociceptive MDH neurotransmission. This inhibition is associated with a blockade of neuronal activity of Aδ- and C-fibers. Since this antinociception was abolished by pretreatment (in the MDH) with the potent and selective OTR antagonist (L-368,899; 20 nmol) and remained unaffected after the V_1AR antagonist (SR49059; 20 nmol or 200 nmol), the role of OTR is implied. This electrophysiological study demonstrates that oxytocin inhibits the peripheral-evoked neuronal activity at MDH, through OTR activation. Thus, OTR may represent a new potential drug target to treat craniofacial nociceptive dysfunction in the MDH.

Effect of Pregabalin and Diclofenac on tactile allodynia, mechanical hyperalgesia and pro inflammatory cytokine levels (IL-6, IL-1β) induced by chronic constriction injury of the infraorbital nerve in rats

The present study evaluated the effects of systemic pregabalin (PG) and diclofenac (Dic) on neuropathic orofacial pain induced by chronic constriction injury (CCI) of the infraorbital nerve (ION) and on the pro-inflammatory cytokines levels in the affected nerve. Fifty-four rats underwent left infra orbital nerve CCI, and 7 days after the procedure as the pain developed, the rats were randomly assigned to one of the treatment groups: PG 300, 30 or 10 mg/kg, Dic 10, 5 or 1 mg/kg or saline group (Sal) (n/group = 8). Addiitonal 8 rats served as naïve control group. Tactile-allodynia and Mechano-hyperalgesia were tested before the surgical procedure and at days 7, 8, and 9 postoperatively. On the 9th day, the rats were euthanized and the affected and contralateral sciatic nerves were harvested to assess IL-6 and IL-1β nerve levels employing enzyme linked immunosorbent assay (ELISA). Daily injection of PG (all doses) significantly reduced tactile-allodynia and mechano-hyperalgesia (p < .05) while Dic did not. On the 9th day, the ipsilateral nerve IL-6 levels were significantly decreased (p < .05) in the PG and DIC groups compared to the Sal group. IL-1β levels demonstrated a significant reduction (p < .05) in the PG group when compared to saline. These results suggest that PG but not Dic may be effective in reducing neuropathic orofacial pain. The mechanisms of action may be associated to some extent with reduction in IL-1β levels in the affected nerve.

Leiomyosarcoma of maxilla: a case report with review of literature

OBJECTIVE

One challenging feature of head and neck pathology is that a dizzying array of spindle cell lesions occurs here which ranges all the way from reactive, very aggressive forms to malignant lesions. Leiomyosarcoma is one such malignant tumour of mesenchymal origin exhibiting smooth muscle differentiation; presenting generally nonspecific signs and symptoms. Here we present a case of leiomyosarcoma in a 21 year old female patient associated with single reddish pink swelling present in the posterior right maxillary tuberosity region with moderate facial asymmetry. On histopathological analysis, all the classic features were noted and diagnosis of a spindle cell neoplasm was made without any obscurity. There are many lesions like rhabdomyosarcoma, fibrosarcoma, liposarcoma, multiple peripheral nerve sheath tumour, angiosarcomas, melanomas, kaposi sarcoma, solitary fibrous tumors, etc., which mimic leiomyosarcoma clinically and histopathologically and therefore immunohistochemical staining with specific markers plays a vital role in arriving at a conclusive diagnosis.

Constriction of the buccal branch of the facial nerve produces unilateral craniofacial allodynia

Despite pain being a sensory experience, studies of spinal cord ventral root damage have demonstrated that motor neuron injury can induce neuropathic pain. Whether injury of cranial motor nerves can also produce nociceptive hypersensitivity has not been addressed. Herein, we demonstrate that chronic constriction injury (CCI) of the buccal branch of the facial nerve results in long-lasting, unilateral allodynia in the rat. An anterograde and retrograde tracer (3000MW tetramethylrhodamine-conjugated dextran) was not transported to the trigeminal ganglion when applied to the injury site, but was transported to the facial nucleus, indicating that this nerve branch is not composed of trigeminal sensory neurons. Finally, intracisterna magna injection of interleukin-1 (IL-1) receptor antagonist reversed allodynia, implicating the pro-inflammatory cytokine IL-1 in the maintenance of neuropathic pain induced by facial nerve CCI. These data extend the prior evidence that selective injury to motor axons can enhance pain to supraspinal circuits by demonstrating that injury of a facial nerve with predominantly motor axons is sufficient for neuropathic pain, and that the resultant pain has a neuroimmune component.

Sex differences underlying orofacial varicella zoster associated pain in rats

Background

Most people are initially infected with varicella zoster virus (VZV) at a young age and this infection results in chickenpox. VZV then becomes latent and reactivates later in life resulting in herpes zoster (HZ) or “shingles”. Often VZV infects neurons of the trigeminal ganglia to cause ocular problems, orofacial disease and occasionally a chronic pain condition termed post-herpetic neuralgia (PHN). To date, no model has been developed to study orofacial pain related to varicella zoster. Importantly, the incidence of zoster associated pain and PHN is known to be higher in women, although reasons for this sex difference remain unclear. Prior to this work, no animal model was available to study these sex-differences. Our goal was to develop an orofacial animal model for zoster associated pain which could be utilized to study the mechanisms contributing to this sex difference.

Methods

To develop this model VZV was injected into the whisker pad of rats resulting in IE62 protein expression in the trigeminal ganglia; IE62 is an immediate early gene in the VZV replication program.

Results

Similar to PHN patients, rats showed retraction of neurites after VZV infection. Treatment of rats with gabapentin, an agent often used to combat PHN, ameliorated the pain response after whisker pad injection. Aversive behavior was significantly greater for up to 7 weeks in VZV injected rats over control inoculated rats. Sex differences were also seen such that ovariectomized and intact female rats given the lower dose of VZV showed a longer affective response than male rats. The phase of the estrous cycle also affected the aversive response suggesting a role for sex steroids in modulating VZV pain.

Conclusions

These results suggest that this rat model can be utilized to study the mechanisms of 1) orofacial zoster associated pain and 2) the sex differences underlying zoster associated pain.

Therapeutic potential of stellate ganglion block in orofacial pain: a mini review

Orofacial pain is a common complaint of patients that causes distress and compromises the quality of life. It has many etiologies including trauma, interventional procedures, nerve injury, varicella-zoster (shingles), tumor, and vascular and idiopathic factors. It has been demonstrated that the sympathetic nervous system is usually involved in various orofacial pain disorders such as postherpetic neuralgia, complex regional pain syndromes, and atypical facial pain. The stellate sympathetic ganglion innervates the head, neck, and upper extremity. In this review article, the effect of stellate ganglion block and its mechanism of action in orofacial pain disorders are discussed.

An Audit of Malignant Oro-facial Tumors Presenting at a Tertiary Hospital in Lagos

Oro-facial malignancies are reported to have a high mortality and morbidity, this is further worsened when patient report late. To analyze the malignant oro-facial lesions seen at a Hospital in the Lagos, Nigeria. Successive patients that presented in the hospital and met criteria of study during 15 months period were recruited into the study. Demographics, clinical variables, and treatment provided for each patient in the hospital was recorded. Data collected were presented as tables and percentages. There were 36 cases seen, their ages ranged from 10 to 72 years (median 49 years), and there were 21 males and 15 females. Time lapse before presentation to the clinic ranged from 2 to 30 months, mean (9.9 (±5.5 months and the largest dimension of lesions at presentation ranged from 2 cm to 12 cm (mean 6.4 ± 2.0 cm). Most common site of presentation was posterior tongue (16.7%; 6/36) and Squamous cell carcinoma (41.6%; 15/36) was the most common histopathologic diagnosis. Twenty-three patients (63.9%; 23/36) had primary surgeries in the hospital. Patients seen in this case series generally reported late with large lesions.

Using frogs faces to dissect the mechanisms underlying human orofacial defects

In this review I discuss how Xenopus laevis is an effective model to dissect the mechanisms underlying orofacial defects. This species has been particularly useful in studying the understudied structures of the developing face including the embryonic mouth and primary palate. The embryonic mouth is the first opening between the foregut and the environment and is critical for adult mouth development. The final step in embryonic mouth formation is the perforation of a thin layer of tissue covering the digestive tube called the buccopharyngeal membrane. When this tissue does not perforate in humans it can pose serious health risks for the fetus and child. The primary palate forms just dorsal to the embryonic mouth and in non-amniotes it functions as the roof of the adult mouth. Defects in the primary palate result in a median oral cleft that appears similar across the vertebrates. In humans, these median clefts are often severe and surgically difficult to repair. Xenopus has several qualities that make it advantageous for craniofacial research. The free living embryo has an easily accessible face and we have also developed several new tools to analyze the development of the region. Further, Xenopus is readily amenable to chemical screens allowing us to uncover novel gene-environment interactions during orofacial development, as well as to define underlying mechanisms governing such interactions. In conclusion, we are utilizing Xenopus in new and innovative ways to contribute to craniofacial research.

Efficacy of regional nerve block in management of myofascial pain of masseteric origin

OBJECTIVE

To compare the efficacy of a regional masseteric nerve block (MNB) in the management of myofascial pain of masseteric origin, relative to trigger point injection (TrP-Inj) and intra-oral stabilization appliance (IOA).

STUDY DESIGN

A retrospective chart review of 200 patients treated for myofascial pain of masseteric origin was performed. Sixty patients met the eligibility criteria and were grouped based on their treatment regimen; IOA, TrP-Inj or MNB. Pain scores recorded at pre-treatment (baseline), 30 minutes post-treatment, and 2 weeks post-treatment were analyzed.

RESULTS

Treatment with MNB resulted in significant reduction in pain at 30 minutes and two weeks post-treatment compared to TrP-Inj and IOA.

CONCLUSION

MNB provided an immediate and sustained therapeutic effect for the management of myofascial pain for at least up to two weeks. MNB is a simple and valuable tool in the management of myogenous pain, especially for the non-orofacial pain practitioner.

Role of gingival manifestation in diagnosis of granulomatosis with polyangiitis (Wegener's granulomatosis)

Purpose

This report describes a case of granulomatosis with polyangiitis (GPA) in which the gingival manifestation was crucial in both making an early diagnosis and possibly in deciding the approach to treatment.

Methods

A 57-year-old sailor presented to the Department of Dentistry at Ulsan University Hospital complaining of gingival swelling since approximately 2 months. He had orofacial granulomatous lesions and the specific gingival manifestation of strawberry gingivitis.

Results

The diagnosis of GPA was made on the basis of clinical symptoms and signs, and confirmed by the presence of the anti-neutrophil cytoplasmic antibody and a positive biopsy. The patient was admitted to the hospital and subsequently placed on a disease-modifying therapy regimen that included methotrexate and prednisone.

Conclusions

Identification of the gingival manifestation of the disease permitted an early diagnosis and prompt therapy in a disease in which time is a crucial factor. Because of its rapid progression and potentially fatal outcome, an early diagnosis of GPA is important. Therefore, dentists should be aware of the oral signs and symptoms of such systemic diseases.

Expression and function of purinergic P2Y12 receptors in rat trigeminal ganglion neurons

Purinergic receptors play key signaling roles in neuropathic pain in the orofacial region, which is innervated by trigeminal ganglion (TG) neurons. The neuropathology of purinergic P2Y12 receptors is well characterized in glia; however, their physiological role in TG neurons remains to be fully elucidated. The present study investigated the expression and function of P2Y12 receptors in rat TG neurons. P2Y12 receptor immunoreactivity was intense in the soma, dendrites, and axons, and colocalized with a pan-neuronal marker, neurofilament H, isolectin B4, and substance P. In the presence of extracellular Ca(2+), 2-methylthio-ADP (an agonist of P2Y1, 12, 13 receptors) transiently increased intracellular free Ca(2+) concentrations ([Ca(2+)]i), an effect that was abolished by P2Y12 receptor antagonists. In the absence of extracellular Ca(2+), ryanodine receptor/channel inhibitors diminished the 2-methylthio-ADP-induced increases in [Ca(2+)]i. A sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor gradually increased [Ca(2+)]i, and after a plateau, application of 2-MeS-ADP induced a rapid and transient, but additive increase in [Ca(2+)]i. An adenylate cyclase inhibitor transiently increased [Ca(2+)]i, while a phosphodiesterase inhibitor prevented the 2-methylthio-ADP-induced increase in [Ca(2+)]i. Our study shows that P2Y12 receptors are expressed in TG neurons, and act via a cAMP-dependent pathway to release intracellular Ca(2+) from ryanodine-sensitive Ca(2+) stores.

A potent and selective calcitonin gene-related peptide (CGRP) receptor antagonist, MK-8825, inhibits responses to nociceptive trigeminal activation: Role of CGRP in orofacial pain

Temporomandibular disorders (TMDs) are orofacial pains within the trigeminal distribution, which involve the masticatory musculature, the temporomandibular joint or both. Their pathophysiology remains unclear, as inflammatory mediators are thought to be involved, and clinically TMD presents pain and sometimes limitation of function, but often appears without gross indications of local inflammation, such as visible edema, redness and increase in temperature. Calcitonin gene-related peptide (CGRP) has been implicated in other pain disorders with trigeminal distribution, such as migraine, of which TMD shares a significant co-morbidity. CGRP causes activation and sensitization of trigeminal primary afferent neurons, independent of any inflammatory mechanisms, and thus may also be involved in TMD. Here we used a small molecule, selective CGRP receptor antagonist, MK-8825, to dissect the role of CGRP in inducing spontaneous nociceptive facial grooming behaviors, neuronal activation in the trigeminal nucleus, and systemic release of pro-inflammatory cytokines, in a mouse model of acute orofacial masseteric muscle pain that we have developed, as a surrogate of acute TMD. We show that CFA masseteric injection causes significant spontaneous orofacial pain behaviors, neuronal activation in the trigeminal nucleus, and release of interleukin-6 (IL-6). In mice pre-treated with MK-8825 there is a significant reduction in these spontaneous orofacial pain behaviors. Also, at 2 and 24h after CFA injection the level of Fos immunoreactivity in the trigeminal nucleus, used as a marker of neuronal activation, was much lower on both ipsilateral and contralateral sides after pre-treatment with MK-8825. There was no effect of MK-8825 on the release of IL-6. These data suggest that CGRP may be involved in TMD pathophysiology, but not via inflammatory mechanisms, at least in the acute stage. Furthermore, CGRP receptor antagonists may have therapeutic efficacy in the treatment of TMD, as they do with migraine.

A novel operant-based behavioral assay of mechanical allodynia in the orofacial region of rats

BACKGROUND

Detecting behaviors related to orofacial pain in rodent models often relies on subjective investigator grades or methods that place the animal in a stressful environment. In this study, an operant-based behavioral assay is presented for the assessment of orofacial tactile sensitivity in the rat.

NEW METHODS

In the testing chamber, rats are provided access to a sweetened condensed milk bottle; however, a 360° array of stainless steel wire loops impedes access. To receive the reward, an animal must engage the wires across the orofacial region. Contact with the bottle triggers a motor, requiring the animal to accept increasing pressure on the face during the test. To evaluate this approach, tolerated bottle distance was measured for 10 hairless Sprague Dawley rats at baseline and 30 min after application of capsaicin cream (0.1%) to the face. The experiment was repeated to evaluate the ability of morphine to reverse this effect.

RESULTS

The application of capsaicin cream reduced tolerated bottle distance measures relative to baseline (p<0.05). As long as morphine did not cause reduced participation due to sedation, subcutaneous morphine dosing reduced the effects of capsaicin (p<0.001). Comparison with existing method: For behavioral tests, experimenters often make subjective decisions of an animal's response. Operant methods can reduce these effects by measuring an animal's selection in a reward-conflict decision. Herein, a method to measure orofacial sensitivity is presented using an operant system.

CONCLUSIONS

This operant device allows for consistent measurement of heightened tactile sensitivity in the orofacial regions of the rat.

Orofacial plasmacytosis: a management conundrum

Plasmacytosis of the mucous membrane is a rare, benign, inflammatory condition of poorly understood aetiology that affects the mucous membranes. Most reported cases involve the gingival tissues, larynx, and occasionally the lips. We describe an interesting case of orofacial plasmacytosis that affected the lower lip, mandibular gingiva, and buccal mucosa. It mimicked an oral squamous cell carcinoma and presented a management dilemma.

The nucleus raphe magnus OFF-cells are involved in diffuse noxious inhibitory controls

Diffuse noxious inhibitory controls (DNIC) are very powerful long-lasting descending inhibitory controls which are pivotal in modulating the activity of spinal and trigeminal nociceptive neurons. DNIC are subserved by a loop involving supraspinal structures such as the lateral parabrachial nucleus and the subnucleus reticularis dorsalis. Surprisingly, though, whether the nucleus raphe magnus (NRM), another supraspinal area which is long known to be important in pain modulation, is involved in DNIC is still a matter of discussion. Here, we reassessed the role of the NRM neurons in DNIC by electrophysiologically recording from wide dynamic range (WDR) neurons in the trigeminal subnucleus oralis and pharmacologically manipulating the NRM OFF- and ON-cells. In control conditions, C-fiber-evoked responses in trigeminal WDR neurons are inhibited by a conditioning noxious heat stimulation applied to the hindpaw. We show that inactivating the NRM by microinjecting the GABAA receptor agonist, muscimol, both facilitates C-fiber-evoked responses of trigeminal WDR neurons and strongly attenuates their inhibition by heat applied to the hindpaw. Interestingly, selective blockade of ON-cells by microinjecting the broad-spectrum excitatory amino acid antagonist, kynurenate, into the NRM neither affects C-fiber-evoked responses nor attenuates DNIC of trigeminal WDR neurons. These results indicate that the NRM tonically inhibits trigeminal nociceptive inputs and is involved in the neuronal network underlying DNIC. Moreover, within NRM, OFF-cells might be more specifically involved in both the tonic and phasic descending inhibitory controls of trigeminal nociception.

Palatal myoclonus associated with orofacial buccal dystonia

Palatal myoclonus is a rare condition in which there are rhythmic jerky movements of the soft palate and sometimes of the other muscles innervated by the brainstem A particularly annoying symptom is a rhythmic clicking sound in the ear due to the opening and closing of the Eustachian tube. Orofacial buccal dystonia is a focal dystonia with sustained spasms of the masticatory, facial or lingual muscles. The frequent symptoms of this disease have mainly been reported to be involuntary and possibly painful jaw opening, closing, deflecting and retruding, or a combination of the above. However, the subtle and unnoticeable involuntary movement of multiple facial muscles, which might be an infrequent symptom of orofacial buccal dystonia, makes this disease hard to diagnose. Understanding the functional orofacial anatomy that is responsible for the clinical signs and symptoms is necessary for making a proper diagnosis. Here we report on a rare case of palatal myoclonus that was associated with orofacial buccal dystonia, and such a case has not been previously reported. We describe the diagnostic approach and excellent treatment results after Botulinum toxin A (Dysport) injection and proper counseling.

A clinico-pathologic study of 142 orofacial tumors in children and adolescents in southern iran

OBJECTIVE

The prevalence, patients' age and sex and the site of the lesions are important factors for diagnosis and they may be different in various populations. The aim of this study was to determine the type and distribution of orofacial tumors among children and adolescents in an Iranian population

METHODS

In this retrospective, case series study, data about the type, age, sex and site of 142 tumors in patients ≤18 years afflicted with orofacial neoplasms referred 2005-2009 to two referral centers in Shiraz, Southern Iran, were collected and analyzed.

FINDINGS

There were 142 (2.8%) tumors among the subjects. The most common types of benign and malignant tumors were odontoma and lymphoma in children and pleomorphic adenoma and rhabdomyosarcoma in adolescents. Parotid and posterior parts of the mandible were the most common sites of soft tissue and intrabony tumors. In the oral cavity, the palate was the most common affected site. The tumors were found in boys with higher frequency (Male:Female ratio was 1.4:1).

CONCLUSION

The observed differences in tumor type and distribution in comparison with previous studies may be attributed to genetic and geographic variations in the populations; however the design and methods of the studies are different, too.

A comparative study on anti-hyperalgesia effect of MTA and Ketoprofen in inflammatory pain

INTRODUCTION

Mineral trioxide aggregate (MTA) is an endodontic material with different clinical applications e.g. root-end filling, pulp capping and perforation repair. It has been reported to possess antimicrobial and antifungal activities. The aim of this study was to examine the effect of White MTA on formalin-induced hyperalgesia in a rat with inflammatory pain.

MATERIALS AND METHODS

Inflammatory pain was induced by subcutaneous (SC) injection of formalin (40 µL, 2.5%) into the rat upper lip. The nociceptive behavioral responses i.e. shaking of the lower jaw and face rubbing were quantified. 40 µL of eugenol (50 mg/kg), WMTA (20 mg/0.2 mL) or ketoprofen were injected solely or in combination with formalin 2.5% and the behavioral responses were compared with those observed after formalin treatment alone. One-way ANOVA, Tukey were used for analysis of data.

RESULTS

Formalin 2.5% provoked a biphasic nociceptive response, with an early and short lasting first tonic phase followed by a second phase. Solely SC injection of either WMTA or ketoprofen (a non steroidal anti-inflammatory drug) did not stimulate any significant nociceptive behaviour. However, injection of eugenol (a pain relieving agent) induced the early phase not the tonic phase of nociceptive response. WMTA, eugenol or ketoprofen injection 20 min before formalin injection attenuated the first phase but somehow prevented the induction of the second phase of nociceptive responses which were produced by formalin. Behavioural nociceptive responses including shaking of the lower jaw and face rubbing were significantly reduced when the subject was pretreated with either WMTA or ketoprofen (P<0.001).

CONCLUSION

In this study, WMTA induced pain reduction by suppression of the formalininduced nociceptive response.