Substance P expression in the gingival tissue after upper third molar extraction: effect of ketoprofen, a preliminary study.

The aim of this study was to evaluate substance P (SP) levels and the effect of a non-steroidal anti-inflammatory drug (NSAID), ketoprofen, on SP in the pericoronal gingival tissue after extraction of upper third molars. A sample of 20 young non-smoking systemically healthy adults of both sexes, with a healthy upper third molar to extract for orthodontic purposes, was selected. After extraction, a sample of the gingival tissue of the pericoronal region was collected with a sterile scalpel, placed into test tubes and kept frozen at -20°C until the SP determination. SP levels were determined by using a commercially available enzyme immunoassay (ELISA) kit. The subjects were randomly divided into two groups: group 1 received a single dose of ketoprofen 30 minutes prior to the experimental procedure. The subjects of group 2 did not receive any kind of drug administration before extraction. The patients were asked to complete a diary on the postoperative pain. A relevant amount of SP was measured in all the gingival samples. No statistically significant difference could be detected in SP expression between the two groups. In group 1 pain appearance was significantly delayed (6.2±0.13 hours) in comparison with group 2 (3.95±0.2 hours). In this small selected group of subjects and limited study design, preventive administration of ketoprofen did not significantly affect the gingival levels of SP, the clinical recommendation emerging is that of NSAID administration postoperatively but before pain appearance in order to optimize the management of pain of the patient.

Trigeminal Neuralgia Induced by Sour and Spicy Foods: What Is the Underlying Mechanism? A Case Report.

This article is a case report of a female patient in whom sour and spicy foods evoked trigeminal neuralgia (TN). An attempt to reveal the underlying pain mechanism is described and discussed. The 81-year-old woman had been suffering from classical TN since the age of 50. Attacks occurred spontaneously or in response to mechanical stimuli. In addition, sour and spicy foods also evoked TN attacks and were therefore avoided for years. Medical treatment was initially effective, but two radiofrequency ablations of the gasserian ganglion were required later on and yielded good, albeit incomplete, pain relief. Sensory examination consisted of application of a mechanical stimulus and sweet, salty, sour, and spicy solutions to the anterior part of the tongue and the mandibular mucosa on both sides. Mechanical stimuli were felt but produced no pain. When applied to the tongue, the tastes of all solutions were identified but produced no pain. When applied to the mucogingival line, none of the solutions was identified but the sour and the spicy solutions provoked TN immediately following their application. These findings suggest that in this patient, sour and spicy solutions may have evoked TN attacks by direct activation of trigeminal C-nociceptors, possibly via interactions with transient receptor potential vanilloid 1 receptors.

The occurrence of paraesthesia of the maxillary division of the trigeminal nerve after dental local anaesthetic use: a case report.

Paraesthesia can be a complication of surgical intervention. Its occurrence after dental local anaesthetic use is a rare event in general dental practice. Reported cases have mainly described its presentation for the mandibular division of the trigeminal nerve with very few reports for the maxillary division of this nerve. This report describes a case of paraesthesia in the maxillary region following local anaesthetic use prior to removal of an upper molar tooth.

Distribution of transient receptor potential melastatin-8-containing nerve fibers in rat oral and craniofacial structures.

The transient receptor potential melastatin-8 (TRPM8) is a cold and menthol receptor located in the sensory ganglia. Immunohistochemistry for TRPM8 was performed on oral and craniofacial structures of the rat. TRPM8-immunoreactive (-IR) nerve fibers were detected in the oral mucous membrane. In the gingiva, TRPM8-IR nerve fibers were abundant beneath and within crestal and outer epithelia. Such nerve fibers were also common beneath and within taste buds in the incisive papilla. In addition, TRPM8-immunoreactivity was expressed by some taste bud cells in the papilla. Lips, periodontal ligaments and salivary glands as well as masticatory muscles and temporomandibular joints were mostly devoid of TRPM8-IR nerve fibers. A double immunofluorescence study indicated different distribution patterns of nerve fibers containing TRPM8 and calcitonin gene-related peptide in oral and craniofacial tissues. Retrograde tracing method also indicated that TRPM8-IR nerve fibers in the gingiva and incisive papilla originate from small sensory neurons in the trigeminal ganglion. TRPM8 may be associated with cool, cold nociceptive (

Identification of autonomic neuronal chains innervating gingiva and lip.

The major goals of this present study were 1) to further clarify which parasympathetic ganglion sends postganglionic fibers to the lower gingiva and lip that may be involved in the inflammatory processes besides the local factors; 2) to separately examine the central pathways regulating sympathetic and parasympathetic innervation; and 3) to examine the distribution of central premotor neurons on both sides. A retrogradely transported green fluorescent protein conjugated pseudorabies virus was injected into the lower gingiva and lip of intact and sympathectomized adult female rats. Some animals received virus in the adrenal medulla which receive only preganglionic sympathetic fibers to separately clarify the sympathetic nature of premotor neurons. After 72-120h of survival and perfusion, the corresponding thoracic part of the spinal cord, brainstem, hypothalamus, cervical, otic, submandibular and trigeminal ganglia were harvested. Frozen sections were investigated under a confocal microscope. Green fluorescence indicated the presence of the virus. The postganglionic sympathetic neurons related to both organs are located in the three cervical ganglia, the preganglionic neurons in the lateral horn of the spinal cord on ipsilateral side; premotor neurons were found in the ventrolateral medulla, locus ceruleus, gigantocellular and paraventricular nucleus and perifornical region in nearly the same number on both sides. The parasympathetic postganglionic neurons related to the gingiva are present in the otic and related to the lip are present in the otic and submandibular ganglia and the preganglionic neurons are in the salivatory nuclei. Third order neurons were found in the gigantocellular reticular and hypothalamic paraventricular nuclei and perifornical area.

Toll-like receptor 4 expression in trigeminal neurons is increased during ligature-induced periodontitis in rats.

BACKGROUND: Periodontitis, activated by oral bacteria and orchestrated by innate immune response, is regulated by primary nociceptive neurons, which are generally considered to have small- to medium-sized perikaryons. Bacterial byproducts (e.g., lipopolysaccharides) activate primary nociceptive neurons directly through Toll-like receptors (TLRs). Therefore, this study aims to morphometrically characterize rat trigeminal neurons, which express TLR4, and to investigate the changes in the TLR4 expression in neurons during periodontal inflammation. METHODS: Trigeminal neurons innervating gingivomucosa were identified by application of the retrograde tracer hydroxystilbamidine into the gingival sulcus of the maxillary molar in 14 rats. Periodontitis was induced by ligature around the same molar in seven rats. TLR4 expression was investigated by immunohistochemistry on paraffin sections of the trigeminal ganglia (TG). Semiquantitative method was used to identify the intensity of TLR4 expression. RESULTS: In the control group without the ligatures, TLR4 was detected in 19% of the neurons in the maxillary region of TG and in 29% of neurons innervating gingivomucosa. Expression of TLR4 was more frequent and intensive in small- to medium-sized neurons than in large-sized neurons. One week after ligature-induced periodontitis, the percentage of TLR4-positive neurons in the maxillary region and among the neurons innervating inflamed gingivomucosa significantly increased statistically to 32% and 41%, respectively. CONCLUSIONS: TLR4 is predominantly, but not exclusively, expressed in smaller trigeminal nociceptive neurons in the rat. Experimental periodontitis upregulates TLR4 expression in the trigeminal neurons. The hypothesis that bacterial byproducts regulate the pathogenesis of periodontitis by activation of trigeminal nociceptors through TLR4 should be explored.

Electrophysiologic evaluation of inferior alveolar nerve regenerated by bifocal distraction osteogenesis in dogs.

BACKGROUND: Bifocal distraction osteogenesis has been shown to be a reliable method for reconstructing missing bone segments. However, there are no reports regarding inferior alveolar nerve regeneration during bifocal distraction. In the present study, the authors evaluated the function of inferior alveolar nerve regenerated by bifocal distraction after segmental resection in the mandibles of dogs. METHODS: Using a bifocal distraction osteogenesis method, the authors produced a 10-mm mandibular defect and distracted the transport disk at a rate of 1 mm/day. The regenerated inferior alveolar nerve was evaluated by electrophysiologic analysis that was performed on all dogs after euthanasia at 3, 6, and 12 months after the first operation. RESULTS: At 6 and 12 months, stable evoked potential measurements were obtained from the nerves throughout the study on electrophysiologic analyses. CONCLUSIONS: The authors' results indicate that the inferior alveolar nerve regenerated by bifocal distraction osteogenesis functioned electrophysiologically at 6 months after the first operation. Although our research is still at the stage of animal experiments, future application in humans is considered to be possible.

Dental pulp and gingivomucosa in rats are innervated by two morphologically and neurochemically different populations of nociceptors.

OBJECTIVES: Difference in phenotypes of sensory neurons innervating dental pulp or gingivomucosa may be responsible for intense pain sensations in pulpitis in contrast to relatively painless chronic periodontitis. Therefore, we classified these neurons according to their size and two neurochemical characteristics of nociceptors, their TrkA expression and isolectin IB4 binding. DESIGN: In rats (n=6) fluorescent tracers Fluorogold and TrueBlue were simultaneously applied into the standard-sized tooth cavity and nearby gingival sulcus, respectively. After the fluorescence on paraffin trigeminal ganglia (TG) sections was identified and photographed, immunohistochemistry for TrkA expression and IB4 binding was performed on the same sections. RESULTS: The average sizes of TG neurons projecting to the gingivomucosa and dental pulp were 894±441µm(2) and 1012±381µm(2), respectively. The proportions of small-sized gingival and pulpal neurons were 14% and 5%, respectively (p<0.05). The proportions of TrkA-positive neurons among all gingival or pulpal neurons were 76% and 86%, respectively (p<0.05). Among all gingival or pulpal neurons the proportions of IB4-positive neurons were 46% and 3% (p<0.001), respectively, and the majority of them were small-medium sized. CONCLUSIONS: Dental pulp and gingivomucosa are richly innervated by nociceptive TrkA-expressing neurons. However, while great majority of pulpal neurons are larger NGF-dependent A-fibre nociceptors without affinity to bind IB4, almost half of the gingival neurons are smaller IB4 binding C-fibre nociceptors. The difference in phenotype of sensory neurons might partially explain the different sensitivity of both tissues during normal and pathological conditions.

Functional properties of tooth pulp neurons responding to thermal stimulation.

The response properties of tooth pulp neurons that respond to noxious thermal stimulation of the dental pulp have been not well-studied. The present study was designed to characterize the response properties of tooth pulp neurons to noxious thermal stimulation of the dental pulp. Experiments were conducted on 25 male ferrets, and heat stimulation was applied by a computer-controlled thermode. Only 15% of tooth pulp neurons (n = 39) responded to noxious thermal stimulation of the teeth. Tooth pulp neurons were found in both the superficial and deep nuclear regions of the subnucleus caudalis (Vc) and in the interface between the nucleus caudalis and interpolaris (Vc/Vi). Thirty-seven neurons had cutaneous receptive fields and were classified as either NS (16) or WDR (21) neurons. Repeated heat stimulation of the dental pulp sensitized and increased the number of electrically evoked potentials of tooth pulp neurons. These results provide evidence that both the Vc and Vc/Vi regions contain neurons that respond to noxious thermal stimulation of the dental pulp, and that these cells may contribute to the sensitization process associated with symptomatic pulpitis.

The two main theories on dental bruxism.

Bruxism is characterized by non-functional contact of mandibular and maxillary teeth resulting in clenching or grating of teeth. Theories on factors causing bruxism are a matter of controversy in current literature. The dental profession has predominantly viewed peripheral local morphological disorders, such as malocclusion, as the cause of clenching and gnashing. This etiological model is based on the theory that occlusal maladjustment results in reduced masticatory muscle tone. In the absence of occlusal equilibration, motor neuron activity of masticatory muscles is triggered by periodontal receptors. The second theory assumes that central disturbances in the area of the basal ganglia are the main cause of bruxism. An imbalance in the circuit processing of the basal ganglia is supposed to be responsible for muscle hyperactivity during nocturnal dyskinesia such as bruxism. Some authors assume that bruxism constitutes sleep-related parafunctional activity (parasomnia). A recent model, which may explain the potential imbalance of the basal ganglia, is neuroplasticity. Neural plasticity is based on the ability of synapses to change the way they work. Activation of neural plasticity can change the relationship between inhibitory and excitatory neurons. It seems obvious that bruxism is not a symptom specific to just one disease. Many forms (and causes) of bruxism may exist simultaneously, as, for example, peripheral or central forms.

Clinical measurements of hard palate and implications for subepithelial connective tissue grafts with suggestions for palatal nomenclature.

PURPOSE: The objectives of the present study were to 1) identify a reliable measuring technique for a palatal graft, 2) observe the patterns of the neurovascular bundle, and 3) identify the morphology of the hard palate. Subepithelial connective tissue grafts are performed at an increasing rate to improve esthetics and oral health. Palatal graft techniques began in 1963, and today the subepithelial connective tissue graft is the most widely accepted technique. The greater palatine nerve and artery are critical neurovascular structures to identify. Their pattern and palate morphology are not well defined. MATERIALS AND METHODS: Anatomy texts, atlases, and specialty texts were analyzed. We dissected 17 palates (17 left and right halves) from embalmed human cadavers, implementing a measuring technique to locate the most coronal structure of the greater palatine artery and greater palatine nerve bundle, observing the patterns and palatal morphology. Electronic digital calipers and a periodontal probe were used for data collection. RESULTS: The dissection results revealed a reliable measuring technique, a common pattern of the bundle, and osseous palatal landmarks not clearly defined in contemporary texts. The dissections also demonstrated a medial and lateral groove, along with a crest in the palatine process of the maxillary bone. The greater palatine artery traversed the lateral groove, and the greater palatine nerve traversed the medial groove consistently. The crest was located anteroposteriorly between the grooves. CONCLUSIONS: The results of our study suggest a useful measurement technique, a consistent neurovascular pattern, and the need to reconsider the palatal nomenclature.

Orofacial thermal thresholds: time-dependent variability and influence of spatial summation and test site.

AIM: To investigate time-dependent variability and influence of test site and stimulation area size on intraoral cold detection, warmth detection, and heat pain thresholds. METHODS: Thirty healthy volunteers (15 women and 15 men) participated. Six extra- and intraoral sites were examined, and cold detection, warmth detection, and heat pain thresholds were measured. Time variability and influence of spatial summation were also studied at one site-the tip of the tongue-three times over a 6-week period. One-way ANOVA for repeated measures and paired sample t test compared mean values and SD within and between sites for all thresholds. RESULTS: Several between-site differences were significant (P < .05). Lowest intraoral thresholds for all stimuli were measured at the tongue site, and at the tongue, thresholds for warmth detection and heat pain, but not cold detection, decreased with increasing size of stimulation area (P < .05). Overall, thresholds at the tongue site varied nonsignificantly over time (P > .05). CONCLUSION: Test site affects orofacial thermal thresholds substantially, whereas time variability and spatial summation on the tongue appear to be modest.

Area extent anaesthesia from buccal nerve block.

This study investigated the extent of complete anaesthesia from buccal nerve block. 40 healthy Thai patients (20 males; 20 females) requiring buccal nerve block for surgery were studied. After the buccal nerve was blocked, the buccal mucosa was explored using a sharp probe to map out the extent of anaesthesia. The operation was carried out after inferior alveolar and lingual nerve block. The extent of the anaesthesia was mainly from the retromolar area to the second molar, followed by the first molar to the second premolar, whilst the first premolar to the central incisor was the area least affected. An important finding of this study was that the anaesthetized extent of some patients extended to the anterior region on the same quadrant. This study showed the affected areas of buccal nerve anaesthesia extended through the buccal mucosa from the first premolar to the central incisor in some patients. It can serve as another informative indication for lower anterior surgery.

SEM and neurohistological observations of nerve endings in the middle region of the tongue of the collared peccary (Tayassu tajacu): a silver impregnation method.

The presence of lingual papillae and the nerve endings in the middle region of the tongue mucosa of collared peccary (Tayassu tajacu) were studied using scanning electron microscopy and light microscopy, based upon the silver impregnation method. The middle region of tongue mucosa revealed numerous filiform and fungiform papillae. The thick epithelial layer showed epithelial cells and a dense connective tissue layer containing nerve fibre bundles and capillaries. The sensory nerve endings, intensely stained by silver impregnation, were usually non-encapsulated and extended into the connective tissue of the filiform and fungiform papillae very close to the epithelial cells. In some regions, the sensory nerves fibres formed a dense and complex network of fine fibrils. The presence of these nerve fibrils may characterize the mechanisms of transmission of sensitive impulses to the tongue mucosa.

Trigeminal nerve injuries in relation to the local anaesthesia in mandibular injections.

OBJECTIVE: This study reports the signs and symptoms that are the features of trigeminal nerve injuries caused by local anaesthesia (LA). METHODS: Thirty-three patients with nerve injury following LA were assessed. All data were analysed using the SPSS statistical programme and Microsoft Excel. RESULTS: Lingual nerve injury (LNI; n = 16) and inferior alveolar nerve injury (IANI; n = 17) patients were studied. LNI were more likely to be permanent. Neuropathy was demonstrable in all patients with varying degrees of paraesthesia, dysaesthesia (in the form of burning pain) allodynia and hyperalgesia. All injuries were unilateral. A significantly greater proportion of LNI patients (75%) had received multiple injections, in comparison to IANI patients (41%) (p <0.05). Fifty percent of patients with LNI reported pain on injection. The presenting signs and symptoms of both LNI and IANI included pain. These symptoms of neuropathy were constant in 88% of the IANI group and in 44% of LNI patients. Functional difficulties were different between the LNI and IANI groups, a key difference being the presence of severely altered taste perception in nine patients with LA-induced LNI. CONCLUSIONS: Chronic pain is often a symptom after local anaesthetic-induced nerve injury. Patients in the study population with lingual nerve injury were significantly more likely to have received multiple injections compared to those with IANI.

Evaluation of a magnetic resonance-compatible dentoalveolar tactile stimulus device.

BACKGROUND: Few methods exist to study central nervous system processes following dentoalveolar tactile stimulation using functional magnetic resonance imaging (fMRI), likely due to inherent technical difficulties. Our primary goal was to develop and perform feasibility testing of a novel device capable of delivering valid and reliable dentoalveolar stimuli at dental chair-side and during MRI. Details of a device designed to deliver dentoalveolar dynamic pressure stimuli are described. Device testing took place in three settings: a) laboratory testing to assess range of stimulus force intensities, b) dental chair-side to assess reliability, validity and discriminant ability in force-pain relationship; and c) MRI to evaluate magnetic compatibility and ability to evoke brain activation in painfree subjects similar to those described in the literature. RESULTS: A novel device capable of delivering valid and reliable dentoalveolar somatosensory stimulation was developed (ICC = 0.89, 0.78-1 [95% CI]). Psychophysical data analysis showed high discriminant ability in differentiating painfree controls from cases with chronic dentoalveolar pain related to deafferenting dental procedures (sensitivity = 100%, specificity = 86.7%, area under ROC curve = 0.99). FMRI results of dentoalveolar dynamic pressure pain in painfree subjects revealed activation of brain areas typically associated with acute pain processing including thalamus, primary/secondary somatosensory, insular and prefrontal cortex. CONCLUSIONS: A novel psychophysical method to deliver dynamic dentoalveolar pressure stimulation was developed and validated, allowing non-invasive MRI-based exploration of central nervous system function in response to intraoral somatosensation. BACKGROUND: The organization of the trigeminal system is unique as it provides somatosensory innervation to the face, masticatory and oral structures, the majority of the intracranial contents 1 and to specialized structures (tongue, nasal mucosa, auricle, tympanic membrane, cornea and part of the conjunctiva) 2. Somatic sensory information transmitted by the trigeminal nerve is crucial for normal orofacial function; however, the mechanisms of many chronic pain conditions affecting areas innervated by this sensory system are not well understood 345. The clinical presentation of chronic intraoral pain in the area of a tooth or in a site formally occupied by a tooth with no clinical or radiological signs of pathology, referred to as atypical odontalgia (AO) 67, is one such chronic pain condition of particular interest to dentists that is difficult to diagnose and manage. Recent research suggests both peripheral and central nervous system mechanisms being involved in AO pathophysiology 8910, but the majority of mechanism-based research of patients with AO has focused on the "peripheral aspect" 7.Functional magnetic resonance imaging (fMRI) is an established research technique to study the central aspects of pain 11. Of existing neuroimaging techniques, fMRI provides good spatial resolution of cortical and subcortical structures critical in the processing of nociception, acceptable temporal resolution, does not involve ionizing radiation, and can be performed using most MRI systems that already exist in research centers and the community. For these reasons, we sought to develop a protocol that allows us to use this tool to investigate the central mechanisms involved in the processes of intraoral pain arising from the dentoalveolar region. Using this device, our long-term objective is to improve our understanding of the underlying mechanisms of persistent dentoalveolar pain.In the past few years several studies used fMRI to investigate the human trigeminal system 1213, with a limited subset focusing on intraoral stimulation - specifically on the dentoalveolar processes, such as lip, tongue and teeth stimulation 14 or only teeth 151617. Some reasons for scarce literature on this topic may be the technical challenges involved in delivering facial/intraoral stimulation inside a MR scanner 1718: possibility of magnetic interference, detriment of image quality, subject discomfort and reduced working space between the subject's head and the radiofrequency coil. As a consequence a MR-compatible device would need to not only overcome these challenges but also be capable of delivering a controlled and reproducible stimuli 19, as reliability/reproducibility is a necessary feature of sensory testing 20.Existing MR-compatible methods of dentoalveolar stimulation are limited and do not adequately deliver stimuli across a range of non-painful to painful intensities and/or cannot be adjusted to reach posterior aspects of the dentoalveolar region. Therefore our goal was to develop and test the feasibility of a device able to: 1) provide reliable and valid dentoalveolar stimuli, 2) deliver such stimulation within the restricted space of an MR head coil, 3) be compatible for use within an MR environment, and 4) produce brain activation in painfree controls consistent to those observed by others using fMRI.

Inferior alveolar nerve paresthesia after overfilling of endodontic sealer into the mandibular canal.

The present study describes a case of endodontic sealer (AH Plus) penetration within and along the mandibular canal from the periapical zone of a lower second molar after endodontic treatment. The clinical manifestations comprised anesthesia of the left side of the lower lip, paresthesia and anesthesia of the gums in the third quadrant, and paresthesia and anesthesia of the left mental nerve, appearing immediately after endodontic treatment. The paresthesia and anesthesia of the lip and gums were seen to decrease, but the mental nerve paresthesia and anesthesia persisted after 3.5 years. This case illustrates the need to expend great care with all endodontic techniques when performing nonsurgical root canal therapy, especially when the root apices are in close proximity to vital anatomic structures such as the inferior alveolar canal.

Effects of CO2 laser irradiation of the gingiva during tooth movement.

Patients often feel pain or discomfort in response to orthodontic force. It was hypothesized that CO(2) laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos-immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evaluated. Two hrs after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO(2) laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. The maximum temperature below the mucosa during CO(2) laser irradiation was less than 40 degrees C. It was suggested that CO(2) laser irradiation reduced the early responses to nociceptive stimuli during tooth movement and might not have adverse effects on periodontal tissue.

Anti-NGF treatment reduces bone resorption in periodontitis.

Periodontitis is characterized by periodontal tissue destruction, including the alveolar bone. One of its critical components is the release of pro-inflammatory neuropeptides from sensory nerve endings innervating the periodontium. Since nerve growth factor (NGF) has been reported to up-regulate neuropeptides in sensory neurons, we hypothesized that it would be increased in ligature-induced periodontitis in rats, and that systemic NGF neutralization would reduce the periodontitis-associated alveolar bone resorption. Real-time PCR analysis disclosed a statistically significant time-dependent up-regulation of NGF mRNA in gingiva during 2 weeks of periodontitis. Interestingly, NGF up-regulation was also detected in the contralateral gingiva. In addition, immunohistochemistry of trigeminal ganglion neurons innervating the gingivomucosa demonstrated increased expression of TrkA receptor for NGF. Systemic anti-NGF treatment during periodontitis significantly reduced interleukin-1beta expression in gingiva and bilateral alveolar bone resorption. This suggests that NGF promotes periodontal inflammation and implicates a possible use of anti-NGF treatment in periodontitis.