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.

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.

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.

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.

The human periodontal membrane: focusing on the spatial interrelation between the epithelial layer of Malassez, fibers, and innervation.

OBJECTIVE: The purpose of the present study was to map the spatial interrelation of fibers, peripheral nerves, and epithelial layer of Malassez in human periodontal membrane in areas close to the root surfaces. MATERIAL AND METHODS: Four healthy permanent teeth extracted from four patients during puberty due to orthodontic treatment planning were analyzed. The extracted teeth, fixed in 4% neutral buffered formaldehyde for 5 days, were decalcified in 0.5 M EDTA. Paraffin blocks were sagittally cut in 5 microm thick serial sections and mounted on Superfrost Plus microscope slides. For survey, every fifth slide was stained with Alcian Blue/Van Gieson. Immunohistochemical reactions: Cytokeratin (wide spectrum screening) for epithelium, anti-vimentin for fibers, and anti-neuronal nuclei (NeuN) for innervation. RESULTS: The study indicates that the epithelial layer of Malassez is a border between different fiber morphologies and innervation patterns. Innervation is identified predominantly in the periodontal layer with tightly packed fibers close to the root surface. CONCLUSION: It is suggested that the genetic composition of the epithelial layer of Malassez in the periodontal membrane may be the key to understanding the different functions of the periodontal membrane and also the individual differences of these functions.

Local peptidergic innervation of gingiva in smoking and non-smoking periodontitis patients.

BACKGROUND: The present study aimed to investigate the local peptidergic innervation of diseased and healthy periodontia in smokers and non-smokers. METHODS: Fifteen smokers and 12 non-smokers, all with localized chronic periodontitis, participated in the study. Periodontally diseased and healthy tooth sites were selected in smokers (groups 1 and 2, respectively) and non-smokers (groups 3 and 4, respectively). Local peptidergic innervation was assessed by the concentrations of two neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP), in the gingival biopsies obtained from the groups. Clinical data and biopsies were collected from the same two tooth sites in each group. SP and CGRP levels were measured by enzyme immunosorbent assay in the supernatants of gingival samples. RESULTS: Increased probing depth and attachment loss were found in group 1 compared to group 3 (P<0.05). SP was higher in group 1 compared to groups 2, 3, and 4, and it was higher in group 3 compared to groups 2 and 4 (P<0.05). CGRP was higher in group 1 than in groups 2, 3, and 4, but it was lower in group 3 than in groups 2 and 4 (P<0.05). CONCLUSION: The study results suggested that 1) although smoking may affect the neurogenic inflammation in the presence of periodontitis by increasing local peptidergic innervation, this effect may not be seen in periodontal health, and 2) SP may be regarded as an indicator of periodontitis, whereas CGRP may be important in the acute and/or initial periodontal inflammation.

Unilateral ligature-induced periodontitis influences the expression of neuropeptides in the ipsilateral and contralateral trigeminal ganglion in rats.

OBJECTIVES: Expression of neuronal neuropeptides in inflammatory conditions is altered. The changes in expression of substance P (SP) and calcitonin gene-related peptide (CGRP) in ipsilateral and contralateral trigeminal ganglion (TG) neurons were investigated by immunohistochemistry one week after unilateral ligature-induced periodontitis in rats. DESIGN: A retrograde nerve tracer Fluorogold (FG) was applied into the gingival sulcus of the second maxillary molar to identify the neurons in TG that specifically innervate the inflamed gingivomucosa. In addition, neurons from the corresponding maxillary and the adjacent mandibular-ophthalmic regions in TG were analysed. RESULTS: Statistically significantly higher frequencies of CGRP-positive neurons, regardless of their size, were found in TG ipsilateral to the periodontitis (83% and 73% in FG-labelled and maxillary regions, respectively) than in the control group without periodontitis (52% and 42% in FG-labelled and maxillary regions, respectively). The frequency of small FG-labelled SP-positive neurons in the ipsilateral TG (60%) was significantly higher than in the control TG (25%). In the contralateral TG the frequency of CGRP-positive neurons in maxillary region (66%) was significantly higher than in the control group. Surprisingly, the number of SP-positive neurons in all regions of contralateral TG decreased when compared to control and ipsilateral TGs. CONCLUSIONS: Taken together, these results implicate a role of neurogenic component in the pathogenesis of periodontitis. The contralateral response in the TG could be mediated through the transmedian neurological pathways crossing in the trigeminal nuclear complex or through the systemic inflammatory reaction and the activation of the so called "neuro-immune axis".

Mechanical allodynia and thermal hyperalgesia induced by experimental squamous cell carcinoma of the lower gingiva in rats.

UNLABELLED: We developed a rat model of oral cancer pain by inoculating cancer cells into the lower gingiva. A squamous cell carcinoma (SCC) derived from Fisher rats, SCC-158, was inoculated into the subperiosteal tissue on the lateral side of the lower gingiva in male Fisher rats. Inoculation of cancer cells induced marked mechanical allodynia and thermal hyperalgesia in the ipsilateral maxillary and mandibular nerve area. Infiltration of the tumor cells into the mandible and the completely encompassed inferior alveolar nerve was observed. Calcitonin gene-related peptide (CGRP)-, substance P (SP)-, ATP receptor (P2X(3))-, and capsaicin receptor (TRPV1)-immunoreactive cells strikingly increased in the small-cell group of trigeminal ganglia (TGs) after tumor cell inoculation. The TRPV1-immunoreactive cells also increased in the medium- and large-cell groups. Retrograde tracing combined with immunofluorescence techniques revealed the increased expression of peptides and the receptors in maxillary nerve afferent neurons. These results suggest that inoculation of SCC cells into the lower gingiva produces mechanical allodynia and thermal hyperalgesia, indicating the establishment of a novel rat model of oral cancer pain. Increased expression of CGRP, SP, P2X(3), and TRPV1 in the TG may be involved in the behavioral changes in this model. PERSPECTIVE: To clarify the mechanisms of oral cancer pain, we examined the expression of calcitonin gene-related peptide, substance P, ATP receptor P2X(3), and capsaicin receptor TRPV1 in trigeminal ganglia. Characterizations of these molecular systems which mediate pain perception are important to develop novel clinical tools for promoting relief of oral cancer pain.

Identification and neuropeptide content of trigeminal neurons innervating the rat gingivomucosal tissue.

OBJECTIVES: The purpose of this study was to identify and characterise the neuropeptide content and the size of trigeminal ganglion (TG) neurons innervating the rat gingivomucosal tissue. DESIGN: Retrograde nerve tracer Fluorogold (FG) was injected into the gingiva (group 1, n=5) or applied into the gingival sulcus (group 2, n=5) of the first right maxillary molar. After 10 days, the ganglia were dissected and FG fluorescence was observed under UV light microscope. Expression of calcitonin gene-related peptide (CGRP) and substance P (SP) in FG-labelled neurons was investigated by immunohistochemistry. Cross-sectional areas of neuron cell bodies containing FG were determined. As a control group, approximately 1000 neuron cell bodies representing the entire TG neuron population was evaluated in five trigeminal ganglia. RESULTS: In group 1, the percentages of neurons containing CGRP (median 63%, range 48-72%) and SP (median 64%, range 54-64%) were significantly greater than in the control group (CGRP: median 43%, range 42-47% and SP: median 23%, range 21-27%). In group 2, only the percentage of neurons containing SP (median 50%, range 40-56%) was significantly greater than in the control group. FG-labelled neurons were predominantly small or medium sized (less than 1200 microm2). The neurons in the group 1 were significantly smaller than in group 2. In both experimental groups, immunopositive neurons were significantly smaller than immunonegative neurons. CONCLUSIONS: The majority of neurons in TG that innervate the rat gingivomucosa are small or medium sized and contain CGRP and SP.

Teeth and tooth nerves.

(1) Although our knowledge on teeth and tooth nerves has increased substantially during the past 25 years, several important issues remain to be fully elucidated. As a result of the work now going on at many laboratories over the world, we can expect exciting new findings and major break-throughs in these and other areas in a near future. (2) Dentin-like and enamel-like hard tissues evolved as components of the exoskeletal bony armor of early vertebrates, 500 million years ago, long before the first appearance of teeth. It is possible that teeth developed from tubercles (odontodes) in the bony armor. The presence of a canal system in the bony plates, of tubular dentin, of external pores in the enamel layer and of a link to the lateral line system promoted hypotheses that the bony plates and tooth precursors may have had a sensory function. The evolution of an efficient brain, of a head with paired sense organs and of toothed jaws concurred with a shift from a sessile filter-feeding life to active prey hunting. (3) The wide spectrum of feeding behaviors exhibited by modern vertebrates is reflected by a variety of dentition types. While the teeth are continuously renewed in toothed non-mammalian vertebrates, tooth turnover is highly restricted in mammals. As a rule, one set of primary teeth is replaced by one set of permanent teeth. Since teeth are richly innervated, the turnover necessitates a local neural plasticity. Another factor calling for a local plasticity is the relatively frequent occurrence of age-related and pathological dental changes. (4) Tooth development is initiated through interactions between the oral epithelium and underlying neural crest-derived mesenchymal cells. The interactions are mediated by cell surface molecules, extracellular matrix molecules and soluble molecules. The possibility that the initiating events might involve a neural component has been much discussed. With respect to mammals, the experimental evidence available does not support this hypothesis. In the teleost Tilapia mariae, on the other hand, tooth germ formation is interrupted, and tooth turnover ceases after local denervation. (5) Prospective dental nerves enter the jaws well before onset of tooth development. When a dental lamina has formed, a plexus of nerve branches is seen in the subepithelial mesenchyme. Shortly thereafter, specific branches to individual tooth primordia can be distinguished. In bud stage tooth germs, axon terminals surround the condensed mesenchyme and in cap stage primordia axons grow into the dental follicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Failure to obtain adequate anaesthesia associated with a bifid mandibular canal: a case report.

The inferior alveolar nerve (IAN) block is the most common method for obtaining mandibular anaesthesia in dental practice but it is estimated to have a success rate of only 80 to 85 per cent. Causes of failure include problems with operator technique and anatomical variation between individuals. This case report involves a patient who received IAN blocks on two separate occasions that resulted in only partial anaesthesia of the ipsilateral side of the mandible. Radiographic assessment disclosed the presence of bifid mandibular canals that were present bilaterally and that may have affected the outcomes of the local anaesthetic procedures. Previous studies of bifid mandibular canals are reviewed and suggestions provided that should enable clinicians to differentially diagnose, and then manage, cases where IAN blocks result in inadequate mandibular anaesthesia.

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.

Predictive factors in infraorbital sensitivity disturbances following zygomaticomaxillary fractures.

The aim of this study was to define if the alterations in sensory modalities could be a predictive factor in the prognostic recovery of the ION. Ten patients that had suffered facial trauma, associated with sensitivity alterations of the ION were evaluated prospectively. Touch detection thresholds (TD) were measured using Von Frey's filaments aesthesiometer. A warm/cold discrimination (W/C) was also done to the patients, on the same areas. The patients were examined in both sides of the face, using the non-traumatized side as control. The tests were done before surgery and several times postoperatively. For statistical analysis of the results, the two-sample t test was used. A significant difference (P < 0.0001) in the mean tactile recovery time between the areas without thermal sensitivity before surgery and those with normal thermal sensitivity before surgery was observed. Therefore, we propose that during the preoperative examination, the surgeon examines the thermal discrimination in order to establish prognosis and approximate recovery times.

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.

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 and characterization of afferent periodontal C fibres in the cat.

The presence of afferent periodontal C fibres was studied in pentobarbitone-anaesthetized cats. Extracellular single-fibre recordings were made from fine nerve filaments split from the proximally cut end of the inferior alveolar nerve. Periodontal nerve fibres were identified by constant-current stimulus pulses applied via platinum wire electrodes inserted into the periodontal space. Of 260 periodontal nerve fibres, 142 (55%) were classified as C fibres according to their conduction velocities (less than or equal to 2.5 m/sec) as determined by electrical stimulation of the periodontal ligament (c.v.p). The mean (+/- S.D.) c.v.p was 1.2 +/- 0.6 m/sec (n = 142; range: 0.3-2.5 m/sec). In addition, the axonal conduction velocity of 14 periodontal C fibres was determined by bipolar electrical stimulation of the trunk of the inferior alveolar nerve (c.v.n). On average the c.v.n was 42% higher than the c.v.p; the mean value was 1.7 +/- 0.8 m/sec (n = 14; range: 0.6-3.9 m/sec). Nevertheless, the classification of nerve fibres based on c.v.p proved to be reliable; only 1 fibre had a c.v.p less than 2.5 m/sec and a c.v.n greater than 2.5 m/sec and a c.v.n greater than 2.5 m/sec and was therefore reclassified as an A delta fibre. The responses of 30 electrically identified periodontal C fibres were tested by mechanical, thermal and chemical stimuli applied to the periodontal space. Thirteen of 19 periodontal C fibres tested responded to a strong mechanical force applied to the tooth from different directions while none could be activated by slight touch. A rudimentary directional sensitivity was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental nerve regeneration in rats. II. Autoradiographic studies of nerve regeneration to molar pulp and dentin.

The autoradiographic technique was used to analyze the degeneration and regeneration of sensory nerves to rat molars and gingiva following cut or crush injury to the right inferior alveolar nerve. At 2 days after nerve injury there was almost complete denervation of the first molar, partial denervation of the second molar, and minimal effect on the innervation to the third molar and gingiva. The degree of sensory deficit and recovery for these same rats had been previously determined. Reinnervation of the first molar was analyzed in terms of axon number and location, intensity of axon labeling, and type of nerve injury. At 6 days, neither the cut injury nor crush injury rats had any reinnervation of their first molars. By 7 days, 3 of 4 rats had axons reinnervating first molars; in those teeth there was approximately one-fourth of the normal number of axons in the pulp, and very few axons in the dentin. These rats still had as large a molar sensory deficit as the 7 day rat and 6 day rats that had no reinnervation. By 3 weeks there were one-half to three-fourths of the normal axon numbers in the pulp, one-fourth to one-half of the normal axon numbers in dentin; and sensitivity was at least half-recovered. By 6 weeks, numbers of axons in the pulp and dentin were either normal or slightly less than normal; axons had grown back into dentin to the same depth as in normal teeth; and complete recovery of sensitivity had occurred. The regenerating axons had greater than normal labeling intensity at 1 week and 3 weeks in all rats. Those with the crush nerve injury had somewhat greater numbers of reinnervating axons at 1 week and 3 weeks than the cut injury rats. A structure-function comparison for the molars showed that return of sensitivity correlated with reinnervation of both pulp and dentin.

Dental nerve regeneration in rats. I. Electrophysiological studies of molar sensory deficit and recovery.

Return of sensory nerve function in rat molars following cut or crush injury to the inferior alveolar nerve (IAN) was measured by observing the jaw opening reflex (JOR) response of the digastric muscle to electrical stimulation of individual molars or the gingiva. The IAN was injured from a lateral approach to the mandibular ramus at a site approximately 2 mm proximal to the incisor apex. Following nerve injury, the JOR threshold to stimulation of the first molars increased 6-fold: preoperative threshold mean = 47.4 +/- 21.3 microA (n = 27), postoperative threshold mean = 248.5 +/- 127.1 microA (n = 25). A 4-fold postoperative increase in JOR threshold was found for the second molars, and the thresholds were not significantly affected for third molars or gingiva. These postoperative results indicated that the major pathway of sensory innervation to the first and second molars was affected by the IAN injury, whereas the third molars and gingiva had alternate sources of innervation which remained unaffected by the IAN injury. At 1 week following injury, there was partial return of sensitivity, by 3 weeks there was approximately 50% recovery, and by 6 weeks complete return to normal JOR thresholds was found. The degree of sensory deficit, as reflected in JOR inhibition, and the rate of recovery were not significantly different after cut or crush injury in these experiments; however, there was a tendency for greater sensory loss and for more rapid recovery after crush injury. This study forms the basis for a subsequent autoradiographic analysis of nerve location in rat molars of known sensory deficit, partial recovery, or full sensory recovery.

Periodontal and gastric convergences within the hypothalamic ventromedial nucleus area--single unit study on anesthetized rats.

Unitary activities were recorded in the ventromedial nucleus of the hypothalamus (VHM) of anesthetized rats. Cells responding to periodontal stimulation (100-200 g disto-mesial traction applied to an upper incisive) were selected. The effects of gastric stimulation (2-5 ml distension) were then investigated. Out of the 40 cells activated (22 cells) or inhibited (18 cells) by periodontal stimulation, only seventeen were influenced by gastric stimulation. Eight of them responded in the same way and nine in the opposite way. Unlike the periodontal stimulation, which elicited specific spatio-temporal patterns, the gastric stimulation had only weak effects. These data nevertheless demonstrate that periodontal-gastric convergences exist in the VHM nucleus, which is consistent with the role previously ascribed to this area in alimentary behaviour.