Electrical Stimulation Of Tooth Pulp Research Articles

A problem in electrical stimulation of incisor tooth pulp in rats

The question of can electrical stimulation of the rat lower incisor pulp with a bipolar wire electrode selectively activate the pulp nerve without excitation of nerves outside the pulp was tested. Virtually all responses recorded from the mandibular nerve to stimulation of the pulp originated from the inferior alveolar nerve trunk and the response deriving from the pulp nerve was too small to be recorded.

Some anatomical and electrophysiological properties of tooth-pulp afferents in the cat

Pain: October 1979 - Volume 7 - Issue 2 - p 212 doi: 10.1016/0304-3959(79)90019-8

Alcohol-induced pituitary adenolysis: how does it control intractable cancer pain?--An experimental study using tooth pulp-evoked potentials in rhesus monkeys.

The mechanism by which chemical hypophysectomy may relieve intractable pain in patients with cancer was evaluated in six adult rhesus monkeys. Pain was produced by electrical stimulation of the tooth pulp, and evoked potentials were recorded from the primary somatosensory cortex (PSC), the centrum medianum of the thalamus (CM), and the midbrain reticular formation (MRF) before and after injection of absolute alcohol into the pituitary gland and again following intramuscular administration of naloxone. At autopsy pituitary ablation was found to be complete in three animals and incomplete in the other three. A marked decrease in amplitude without change in latency was observed in the PSC, CM, and MRF in all animals following tooth pulp stimulation, indicating that the hypophysectomy was equally effective regardless of the degree of destruction of the pituitary gland. Naloxone reversed the hypophysectomy-induced changes in tooth pulp-evoked potentials (TPEPs) recorded from PSC in animals with complete destruction of the pituitary but had no effect in any animals on TPEPs recorded from CM and MRF and had no effect on TPEPs recorded from PSC in animals with incomplete destruction of the pituitary. These findings are compatible with the possibility that interference with sensory pathways produced by injection of alcohol may be a causative factor in the decrease in TPEPs recorded and suggest that overproduction of endorphine activated by alcohol-induced hypophysectomy may contribute to the relief of pain in patients with cancer following chemical hypophysectorny.

Dental dolorimetry for human pain research: Methods and apparatus

Electrical stimulation of human tooth pulp provides a means of safely producing human pain in the laboratory. This paper describes a dolorimetry and data collection system for stimulating volunteers, recording responses and analyzing data. The system allows multilevel stimulation in pseudorandom sequences and analysis of results using the methods of Sensory Decision Theory. It consists of modified commercial equipment, specially designed circuitry, an interface, and a programmable calculator. Fundamental problems and safety considerations for electrical dental stimulation are reviewed. Reliability of stimulation and response measurement is discussed.

Narcotic Analgesia: Fentanyl Reduces the Intensity But Not the Unpleasantness of Painful Tooth Pulp Sensations

Forty subjects rated the magnitude of painful electrical stimulation of tooth pulp before and after the intravenous administration of either fentanyl, a short-acting narcotic, or a saline placebo. The responses were choices of verbal descriptors from randomized lists of either sensory intensity (that is, weak, mild, intense) or unpleasantness (annoying, unpleasant, distressing) descriptors. The fentanyl significantly reduced the sensory intensity without reducing the unpleasantness of the tooth pulp stimuli, indicating that the mechanisms of narcotic analgesia may include a significant attenuation in pain sensation in addition to effects on pain reaction. These results stress the importance of using multiple measures of pain.

Possible modulation of tooth pain in the rat by a brain stem noradrenaline-containing structure

Electrical stimulation of tooth pulp produced excitatory and/or inhibitory responses in the neurones of the rat locus coeruleus (LC) sending axons to the dorsal noradrenergic pathway. The inhibitory response lasted for several hundred milliseconds and seemed to be triggered by the activation of axon-collaterals of the LC neurones, suggesting that the LC neurones have an important modulatory function in the information processing concerned with tooth pain.

Analgesic activity of a non-steroidal anti-inflammatory agent, tolmetin sodium in experimental animals (author's transl)

Effect of tolmetin sodium on the pain-like responses caused by various nociceptive stimuli was examined in experimental animals. Tolmetin sodium showed a potent inhibitory activity on the acetic acid-induced writhing in mice and rats, and its potency, (ED50 = 23.4 and 3.01 mg/kg, p.o.) was about 2.4--10.3 times that of ibuprofen and aspirin. The hypertension induced by intraarterial injection of bradykinin toward the spleen of dogs was inhibited by tolmetin sodium (ED50 = 80 mg/kg, i.v.), but the hypertension by a simultaneous injection of bradykinin and PGE1 was not inhibited by tolmetin sodium and sulpyrine, though pentazocine inhibited both hypertensions. The pain-like response caused by pressing mechanically the inflamed paws or joints of rats induced by kaolin-carrageenin or adjuvant was inhibited by tolmetin sodium (30--100 or 20--40 mg/kg, p.o., respectively), and the potency was approximately equal that of ibuprofen and phenylbutazone. Tolmetin sodium produced a significant inhibition of the pain-like response induced by electrical stimulation of tooth pulp of dogs, but showed no effect when the methods of Haffner and D'Amour-Smith were applied to mice. Anti-writhing action of tolmetin sodium was not antagonized by naloxone. From these results, it was concluded that tolmetin sodium has a potent inhibitory activity on the pain-like responses induced by the chemical nociceptive stimuli and by the mechanical pressure stimulus of the inflamed tissue, especially on the writhing. The analgesic activity probably involves a peripheral mechanism.

Effects of variations in rectangular pulse duty cycle and intensity on pulsating direct current electro-analgesia of cat tooth pulp

Action potentials in single pulp-driven units of the trigeminal ganglion were elicited by bipolar electrical stimulation of the maxillary canine tooth pulp in cats anaesthetized with a barbiturate. The effects of electro-analgesia currents ranging in peak values from 10 to 100 μA applied to the test tooth were investigated independently for three pulsating direct-current waveforms comprised of trains of monopolar anodal rectangular pulses of various duty cycles. The effects of constant direct-current analgesia were used as a standard for comparison. Logarithmically-spaced duty cycles (per cent on time) of 1.00, 3.16 and 10.0 per cent were investigated, using a fixed frequency of 1000 Hz. Intensity-dependent pulp threshold elevations reaching approximately 400–500 per cent were observed for both constant direct current and 10 per cent duty cycle pulsating direct current analgesia of 20–70μA. In contrast, pulsating direct current analgesia waveforms having duty cycles of 3.16 and 1.00 per cent were approximately 25 per cent effective and ineffective, respectively, when compared to continuous direct current analgesia. The maximum effect was attained with waveforms of 70 μA. Averaged pulp thresholds dropped to near normal values within a few minutes following the termination of effective electro-analgesia. The results indicate that pulsating direct-current analgesia composed of rectangular anodal pulses of 10 per cent duty cycle and 1000 Hz frequency produces effects indistinguishable from that of continuous direct current analgesia at comparable peak intensities.

Some anatomical and electrophysiological properties of tooth-pulp afferents in the cat.

1. The responses of nerves which could be excited by electrical stimulation of the canine tooth-pulp were recorded from the trigeminal ganglion. 2. Preliminary experiments showed that the responses of mandibular canine pulpal afferents were recorded from the postero-lateral part of the trigeminal ganglion whereas the responses of maxillary canine pulpal afferents were recorded from the central part of the ganglion. 3. The conduction velocity differed in various parts of these nerves; the conduction velocity inside the tooth tended to be slower than that from the tooth to the trigeminal ganglion; the mean conduction velocity in the part of the nerve peripheral to the trigeminal ganglion was faster than that in the part central to the ganglion, and in the central part the conduction velocity decreased caudally. 4. Collision experiments combining tooth stimulation and stimulation of sites in the trigeminal sensory nuclear complex were carried out to investigate the projections of individual pulpal afferents. 5. The results of these experiments showed that some tooth-pulp afferents bifurcate and project to both the main sensory nucleus and the nucleus caudalis. For other pulpal afferents only a projection to the main sensory nucleus or the nucleus caudalis could be demonstrated. 6. Pulpal afferents that bifurcated had faster conduction velocities than those for which no bifurcation could be shown.

Localization of the cortical potentials evoked by electrical stimulation of the selective tooth pulp in cats.

Localization of the cortical potentials evoked by electrical stimulation of the selective tooth pulp in cats.

Detection and decision factors in pain perception in young and elderly men

The effect of age on ability to discriminate between levels of electrical stimulation of tooth pulp and willingness to report shocks as painful was evaluated using the Sensory Decision Theory. While threshold did not increase with age for tooth pulp stimulation as is often observed for thermal pain thresholds, a significant age deficit in ability to discriminate between suprathreshold shocks was observed. Significant changes with age in willingness to report the electrical shocks as painful were also observed. These results indicate that changes with age in pain perception are complex, involving not only possible discrimination deficits but also changes in bias for and against labeling noxious events as painful. These findings stress the need for within individual comparisons of laboratory techniques for evoking acute pain experiences where variables such as age are under consideration.

Responses of neurons in rostral and caudal trigeminal nuclei to tooth pulp stimulation

Using immobilized, lightly anesthetized cats, the responses of neurons in the nucleus principalis-subnucleus oralis and subnucleus caudalis regions of the sensory trigeminal complex were studied following electrical stimulation of the canine tooth pulp. Recording loci were verified histologically. Pulpal stimulation activated 122 cells in the rostral nuclei and 44 in the caudal one. Neurons in the two, spatially segregated, regions exhibited different, though overlapping distributions of response and receptive field properties. More specifically, the rostral region cells tended to have lower thresholds and to reach peak firing rates at lower stimulus intensities. Their peripheral fields were generally more restricted and more frequently homolateral. Following supra-maximal stimulation, they ordinarily had briefer initial spike latencies and their response bursts typically contained a greater number of spikes. These findings are consistent with the view that each of the regions operates in a different manner in the mediation of oro-facial pain.

Electrical stimulation of the tooth pulp in the study of pain

Unit activity was recorded from bulbar neurons in the immobilized, lightly anesthetized cat following bipolar, electrical stimulation of the canine tooth pulp and the immediately proximal gingiva. When feasable, variations in neuronal responding were studied subsequent to the application of a topical anesthetic to the portion of the gingiva being stimulated. The results indicate that (1) stimulation of the pulp with insulated, embedded, dental electrodes does not excite receptors in adjacent, nondental tissue and (2) stimulation of the gingiva through insulated, concentric electrodes does not activate pulpal receptors in near-by teeth. In addition, the results corroborate previous demonstrations that current spread beyond the pulpal cavity is unlikely when appropriate stimulating procedures are used. Together, the data lend support to the position that electrical stimulation of the tooth pulp provides a unique means for the selective, parametric study of a known pain sensor.

Experimental modulation of medullary dental pulp units by mechanical stimulation of oro-facial fields

Extracellular recordings were made from 97 units in trigeminal nucleus caudalis of the cat which were responsive to electrical stimulation of the canine tooth pulp. Fifty of these units were also activated by non-noxious graded mechanical stimuli applied to nondental trigeminal fields. Firing characteristics in response to mechanical stimuli were similar to those seen with electrical pulp stimuli. Suppression of a pulpal response could be effected if an electrical dental pulp stimulus was preceded by a conditioning mechanical stimulus applied to the ipsilateral face at specific interstimulus values. Similarly, unit responses to a mechanical facial stimulus could be suppressed by a preceding electrical pulp conditioning stimulus. No evidence of response enhancement was seen with either stimulus combination at interstimulus intervals of 50–800 msec. The 50 pulp-mechanical units were located along the ventromedial border of trigeminal nucleus caudalis. Neurons such as those reported here might possibly provide the neural basis for psychophysical responses which have been noted to result from the interaction of noxious and non-noxious facial stimuli.

Cerebral responses to electrical tooth pulp stimulation in man. An objective correlate of acute experimental pain.

The pulp of individual teeth of 17 normal adult volunteers was electrically stimulated via pairs of electrodes implanted into dentine. Computer-summated responses recorded from the surface of the head were composed of two concurrent sequences of events, one of which was seen maximally over midline areas and the other over the lower portions of the postcentral regions. Appropriate tests demonstrated that these wave forms represented cerebral tooth pulp-evoked potentials. Because tooth pulp-evoked potentials represent objective, quantifiable, nonverbal concomitants of central events associated with the perception of noxious stimuli, they may prove helpful in investigating acute experimental pain in man.

Projection of tooth pulp afferents to the cat trigeminal nucleus caudalis

Unit activity was recorded extracellularly from cat medullary neurons following electrical stimulation of the canine tooth pulp. Response characteristics of the neurons quickly stabilized at specific suprathreshold stimulus intensities but such properties as spike latency, interspike interval and spike density varied systematically as intensity was raised to maximally effective values. Receptive fields were principally unilateral. The majority included both canines and extended into other oro-facial areas. Suppression of a pulpal response could be effected by preceding tooth stimulation with a conditioning stimulus applied to some other point in the receptive field of the responding cell at an appropriate interstimulus interval. In contrast, a pulpal response could be enhanced by presenting two stimuli successively to the same canine at such intervals. Similar enhancing effects followed simultaneous stimulation of spatially segregated loci in a field. The pulp-responsive neurons were localized histologically in, or in the immediate vicinity of, the nucleus caudalis of the spinal trigeminal complex where the possibility of their existence has been questioned previously. Most of the cells were situated along the ventromedial border of the nucleus, a region reported to contain other pain-related neurons with trigeminal fields.

Congenital insensitivity to noxious stimuli.

Cerebral-evoked potentials were used to study a 25-year-old man, the older of two siblings with congenital insensitivity to all noxious stimuli, gross impairment of temperature perception, and anhidrosis. Electrical stimulation of tooth pulp consistently eliciting pain and cerebral responses in normal subjects evoked neither cerebral potentials nor painful or other sensations in our patient. However, ordinarily painful electric shocks to the skin of his face evoked cerebral responses as well as sensations lacking disagreeable qualities. Those cerebral potentials elicited by electrical stimulation of the median nerve, clicks, and light flashes were within normal limits. These findings strongly suggest that a defect in transmission of noxious impulses presumably involving first order sensory neurons exists in our patient.

Cerebral responses to electrical stimulation of tooth pulp in man.

Cerebral responses to electrical stimulation of tooth pulp in man.

Analgesic action of lidoflazine (R 7904)

The analgesic action of lidoflazine was examined by means of the “hot-plate” method in the mouse, and by electrical stimulation of tooth pulp in the rabbit and dog. In the mouse, lidoflazine increased significantly reaction time to thermal stimulation. Oral administration was more effective and longer-lasting than intraperitoneal injection in the mouse. Pretreatment of the mouse with reserpine, abolished the analgesic effect of lidoflazine. The threshold to tooth pulp stimulation was increased in the rabbit by lidoflazine; this effect was significant 2 hr after oral administration of 20 mg/kg. Lidoflazine did not alter threshold to tooth pulp stimulation in the dog. The possible mechanism of the analgesic action of lidoflazine is discussed.

Sensory mechanisms in mammalian teeth and their supporting structures.

Sensory mechanisms in mammalian teeth and their supporting structures.