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Biomedical subjects

Y Sharav

Publications and source records attributed to Y Sharav.

At least 19 recordsLinked to original sources
PubMed1991

Idiopathic trigeminal pain associated with gustatory stimuli.

We present a unique case of a patient with facial pain evoked by gustatory stimuli. Pain was typically evoked by application of sucrose to the ipsilateral anterior 2/3 of the tongue, but not to the contralateral aspect. Pain was referred to the maxillary tuberosity area and, when stronger, to the infraorbital and supraorbital regions. Sucrose was most effective in eliciting pain, whilst saline, citric acid and water had a minimal effect. Spatial or temporal summation of gustatory stimuli was associated with stronger pain of longer duration and shorter latency. Some of the pain characteristics were similar to those of idiopathic trigeminal neuralgia. Thus, pain was elicited by innocuous ipsilateral stimuli, referred out of the stimulus zone, persisted beyond the period of stimulation and could be controlled with carbamazepine. We proposed a central neural mechanism for pain induction with convergence between gustatory stimuli afferents and pain pathways in the trigeminal system.

Carbamazepine↗
PubMed1991

Faculty and staff development in dental education.

While five dental schools in the United States closed, and the total number of faculty shrunk from 3789 to 3335 in the last decade, the overall quality of faculty went up. This is because of a healthy turnover of staff; about half of the new faculty are recruited from advanced education programs, and present faculty members retire at a higher rate. Dental schools are in the midst of a revolution of health care delivery resulting from changes in disease patterns, in particular decreased caries prevalence in children, less edentulousness in adults, and increasing numbers of aging, medically compromised patients. These changes have an effect on faculty buildup and development, and there is a growing need for teachers who are more knowledgeable in medicine and better skilled in adult general dentistry. Clinical faculty will be trained in treating medically compromised patients and will be better acquainted with subjects such as oral medicine, medical emergencies, pain and anxiety control, pharmacology, anesthesia, and geriatric dentistry. Staff and faculty should also be qualified in management skills and cost effectiveness.

Administrative Personnel↗
PubMed1990

Effects of one- or two-stage deafferentation of mandibular and maxillary tooth pulps on the functional properties of trigeminal brainstem neurons.

We have recently demonstrated that deafferentation of the adult cat's maxillary or mandibular posterior tooth pulps results in statistically significant changes in mechanoreceptive field and response properties of low-threshold mechanoreceptive (LTM) brainstem neurons in trigeminal (V) subnucleus oralis. These effects were however reversible, and the statistically significant changes were apparent only for 1-2 weeks after the deafferentation procedure. The aim of this study was to examine the effects of a more extensive deafferentation involving both maxillary and mandibular pulps. In accordance with our earlier study, the pulps of the teeth were deafferented and, in a 'blind' design, the physiological properties of oralis LTM neurons were studied in each of these animals and compared with those from control, unoperated cats. Statistically significant changes in mechanoreceptive field and response properties were produced in these animals with both maxillary and mandibular quadrants deafferented and were similar to those documented in our earlier study involving deafferentation of only one quadrant. However, as well as occurring at 1-2 weeks after the deafferentation procedures, the changes were still apparent at 4 weeks following the deafferentation. In addition, we also documented that changes could be produced by a two-stage deafferentation procedure involving first the mandibular pulps and then, 3 weeks later, the maxillary pulps. These findings thus demonstrate that an extensive deafferentation procedure involving mandibular as well as maxillary tooth pulps can produce statistically significant changes in the physiological properties of V brainstem neurons of adult cats that may last at least 4 weeks postoperatively.

Action Potentials↗
PubMed1989

Masseter inhibitory periods and sensations upon electrical tooth-pulp stimulation in children and adults.

Sensations and masseter inhibitory periods (MIP) evoked by electrical tooth-pulp stimulation were recorded in 5 adults and 10 children. In the adult group there was always a sensation and it was usually associated with a two-phase MIP, with an early and a late component. Sensory detection in teeth with partially formed roots in the younger children (7-9 years old) was markedly reduced, and the MIP was mostly monophasic with a predominantly early component. In the older children with fully formed roots (10-12 years old) sensations did not differ from those in the adults, but the late MIP component occurred in significantly fewer trials (P less than 0.01). It is concluded that response to electrical tooth-pulp stimulation develops in the following stages: (1) early, oligosynaptic MIP, (2) sensation, and (3) the late, polysynaptic component of the MIP.

Adult↗
PubMed1989

Masseter inhibitory periods and sensations evoked by electrical tooth-pulp stimulation in subjects under hypnotic anesthesia.

Sensation and masseter inhibitory periods (MIP) to electrical tooth-pulp stimulation were recorded under hypnotic anesthesia and placebo to local anesthesia. In the first experiment, 8 subjects were tested for the effect of hypnotic anesthesia on sensory detection and MIP at non-painful stimulus levels (mean = 42.1 microA) and painful levels (mean = 86.5 microA). The percentage of detection for non-painful stimuli changed from 94.3% to 14.1% and for painful stimuli from 100% to 28%; both changes were significant (P less than 0.001). Hypnotic anesthesia blocked sensation without interrupting the initiation of the early component of the MIP, but did suppress its late component. In the second experiment, 8 subjects were tested for the perceived intensity of 5 levels of electrical tooth-pulp stimulation under hypnotic anesthesia and placebo. Sensory intensity was measured by the visual analog scale (VAS). Hypnotic anesthesia was significantly more effective than placebo (P less than 0.001) in reducing sensation. The differential effect of hypnotic anesthesia on the early and late component of the MIP lends further support to the hypothesis that hypnotic anesthesia operates primarily at suprasegmental, higher levels in the brain.

Adolescent↗
PubMed1987

Idiopathic trigeminal neuralgia: sensory features and pain mechanisms.

We present a case report of a patient with the typical sensory features of idiopathic trigeminal neuralgia (ITN). The pain was elicited by innocuous stimuli, summated with repeated stimulation, radiated outside the stimulus zone, referred to a distant site, persisted beyond the period of stimulation, and exhibited a variable refractory period. Unusual sensory features included multiple trigger zones that changed over time and involved all 3 trigeminal divisions. Our sensory evaluation indicated that the pain was evoked by repetitive activation of rapidly adapting, A beta, low-threshold mechanoreceptive afferents. However, activation of such mechanoreceptive afferents alone never produces pain in normal situations and often leads to a suppression of pain responsivity. The findings support the idea that the mechanism of pain in ITN involves pathophysiological mechanisms in the central nervous system. Our hypothesis is that structural and functional changes in the trigeminal system result in an alteration in the receptive field organization of wide-dynamic-range (WDR) neurons. There appears to be an alteration in the surround inhibition mechanism of these neurons leading to an expansion of their touch receptive fields. This results in touch stimuli producing activity in WDR neurons that mimics the activity produced under normal conditions by noxious stimuli. Since WDR neurons participate in the encoding of the perceived intensity of noxious stimuli, a series of punctate tactile stimuli are now perceived as localized, pin-prick or electric shock-like sensations. Similar pathophysiological mechanisms may explain, in part, the pain of peripheral neuropathies associated with postherpetic neuralgia, diabetes and causalgia.

Electric Stimulation↗
PubMed1985

Development of sensory and reflex responses to tooth-pulp stimulation in children.

Electric stimulation was applied to the tooth-pulp and tongue in 12 children divided into 3 groups according to the development of the roots of the upper first incisors, i.e. 1/2, 3/4 and fully formed. The masseter inhibitory periods (MIP) could be evoked by electric stimulation of the tongue at sensory threshold current levels in all children, but only for incisors with fully-formed roots. Stimulation of incisors with 3/4 formed roots at detection-threshold currents produced sensation 56 per cent of the time and detectable MIP on 65 per cent of stimuli. No sensation was obtained with stimuli up to 100 microA in incisors with 1/2-formed roots, but MIP was recorded with 31 per cent of stimuli. The findings indicate that reflex activity precedes sensation in the normal development of teeth, and that segmental, reflex, connections appear to be established before the cortical, sensory, projections are fully functional.

Child↗
PubMed1984

A computerized decision support system for patient selection in dental education.

A computerized decision support system is presented. The system is used to aid in the situation of patient selection for the purpose of dental education and utilizes the PERT/CPM methodology and decision tables. It runs on a microcomputer and written in Basic. The input is a list of patient's needs, and the output is a tentative treatment plan, the chair time needed to complete the treatment, its cost, and the probability that the student will finish it on time.

Appointments and Schedules↗
PubMed1984

The spatial distribution, intensity and unpleasantness of acute dental pain.

The distribution, intensity and unpleasantness of acute dental pain were studied in 196 patients. Dental pain was classified by source according to 7 anatomical sites: dentinal, pulpal, pulpal and periapical, periapical, pericoronal, papillar, and periodontal. The distribution of dental pain was classified by the frequency of pain spread throughout the sample, by the extent of pain spread for a particular pain source, that is, the number of vectors of spread, and by the pain reference locations in the face and head. Pain-intensity and pain-unpleasantness were assessed on Visual Analogue Scales. The frequency and extent of pain spread varied as a function of source. However, specific patterns of pain spread were not associated with particular pain sources. There was considerable overlap in patterns of spread between maxillary and mandibular pain sources. The frequency and extent of pain spread was correlated positively with both pain intensity and pain unpleasantness. The correlation between pain ratings and pain spread may be attributed to central mechanisms and interactions between trigeminothalamic neurons. Spatial overlap of pain from maxillary and mandibular pain sources may be due to the large receptive fields of wide dynamic range neurons, that can extend beyond one trigeminal division. These observations indicate that the spatial distribution of acute dental pain is not sufficient as a diagnostic tool for indentifying pain source.

Adult↗
PubMed1982

Masseter inhibitory periods and sensations evoked by electrical tooth pulp stimulation in patients with oral-facial pain and mandibular dysfunction.

The masseter inhibitory period (silent period) and sensations evoked by tooth-pulp stimulation were examined in 12 healthy subjects and 12 patients with oral-facial pain and mandibular dysfunction (MPD). Trains of 30 pulses were applied to an upper incisor and the threshold intensities for detecting sensation, for detecting pain sensation and for the masseter inhibitory period were determined. Masseter activity was monitored during tooth stimulation by electromyographic recordings from surface electrodes. Electrical tooth stimulation elicited three different configurations of masseter inhibitory periods in both groups: single, double and merged. MPD patients exhibited a greater proportion of single inhibitory periods. The combined average total durations of the three types of configurations were less in MPD. The findings are consistent with the hypothesis that there is an increase in excitability of the central masseter motorneuron pool in MPD, resulting in a reduction in the effective duration of the masseter inhibitory period. The higher incidence of single inhibitory periods in MPD patients also could result from this increased central excitatory state. There was no difference between masseter inhibitory periods evoked in either painful or non-painful muscles, and no particular configuration associated with pain sensation. The findings do not support the hypothesis that nociceptive input contributes to the increase in duration of the silent period in MPD. Although there were no significant differences between masseter inhibitory period threshold, detection thresholds or pain threshold for both groups, MPD patients had detection thresholds higher than their masseter inhibitory thresholds. These effects may be related to differential central neural influences on sensory-discriminative and reflex pathways in the trigeminal system.

Adolescent↗
PubMed1977

Distinct properties of Thy-1 antibodies elicited in rats by immunization with mouse brain.

Rats are known to possess antigenic determinants related to the Thy-1.1 allele. Immunization of rats with brain homogenates from mice carrying either the Thy-1.1 or the Thy-1.2 alleles resulted in the production antisera which were cytotoxic for thymus cells of both strains of mice. Lymph node, spleen and cortisone-resistant thymus cells were refractory to the cytotoxic effect of rat anti-mouse brain sera. Peripheral lymphocytes were fully capable of absorbing the cytotoxic activity of the sera on thymus cells, although the concentration of the antigen on their cell surface was considerably less than on thymus cells. Blocking experiments with allo- and xenoantisera to Thy-1 antigens suggested that the antigen detected by rat anti-mouse brain sera is related to the Thy-1 system. The Thy-1 specificity detected by rat antisera seems to differ from previously described Thy-1 antigens in that it attains a high concentration on thymus cells but is relatively deficient in its expression on peripheral T cells.

Animals↗
PubMed1977

Nasopharyngeal tumor initially manifested as myofascial pain dysfunction syndrome.

A patient with facial pain of 1 1/2 years' duration, associated with limitation of opening of the mouth, click, and osteodegenerative changes of the temporomandibular joint, was initially thought to be suffering from a myofascial pain dysfunction syndrome. At first, the patient reacted favorably to muscle exercises and an antidepressive drug, but reduced lacrimation and the development of deafness on the affected side led to re-evaluation and a diagnosis of nasopharyngeal tumor. Biopsy confirmed the presence of an adenocarcinoma of the nasopharynx. The variability of symptoms and the diagnostic problems presented by this tumor are discussed.

Carcinoma, Adenoid Cystic↗