Change in the nociceptive reactions caused by dental pulp stimulation during excitation of the midbrain]

It was demonstrated in chronic experiments on cats that stimulation of certain midbrain regions decreased or fully depressed the pain reaction evoked by dental pulp stimulation. The antinociceptive effect depending on the parameters of the brain stimulation was shown in differential change of the separate motor and vegetative and emotional - behaviour components, forming a general pain reaction. A poststimulation analgesia was revealed and the dynamic of restoration of different pain manifestations after the cessation of brain stimulation was traced. Possible mechanism of the realization of the antinociceptive effect are discussed.     

Fluid mechanics in dentinal microtubules provides mechanistic insights into the difference between hot and cold dental pain

Dental thermal pain is a significant health problem in daily life and dentistry. There is a long-standing question regarding the phenomenon that cold stimulation evokes sharper and more shooting pain sensations than hot stimulation. This phenomenon, however, outlives the well-known hydrodynamic theory used to explain dental thermal pain mechanism. Here, we present a mathematical model based on the hypothesis that hot or cold stimulation-induced different directions of dentinal fluid flow and the corresponding odontoblast movements in dentinal microtubules contribute to different dental pain responses. We coupled a computational fluid dynamics model, describing the fluid mechanics in dentinal microtubules, with a modified Hodgkin-Huxley model, describing the discharge behavior of intradental neuron. The simulated results agreed well with existing experimental measurements. We thence demonstrated theoretically that intradental mechano-sensitive nociceptors are not "equally sensitive" to inward (into the pulp) and outward (away from the pulp) fluid flows, providing mechanistic insights into the difference between hot and cold dental pain. The model developed here could enable better diagnosis in endodontics which requires an understanding of pulpal histology, neurology and physiology, as well as their dynamic response to the thermal stimulation used in dental practices.     

Relief of dental pain by ice massage of the hand.

Patients suffering from acute dental pain were treated with ice massage of the web between the thumb and index finger of the hand on the same side as the painful region. Control groups received tactile massage alone or with explicit suggestion that the massage was intended to alleviate their pain. Changes in pain intensity produced by the procedures were measured with the McGill Pain Questionnaire. Ice massage decreased the intensity of the dental pain by 50% or more in the majority of patients. Furthermore, the pain reductions produced by ice massage were significantly larger than those produced by tactile massage alone or with explicit suggestion. The results indicate that ice massage has pain-reducing effects comparable to those of transcutaneous electrical stimulation and acupuncture. The fact that cold signals are transmitted to the spinal cord exclusively by A-delta fibres and not by C fibres provides a potential method for differentiating the various feedback systems that mediate analgesia produced by different forms of intense sensory input. Ice massage provides a simple method for the palliative control of pain in dental clinics.     

Effect of the spinal pain syndrome on pain reactions caused by nociceptive thermal stimuli

It has been shown that the reaction of both limbs to thermal pain stimulation was suppressed during spinal pain syndrome development caused by generators of pathologically enhanced excitation (GPEE) formed in the dorsal horns of the spinal cord lumbosacral segments on one side. The analgetic effect on physiological pain was retained long after pain syndrome disappearance (48 hours), the effect was bilateral and was independent of the type of agent producing GPEE. It was shown that neuronal activity in the antinociceptive system key structure (nucleus raphe dorsal) increases. It is assumed that physiological pain relief is caused by enhanced activity in antinociceptive system structures in pain syndrome.     

Relationship of transformation of newborn human lymphocytes by dental plaque antigen to the degree of maternal periodontal disease.

The incorporation of tritiated thymidine by 70 human cord blood leukocyte cultures in response to dental plaque was tested. There was a direct correlation between the number of significant lymphoproliferative responses of cord blood leukocyte cultures to either of two preparations of dental plaque and the severity of periodontal disease in mothers. Such a correlation was not observed in the case of streptolysin-O, even though this common environmental antigen manifested a similar incidence and stimulation ratio in the cord blood cultures. It suggests that pregnant women with chronic periodontal disease must therefore frequently seed dental plaque antigens, presumably via their circulation during episodes of bacteremia, across the placenta to sensitize fetal lymphocytes.     

Changing trends in the outpatient dental visits during the COVID – 19 pandemic in a tertiary care hospital

The coronavirus pandemic has caused a global public health crisis with an unprecedented shutdown of major establishments and non-emergency services. Disruptions across the country in dental hospitals led to challenges in addressing patient’s dental complaints. The present study aimed to analyse the difference in the pattern of the Outpatient dental visits during the pandemic period in comparison to that of the pre-pandemic period in a tertiary care hospital. This retrospective study was carried out by retrieving the patient data from the diagnostic register of the Department of Oral Medicine and Radiology for a period of one year. The data that was retrieved from 24th September 2019 to 23rd March 2020 was categorized under the pre-pandemic period and the data from 24th March 2020 to 24th September 2020 was grouped under the pandemic period. Patient data regarding the age, gender and clinical diagnosis was recorded and categorized under three main categories: “Emergency”, “urgent” and “elective”. 7550 patients during pre-pandemic period and 4035 patients during the pandemic period visited the dental hospital during the study period. Under the “emergency dental care” category, during the pre-pandemic period, majority of the cases reported of acute dental pain (71.0%) followed by cellulitis and space infection (20.1%) and maxillofacial trauma (8.7%). During the pandemic period, acute dental pain consisted of all emergency visits (n = 307). The proportion of emergency dental visits during the pandemic were significantly higher than the pre-pandemic period. Elective dental visits were significantly higher during pre-pandemic period in comparison to the pandemic period. (P < 0.001). There was a notable change in the outpatient trend of the dental visits during the COVID-19 pandemic in comparison to the pre-pandemic period. Emergency dental services were utilized at a higher rate during the pandemic period in comparison to the pre-pandemic counterpart.     

The proprioceptive activation of stretch tension in pretibial flexor muscles induced by stimulation of antagonistic muscle afferents.

1. The effect of tetanic stimulation of ipsilateral group I afferents from the GS muscle on a synchronous stretch of the flexor EDL/TA muscles has been investigated in precollicular decerebrate cats. 2. The stretch-induced tension of the EDL/TA muscles increases remarkably during simultaneous stimulation of the GS nerve with maximal intensities corresponding to 1.5 times the threshold for the group 1 afferents. This increas appears above all in the dynamic part of stretch. 3. Under our experimental conditions there is no activation fo flexor-alpha-motoneurones during tetanic stimulation of the GS afferents without muscle stretch, as measured by the resting tension of the EDL/TA muscles. 4. Desptie an increase in the stretch-induced tension during fusimotor stimulation of antagonistic group I afferents, a transmission loss in the excitation via the psi-loop to the flexor-alpha-motoneurones occurs. This could be demonstrated by the ratio: increase in the tension T /increase in the number of Ia spikes. This is explained by snychronous convergence of the discharges of Ia inhibitory interneurones to the flexor-alpha-motoneurones. 5. The system studied demonstrates an input-output relation of the stretch reflex during conditions in which both reciprocal inhibition and autogenetic excitation via the psi-loop occur. It appears however, that the reciprocal inhibition is partly overwhelmed by the autogenetic excitation which results from the increase in the Ia discharge rate during fusimotor reflex. 6. It is postulated that static rather than dynamic psi-moto-neurones are involved in the investigated reflex arc.     

Comparison of short-latency trigeminal evoked potentials elicited by painful dental and gingival stimulation

Painful stimulation of tooth pulp and of the maxillary gingiva was undertaken in 16 volunteers. Short-latency evoked potentials (15–20 msec) were recorded over 800 trials in each case at F3-P3 of F4-P4, and the resultant averaged wave forms were compared. The gingival wave was distinct in all subjects and could be averaged across subjects while the dental waves were either noise or very inconsistent over subjects. Averaging of the dental wave forms across subjects yielded an uninterpretable result. It was clear that dental evoked potentials could not be recorded at these sites. These findings could be explained by either or both of two hypotheses: (1) dental afferents are predominantly small fiber, nociceptive end organs that conduct more slowly than soft tissue afferents whereas gingival stimulation activates both large and small fiber populations; and (2) dental representation in somatosensory cortex is different and phylogenetically more primitive than that of neighboring soft tissue. Therefore, the location of the generator sites in cortex and the orientation of the dipole may be different for dental than for gingival wave forms.     

Cognitive behavioral therapy for psychosomatic problems in dental settings

Cognitive behavioral therapy (CBT) has been applied for various problems, including psychiatric diseases such as depression and anxiety, and for physical symptoms such as pain. It has also been applied for dental problems. Although the effect of CBTs on temporomandibular disorders and dental anxiety are well documented, its effectiveness on other types of oral symptoms remain unclear. Little information comparing the different types of CBTs in the dental setting is currently available. Because dental professionals are often expected to conduct CBTs in the dental setting, it is important to develop proper training programs for dental professionals.In this review article, we demonstrate and discuss the application of CBTs for psychosomatic problems, including temporomandibular disorders, dental anxiety, burning mouth syndrome, and other oral complaints in dental settings.     

Application of the glycine labelling method to the cerebellum, hippocampus and spinal cord

3H-glycine was applied to the cat cerebellar cortex under resting conditions and during inferior olive stimulation which activated the climbing fiber system on a restricted area. Electric recording was made. The autoradiograms showed, that under resting condition labelled glycine was incorporated mainly in granule, Golgi and basket cells and only a few Purkinje and stellate cells were active. Also cerebellar glomeruli remained without labelling. On climbing fiber stimulation Purkinje cells became activated singly and grouped, also Golgi and stellate cells increased in number. Granule cells were totally inhibited. 3H-glycine, when applied to the rat hippocampus, the dentate gyrus, CA1 and CA4 fields showed labelling at low frequency stimulation. When 400 Hz high frequency stimulation periods were interposed, long-term potentiation ensued. The overall labelling of each hippocampal region was intensified significantly, indicating that glycine incorporation may be a sign not only of excitation but also of long-term potentiation. 3H-glycine was applied to frog spinal cord during rest and dorsal root stimulation. Interneurons and motor neurons excited by the afferent fibers showed intensive glycine uptake. It is concluded that the glycine labelling method is suitable for detecting neural excitation in the structures dealt with in this paper.     

Morphometric evolutionary trends in the dental complex ofPongo

This paper examines whether there has been an overall reduction in the likely size ofPongo from the Pleistocene to the present day. It is concluded that the original suggestion byHooijer (1948) that the evolution ofPongo over the last half-million years was characterized by a reduction in dental size, corresponding to a reduction in overall body size, is likely. There were, however, fluctuations in dental size during the Pleistocene. Overall, in the Sundaic region a slight reduction in overall dental size continued from Late Pleistocene to the present day.     

Electric stimulation of the dental pulp in the evaluation of the central effect of analgesics

We conducted a double-blind cross-over study in ten volunteers aged from 19 to 30 years, to compare the pain control effects of a single oral dose of two analgesic compounds (drug A: propyphenazone mg 250, ethylmorphine mg 5, caffeine mg 5; drug B: dipyrone mg 500, diphenhydramine mg 12.5, adiphenine mg 5, ethyl aminobenzoate mg 2.5) in an experimental pain model using stimulation of dental pulp. Constant voltage stimuli were delivered through silver chloride electrodes placed in contact with the vestibular surface of the upper medial incisor. At the beginning of the session, the pain input was graded by asking the subject to identify the weakest stimulus perceived (threshold level) and the strongest stimulus endurable (tolerance level). The range between threshold and tolerance level was divided in nine steps plus a subliminal step. The ten steps were delivered randomly, and each series of steps was repeated eight times. The subjects were instructed to rate the pain sensation in an arbitrary scale of 5 degrees. The procedure was repeated at 60 min and 180 min after drug administration. Each subject received two tablets of drug A or drug B in two different sessions at weekly intervals. Statistical analysis of the procedures showed that neither drug A nor drug B significantly affected the pain threshold. Drug A significantly reduced the total pain score (P less than 0.01) and its action peaked 60 min after administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Temporospatial localization of acetylcholinesterase activity in the dental epithelium during mouse tooth development

Acetylcholinesterase (AChE), a principal modulator of cholinergic neurotransmission, also has been demonstrated to be involved in the morphogenetic processes of neuronal and non-neuronal tissues. This study shows that AChE exhibits temporospatial activity in the dental epithelium of the developing mouse tooth. To identify the AChE activity in the mouse tooth during development, we performed enzyme histochemistry on the mouse embryos from embryonic day 13 (E13) to E18 and on the incisors and molars of the neonatal mouse at 10 days after birth (P10). In the developing molars of mouse embryos, AChE activity was not found in the dental epithelium at E13 (bud stage). AChE activity first appeared in the developing cervical loops of the enamel organ at E14 (cap stage), but was not found in the enamel knot. At E18 (bell stage), AChE activity was localized in the inner enamel epithelium except the cervical-loop area. In the incisors and molars of neonatal mice (P10), AChE activity was localized in the inner enamel epithelium of the cervical-loop and enamel-free area. Overall, AChE activity was localized in the differentiating dental epithelium while the activity of butyrylcholinesterse, another cholinesterase, was located primarily in the cells of the dental follicle. The results suggest that AChE may play a role in the histo- and cytodifferentiation of dental epithelium during tooth development.     

Unit responses in the anterior and posterior hypothalamus to stimulation of the splanchnic and sciatic nerves and to photic stimulation

By extracellular recording of spike discharges the sensory properties of neurons of the anterior and posterior regions of the cat hypothalamus were studied during stimulation of the splanchnic and sciatic nerves and during photic stimulation. Hypothalamic neurons were shown to be characterized by wide convergence of heterosensory excitation: 68% of spontaneously active hypothalamic neurons responded to somatovisceral and photic stimulation. Some posterior hypothalamic neurons responded to somatovisceral stimulation but not to photic stimulation. Neurons responding only to photic stimulation were found in the anterior hypothalamus; no neurons responding only to visceral stimulation were found in the hypothalamus. Total convergence of somatic and visceral afferentation of neurons of the posterior and anterior hypothalamus was observed. Mostly responses of phasic type were obtained to stimulation of all modalities. The study of the quantitative ratio between responses of excitatory and inhibitory types showed that the former predominate. The principles governing the functional organization of hypothalamic afferent systems are discussed.Academician L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 276–282, May–June, 1976.     

A comparison of treatment modes in the management of myofascial pain dysfunction syndrome

This research compares different treatment regimes for the management of chronic facial pain associated with the masticatory musculature. Twenty-one females meeting specific criteria were randomly assigned to one of three treatment conditions: a dental splint and physiotherapy program; a relaxation program utilizing progressive muscle relaxation, biofeedback, and stress management techniques; or a minimal treatment program involving transcutaneous electrical nerve stimulation. Improvement was assessed through a dental examination, self-monitoring of pain, and an assessment of EMG activity during resting and task conditions. Significant changes were obtained in response to all treatment programs. The treatment programs differed only in the relative pattern of treatment effects obtained from the self-report monitoring of pain. The data are consistent with the concept of MPD as a psychological response to stress which maintains chronic pain through increased muscle tension in the jaw.     

Mapping of the trigeminal sensory complex of the cat. Characterization of its neurons by stimulations of peripheral field, dental pulp afferents and thalamic projections.

From a new systematic investigation of the 4 divisions of the trigeminal sensory complex, the following points are emphasized: 1. The subnucleus oralis receives a large representation from the oral cavity, a region also represented in the three other divisions of the trigeminal sensory complex. 2. Units responding to noxious mechanical stimulation have been found in two different loci: the subnucleus caudalis for the whole trigeminal area, and the subnucleus oralis for the oral cavity. 3. The dental pulp projects to the four divisions of the trigeminal sensory complex, but the heaviest projection is found in its rostral part (the main nucleus and subnucleus oralis). 4. Three distinct types of responses were found following dental pulp stimulation: primary, non primary and responses strongly enhanced by an increase in stimulus parameters.     

A method for studying the peripheral mediators of the dental pain induced by electrical stimulation.

A useful method is described in this paper for studying the mediators released from tooth pulp of the dog during the electrical stimulation of dentine. This method is based upon the perfusion of the pulp and superfusing the return continuously over the isolated, in cascade, cat jejunum and rat stomach fundus strip. The presented evidences in this study indicate the possibility of the release of bradykinin and prostaglandin - like materials from the tooth pulp during the electrical stimulation of dentine. Possible relationship of these mediators and tooth pain due to the electrical stimulation of dentine is discussed.     

Analgesia following electrostimulation of midbrain nuclei of rats with a pain syndrome of spinal origin]

The effect of electrostimulation of the mesencephalic grey matter and of the dorsal nucleus raphe on physiological pain produced by nociceptive stimulation (compression of the tail or the skin on the limb by a clamp) and on pathological pain (the pain syndrome of spinal origin) were studied in experiments on albino rats. Pathological pain was induced by creating a generator of pathologically enhanced excitation in the dorsal horn of the spinal cord by local disturbance of the inhibitory mechanisms with the aid of tetanus toxin. It was shown that electrostimulation of the indicated areas abolished both physiological and pathological pain. A conclusion was drawn that analgesia produced by electrostimulation of certain structure of the brain was connected not only with augmentation of the descending inhibition in the spinal cord as in the case of physiological pain caused by peripheral nociceptive stimulation (as shown by several authors), but also with the block of excitation at the supraspinal level. This mechanism should play a decisive role in analgesia realization in the pain syndrome of central origin, both under experimental and natural conditions.     

Excitation-dependent relaxation in the cardiac muscle

Isolated trabeculae of rabbit and guinea pig atrium exposed to low-sodium solution developed after-contractions and increased diastolic tension when rhythmic steady-state stimulation was stopped. Single excitation applied during rest or at the peak of after-contraction brought the resting tension to the low, control level. Tension of isolated cat papillary muscle increased due to action of 17 mmol of caffeine applied during rest was reduced during rhythmic post-rest stimulation. Early extra-excitation potentiated relaxation of atrial muscle exposed to low-sodium solution. It is concluded that relaxing factor of cardiac muscle is activated by excitation of the cell.     

On the relationship of dental microwear to dental macrowear

Dental microwear analysts have demonstrated that hard diets leave numerous microscopic pits on occlusal surfaces. The relationship between occlusal pitting and gross macrowear, however, is not well known. The current study seeks to elucidate the relationship between dental microwear and macrowear by determining if microscopically pitted teeth are associated with greater expressions of macrowear. This study examined microwear and macrowear on mandibular second molars from 60 prehistoric adult Native Americans representing three dietary regimes (foraging, mixed economy, and agriculture). Initially, two dental microwear feature variables were studied: percentage of pits and mean scratch width. Standard macrowear scores ranged from 4 to 40. ANOVAs suggested that neither of the microwear variables was affected by age or sex, but age affected macrowear scores. Because of this, the sample had a balanced number of young and old adults (i.e., those below and above skeletal age 35). A Pearson's correlation showed no covariation between scratch width and the percentage of pits. Regression analysis indicated that macrowear was not a function of the percentage of pits. However, a significant positive relationship was found between dental macrowear and scratch width. A post priori test found a significant negative relationship between macrowear and the total number of scratches. It is concluded, then, that wide scratches remove more enamel and dentin than do numerous pits, although both cause dental wear. It is suggested here that the term “abrasive” be used to describe those microwear profiles that lead to heavy macrowear and have relatively wide scratches. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.