Encoding of the subjective intensity of sharp dental pain

ISP Good Clinical Practice Recommendations for the management of Dentin Hypersensitivity

Dentin hypersensitivity (DH) is a rising concern in clinical dentistry that causes pain and discomfort and negatively affects the quality of life of patients. Indian Society of Periodontology conducted a nationwide survey, involving 3000 dentists in December 2020, which revealed significant knowledge gaps regarding DH, viz., under-diagnosis, incorrect differential diagnosis, and treatment strategies/recommendations for the management of DH patients in daily clinical practice. The current paper has been envisioned and conceptualized to update the practicing Indian dentists regarding the so-called enigma of dentistry "Dentin Hypersensitivity," based on the best available contemporary evidence. An expert panel was constituted comprising 30 subject experts from across the country, which after extensive literature review and group discussions formulated these recommendations. The panel advocated routine screening of all dentate patients for exposed dentin areas and DH to avoid under-diagnosis of the condition and suggested an early preventive management. Consensus guidelines/recommendations for the use of desensitizing agents (DAs) at home, including the use of herbal agents, are also provided within the backdrop of the Indian context. The guidelines recommend that active management of DH shall be accomplished by a combination of at home and in-office therapies, starting with the simplest and cost-effective home use of desensitizing toothpastes. A diagnostic decision tree and a flowchart for application in daily practice are designed to manage the patients suffering from DH or presenting with exposed dentin areas in dentition. Various treatment methods to manage DH have been discussed in the paper, including the insights from previously published treatment guidelines. Further, a novel system of classification of DH patients based on specific case definitions has been developed for the first time. Explicit charts regarding the available treatment options and the chronology of institution of the agent, for the management in different case categories of DH, have been provided for quick reference. The management strategy takes into account a decision algorithm based on hierarchy of complexity of treatment options and intends to improve the quality of life of the patient by long-term maintenance with an innovatively defined triple C's or 3Cs approach.

Current Concepts of Dentinal Hypersensitivity

INTRODUCTION

Although many clinical studies have reported on the prevalence of dental pain, far fewer studies have focused on the mechanisms of dental pain. This is an important gap because increased understanding of dental pain mechanisms may lead to improved diagnostic tests or therapeutic interventions. The aim of this study was to comprehensively review the literature on the mechanisms of dentinal sensitivity.

METHODS

PubMed and Ovid were searched for articles that addressed dentinal pain and or pulpal sensitivity. Because of the breadth of research ranging from cellular/molecular studies to clinical trials, a narrative review on the mechanisms of dentinal sensitivity was constructed based on the literature.

RESULTS

Five various mechanisms for dentinal sensitivity have been proposed: (1) the classic hydrodynamic theory, (2) direct innervation of dentinal tubules, (3) neuroplasticity and sensitization of nociceptors, (4) odontoblasts serving as sensory receptors, and (5) algoneurons.

CONCLUSIONS

These theories are not mutually exclusive, and it is possible that several of them contribute to dentinal sensitivity. Moreover, pulpal responses to tissue injury may alter the relative contribution of these mechanisms. For example, pulpal inflammation may lead to neuronal sprouting and peripheral sensitization. Knowledge of these mechanisms may prompt the development of therapeutic drugs that aim to disrupt these mechanisms, leading to more effective treatments for pulpal pain.

Orofacial quantitative sensory testing: Current evidence and future perspectives

BACKGROUND AND OBJECTIVE

Orofacial quantitative sensory testing (QST) is an increasingly valuable psychophysical tool for evaluating neurosensory disorders of the orofacial region. Here, we aimed to evaluate the current evidence regarding this testing method and to discuss its future clinical potential.

DATA TREATMENT

We conducted a literature search in Medline, Embase and Scopus for English-language articles published between 1990 and 2019. The utilized search terms included QST, quantitative, sensory testing and neurosensory, which were combined using the AND operator with the terms facial, orofacial, trigeminal, intraoral and oral.

RESULTS

Our findings highlighted many methods for conducting QST-including method of levels, method of limits and mapping. Potential stimuli also vary, and can include mechanical or thermal stimulation, vibration or pinprick stimuli. Orofacial QST may be helpful in revealing disease pathways and can be used for patient stratification to validate the use of neurosensory profile-specific treatment options. QST is reportedly reliable in longitudinal studies and is thus a candidate for measuring changes over time. One disadvantage of QST is the substantial time required; however, further methodological refinements and the combination of partial aspects of the full QST battery with other tests and imaging methods should result in improvement.

CONCLUSIONS

Overall, orofacial QST is a reliable testing method for diagnosing pathological neurosensory conditions and assessing normal neurosensory function. Despite the remaining challenges that hinder the use of QST for everyday clinical decisions and clinical trials, we expect that future improvements will allow its implementation in routine practice.

Expression of pain and distress in children during dental extractions through drawings as a projective measure: A clinical study

AIM: To evaluate the efficacy of drawings as a projective measure of pain and distress in children undergoing dental extractions.

METHODS: Children in the age range of 4-13 years with existence of untreatable caries or over-retained primary teeth, indicated for extractions were included. Pain was assessed using one behavioral, faces, legs, activity, cry and consolability (FLACC) scale; and a self report measure; faces pain scale-revised (FPS-R), at two points of time, after completion of local anesthetic administration and after extraction. The general behavior of children was assessed with Wright’s modification of Frankl rating scale. At the end of the session, children were instructed to represent, themselves along with the dentist and their experiences of the dental treatment through drawing. The drawings were scored utilizing Child drawing: Hospital scale (CD: H) manual and correlated with FLACC, FPS-R and Frankl using Pearson correlation test.

RESULTS: A positive correlation, though statistically not significant, was observed between CD: H scores and all other considered parameters (Frankl, FPS-R and FLACC) in the present study.

CONCLUSION: Drawings could not act as surrogate measure of child’s pain; however, they acted as a narrative of his/her experiences and reflection of inner emotions. Hence, drawings can be used as an additional dental armamentarium.

Sodium channel expression and localization at demyelinated sites in painful human dental pulp

The expression of sodium channels (NaCh(s)) change after inflammatory and nerve lesions, and this change has been implicated in the generation of pain states. Here we examine NaCh expression within nerve fibers from normal and painful extracted human teeth with special emphasis on their localization within large accumulations, like those seen at nodes of Ranvier. Pulpal tissue sections from normal wisdom teeth and from teeth with large carious lesions associated with severe and spontaneous pain were double-stained with pan-specific NaCh antibody and caspr (paranodal protein used to visualize nodes of Ranvier) antibody, while additional sections were triple-stained with NaCh, caspr and myelin basic protein (MBP) antibodies. Z-series of images were obtained with the confocal microscope and evaluated with NIH ImageJ software to quantify the density and size of NaCh accumulations, and to characterize NaCh localization at caspr-identified typical and atypical nodal sites. Although the results showed variability in the overall density and size of NaCh accumulations in painful samples, a common finding included the remodeling of NaChs at atypical nodal sites. This remodeling of NaChs included prominent NaCh expression within nerve regions that showed a selective loss of MBP staining in a pattern consistent with a demyelinating process.

PERSPECTIVE

This study identifies the remodeling of NaChs at demyelinated sites within the painful human dental pulp and suggests that the contribution of NaChs to spontaneous pulpal pain generation may be dependant not only on total NaCh density but may also be related to NaCh expression at atypical nodal sites.

Automatic stimulus breaker for electric dental pulp tester using pain response

The pulp test provides a means of examining the vitality of dental pulp using physical or chemical stimulation. During electrical pulp testing, an electrical current stimulates the intradental nerve, which may be painful and stressful to patients. The study involved measurement of the electromyogram (EMG) from the anterior belly of the digastric muscle, finger movement and voice response during electrical pulp testing. The excessive stimulus time from the onset time of response (EMG, voice and finger movement) to the end of the stimulation was obtained. The results indicated that the responses occurred in the order: EMG, finger and voice. Based on these results, an automatic stimulus shut-off circuit was developed using the above-mentioned responses to stimulus during electric pulp testing. Excessive stimulus time was reduced by prompt switching-off of the pulp tester output, 64 ms on average after the first detected response (EMG). Consequently, excessive stimulus times were reduced by 284 and 152 ms on average for the subject and examiner disconnection, respectively, using the developed automatic shut-off circuit. Therefore it was possible to minimise pain and stress by reducing excessive pulp stimulation.

High-dose adenosine infusion provokes oscillations of chest pain without correlation to opioid modulation: A double-blind controlled study

Adenosine is a neuromodulator with both excitatory and inhibitory effects in different organs. High-dose adenosine infusion provokes chest pain in patients and healthy volunteers. This study examines the nature of chest pain and whether it is modified by the mu opioid receptor agonist (beta-endorphin) or a nonselective opioid antagonist (naloxone). Ten healthy volunteers with a mean age of 26 +/- 3 years participated in the study. The study was performed during 3 sessions. During every session the subjects were given a high dose of adenosine infusion (140 microg/kg/min) for 22 minutes. After 5 minutes, the subjects were randomized in a double-blind order on 1 of the 3 categories: (1) as placebo, NaCl bolus for 2 minutes followed by NaCl infusion for 15 minutes; (2) beta-endorphin bolus followed by infusion; and (3) naloxone bolus followed by NaCl infusion. Hemodynamic and pain parameters were monitored. During adenosine infusion, all volunteers experienced chest pain with oscillations of pain intensity. The oscillations continued during beta-endorphin and naloxone. There were no significant differences between hemodynamic and pain parameters during beta-endorphin or naloxone compared to adenosine infusion. High-dose infusion of adenosine provokes chest pain with oscillations of algesia and pain-free intervals. Peripheral opioid administration did not influence the adenosine-provoked chest pain.

PERSPECTIVE

Adenosine-induced oscillations of pain and pain-free intervals could theoretically be a sign of neuronal reflex activity dependent on spatiotemporal summation of adenosine excitatory and inhibitory properties. This could contribute to the complex nature of angina pectoris. Peripheral opioid receptors might not be involved in the oscillations.

The effectiveness of manual and rotary techniques in the cleaning of root canals: a scanning electron microscopy study

AIM

The purpose of this scanning electron microscope (SEM) study was to compare the cleanliness of the root canal walls following either a manual or a rotary technique of canal instrumentation. The hypothesis was that a rotary technique would produce a cleaner root canal.

METHODOLOGY

Manual filing was performed on 10 extracted teeth using stainless steel S-files (Sjodings, Sendoline, Sweden). Powered instrumentation was carried out on a further 10 extracted teeth, using ProFile rotary nickel-titanium files in a handpiece (250 r.p.m.) according to the manufacturer's instructions. A solution of 0.5% sodium hypochlorite was used for irrigation. The roots were cut longitudinally and the canal walls were examined for debris and smear layer at the apical, middle and coronal level.

RESULTS

Significantly less debris was found in the apical region using the manual filing technique (P < 0.05); no significant differences could be found at the other levels. Overall, significantly less debris was found on the root canal walls using the manual technique when the data from the three levels were compared (P = < 0.05).

CONCLUSIONS

The manual technique employed in this study produced cleaner root canal walls than the rotary ProFile technique.

Oscillation of pain intensity during adenosine infusion. Relationship to beta-endorphin and sympathetic tone

Adenosine is a neuromodulator with both excitatory and inhibitory effects dependent in part upon preconditions; it can act as an algesic or an analgesic agent. Previously we found variations of pain intensity during constant infusion of adenosine. We therefore quantified pain intensity during constant infusion of adenosine at a rate of 140 microg/kg/min intravenously in healthy volunteers, placebo controlled, double blind, and the relation to hemodynamic, vasomotor and sudomotor responses of the sympathetic nervous system and to the role of peripheral beta-endorphin response. The perceived chest pain during adenosine infusion showed an oscillatory pattern. Painful periods of about 30s were interrupted by painfree periods, and pain was always preceded by an increase in vasomotor sympathetic activity and by increased sudomotor activity. Plasma beta-endorphin values were heterogenous but exhibited an increase during infusion.

Response of feline intradental nerve fibers to tooth cutting by Er:YAG laser

BACKGROUND AND OBJECTIVE

The aim of this study was to investigate the response of intradental A- and C-fibers during tooth cutting by Er:YAG laser.

STUDY DESIGN/MATERIALS AND METHODS

Bipolar electrical stimulation was applied to the cat's canine to identify functional single nerve fibers of the inferior alveolar nerve. The tip of the canine tooth was cut in 0.5-mm steps until the pulp was exposed. Teeth were alternately cut by using Er:YAG laser (50 mJ, 5 pps) and micromotor under water cooling. The nerve response recorded from the single nerve fibers during laser cutting was compared with that during micromotor cutting.

RESULTS

All 26 A-fibers responded to laser cutting with high frequency of nerve firings. The nerve firing rate was significantly higher during laser cutting compared with that during micromotor cutting of superficial dentin (Chi(2) test, P < 0.05) but was not significantly different at deep dentin (P > or = 0. 05). Nine of 11 C-fibers responded to laser cutting when the deep dentin was cut. Among those nine nerve fibers, three also showed a low frequency response to laser cutting of the superficial dentin.

CONCLUSION

During the tooth cutting, Er:YAG laser was more effective in activating intradental A-fibers compared with micromotor and also caused the activation of intradental C-fibers.

Pulpal ischemia in man: effects on detection threshold, A-delta neural response and sharp dental pain

Preferential blocks of peripheral nerves have shown that myelinated nerves are more susceptible to local compression and less resistant to asphyxia than unmyelinated fibers. Since two groups of functionally different nociceptors exist in the dental pulp, it is of theoretical and clinical interest to determine the influence of ischemia on the sensitivity of human dental pulp, using standard means for testing tooth vitality and at the same time investigating the intensity coding in one pathway of the afferent trigeminal system. Adrenaline was used to study the differential effect of adrenaline-induced ischemia on intradental A-delta nerve activity (INA) and the concomitant sharp pain, as well as on the detection threshold for monopolar electrical stimulation. Cold (ethyl chloride) and heat (heated gutta-percha) stimulation was applied to the tooth surface. In accordance with the hydrodynamic theory of dentin sensitivity the rapid fluid flow induced in the dentinal tubuli by these thermal stimuli is an adequate stimulus for selectively activating the A-delta nerves in healthy pulps. Consistency plots of the magnitude of the perceptual experience of sharp pain against the neural population response in linear coordinates yielded a high product-moment correlation, implying linearity for the intensity coding relationship. In contrast to the significant reduction of INA and its perceptual correlate of sharp pain after adrenaline administration, the electrical detection threshold remained constant during the full test period, suggesting that electrical threshold measurements have their limitations as a diagnostic tool or criterion for assessing the sensitivity of the dental pulp. The absence of A-delta activity was parallelled by no sensation of sharp pain. These findings suggested that the integrated neural A-delta activity constituted the underlying peripheral neurophysiological mechanism of the sensory intensity of sharp dental pain.

Inflammation and dental pain in man

In the present article special interest has been focused on indicators of latent and manifest pulpal inflammation studied by psychophysical and electrophysiological techniques. Intradental A-delta nerve activity was recorded from two electrodes placed in the dentin on the labial tooth surface. The psychophysical measures were obtained by means of direct scaling methods in combination with sensory verbal descriptors. For stimulation cooling (ethyl chloride) and heating (hot guttapercha) of the tooth surface were employed. In addition, potentially algogenic substances, bradykinin and histamine, were administered on partly exposed pulps. Hot guttapercha induced a more complex neural response pattern than ethyl chloride. In all the recordings the responses evoked by heat showed a characteristic pattern consisting of three phases: an initial phase of short duration (i) followed by a depression in activity relative to the baseline (ii) and a slow spontaneously emerging activity in the absence of a physical stimulus (iii). The latter neutral event (iii) passed unnoticed by all the subjects. In the light of earlier experiments on feline pulp it was hypothesized that this third phase of the neural response was an indication of hyperexcitability in dental pulps and thus inflammation. Those subjects who experienced pulsating, dull, lingering pain (clinically diagnosed as pulpitis) showed a poor correlation between magnitude estimates of their mixed pain percepts and the total flux of A-delta nerve activity. Bradykinin and histamine evoked dull pain in the majority of cases probably caused by excitation of pulpal C fibers. In one experiment A-delta neural discharge of short duration could also be triggered by histamine.(ABSTRACT TRUNCATED AT 250 WORDS)