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.     

Immunocytochemical investigation of neurovascular relationships in human tooth pulp

This study sought to explore the anatomical relationships between peptidergic nerves and blood vessels within human primary and permanent teeth. Extracted primary and permanent molars (n = 120) were split longitudinally, placed in Zamboni's fixative and the coronal pulps were processed for indirect immunofluorescence. Ten-micrometre-thick serial frozen pulp sections were triple-labelled using combinations of the following antisera: (1) protein gene-product 9.5 (PGP 9.5), a general neuronal marker; (2) one of the neuropeptides, calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP) or neuropeptide Y (NPY); and (iii) the lectin Ulex europeus, a label for vascular endothelium. The mid-coronal pulp region was examined, using fluorescence microscopy, to determine the proportion of blood vessels showing a positive innervation (recorded when PGP 9.5-labelled nerves appeared to intersect the vessel wall). In addition, the percentage of these vascular-related nerves expressing each of the above neuropeptides was recorded. Overall, 20% of pulpal blood vessels appeared to have a positive innervation. In the main these were thick-walled arterioles. Capillaries, venules and lymphatics were mostly devoid of an associated innervation. Ninety-two per cent of vascular-related nerves expressed CGRP, 87% expressed SP, 15% expressed VIP and 80% expressed NPY. There were no significant differences in overall innervation or peptide-related innervation between primary and permanent teeth (P < 0.05, ANOVA), indicating that pulpal blood flow is likely to be subject to similar neurological control mechanisms in both dentitions.     

The limits of tooth pulp evoked potentials for pain quantitation

Tooth pulp evoked potentials (TPEPs0 and subjective evaluation of painful dental stimuli have been recorded in healthy volunteers. The amplitude of TPEPs late components and the subjective rating have been studied in different psychological states, by changing the expectancy of pain with a placebo and by providing foreknowledge of stimulus timing with self-stimulation. The placebo induced a significant depression of TPEPs and pain sensation. The amplitude of TPEPs evoked by self-delivered stimuli was reduced but the subjective report remained unchanged. These results demonstrate that TPEPs are not a stable correlate of the pain perceived or of the painful input.