Tackling Local Anesthetic Failure in Endodontics

Achieving anesthesia in a hot tooth or tooth with inflamed pulp is challenging, especially during endodontic treatment. In the presence of symptomatic irreversible pulpitis, mainly in mandibular teeth, pose even more challenge to attain profound anesthesia. Tetradoxin resistant channel is a class of sodium channel that is found to be increased in such condition and is found to resist local anesthesia. The pH also determines the success of local anesthesia. In inflammatory conditions, the surrounding area\'s pH, which eventually decreases the amount of base form of local anesthetic penetration into the nerve membrane, thereby causing anesthetic failure. In such conditions, the excitability threshold is reduced, leading to failure in achieving anesthesia. This chapter highlights and discusses the cause of anesthetic failure and its management in obtaining profound anesthesia during endodontic treatment.

Using interleaved stimulation to measure the size and selectivity of the sustained phaselocked neural response to cochlear-implant stimulation

We measured the sustained neural response to electrical stimulation by a cochlear implant(CI). To do so we interleaved two stimuli with frequencies F1 and F2 Hz and recorded a neuraldistortion response (NDR) at F2-F1 Hz. We show that, because any one time-point containsonly the F1 or F2 stimulus, the instantaneous nonlinearities typical of electrical artefactshould not produce distortion at this frequency. However if the stimulus is smoothed, such asby charge integration at the nerve membrane, subsequent (neural) nonlinearities can producea component at F2-F1 Hz. We stimulated a single CI electrode with interleaved sinusoids orinterleaved amplitude-modulated pulse trains such that F2=1.5F1, and found no evidence foran NDR when F2-F1 was between 90-120 Hz. However, interleaved amplitude-modulated pulsetrains with F2-F1 40 Hz revealed a substantial NDR with a group delay of about 45 ms,consistent with a thalamic and/or cortical response. The NDR could be measured even fromrecording electrodes adjacent to the implant and at the highest pulse rates (>4000 pps) usedclinically. We then measured the selectivity of this sustained response by presenting F1 andF2 to different electrodes and at different between-electrode distances. This revealed abroad tuning that, we argue, reflects the overlap between the excitation elicited by the twoelectrodes. Our results also provide a glimpse of the neural nonlinearity in the auditorysystem, unobscured by the biomechanical cochlear nonlinearities that accompany acousticstimulation. Several potential clinical applications of our findings are discussed.

CLINICAL EVALUATION OF EFFECTS OF LOW-LEVEL LASERS ON PAIN DURING CAVITY PREPARATION

Aim: To study the effects of low level laser on pain during cavity preparation. Background: Laser irradiation stabilizes the nerve membrane through an increase in adenosine triphosphate (ATP) production and enhanced redox system of the cell. Dental pulp is innervated by non- myelinated C fibres. Laser irradiation reduces the conduction of Ad and C fibres (small diameter fibres), both of which transmit nociceptive pain. The stabilization of the nerve membrane increases neural latency and decreases pain transmission. This study explores whether pre-irradiation with laser reduces pain perception during cavity preparation. Methodology: A clinical study was done on 50 patients reporting to Army Dental Centre(R&R) having moderate and deep size carious lesions on first/second premolar’s bilaterally. The patients selected was apprehensive. On one side, low level lasers irradiation was done prior cavity preparation (Test). On the other contralateral tooth type cavity preparation was done without local anesthesia (Control). The patients pain threshold was noted for both control and test groups using Visual Analogue Scale (VAS). The data was computed and statiscally analyzed. Results: The patients exhibited reduce pain perception in tooth which had prior laser irradiation as compared to the control group. Conclusion: Laser analgesia with low level lasers can be used as routine protocol for reducing pain perception in apprehensive patients undergoing cavity preparation.

BREVETOXINAS EN LAS COSTAS DE MÉXICO: EFECTOS POTENCIALES EN LA SALUD PÚBLICA

Las brevetoxinas provocan la intoxicación neurotóxica por mariscos. Las rutas principales son por ingesta e inhalación con efectos adversos en la salud. A nivel celular las brevetoxinas activan los canales de sodio sensibles al voltaje, permitiendo la entrada de iones de sodio y despolarizando la membrana nerviosa. Diversas especies de microalgas producen estas toxinas, principalmente dinoflagelados del género Karenia, así como rafidofíceas de los géneros Chattonella, Fibrocapsa y Heterosigma. El objetivo de este manuscrito es describir las brevetoxinas, los organismos que las producen, sus mecanismos de acción, los efectos que tienen en la salud pública y las áreas geográficas donde se ha detectado la presencia de especies productoras de brevetoxinas en costas mexicanas. Brevetoxins off the coasts of Mexico: potential effects on public health Brevetoxins cause neurotoxic shellfish poisoning. The main routes are ingestion and inhalation with adverse health effects. At the cellular level brevetoxins activate the voltage-sensitive sodium channels allowing the entry of sodium ions that depolarize the nerve membrane. Different species of microalgae produce these toxins, mainly dinoflagellates of the genus Karenia, and raphidophyceans of the genera Chattonella, Fibrocapsa, and Heterosigma. The aim of this manuscript is to describe the brevetoxins, the organisms that produce them, their mechanisms of action, and the effects on public health and geographic areas where it has detected the presence of brevetoxin-producing species in Mexican coasts.