Non-cytotoxic Root Canal Dressing with Improved Antimicrobial Efficacy.

INTRODUCTION: Recurrent endodontic infections are primarily caused by Enterococcus faecalis and are more challenging to treat, compared with primary infection of the root canal system. Calcium hydroxide (CH) is used as an interappointment dressing in endodontics despite its inefficacy against E. faecalis and other pathogens. To improve antimicrobial properties and limit cytotoxicity of CH, we added salicylic acid to CH (CASA) to disinfect the canal. CASA overcomes the main pathogen responsible for recurrent endodontic infections. The aim of this study was to evaluate the antimicrobial activity of CASA and its cytotoxicity against dental pulp stem cells (DPSCs) and its effect on the differentiation potential of DPSCs. METHODS: Mature E. faecalis biofilm cultured on dentin chips was exposed to CASA and studied using confocal laser scanning microscopy. The dose-dependency of CASA was also studied using the liquid suspension test. The cytotoxicity was tested against DPSCs, and its effect on the expression of osteocalcin and alkaline phosphatase was studied. RESULTS: CASA produced larger zones of inhibition than CH for all species tested and demonstrated superior efficacy than CH against E. faecalis biofilm. Cytotoxicity studies indicated DPSC's high tolerance for CASA; addition of CASA to DPSCs was observed to increase the expression of biological markers related to mineralization. CONCLUSIONS: CASA was proved to have superior antibacterial efficacy against E. faecalis when compared with CH. It also increased the expression of some DPSC differentiation markers involved in mineralization.

The role of the central nucleus of the amygdala in nociception and aversion.

The role of the central nucleus of the amygdala in nociception--conditioned and unconditioned aversion--was studied. Rats received microinjection of vehicle or the N-type Ca2+ channel blocker omega-conotoxin GVIA (0.2 microg/250 nl) into the central amygdaloid nucleus prior to intra-plantar injection of formalin, ultrasound exposure or immediately prior to the acquisition phase of an aversive conditioning trial. Intra-amygdala omega-conotoxin GVIA resulted in an earlier onset of nociceptive response to formalin and increased nociceptive behaviour during the first 5 min. Omega-conotoxin GVIA significantly reduced conditioned freezing behaviour with no effect on ultrasound-induced unconditioned aversive behaviour. These data indicate that N-type Ca2+ channels in the central amygdaloid nucleus play a role in mediating behavioural responses to nociceptive and conditioned aversive stimuli.