Biomechanical preparation followed by irrigation in endodontic treatment of infected root canals has been shown effective promoting significant reduction of microorganisms in the canals. However, some micro-organisms still survive. The bacteria associated with primaries endodontic infections are predominantly anaerobic Gram-negative bacteria, whereas the bacteria associated with secondary infections comprising one or a few species, of which the most important is Enterococcus faecalis. Most effective means to combat it have been studied, such as the use of different medications intra-canal, and the paste of choice are usually the basis of calcium hydroxide. But, this medication is not effective against Enterococcus faecalis. The most commonly used vehicles with calcium hydroxide are propylene glycol and distilled water. To extend the antibacterial spectrum of the calcium hydroxide has been suggested associated with the sames substances in paste form. The ethanolic extract of propolis (EEP) shows anti-inflamatoria, ansthesic and antimicrobial activity and low toxicity. Chlorhexidine is an antimicrobial agent with broad spectrum action. The combination of calcium hydroxide with camphorated parachlorophenol (PMCC) is also proposed and used for some time. Therefore, it's relevant to compare the antimicrobial capacity of calcium hydroxide with different vehicles in a in vitro study with a single tracer microorganism with microbiological culture and confocal laser scanning microscopy (CLSM). For this, standard dentin fragments will be sterilized and then infected with the bacteria and will be divided in five test-groups, submitted to medication for 15 days with calcium hydroxide paste and propylene glycol, clacium hydroxide with ethanolic extract of propolis (EEP), calcium hydroxide and camphorated parachlorophenol, calcium hydroxide and chlorexidine, and calcium hydroxide and distilled water. The bacterial collection of the dentin´s fragments will be done to count micro-organisms still viable in colony forming units and the penetration of the medication in dentinal tubules will be evaluated by confocal laser scanning microscopy (CLSM).
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