RESUMEN
One of the most important objectives of root canal therapy is the elimination of micro organisms from the root canal system. In order to achieve maximum disinfection of the root canal system, irrigation should be done during treatment. The aim of this in vitro study was to compare the sustainable antimicrobial activity of 2% chlorhexidine solution, 100 mg/ml doxycycline solution, and 2.6% NaOCL solution in bovine root dentine. Fifty dentine tubes prepared from intact freshly extracted bovine maxillary central incisors were infected invitro for 14 days with Enterococcus faecalis. The specimens were divided into five groups according to the intracanal irrigant used. Group1: 100mg/ml doxycycline hydrochloride solution [n=10]; Group2: 2% chlorhexidine gluconate solution [n=10]; Group 3: 2.6% NaOCL solution [n=10]; Group 4: Infected dentinal tubes [positive control] [n=10] and Group 5: Sterile dentinal tubes [negative control] [n=10]. Dentine chips were removed from the canal with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing 1 ml tryptic soy broth [TSB]. Thereafter, 100 micro1 from each test tube was cultured on blood agar and number of CFUs was counted. The number of CFUs from three experimental groups were compared using Univariate analysis of variance [ANOVA] and Duncan analysis .Sustainable antimicrobial effect was evaluated at days 0,7,14 ,21 and 28. The number of CFUs in all three experimental groups were minimum in the first cultures, but the results obtained were significantly different from each other at any time period [P<0.05] .In the first culture, 2.6% NaOCL group [0.400 +/- 0.699]and 100 mg/ml doxycycline HCL group [4.700 +/- 3.683]showed the lowest and highest number of CFUs respectively . In each group, the number of CFUs increased significantly with time -lapse [p<0.05] .NaOCL did not have a sustainable effect. It can be concluded that chlorhexidine and to some extent, doxycycline HCL may be useful as sustainable antimicrobial root canal irrigants