Calcium hydroxide pastes activity over biofilms of Enterococcus faecalis strains isolated from primary and secondary endodontic infections

Abstract

The objective of this work will be to evaluate the biovolume and cell viability of biofilms of three strains of Enterococcus faecalis, one ATCC 29212, one clinical isolate of primary endodontic lesion and one clinical isolate from secondary lesion, after exposition to calcium hydroxide paste with viscous vehicle. Dentin blocks, derived from bovine teeth, will be made by means of trephine bone burs. They will be screwed in polishing machine, kept in saline solution, autoclaved and divided into 5 groups (n = 8) according to the strains, which will be: G1- ATCC 29212 + Calcium Hydroxide (HC); G2- strain isolated from primary lesion + HC; G3 - isolated strain of secondary lesion + HC; G4- Positive control, infected blocks without medication; G5- Negative control, uninfected blocks and no medication. The dentin blocks will be inserted into a plate containing 24 wells with the inocula, allowing biofilm formation for one week, and daily exchanges of the culture medium. The biofilms, after being exposed to the medications for seven days more, will be visualized through the Life & Dead dye in CLSM, using Leica LAS AF Lite software in four areas of each dentin block. In the Bioimage v2-1 program, the percentage of live (green) and dead (red) bacteria, as well as the biovolume of the biofilms, will be quantified by means of the fluorescence emitted in the evaluated images. After the image processing, the data will be statistically analyzed by the normality and comparative tests (p <0.05), demonstrating which strain is more resistant to calcium hydroxide paste.