Ex vivo antimicrobial activity of several bleaching agents used during the walking bleach technique

To investigate ex vivo the antimicrobial activity of a paste of sodium perborate associated with various vehicles comparing it with 37% carbamide peroxide and 35% hydrogen peroxide.

The antimicrobial activity of these agents was evaluated against three microorganisms: Enterococcus faecalis, Streptococcus mutans and Candida albicans. One millilitre of each tested substance was placed on the bottom of wells of 24-well cell culture plates. Six wells were used for each time period and group. Two millilitres of the microbial suspension was ultrasonically mixed for 10 s with the bleaching pastes and placed in contact with them for 10, 30, 45 s; 1, 3, 5, 10, 20, 30 min; and 1 and 2 h. After each period of time, 1 mL from each well was transferred to tubes containing 2 mL of freshly prepared brain heart infusion agar + neutralizers. Agar plates were inoculated in appropriate gaseous conditions. Data were analysed statistically by the Kruskal-Wallis test with the level of significance set at P < 0.05.

In all groups containing chlorhexidine (groups 3, 5 and 7), the antimicrobial activity of the bleaching paste was significantly increased when compared with groups with other kinds of vehicle (groups 1, 2, 4, 6 and 8). For all tested groups, the most resistant microorganism was E. faecalis.

Chlorhexidine when used as a vehicle for sodium perborate enhanced its antimicrobial activity.