Methods: Antibacterial activity of both mouth rinses were assessed by determining disk diffusion and minimal inhibitory concentration (MIC) methods against five microorganisms including Streptococcus Mutans, Streptococcus Sanguis, Enterococcus Faecalis, Psedomonas Aerogenosa and Eshershia Coli. Zones of growth inhibition were measured in millimeters after 24 hours of incubation at 37 °C. MIC for both agents were assessed at concentrations of 1, 2, 4, 8, 16, 32, 64, 128, 256 and 512 per milliliter and interpreted as the lowest concentration of agents that completely inhibited growth of the test species.
Results: 0.2% Chlorhexidine produced larger zone of growth inhibition compared to the mouth rinse containing green tea extract (P<0.01). Paradoxically, growth inhibition zones of tested bacteria were significantly larger in pure extract of green tea than 0.2% chlorhexidine (P<0.01). The chlorhexidine mouth rinse inhibited growth of all tested species and exhibited significantly lower MICs than the green tea mouth rinse (P<0.01).
Conclusions: Even though the mouth rinse containing green tea extract presented an in-vitro antimicrobial activity inferior to 0.2% chlorhexidine, pure extract of green tea had considerable bactericidal effect.
Keywords: Antibacterial effect, Green tea, 0.2% Chlorhexidine, Mouth rinse.