Black and Green Tea Antimicrobial Properties: in-vitro and in-vivo Study

Objectives: Finding an affordable natural product with anti-cariogenic potential will have a great impact on the management of dental caries worldwide. There is some published evidence supporting the effect of green tea (GT) but studies of the antibacterial potential of black tea (BT) is scanty. This preliminary study aimed to test the activity of aqueous and alcoholic extracts of BT and GT in comparison with sodium fluoride, chlorhexidine and distilled water, on isolates of Mutans Streptococci (MS) and Lactobacillus (LB).
Methods: MS and LB sensitivity and viable counts were tested with different concentrations of aqueous and alcoholic extracts of BT and GT to determine the minimum bactericidal concentration of tea extract. The time required for killing MS and LB in the presence of tea extract was calculated. Additionally, an in-vivo study of sequential saliva samples collected from 30 volunteers after rinsing with BT and GT aqueous tea extracts was conducted to study the longevity of the tea extract antimicrobial activity in the mouth.
Results: The bacterial counts of MS and LB were reduced with BT or GT aqueous extract significantly and progressively with time. The largest inhibition zone was produced by 50% GT aqueous extract. The least viable count of LB was recorded with 30% BT aqueous extract. The minimum bactericidal concentration was 35% for BT and 30% for GT aqueous and alcoholic extracts. In the in-vivo study, the maximum reduction of MS viable count was at 30 minutes and for LB was at 15 minutes after rinsing with 50% GT.
Conclusions: BT and GT extracts demonstrated antimicrobial activity against MS and LB (p<0.001) suggesting the need for large scale clinical trials to provide strong evidence for the effectiveness of using BT and GT extracts as an antibacterial agents and caries prevention.