Toothbrush bristle wear and adherence of Streptococcus mutans

The purpose of this study was conducted to determine if bristle wear impacts the adherence of Streptococcus mutans on toothbrushes and to evaluate whether it affects the extent of adherence at 0, 8, and 24 hours after air-drying.

Sixty toothbrushes--composed of 20 each from 3 different groups and defined by brand, brush trim, and head shape--were used in this study. Bristle wear on half of the toothbrushes was achieved using an orthodontic typodont with metal bonds and brackets and evaluated by 4 independent observers. New and worn toothbrushes were inoculated with 5 mutans, rinsed in tap water, and air-dried for 0, 8, and 24 hours. Four tufts were removed from the brush heads at each time point, placed in saline and vortexed to remove bacteria. Bacteria were aerobically grown on Mitis Salivarius Agar plates until colony-forming units could be counted.

The toothbrush group impacts adherence of 5 mutans on both new and worn toothbrushes at 0, 8, and 24 hours after air-drying, with new toothbrushes harboring significantly more S mutans than worn toothbrushes at 0 hours.

The results have implications for the design of toothbrush tufts as well as storage of toothbrushes in the home.