[Studies on bacterial contamination of chlorhexidine coated filaments of the toothbrush]

The purpose of the present investigation was to determine bacterial contamination of chlorhexidine coated and uncoated (normal) nylon filaments of toothbrushes. Ten healthy subjects were employed in this study and the test toothbrush of four lines and thirty-eight tufts were used twice a day. Test periods were 1, 8, and 20 days for each filaments of toothbrush and after they brushed the used toothbrush was kept at the constant condition (20 degrees C, 65% RH). After each test period, those toothbrushes were immediately collected and kept at the same condition for drying. After 0, 3, 6, 9, and 24 hours of drying, two tufts of filaments were pulled out from the toothbrush and cutted into two parts (end- and root-side of tufts) by sterile scissors. Each cutted part of filaments was washed with PBS and the aliquots was incubated on Brucella blood agar plate at 37 degrees C for 48 hours. The number of bacteria attached to filaments was enumerated. The results were as follows: 1. The number of bacteria attached to both end- and root-sides of chlorhexidine coated filaments decreased with the time of drying. 2. At the root-side of the normal filaments, the number of contaminated bacteria increased with the test periods. 3. The isolated bacteria from tested toothbrushes were mainly gram positive at shorter period, however, gram negative rods were also found at longer period. 4. The anti-bacterial activity of the end-side of chlorhexidine coated filaments diminished at eight days of the use, however, their activity at the root-side still remained even at twenty days. From these results, it was clear that the bacterial contamination of toothbrush was affected by several factors such as the condition of drying, the site of tufts, the using period of toothbrush and so on. To prevent this problem, it is important to keep it at good storage condition and to change it periodically. The developed chlorhexidine coated filaments of the toothbrush also indicates to be one of the useful way for prevention of bacterial contamination of toothbrush.