Recolonisation pattern of mutans streptococci after suppression by three different modes of chlorhexidine gel application.

Clinical studies have shown conflicting results for the reduction of approximal caries when chlorhexidine gel has been applied either in trays or by flossing. To investigate whether these modes of treatment affect the colonization of mutans streptococci (MS) differently, we quantified MS in saliva and on various tooth surfaces before and after a single chlorhexidine gel application. Twenty-one schoolchildren (15-16 yr old), with high numbers of salivary MS, were randomised into three groups. The subjects were treated with a 1% chlorhexidine gel applied either by: 1) interdental flossing; 2) individually designed mouth trays; or 3) a combination of polishing and flossing. Analysis of saliva and of dental plaque from 12 sites over an 8-wk period showed a greater reduction of both salivary MS counts and total number of colonised sites in the tray group than in the flossing group. The effect on MS in the polishing-flossing group approached that obtained in the tray group. In the interdental areas, more sites had no detectable MS (score 0) after tray treatment than after flossing, whereas the reduction of heavily colonised sites (scores 3+/-4) was higher in the flossing group. The reappearance of sites with score 3+/-4 after the gel treatment was more rapid in the flossing group than in the other two groups. In conclusion, the results showed a transient reduction of MS colonisation by all three methods, and that the application of the chlorhexidine gel both in mouth trays or as a combination of polishing and flossing was more effective in reducing the MS population than flossing alone.