Importance of infection level of mutans streptococci for recolonization of teeth after chlorhexidine treatment

The recolonization pattern of mutans streptococci after reduction by a 1 % chlorhexidine gel was followed in plaque samples of 8 subjects over a 26‐week period. Plaque samples from all available tooth surfaces were examined and the absence or presence of mutans streptococci was expressed on a scale from 0 to 4. Comparison of infection scores showed that heavily infected surfaces (Scores 3 and 4) occurred more frequently on molars than on other teeth before treatment. Such surfaces were most difficult to disinfect. Surfaces with pretreatment Scores 3 and 4 were more readily recolonized than surfaces less infected before treatment. On only about half of the tooth surfaces was the level of infection similar or identical with the pretreatment score after 26 weeks. The results indicate that tooth surfaces with high infection level of mutans streptococci are more rapidly recolonized by mutans streptococci even if these microorganisms have been suppressed to undetectable levels by the antimicrobial treatment.