Microbial conditions and caries increment 2 years after discontinuation of controlled antimicrobial measures in Swedish teenagers.

The purpose of the present study was to examine the long-term effect of a special caries preventive program in teenagers. Over a 3-yr period directed and controlled antimicrobial treatment using Streptococcus mutans as an indicator organism resulted in a remarkable caries reduction especially in children with greater than 10(6) S. mutans per ml of saliva at the start of the study. Two years after discontinuation of the special preventive program 83 out of 101 subjects, 18-19 yr old, were reexamined. All the children had followed the same basic preventive program in the Dental Health Service. The number of S. mutans and lactobacilli per ml of saliva within and between control and test groups was with few exceptions practically the same as 5 yr earlier. During the posttreatment period the caries activity was similar in the control and test groups and lower than during the experimental years especially in the control group. Subjects with initial S. mutans level of greater than 10(6) CFU per ml of saliva continued to show incremental caries scores higher than those subjects with lower S. mutans levels.