A 30-month longitudinal study of the effects of some oral hygiene measures on Streptococcus mutans and approximal dental caries.

The effects of some oral hygiene measures on Streptococcus mutants and approximal dental caries were evaluated. One hundred and eighty-seven 13-year-old individuals with high levels of salivary S. mutans (greater than 10(6)/mL) were selected. They were randomly distributed into three groups. Group I initially received professional mechanical tooth-cleaning, tongue-scraping, chlorhexidine treatment, and oral hygiene instructions concentrated on the approximal surfaces most colonized by S. mutans. The treatment was given four times with intervals of two days, followed by one single treatment every six months throughout the experimental period. The initial treatment period for group II, also consisting of four visits, included the same oral hygiene instructions as for group I. The instructions were repeated every six months. Group III was maintained in the preventive program provided by the local Dental Health Office, based on mechanical plaque control and topical use of fluorides and chlorhexidine at individualized intervals. Group I showed a significant immediate reduction of S. mutans in saliva as well as an approximal tooth surfaces. After six months, there were no differences among the three groups regarding these variables. Compared with baseline, there was a significant reduction of S. mutans in all groups. There was no significant difference in caries progression among the three groups. However, the selected "high-risk" individuals in group I developed 0.25 new manifest caries lesions approximally/year, compared with 0.27 for all children of the same age group in the area. Seventeen individuals had approximal surfaces with consistently high or consistently low S. mutans levels. Forty-six percent of the surfaces with high values developed new or progressive caries, compared with 2% of the surfaces with low values.