Prevalence of Streptococcus mutans and dental decay in schoolchildren living in Genoa (Italy).

In this study population (105 schoolchildren aged 5.5-11.5 yrs), dental decay was detected in 75.2% and S. mutans in 55.2% of the subjects. The presence of S. mutans was assessed - using the selective GSTB medium - in unstimulated saliva and in pooled occlusal and pooled buccal plaques from the four most posterior teeth. All three samples showed association between S. mutans presence and caries prevalence. Of the two types of plaque, the occlusal not only had a higher frequency of isolation but also a significantly higher proportion of S. mutans. The presence of S. mutans was significantly associated with both caries prevalence and extent of caries experience. Both S. mutans prevalence and S. mutans proportion in plaque increased with the number of decayed teeth present among those sampled. Sucrose consumption between meals appeared to be more correlated with the degree of caries experience rather than with caries or S. mutans prevalence. A second clinical examination was scheduled six months after the first for S. mutans-positive children who either were free of active carious lesions, or were caries-active but without signs of dental decay in the sampled teeth. Caries-active subjects proved to be more prone to new carious lesions than caries-free subjects, who tended to remain caries-free even when they had a high proportion of S. mutans in plaque, thus indicating the basic importance of the host factor in the caries process.