Longitudinal clinical and microbiological study on the relationship between infection with Streptococcus mutans and the development of caries in humans

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Abstract
This 24 months prospective study was undertaken to test the principle that infection with S. mutans on human fissure and smooth tooth surfaces at risk for caries will lead to decalcification and/or cavitation lesions. Forty‐eight elementary school students aged 7‐8 years were recruited and enrolled in the study in an overlapping fashion. The children were examined annually for plaque, gingivitis and dental caries which was scored both clinically and radiographically. In addition, 4‐6 microbiological samples were obtained every 3 months from each participant on predetermined sites of mesial aspects or fissures of first molars using sterile floss or hypodermic needles. The test sample represented 258 tooth surfaces at risk producing a total of 1528 microbiological samples. The samples were processed and identified on selective and non‐selective media using anaerobic techniques. The total colony forming units (CFU/ml) and % of anaerobic and facultative organisms and S. mutans were enumerated. During the entire duration of the study 40 initial (DI) and 6 carious lesions with cavitation (DC) developed in 36 subjects. Eleven established initial lesions (EI) and 12 remineralized surfaces (R) were followed. The control sample consisted of three groups of sites which remained caries‐free throughout the study: 34 sites in control group (CA) of caries‐free children (DFS = 0), 35 sites in children with some filled teeth (CB) (DFS > 5) and 36 sites in children with only one initial lesion (CC) (DFS= 1 or 2) were followed microbiologically for 1‐2 years. DI and DC showed significantly higher levels of S. mutans than controls 9 and 6 months prior to the clinical diagnosis, while R surfaces yielded significantly lower S. mutans levels 9, 6 and 3 months prior to the diagnosis of the reversal. However, in one single DC lesion, S. mutans could not be documented at any observation period prior to the diagnosis of the cavity. Thus, the results confirmed the role of S. mutans as an important, but not exclusive initiator of dental caries. Furthermore, a temporal relationship between infection with S. mutans and clinical diagnosis could be demonstrated.