Streptococcus mutans genotypes isolated from root and coronal caries.

The aim of the present study was to evaluate the colonization profile and clonal distribution of Streptococcus mutans isolated from oral cavities that presented coronal and root caries lesions. The isolation and biochemical identification of mutans streptococci were carried out by using saliva samples, dental plaque, and tissue from the caries lesions. In order to confirm their molecular identity, S. mutans and Streptococcus sobrinus were submitted to the PCR method, using specific primers for portions of the glucosyltransferase genes (gtfB and gtfI, respectively). The AP-PCR method was used to detect the genetic polymorphism of S. mutans strains. Among the isolated and identified species, S. mutans showed a significantly greater frequency of isolation (59.2%) than the other mutans streptococci. Each of the subjects harbored two to ten genotypes of S. mutans, randomly distributed in different sites. S. mutans genotypes showed no evidence of variability in colonizing noncarious and carious surfaces within the same individual, nor evidence of etiologic differences between coronal and root caries. This study showed that no particular genotype of S. mutans is uniquely associated with the initiation and progression of caries, and that root and coronal caries can emerge in the presence of a broad spectrum of S. mutans clones.