Methods: Dental plaque from children (ages 3-5) was collected from the entire dentition, or from individual sites, including stainless steel crowns, composite and enamel surfaces. MS isolates (N between 10 and 20 isolates) from each collection site were selected on mitis salivarius agar containing bacitracin, subjected to polymerase chain reaction (PCR) for verification as MS and arbitrarily primed-PCR (AP-PCR) for assignment within genotypic strains. Isolates were also characterized for acid tolerance using an ATP-driven bioluminescence assay and acidogenesis based on the final pH after three days of growth in phenol red dextrose.
Results: Stainless steel and composite surfaces harbored different dominant MS strains. For instance, for one patient, composite surfaces contained the AA1 dominant genotype. AA1 was highly acid-tolerant (AT) with an AT index of 0.825 (defined by survival at pH 2.8 divided by survival at pH 7.0) and was highly acidogenic, generating mean pH and standard deviation (SD) values of 4.26 ± 0.01 after 3 days of growth in phenol red dextrose. Stainless steel crowns harbored dominant genotype AA2, while enamel contained more diverse numbers of genotypes, including near equivalent numbers of AA1 and AA2 plus another minor genotype, AA3. Interestingly, AA2 was more acid-susceptible with an AT index of 0.387.
Conclusions: Stainless steel and composite surfaces harbor distinct MS genetic strains that may be reflective of the strain’s adherence to different surfaces. This study may have utility in the selection of restorative materials for the potential reduction of dental caries. Supported by OHSU School of Dentistry.
Keywords: Caries, Caries organisms, Cariogenicity, Cariology and Microbiology