CPP-ACP/SnF₂ Combined Activity in a Polymicrobial Biofilm Caries Model

Objectives: Dental caries is associated with plaque dysbiosis leading to an increase in the proportions of acidogenic and aciduric bacteria at the expense of alkali generating commensal species. Fluoride slows the progression of caries by remineralization of early lesions but has also been suggested to inhibit glycolysis of aciduric bacteria under acid conditions. Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) promotes fluoride remineralization by acting as a salivary biomimetic releasing bioavailable calcium and phosphate ions. The CPP-ACP peptide complex has also been suggested to modify plaque composition. We developed a polymicrobial biofilm model of caries using a constant depth film fermenter containing six oral bacterial species representative of supragingival plaque. We used this model to explore the mechanisms of action of SnF₂ and CPP-ACP.
Methods: The bacteria were cultured on sound human enamel, fed with an artificial saliva medium and pulsed with sucrose four times a day to produce a high cariogenic challenge. Bacterial species were enumerated using 16s rRNA gene sequence analyses and mineral loss and lesion formation were determined in the enamel directly under the polymicrobial biofilms using transverse microradiography. The twice daily addition of fluoride as SnF₂, or CPP-ACP, or both in combination were tested in the model.
Results: SnF₂ treatment reduced the rate of demineralization by 50% and had a slight effect on polymicrobial biofilm composition. CPP-ACP treatment caused a similar 50% inhibition of enamel demineralization rate and also a decrease in Actinomyces naeslundii and Lactobacillus casei abundance and an increase in Streptococcus sanguinis and Fusobacterium nucleatum abundance in the polymicrobial biofilm. A combination of SnF₂ and CPP-ACP resulted in a greater suppression of the acidogenic/aciduric bacteria including Streptococcus mutans, a decrease in the lactate utilizing Veillonella parvula and a 72% inhibition of enamel demineralization rate.
Conclusions: SnF₂ and CPP-ACP had an additive effect in the polymicrobial biofilm caries model.