Demonstration of Scientific Feasibility of High Fluoride-Povidone Iodine Toothpaste

Objectives: To assess the antibacterial activity of a newly formulated toothpaste and confirm its inhibition of demineralization and enhancement of remineralization of enamel in vitro.
Methods: Twelve experimental toothpastes were manufactured with 0-1.1% NaF, 0-5% PVP-I, and 0-1% KI as putatively active ingredients. To assess antibacterial activity, S. mutans (strain 10449) and S. sobrinus (strain 6715) were plated on TSoy agar supplemented with either 1% glucose or 1% sucrose and incubated for 24h (37°C/5%CO₂). Sensitivity-testing discs were blindly coated with coded toothpastes, placed onto the agars for another 24h and then zones of growth inhibition were measured. Chlorhexidine (0.12%) served as a positive control. To confirm enamel de-/remineralization properties, enamel specimens were pH cycled (7d) to evaluate the toothpaste containing 1.1% NaF, 5% PVP-I and 1% KI vs. controls. The primary outcome was the percentage Knoop surface microhardness change (%SMHc).
Results: The toothpastes containing 5% PVP-I and 1% KI demonstrated replicable areas of growth inhibition at 24h with both S. sobrinus and S. mutans with either glucose or sucrose (diameter of zone of growth inhibition, mean±standard deviation; 12.6±1.0mm). There was a trend for the pastes containing 2.5% PVP-I and 0.4% KI to create clearing of the agar (10.5±0.0mm). Varying the concentration of NaF did not change the results. Negative controls showed no areas of clearing, while chlorhexidine did (27.8±6.3mm). The pH cycling study showed that the 1.1% NaF, 5% PVP-I toothpaste was most effective in preventing caries lesion formation (%SMHc, mean±standard deviation; -79.7±8.0%), followed by 1.1% NaF toothpaste without PVP-I (-87.4%±2.1), and a fluoride free toothpaste (-98.9%±1.4).
Conclusions: Complementary studies demonstrated the feasibility of a high fluoride toothpaste containing povidone iodine in preventing dental caries in vitro. No synergy or antagonism was seen. The addition of an antiseptic did not impair the protection against demineralization afforded by fluoride.