In-Vitro Effect of Manuka Honey / Propolis Toothpastes on Bacteria and Biofilm Associated with Caries and Gingivitis

Purpose: To investigate the antibacterial and anti-biofilm effects of two Manuka honey toothpaste formulations containing propolis (Manuka prop) or fluoride (Manuka F), in comparison with the toothpaste base (TP con) and a commercial toothpaste (TP com), on oral bacteria and biofilm.
Materials and Methods: The minimum inhibitory concentration (MIC) of the formulations and controls were tested against five oral bacterial species. Both the effect on a multispecies dental biofilm precultured for 3.5 days as well as the inhibition of de-novo biofilm formation up to 24 h were investigated. Test substances at concentrations of 20%, 10% and 5% were applied to preformed biofilm for 1 min. The reduction in colony-forming units (cfu), metabolic activity, and biofilm mass were determined. Similarly, the test substances were applied to surfaces for 30 min before bacteria and media were added. The reduction of a tetrazolium dye (MTT assay) was used to assess cytotoxicity on gingival fibroblasts.
Results: The MIC values of all toothpaste formulations including TP con were very low with the highest MIC of 0.04%. In precultured biofilms, both the number of colony forming units (cfu) and metabolic activity decreased following addition of any toothpaste. The greatest reductions of cfu were found after addition of 20% TP com (by about 6 log10) and after 20% Manuka prop (by about 2.3 log10). However, the biofilm mass was not reduced. Coating the surface with toothpaste formulation, the cfu in the newly formed biofilm decreased in a concentration-dependent manner, with TP com being most active. Both 20% of Manuka prop and Manuka F reduced the cfu counts more than the TP con at 24 h. The toothpaste formulations affected the viability of gingival fibroblasts in a concentration-dependent manner, with no differences observed among the formulations.
Conclusion: The Manuka-honey containing toothpastes might be an alternative to toothpaste containing conventional chemical agents. Further research is needed to clinically examine the effect on caries and gingivitis prevention.