PROJECT SUMMARY/ABSTRACT The problem: Early childhood caries (ECC) is a lead health problem affecting children. More than half a billion children worldwide have untreated tooth decay. Pain, impaired nutrition, reduction in school productivity, and significant costs for care are some of the negative impacts of this disease. The reduced quality of life, morbidity and even mortality are unacceptable consequences of ECC. Because caries is caused by the metabolism of dietary sugars by a cariogenic biofilm, it is very difficult to control; the widespread consumption of fermentable sugars in modern diets favors cariogenic species such as Streptococcus mutans and the opportunistic fungi Candida albicans in the dental biofilm, perpetuating the caries process. Fluoride is the most effective agent for caries control, but it has very limited antimicrobial effects because most microbes have membrane proteins to expel fluoride and keep intracellular concentrations at sub-inhibitory levels. Different oral microbial species possess different types of fluoride exporters; S. mutans and C. albicans employ CLCF and FEX proteins, respectively, while beneficial oral streptococci use Fluc proteins. This creates an opportunity to specifically target pathogenic oral microbes to modify species dynamics towards health-associated symbiotic communities in biofilms exposed to sugar and fluoride. In this project a team of specialists in structural biology, cariology and modeling and prediction of microbial systems will develop a new class of anticaries therapy, leveraging the species-specific susceptibilities to fluoride to create treatments that revert the cariogenic biofilm dysbiosis, under the same level of fluoride exposure currently available through toothpastes/mouth rinses. This will be pursued under the following specific aims: S.A.#1: A multiscale approach to develop fluoride efflux inhibitor treatments for dental pathogens; S.A.#2: A data-driven approach to tailor fluoride-based therapies to patient- specific oral dysbiosis. Significance: This collaborative effort will develop novel, effective fluoride efflux inhibitors that potentiate the antimicrobial effects of fluoride ion and inhibit growth of oral pathogens, to treat oral dysbiosis and eliminate ECC. This study will also establish methods to predict the effect of different treatments according to the patient's specific oral dysbiosis, so that personalized treatment regimens can be used to maximize anticaries effects.

PROJECT NARRATIVE The goal of this project is to identify fluoride export inhibitors for cariogenic microorganisms, determine their mechanism of action, and their effects on physiologically complex dental biofilms. Fluoride efflux inhibitors will potentiate the anticaries effect of fluoride in over-the-counter products like toothpastes and mouth rinses to combat early childhood caries.