All ETDs from UAB

Advisory Committee Chair

Jessica Js Scoffield

Advisory Committee Members

Noel Nc Childers

Kyounga Kc Cheon

Janice Jj Jackson

Amjad Aj Javed

Ping Pz Zhang

Document Type


Date of Award


Degree Name by School

Master of Dentistry (MDent) School of Dentistry


Introduction: The causative factors of dental caries have been studied for many years, however, preventing the formation of dental caries remains an elusive task. Microorganisms have been the focal point of numerous studies as a prime cariogenic factor. Streptococcus mutans and Candida albicans have been frequently co-isolated from dental biofilm in patients with early childhood caries (ECC) and studies have demonstrated the synergistic effects of these two microorganisms in promoting tooth demineralization. Acid and glucan production, which are two virulence factors produced by S. mutans that mediate biofilm formation and tooth decay, have been shown to be promoted during co-colonization with C. albicans. Interestingly, published reports have demonstrated that licorice extract exhibits both antibacterial and antifungal properties, particularly against S. mutans biofilms. However, no studies have tested the effect of licorice extract on S. mutans and C. albicans synergism. Purpose: The goal of this study was to evaluate the antimicrobial effect of Chinese licorice (Glycyrrhiza uralensis) extract against oral microorganisms and to investigate whether licorice extract inhibits biofilm synergy between S. mutans and C. albcians, as well as test its effect on acid and glucan production by these oral microorganisms. Materials and Methods: Minimal inhibitory and bactericidal concentration was determined utilizing disk diffusion assays on Todd-Hewitt broth (THB) agar plates. Biofilm assays were performed to assess the effect of licorice extract on S. mutans and C. albicans, single and dual species biofilms formation in THB containing 1% sucrose in order to simulate ECC patients that consume high concentrations of dietary sugars. Biofilm biomass was quantified using crystal violet. Fluorescence microscopy was utilized to measure acid and glucan production with pHRodo red and Cascade blue stains, respectively. Furthermore, a Drosophila melanogaster sucrose-dependent model was utilized to evaluate the effect of licorice extract on the colonization of S. mutans and C. albicans in single and dual infection. Results: G. uralensis extract significantly inhibited biofilm formation by S. mutans and C. albicans in a dose dependent manner. Microscopic analysis showed the reduction of acid and glucan production in the presence of 2.5% licorice extract. Less inhibition was observed in S. mutans and C. albicans co-cultures compared to S. mutans single cultures. Lastly, licorice extract reduced the colonization of S. mutans and C. albicans in single and dual infections. Conclusion: Glycyrrhiza uralensis extract displayed significant antimicrobial and antibiofilm activity against S. mutans and C. albicans in both single and co-species cultures. Taken together, this study provides evidence that licorice extract may be an effective and natural therapeutic for the prevention of dental caries.

Included in

Dentistry Commons



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