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PLoS One. 2018 Sep 7;13(9):e0203717. doi: 10.1371/journal.pone.0203717. eCollection 2018.

Cariogenic potential of sweet flavors in electronic-cigarette liquids.

Author information

Volpe Research Center, American Dental Association Foundation, Gaithersburg, Maryland, United States of America.
Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado, United States of America.
National Institute of Standards and Technology, U.S. Department of Commerce, Gaithersburg, Maryland, United States of America.
Molecular Characterization and Analysis Complex, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America.
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America.
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States of America.



Most electronic-cigarette liquids contain propylene glycol, glycerin, nicotine and a wide variety of flavors of which many are sweet. Sweet flavors are classified as saccharides, esters, acids or aldehydes. This study investigates changes in cariogenic potential when tooth surfaces are exposed to e-cigarette aerosols generated from well-characterized reference e-liquids with sweet flavors.


Reference e-liquids were prepared by combining 20/80 propylene glycol/glycerin (by volume fraction), 10 mg/mL nicotine, and flavors. Aerosols were generated by a Universal Electronic-Cigarette Testing Device (49.2 W, 0.2 Ω). Streptococcus mutans (UA159) were exposed to aerosols on tooth enamel and the biological and physiochemical parameters were measured.


E-cigarette aerosols produced four-fold increase in microbial adhesion to enamel. Exposure to flavored aerosols led to two-fold increase in biofilm formation and up to a 27% decrease in enamel hardness compared to unflavored controls. Esters (ethyl butyrate, hexyl acetate, and triacetin) in e-liquids were associated with consistent bacteria-initiated enamel demineralization, whereas sugar alcohol (ethyl maltol) inhibited S. mutans growth and adhesion. The viscosity of the e-liquid allowed S. mutans to adhere to pits and fissures. Aerosols contained five metals (mean ± standard deviation): calcium (0.409 ± 0.002) mg/L, copper (0.011 ± 0.001) mg/L, iron (0.0051 ± 0.0003) mg/L, magnesium (0.017 ± 0.002) mg/L, and silicon (0.166 ± 0.005) mg/L.


This study systematically evaluated e-cigarette aerosols and found that the aerosols have similar physio-chemical properties as high-sucrose, gelatinous candies and acidic drinks. Our data suggest that the combination of the viscosity of e-liquids and some classes of chemicals in sweet flavors may increase the risk of cariogenic potential. Clinical investigation is warranted to confirm the data shown here.

Conflict of interest statement

The authors have declared that no competing interests exist.

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