Cytotoxicity of Electronic Cigarettes on Oral Cells

Objectives: Cigarette smoking is known to increase the risk of periodontal disease. Electronic cigarettes are the new alternative to conventional cigarettes for nicotine delivery. They contain a liquid (E-Juice) that is available in a variety of flavors and nicotine concentrations. The use of electronic cigarettes is now on the rise in the U.S. due to a reported decrease in carcinogenic effects on the body. Previous studies have proposed that the toxic effects of electronic cigarettes are related to the flavor rather than nicotine content. Currently, it is unknown what effects the electronic cigarettes have on oral cells. Therefore, the purpose of this study was to examine the effects of different electronic cigarette (E-juice) flavors on periodontal cells compared to both pure nicotine as well as cigarette smoke extracts (CSE).
Methods: Gingival and periodontal ligament (PDL) fibroblasts were treated for 24 hours with various concentrations (1uM to 3mM) of E-Juice containing 24mg/ml nicotine in 100% glycerol as well as several flavoring agents including unflavored, Virginia blend, menthol and strawberry. Cell survival was assessed fluorometrically using Calcein-AM. Cell motility was assessed using a scrape assay.
Results: Concentrations of E-Juice containing up to 1mM nicotine did not significantly reduce cell survival. Above 1.5mM, nicotine cell survival decreased selectively in the menthol flavored samples. Unflavored, Virginia blend and strawberry flavored E-Juice only slightly reduced cell survival at 2.8mM nicotine. In contrast, cigarette smoke extracts were toxic at nicotine concentrations as low as 3uM. In addition, menthol flavored E-juice preferentially inhibited gingival and PDL cell motility.
Conclusions: Based on these results, E-Juice only slightly reduced the survival and motility of oral cells. The effects were related to flavoring agents, rather than the nicotine content within the E-Juice. This study supports the likelihood that electronic cigarettes would be safer than conventional cigarettes for nicotine delivery.