While the harmful effects of traditional cigarette smoking on human health is well researched, knowledge of the effects of exposition to e-aerosol is limited, and above all there is a lack of long-term studies. The first contact of the various chemicals inhaled with the e-aerosol takes place in the oral cavity, and conclusions on the effects of this interaction come mainly from animal or in vitro studies. Additionally, conflicting results have been reported, corresponding to the various device and e-liquid combinations and different methods of study