Can smoking alter salivary homeostasis? A systematic review on the effects of traditional and electronic cigarettes on qualitative and quantitative saliva parameters.

The available literature indicates that smoking causes quantitative and qualitative changes in saliva. However, there is a lack of studies summarizing the knowledge in this area, and there are no clear guidelines on the use of salivary biomarkers for assessing exposure to cigarette smoke (CS). The present work aimed to provide a systematic review of the literature regarding the influence of smoking traditional and electronic cigarettes, as well as heat-not-burn products, on salivary homeostasis. An electronic search of the literature from 1982 to 2023 was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Based on the inclusion criteria, 65 studies were used for the final review. Smoking traditional as well as electronic cigarettes negatively affects salivary biomarkers, including the salivary flow rate, pH, antibody titer, electrolyte concentration, microflora composition, redox balance, and inflammation, in terms of both quantity and quality. However, to date, only single salivary biomarkers have been compared in traditional and electronic cigarette smokers. It can be concluded that the salivary production rate, pH, microbiome, and cytokines can be used to assess exposure to CS smoke. There is a lack of convincing evidence to compare the toxic influence of traditional and electronic cigarettes on salivary homeostasis. Future experiments should include long-term randomized clinical trials on larger populations of smokers.