Subgingival Microbiome in Young Adult Cigarette Smokers, E-Cigarette Users, and Non-Smokers

Background and Objectives: Cigarette smoking is a recognized risk factor for periodontal disease and subgingival dysbiosis; however, the impact of electronic cigarettes on the subgingival microbiome in young adults is still not sufficiently investigated. This study aimed to characterize and compare the carriage and bacterial load of 20 subgingival species among young adult cigarette smokers, e-cigarette users, and non-smokers, and to evaluate whether e-cigarette use is linked to a periodontopathogen-enriched profile similar to that of smoking. Materials and Methods: In this exploratory cross-sectional study, fifty young adults were divided into three groups: cigarette smokers (n = 18), e-cigarette users (n = 16), and non-smokers (n = 16). Subgingival specimens were examined using real-time Polymerase Chain Reaction (PCR) (Perio panel; ADD Laboral B.V., Malden, The Netherlands) for 20 bacterial species. Carriage was analyzed across groups utilizing Fisher’s exact test with Cramér’s V as the effect size, while bacterial load was assessed using the Kruskal–Wallis test accompanied by Dwass–Steel–Critchlow–Fligner post hoc comparisons (jamovi; significance threshold established at p < 0.05). Results: Red-complex pathogens were more prevalent and present in greater quantities in smokers and e-cigarette groups compared to non-smokers. Porphyromonas gingivalis prevalence was seen in smokers (94.4%), vapers (75.0%), and non-smokers (56.2%; p = 0.028), whereas Tannerella forsythia was found in 100% of smokers, 87.5% of vape users, and 68.8% of the non-smokers (p = 0.022). Aggregatibacter actinomycetemcomitans was not present in non-smokers but was identified in 37.5% of vapers and 16.7% of smokers (p = 0.018), whereas Eubacterium nodatum was significantly elevated in tobacco users (p = 0.012; Cramér’s V = 0.449). In contrast, Prevotella nigrescens was predominant among non-smokers (87.5%; p = 0.022). Conclusions: In young adults, the red-complex bacteria—Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola—were found more frequently and in larger quantities among smokers and vapers as compared to non-smokers.