Relationship of E-cigarette Smoking (Vaping) with Dental Caries in Adolescents: A Systematic Review

Muhammad Omar Niaz^1*, Aleema Khan Swati², Yasmin Akhtar³, Rabia Tariq⁴, Seemin Kashif⁵

¹Associate Professor of Community and Preventive Dentistry, Army Medical College (National University of Medical Sciences) Rawalpindi, Pakistan
²3^rd Year BDS, Army Medical College, Rawalpindi, Pakistan
³MBBS, MPhil (Biochemistry), Khyber Medical College Peshawar, Pakistan
⁴BDS, Vision Colleges, Riyadh, Saudi Arabia
⁵MBBS, MPhil Nutrition, Department of Environmental Sciences, Allama Iqbal Open University, Islamabad, Pakistan

*Correspondence author: Seemin Kashif, MBBS, MPhil Nutrition, Department of Environmental Sciences, Allama Iqbal Open University, Islamabad, Pakistan; E-mail: [email protected]

Citation: Niaz MO, et al. Relationship of E-cigarette Smoking (Vaping) with Dental Caries in Adolescents: A Systematic Review. J Dental Health Oral Res. 2025;6(2):1-9.

Copyright^© 2025 by Niaz MO, et al. All rights reserved. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Figure 1: Flow diagram showing selection of articles for review article.

Table 1: Summary of studies included in the review.

Results

Out of total 15 studies extracted for the review, nine (09) studies were in-vivo human studies and six (06) studies were in-vitro studies (Table 1). Four (04) studies used DMFT index for assessment of caries level. It is the sum of the number of Decayed, Missing due to caries and Filled Teeth in the permanent teeth [6]. One study used DMFS index to assess caries level. It gives the sum of an individual’s decayed, missing and filled permanent teeth surfaces.6 Two studies used CAMBRA (Caries Management By Risk Assessment) CRA (caries risk assessment) tool for assessment of caries. This tool was published in the Journal of the California Dental Association in 2007.7 One study used caries index that was measured by adding decayed teeth.

None of the in-vivo human studies were done specifically for adolescents. All studies included adolescent age within the bracket of late adolescents and young adults. One in-vivo case-control human study, one prospective cohort and three (03) cross-sectional studies showed high levels of caries in e-cigarette smokers [8-12]. In one cross-sectional study, although caries in ECIG-smokers was higher than in non-smokers, but the significance of the difference was not measured in the study [13]. However, three (03) in-vivo human studies could not find any significant differences between the caries levels of control, cigarette and e-cigarette groups. Of these studies, two studies were case-control studies and one study was cross-sectional one [14-16].

In two in-vitro studies, extracted human teeth were used [2,17]. The activity of S. mutans on human teeth enamel was studied under effect of various flavors of e-cigarette aerosols. It was found that viscous aerosols generated by e-cigarette promoted S. mutans growth and attachment. Out of five (5) ECIG liquid flavors chosen, due to their ability of producing caries i.e., pH or sweetness, four (04) flavors i.e., sucralose, triacetin, ethyl butyrate and hexyl acetate enhanced formation of biofilm, however, ethyl maltol decreased biofilm formation as compared to the control [17]. The percentage of the loss of hardness was highest with triacetin and decreased in following order; hexyl acetate > ethyl butyrate > sucralose > ethyl maltol > control.

In one in-vitro study, effect of nicotine only, e-liquid with or without nicotine, air, aerosol with nicotine and smoke bound in growth media containing oral commensals Streptococcus gordonii, Streptococcus mitis and Streptococcus oralis was studied [18]. Only smoke-treated growth media inhibited the growth of oral commensal streptococci. Two other studies showed greater inhibition of oral commensal bacteria (S. gordonii, S. intermedius, S. mitis and S. oralis) growth by flavored (tobacco, cinnamon, menthol, blueberry and strawberry) e-liquids, especially at higher concentrations, as compared to flavorless ones [1,19]. One of these studies also showed that the aerosol form of e-liquid caused slower growth of bacteria during the exponential phase compared to bacteria exposed to un-aerosolized electronic cigarette liquid [19].

Another in-vitro study showed that electronic cigarette aerosols inhibited growth of Streptococcus sanguinis and Streptococcus gordonii but did not affect growth of Streptococcus mutans [20]. It also showed that when e-liquid was added without heating and aerosolization, it caused only a minor reduction in growth of both S. sanguinis and S. gordonii, showing that heating resulted in the emission of harmful and toxic by-products.

Discussion

Liquids that are used in e-cigarettes are available with or without nicotine. In e-cigarettes, nicotine is transferred from the device to the airway of user in the form of aerosol. The Vegetable Glycerin (VG) and Propylene Glycol (PG), are hygroscopic (water-absorbing) substances, that are used as solvents for nicotine and flavoring agents present in the liquid. They form an aerosol when heated and then inhaled. Glycol is less viscous, produces throat stimulation and mimics the feel of smoking, whereas glycerin has a natural sweet flavor, making it pleasing to exhale. There are thousands of flavors incorporated into e-cigarette liquids, including tobacco, menthol and sweet flavors [2]. The cartridge can be prefilled or refillable [2,21].

In the US, the majority of e-cigarette users are between the ages of 18 and 44 years [3]. It is, however, more common among teens and young adults [22,23]. It actually became popular in cigarette smokers as a tool to stop smoking. Pregnant ladies and youth also considered it to be a safer and acceptable alternative to regular cigarettes.

In-vivo Studies   

Out of 15 studies selected in our review, five (05) human studies showed an association between e-liquids and e-cigarette aerosols and dental caries. Four (04) human studies, however, could not show an effect of the e-cigarettes on dental caries.

The strength of one of the human cross-sectional studies that showed a significant relationship of e-cigarette smoking with dental caries, was that this study included a nationwide representative sample [10]. The second cross-sectional study also had a large sample size, collected over three years from dental clinic [11]. In two human studies that could not show significant difference between dual smokers, e-cigarette/ vape only users and cigarette smokers only, still had more than 65% participants at high risk of caries [13,16]. All human studies included adolescent age within the bracket of late adolescents and young adults. Hence, the results of the study could not be inferred to adolescents alone.

In-vitro Studies

Out of the studies selected in our review, five (05) in-vitro studies showed an association between e-liquids and e-cigarette aerosols and dental caries. However, one (01) in-vitro study also failed to show effect of e-liquid or e-cigarette aerosol on dental caries. In one vitro study, which could only show tobacco smoke inhibiting biofilm growth of oral commensals, only flavorless e-cigarette aerosol was used for comparison [18]. Hence, it can be assumed that if flavored ECIG liquid and its aerosol had been used in the study, it might not have been completely harmless. Tobacco smoke has also been found to promote growth of pathogenic biofilms, including Porphyromonas gingivalis and Streptococcus mutans, in literature [18].

In two in-vitro studies, extracted human teeth were utilized to study the activity of S. mutans on human teeth enamel in presence of various flavors of e-cigarette aerosols [2,17]. Viscous aerosols promoted S. mutans growth and their attachment to the enamel. Although four (04) flavors enhanced formation of biofilm, ethyl maltol lowered formation of biofilm as opposed to the control [17]. The loss of hardness of teeth was highest with triacetin and least with sucralose [17].

Two other in-vitro studies showed greater reduction in oral commensals (Streptococcus gordonii, Streptococcus intermedius, Streptococcus mitis and Streptococcus oralis) due to flavored e-liquids, as compared to flavorless ones [1,19]. One of these studies also showed greater reduction at higher concentrations of these e-liquids [19]. This study also showed greater effect of the aerosol form of e-liquid as compared to un-aerosolized e-liquid [19].

Factors Responsible for Developing Caries in ECIG-Smokers

Various factors in e-cigarettes might act alone or in combination to cause dental caries (Fig. 2)

1. Alteration of Oral Microbiome

 There are various factors responsible for development of dental caries [24]. Alteration in oral microbiome favors dental caries. This shift occurs when either the oral commensals, like S. gordonii, S. intermedius, S. mitis and S. oralis, are suppressed or when there is overgrowth of pathogenic bacteria like S. mutans [17]. S. mutans is the main causative agent of caries [25]. The vegetable glycerin (VG), Propylene Glycol (PG) and nicotine mixture in e-cigarette aerosol alone is enough to inhibit growth of oral commensals, hence promoting overriding of pathogens [1]. The most abundant bacteria in oral microbiome are Streptococcus sanguinis and Streptococcus gordonii. S. mutans is an opportunistic bacterium that disturbs oral homeostasis due to environmental changes. S. mutans is connected with dental caries. E-cigarette aerosols were found to limit Streptococcus gordonii and Streptococcus sanguinis growth, but not of Streptococcus mutans, hence increasing the formation of biofilm by Streptococcus mutans but not of S. gordonii and S. sanguinis [24]. Some components of e-cigarette aerosols are sweet and might act as a substrate for cariogenic bacteria [16]. Glycerin has a natural sweet flavor and thousands of flavors, incorporated into e-cigarette liquids, include sweet flavors [2]

2. Dental Plaque:

Development of dental plaque predisposes to dental caries. This plaque is actually a biofilm that is present on natural teeth and it plays an important role in dental caries whenever there is a shift in oral microbiome balance [17]. Research also observed that amount of calcium in saliva of e-cigarette smokers was elevated than in that of those who did not smoke. A higher amount of calcium in saliva can cause greater mineralization of plaque, which is a risk factor for caries [24]

3. Dental Hardness

A decrease in dental hardness favors development of caries. Certain e-liquid flavors were also found to cause demineralization of the tooth enamel and hence decrease tooth hardness [17]

4. Aerosol Form of E-liquid:

A study also showed greater effect of the aerosol form of e-liquid as compared to un-aerosolized e-liquid [19]. This fact showed that heating of e-liquids through e-cigarettes caused greater damage to dental enamel as compared to plain e-liquids

5. Viscosity of E-liquid:

Caries may also develop due to viscosity of e-cigarette aerosol. This viscosity is due to Propylene Glycol (PG) and glycerol (VG), which seemed to promote bacterial attachment by occupying pits and fissures of human teeth [17]

6. Xerostomia:

Dry mouth (xerostomia) caused by propylene glycol and glycerol in the e-cigarettes might increase the risk of dental caries by causing water absorption [4]. Yet another reason in adolescents might be exposure to caries because of sugar intake and bad dental hygiene [17]

Figure 2: Diagram showing possible effects of e-cigarette on dental caries.

Strengths, Limitations and Future Prospects

The strength of this study was that it included all in-vivo (human) and in-vitro studies since the time e-cigarettes were introduced. All studies were found through MeSH PubMed search. The limitations of this review were the lack of quantitative studies that assess effects of e-liquid aerosols on dental caries, a lack of homogeneity among the studies and smaller number of human studies included in review. Future research should include longitudinal in-vivo human studies, which must include valid tools to study the doses of e-liquid aerosols and to evaluate dental caries, while controlling for confounders and using validation with biomarkers.

Conclusion

Our review suggests that e-cigarettes are cariogenic due to shifting of the oral microbiome in favor of dental caries, high levels of sugars and flavors in the e-liquids and heating of the e-liquids and shift the oral microbiome in favor of dental caries. Although sugars are addictive especially for adolescents and e-cigarettes can affect adolescents more than the older age groups, but all studies in our review included adolescent age within the bracket of late adolescents and young adults. Hence, the results of the study could not be extrapolated to adolescents alone.

Conflict of Interest Statement

All authors declare that there are no conflicts of interest.

Informed Consent Statement

Not applicable.

Authors’ Contributions

1. MON was major contributor to writing manuscript.
2. AKS was major contributor to literature search.
3. YA was major contributor to screen literature.
4. RT was major contributor to proofread the manuscript.
5. SK was major contributor to draft manuscript and correspondence.

Financial Disclosure

The authors received no external financial support for this study.

Ethical Statement

Not applicable.

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