Since they were accessible in the US in 2007, e-cigarettes have seen alarmingly high teenage sales. In the US, 4.7 percent of middle school pupils and 19.6 percent of high school students were found to smoke e-cigarettes as of 2020. Ongoing research has shown a potential effect on brain development in young adults, carcinogenic effects and adverse effects affecting the oral cavity.
This review sought to further analyse the research on whether e-cigarettes have a negative impact on the cells in the head, neck, and mouth.
Methods
Searches were carried out on MEDLINE (PubMed), Dentistry & Oral Sciences (EBSCO), CINAHL, CAPLUS (SciFinder), and Web of Science.
The focused question was “Do e-cigarettes cause adverse effects on the head, neck, and oral cells?”.
PICOS was used to formulate a search strategy where:
- P was research subjects, cell lines derived from donor tissue or cells in culture
- I was exposure of test cells to e-cigarette liquid, vapour or nicotine
- C was test cells in comparison to control cells/e-cigarette users compared to non-users
- O was negative effects of e-cigarettes on the cells in the head/neck and mouth
- S was research involving people, animals, non-cases, experiments, in vitro or clinical trials
Exclusion criteria was articles on the effects of e-cigarettes on cells other than those in the head, neck, or oral cavity as well as views and attitudes toward e-cigarette usage. Articles using e-cigarettes for smoking cessation were also excluded.
From the 18 papers in this study, five separate examiners got together several times to go through their findings.
Results
49 articles out of the 233 that were returned by all search types were deemed possible for use. These papers were thoroughly examined and 18 were ultimately seemed suitable for this review. This included 2 clinical trials and the rest were in-vitro studies. 9 looked at the effects of e-cigarette vapour on oral cells, 4 looked at the effects of cigarette liquid and vapour, and 1 looked at the impact of vapour on DNA. The toxicity of 12 flavours with nicotine concentrations ranging from 0 to 24 mg/ml was examined. 6 investigations studied human gingival fibroblasts (HGFs), 4 studied oral epithelial cells (OEC) and 1 studied oral pharyngeal cells.
Findings from these papers included the following:
- When exposed to harmful chemicals, cells produce more lactate dehydrogenase (LDH), which can cause necrosis and/or apoptosis.
- When HGFs were exposed to e-cigarette liquid with nicotine and warmed nicotine there was a significant rise in LDH (with p = 0.0422, p = 0.0491, respectively).
- Reduced cell viability in HGF’s after exposure, significant decrease in cell proliferation, significant breakage of DNA strands and increased lysosomes.
Because many cells and e-cigarettes were examined for potential negative effects on the head, neck, and oral cells, statistical significance (or meta-analysis) was not possible to calculate.
Conclusions
Sixteen articles in this review found the following when the head, neck, and oral cells were exposed to e-cigarettes, aberrant cell morphology, reduced cell viability, and increased apoptosis and/or necrosis. Additional effects were increased pro-inflammatory cytokines, delayed fibroblast migration, DNA damage, and cell death. Of note, most of the articles in this review found tobacco smoke to be significantly more toxic than e-cigarettes….
Comments
The increased use of e-cigarettes, which has potentially resulted in reduced use of traditional tobacco, and in some instances used as a way of supporting smoking cessation, means there is a need to determine exactly what adverse effects these potentially have.
The limitations of the paper included not being able to carry out statistical analysis. It should be noted also that this review included mostly in-vitro studies, therefore clinical correlation is required as clinical results may differ. The fact that most studies cover a short period of time also limits the take-away of the effects of e-cigarettes, especially long-term.
It has been well established that smoking is a risk factor for periodontal disease and consequently tooth loss and oral cancer, however this review unfortunately does not establish any direct evidence linking e-cigarettes to oral diseases. However, it can be taken away from this study that although there is a high likelihood of e-cigarettes being slightly less toxic than tobacco smoke, e-cigarettes are also not completely safe and without side effects to oral cells.
Links
Primary paper
Wilson, C, Tellez Freitas, CM, Awan, KH, Ajdaharian, J, Geiler, J, Thirucenthilvelan, P. Adverse effects of E-cigarettes on head, neck, and oral cells: A systematic review. J Oral Pathol Med. 2022; 51: 113– 125. doi:10.1111/jop.13273
Other references
Mental Elf – 20th Apr 2015
Ibrahim S, Habiballah M, Sayed IE. Efficacy of Electronic Cigarettes for Smoking Cessation: A Systematic Review and Meta-Analysis. Am J Health Promot. 2021 Mar;35(3):442-455. doi: 10.1177/0890117120980289. Epub 2020 Dec 17. PMID: 33327728.
Larsson SC, Burgess S. Appraising the causal role of smoking in multiple diseases: A systematic review and meta-analysis of Mendelian randomization studies. EBioMedicine. 2022 Jul 8;82:104154. doi: 10.1016/j.ebiom.2022.104154. Epub ahead of print. PMID: 35816897; PMCID: PMC9278068.
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