Oral Health of the Electronic Cigarette Smokers: A Systematic Review

ABSTRACT

Background:

This review aimed to evaluate the impact of e-cigarette usage on oral health, given the rising popularity of e-cigarettes and their perceived lower risk compared to traditional smoking.

Materials and Methods:

Searches were conducted in PubMed, Cochrane, and Scopus databases for studies from January 2014 to December 2023. Eligibility was based on the PICOS criteria. Data extraction was performed by two independent investigators. Studies were assessed using the Effective Public Health Practice Project (EPHPP) Quality Assessment Tool.

Results:

The review included 31 studies, primarily from the USA and Saudi Arabia: 12 cross-sectional, nine case-control, five prospective observational, and five RCTs. Findings showed that clinical periodontal conditions and pro-inflammatory marker levels in e-cigarette users were similar to non-users and lower than conventional cigarette smokers. Dental issues studied included fractures, pain, decay, sensitivity, and loss. Two studies examined harmful metabolites in e-cigarette users. Most studies had low-quality evidence, relying on self-reported data without considering other influencing factors.

Conclusion:

E-cigarette users may experience more changes in oral tissues compared to non-smokers and former smokers.

INTRODUCTION

E-cigarette use has risen in the previous decade, especially among youth. A power supply, heating element, and tobacco-nicotine cartridge make up e-cigarettes. Glycerin/propylene glycol/flavorings dissolve nicotine and the heating component creates aerosols when activated. This aerosol mimics smoking when inhaled.[1] Vaping devices are refillable or non-refillable and vary in size, colour, and shape. Vaping equipment administers nicotine and other substances at varying amounts based on liquid components, user behaviour, and gadget features.[2] E-cigarettes are promoted as a safe alternative to smoking, however, safety is questioned.[3] E-cigarette vaping damages oral health with inflammatory cytokines and oxidative stress.[4] Genomics showed that e-cigarette aerosol enhanced the prevalence of biofilm-forming, stress-response, and disease-promoting bacterial genes.[5] There is little data on how e-cigarettes influence oral bacteria. E-cigarettes did not influence oral microbial diversity[6] although other research reported differences in Porphyromonas, Veillonella, and Haemophilus diversity and prevalence in e-cigarette users compared to healthy individuals.[7]

The nicotine-containing liquid is swiftly heated and evaporated by an e-cigarette, reaching the respiratory and central nervous systems. Although e-cigarette aerosol may include fewer harmful ingredients than traditional cigarette smoke, its health impacts and safety are being studied.[8] Young e-cigarette users are more nicotine-dependent than tobacco users. Dual users use e-cigarettes more than traditional cigarettes, showing they are more addictive.[9] Compared to the respiratory system, the oral cavity has received minimal research on vaporized aerosol. These aerosols predominantly influence oral microbiomes.[5] This review evaluated the oral health effects of e-cigarettes.

MATERIALS AND METHODS

Study protocol

The systematic review followed the criteria outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), which provide a framework for selecting, synthesizing, and disseminating study data.[10]

Focused question

The research question was formulated using the PICO (Population, Intervention, Comparison, Outcome) criteria as follows: “Does the use of electronic cigarette smokers (ECS) increase the likelihood of exhibiting oral biological tissue changes in comparison with non-smokers (NS), ex-smokers (ES), conventional cigarette smokers (CCS), or additional categories of smokers?”

Information sources and search strategy

We searched PubMed, Cochrane, and Scopus for evidence-based studies on e-cigarettes and oral health. Published studies from January 2014 to December 2023 were searched. The following Medical Subject Headings (MeSH) phrases were used after reviewing the literature: (“Oral Health,” OR “Oral Lesions,” OR “Mucosal Lesions” OR “Candidiasis” OR “Leukoplakia” OR “Cheilitis” OR “Stomatitis” OR “Periodontal Health” OR “Oral Cancer”) AND (“Electronic Cigarettes” OR “Nicontine Replacement” OR “Vaping” OR “e-Smoker” OR “e-Cigarette” OR “Electronic Cigarette Smoker” OR “Conventional Cigarette Smoker” OR “Non-Smoker” OR “Smokerlyzer” OR “Fagerström Test”) AND (“Salivary Nicotine” OR “Exhaled Carbon monoxide” OR “Salivary Cotinine” OR “Tobacco Biomarkers” OR “Nornicotine” OR “Nicotine Dependence Level”). To find studies not found in web-based databases, each publication’s references were manually reviewed. Two independent reviewers conducted the evidence-based inquiry and finalized the screening procedure according to pre-established requirements. The reviewers consulted a third reviewer to resolve disagreements.

Eligibility criteria

The eligibility criteria employed were determined according to the PICOS criteria (Population, Intervention, Comparison, Outcome, and Study design).

Population: Individuals aged 18 and above who engage in smoking.

Intervention: Those who use of e-cigarettes.

Comparison: Those who now smoke, individuals who have quit smoking, individuals who were CCS, and individuals who smoke other forms of cigarettes or non-smokers.

Outcome: Influence on dental health or observable changes in oral tissues.

Study design: Comparative cross-sectional studies, Case-control studies, Cohort studies, and Randomized controlled studies.

Systematic reviews, questionnaire surveys, expert opinion, pilot studies, case reports/series, commentary, and animal models were excluded. Non-English articles and studies that only examined questionnaires and/or variable results on quality of life were also excluded.

Data extraction

The data presented were obtained through a standardized data collection template that included the first author’s name, study title, journal name, publication year, country of study, study design, academic year, tools employed to assess the oral health, study objective, nicotine concentration, outcome measures, and study inference. To reduce errors, the process of extracting data was carried out by two independent investigators who worked concurrently. Upon the need for additional information, the respective author was approached.

Quality assessment

The Effective Public Health Practice Project (EPHPP) Quality Assessment Tool analyzed oral health outcome evidence.[11] The EPHPP was designed to evaluate quantitative research designs. Selection bias, study design, confounding, blinding, data collection, participant withdrawal, and drop-out are EPHPP subcategories. Research design, confounding, and blinding subgroups are appropriate for intervention studies but not for non-intervention studies. Thus, non-intervention studies used a redesigned scoring technique that removed these subgroups.[12]

RESULTS

The initial evaluation was carried out in three databases: PubMed, Scopus, and Web of Science. Following the removal of duplicate entries, a total of 81 articles were acquired, out of which 45 were chosen based on the assessment of their titles and abstracts. Thus the present review included 31 studies Figure 1.[10,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41] Most of the studies emanated from the United States[10,13,19,20,22,23,25,29,33,39] and the Kingdom of Saudi Arabia.[16,18,26,27,28,30,31]

Figure 1.

PRISMA flow chart of the included studies

The review had 31 items categorized as follows: 12 were cross-sectional, 9 were case-control, 5 were prospective observational, and 5 were RCTs [Table 1]. Tatullo et al. looked at the clinical signs of people who switched from regular smokes to e-cigarettes.[36] Also, participants completed self-assessment questionnaires. After the observational study, 71% of individuals felt better. Al-Aali et al. found that e-cigarette users had higher plaque levels, deeper probing, bone loss, localized inflammatory indicators, and gingival crevicular fluid.[28] Ismail et al. followed e-cigarette users over six months.[24] Gingival health and adjacent tissues declined significantly in the study. ECS had twice the risk of periodontal disease as NS, according to an independent study. Over 6 months, dental caries diminished significantly (P = 0.002). Another study found that ECS users had twice as much periodontal disease as non-users.[14]

Table 1.

Demographic and summary of the reviewed studies

Author-Year	Study location	Study design	Sample size	Study inference	Evidence quality
Alhajj et al., 2022 [12]	Yemen	Online, multicounty cross-sectional	20 dental schools (5697) from 11 countries	ECS documented elevated health risks	Weak
Chopyk et al., 2021[13]	USA	Case-control	ECS: 12 NS: 12	Significantly increased colonization rates of Staphylococcus aureus were observed in the ECS group in comparison with the control group	Strong
Pushalkar et al., 2020[10]	USA	Case-control	ECS: 40 CCS: 40 NS: 39	ECS are more prone to acquiring infections.	Strong
Jeong et al. (2020)[14]	South Korea	Case-control	ECS: 222 CCS: 2320 Ex-users: 2667 NS: 8342	There is an increase in periodontal disease in both ECS and CCS	Weak
Hajek et al. (2019)[15]	UK	Two-group, pragmatic, multicenter, RCT	ECS (n=438) and NRT (n=446)	Mouth irritation was documented more commonly in ECS than nicotine replacement group	Weak
ALHarthi et al. (2019)[16]	Riyadh, Saudi Arabia	Clinical prospective study	CCS: 30 ECS: 28 NS: 31	Periodontal inflammatory factors are highly noticed in CCS than in ECS and NS	Weak
Cichonska et al. (2019)[17]	Poland	Case-control	ECS: 40 CCS: 40 NS: 40	There is alterations in salivary antibacterial characteristics in ECS than in NS and CCS	Strong
BinShabaib et al. (2019)[18]	Riyadh, Saudi Arabia	Cross-sectional	CCS: 46 ECS: 44 NS: 45	CCS has worse periodontal health and higher GCF proinflammatory cytokines than ECS and NS.	Weak
Tommasi et al. (2019)[19]	USA	Case-control	ECS: 42 CCS: 24 NS: 27	The signaling pathway of the "Rho family GTPases" was three times more in CCS compared to ECS.	Strong
Vora et al., (2019)[20]	USA	Cross-sectional	Adult data (32300) of PATH study wave 1 (2013-14)	Tobacco use was associated with poor periodontal status when compared with NS	Weak
Fliegar et al., (2019)[21]	Poland	Cross-sectional	8 subjects each in ECS, CS, NS	Salivary thiocyanate concentrations in the ECS were higher than the NS, but not significantly different from the CCS (P<0.05).	Moderate
King et al., (2019)[22]	USA	Cross-sectional	Representative adult sample of USA (n=4964)	Coughing and dry mouth/throat were common in ECS	Weak
Hughes and Hendrickson, (2019)[23]	USA	prospective observational study	poison center cases (193 children and 72 adults)	ECS irritate the epithelium and are hazardous if nicotine is ingested.	Weak
Ismail et al., (2019)[24]	Malaysia	Prospective observational study	E-cigarette users at baseline and at 6 months (n=45)	E-cigarettes are harmful to oral health and increase caries and periodontal diseases.	Moderate
Huilgol et al., (2019)[25]	USA	Cross-sectional	Behavioral Risk Factor Surveillance System data (456343)	Regular e-cigarette use was linked to poor oral health.	Weak
ArRejaie et al., (2019)[26]	Riyadh, Saudi Arabia	Case-control	CCS: 32 ECS – 31, NS -32	Higher concentrations of proinflammatory cytokines in CCS and ECS may enhance inflammatory response around the implant.	Moderate
Mokeem et al., (2019)[27]	Riyadh, Saudi Arabia	Cross-sectional	ECC (n=30) NS (n=32) CCS (n=34) WS (n=33)	The prevalence of oral C.albicans colonization was significantly greater among cigarette smokers, ECS, and WS compared to NS.	Moderate
Al-Aali et al., (2018)[28]	Riyadh, Saudi Arabia	Case-control	NS: 45 (42.6±2.7) EC: 47 (35.8±6.2)	Higher concentrations of proinflammatory cytokines in the fluid around the implant may heighten inflammatory reactions in the surrounding tissues	Moderate
Bustamante et al. (2018)[29]	USA	Cross-sectional	CCS: 20 ECS – 20 NS - 19	The use of salivary NNN, which accounts for just 1-3% of the NNN dose, could be employed to assess susceptibility to the carcinogen in ECS aerosol, as opposed to using urine NNN.	Moderate
AlQahtani et al., (2018)[30]	Riyadh, Saudi Arabia	Case-control	CCS: 45.8±6.8 WS: 43.5±4.9 ECS: 35.6±7.1 NS: 42.6±2.7 n=40 in each group	Elevated levels of inflammatory cytokines in tobacco smokers may suggest an increased peri-implant inflammation	Moderate
Mokeem et al., (2018)[31]	Riyadh, Saudi Arabia	Cross-sectional	ECC (n=37) NS (n=38) CCS (n=39) WS (n=40)	Salivary levels of IL-1β and IL-6 were higher in both CCS and WS compared to ECS and NS.	Moderate
Bardellini et al. (2018)[32]	Italy	Prospective case-control study	ECS: 45 Former smokers: 45	ECS was found to have a higher occurrence of some forms of oral mucosal lesions	Weak
Yao et al., (2017)[33]	USA	Cross-sectional	ECS: 610 288 of them were current (last 30 days) ECS	E-cigarette usage increases the adverse health effects relative to CCS	Weak
Cho (2017)[34]	Taiwan	Cross-sectional	Daily users of e-cigaratte: 0.5% (n=297) 1 to 29 days past month users: 1.9% (n=1259) and Former users: 5.9% (n=3848) NS: 60124.	The incidence of tongue and/or intraoral pain, and cracked/broken teeth, was greater among ECS daily compared to NS	Weak
Rahman et al., (2016)[35]	Malaysia	RCT	ECS: 70 Dual users: 148	Over 60% of participants in both of the groups experienced xerostomia.	Strong
Tatullo et al., (2016)[36]	Italy	clinical observational study	ECC initial (n=359) ECC final (n=110)	The transition from CCS to ECS offers significant advantages for the general well-being.	Moderate
Cravo et al., (2016)[37]	UK	Open label RCT	Cohort1: ECS: n=306 CCS: n=102 Cohort 2: ECS: n=32 CCS: n=8	The ECS group exhibited mouth ulceration (3.9%), dry mouth (2.6%), and oral pain (1%).	Weak
Franco et al., (2016)[38]	Italy	Prospective study	Smokers (n=23), e-cigarette smokers (n=22), and nonsmokers (n=20)	Evidence suggests that ECS have been deemed harmless for oral epithelial cells and may serve as a helpful tool for individuals looking to quit smoking.	Moderate
Oncken et al. (2015)[39]	USA	RCT (cross-over trial)	n=20 e-Juice flavored with tobacco and menthol (45%) or to an e-juice flavored with tobacco only (50%), with no preference (5%)	Mouth irritation (n=4)	Weak
Adriaens et al. (2014)[40]	Belgium	RCT (Cross-over trial)	ECS1: Joyetech eGo-C (n=16) ECS2: Kanger T2-CC (n=16) CCS: 16	Both experimental groups exhibited a significantly reduced aggregate complaint score, encompassing concerns of dry and irritated throat and unpleasant taste (P<0.05).	Weak
Farsalinos et al., (2014)[41]	Greece	Cross-sectional	Former (15671) and current (3682) e-cigarettes smokers	The most common oral health symptoms were sore/dry mouth and throat	Weak

ECS – E-cigarette smokers; CCS – Conventional cigarette smokers; NS – Non-smokers, WS- Waterpipe smokers; RCT – Randomized controlled trials; eCO – Exhaled carbon monoxide; PI – Plaque index, CAL – Clinical attachment loss; BOP – Bleeding on probing; PD – Pocket depth, PIBL – Peri-implant bone loss, MBL – Marginal bone loss

Clinical periodontal condition and pro-inflammatory markers in ECS were equivalent to non-users and substantially lower than CCS.[18] Mokeem et al. found identical periodontal probing depth, clinical attachment level, and marginal bone loss in ECS and NS.[31] However, ECS showed lower plaque levels than CCS but a higher plaque index than NS. Waterpipe smokers and CCS had a mean smoking duration five times longer than ECS, although their salivary cotinine concentrations were statistically negligible.[31] Dental fractures,[34] discomfort,[33,37] decay,[24] sensitivity,[33] and loss or extraction[25] were addressed. In two trials, e-cigarette users were tested for harmful downstream metabolites connected to smoking. Three-quarters of e-cigarette users’ saliva contained mouth cancer-causing N’Nitrosonornicotine (NNN). This suggests a link between e-cigarettes and tobacco’s cancer-causing component. Thiocyanate, a cancer-causing chemical, was discovered in ECS saliva at amounts equivalent to smokers.[21,29]

Tommasi et al. found that oral transcriptome genes relevant to cancer processes and functions were disrupted.[19] Franco et al. found that ECS had similar oral cavity cell micronuclei to healthy individuals but substantially lower than CCS.[38] Bardellini et al. found that e-cigarette users have a higher rate of hyperplastic candidiasis than regular smokers.[32] Cichonska et al. found that NS had the highest levels of these components, followed by ECS and CCS.[17] The ability of ECS to combat pathogens may be reduced compared to non-smokers. Nicotine, a highly addictive stimulant, is raising concerns. It also induces vasoconstriction and periodontal degeneration by decreasing fibroblast binding and collagen and integrin production.[36] Nicotine concentrations up to 4 mg/ml promote oral C. albicans development. Mokeem et al. found decreased Candida spp. concentrations at a higher e-liquid dose (6 mg/ml).[27] Importantly, this variance across groups was statistically insignificant. Only five reviewed studies had strong evidence quality according to EPHPP.[10,13,17,19,35]

DISCUSSION

Our understanding of how vaping affects oral health is incomplete. Few clinical trials have proved conclusive, largely cross-sectional of convenient samples. Therefore, causal inferences and generalizations are impossible. The majority of these studies lacked proof of oral condition since they relied solely on self-reported data and did not take into account other variables. E-cigarette and e-liquid use can cause tongue dryness,[22,35,37,40,41] irritation,[15,22,23,39,40] poor taste,[40] and pain/discomfort.[37] ECS also causes tongue discolouration, oral mucosal anomalies, and heat burns.[33,37,41] ECS had greater nicotine stomatitis and hairy tongue.[32] More exclusive former e-cigarette users had mouth or tongue blisters or irritation than ECS and CCS.[41]

Al-Aali et al.,[28] ArRejaie,[26] AlQahtani,[30] and Bardellini did not take into account ECS smoking history.[32] This absence may significantly impact the findings. Few studies did not calibrate digital radiography assessments of marginal and peri-implant bone loss, which could lead to geometric errors.[26,28,30] Smokers’ poor oral hygiene may enhance peri-implant inflammation and plaque index.[30] Poor dental hygiene increases oral Candida.[27,42] Mokeem et al. found it more common among ECS, waterpipe smokers, and CCS than NS.[27] Despite a statistically negligible difference, age-related hyposalivation and fewer teeth are risk factors.[27,43,44] A potential explanation is that all participants in those experiments were young, averaging 30 years old.

This systematic analysis found that NS had higher bleeding when probed than CCS and ECS. Investigating the second two categories showed similar bleeding.[26,28,30,31] Nicotine in CCS/ECS constricts gum blood vessels. This reduces bleeding, cell repair, and gingivitis.[28,30,36] Crevice fluid flow decreases owing to blood artery constriction, limiting the immune system’s ability to fight microorganisms.[36] ECS, like CCS, may not recognize oral irritation because bleeding is less obvious than NS.[30] Smoking causes more bone loss than NS.[26,31] Some reviewed studies may have been skewed by retrospective evidence and patient-reported outcome measures.[26,28,30] According to several research, CCS and ECS smoke differently.[26,27,30,31] ECS was used less often, which may alter outcomes. Dentists ought to educate ECS about e-cigarette risks and advise quitting smoking. Community health awareness programs should include oral health for smokers. These persons should know they risk gum and dental implant discomfort. The long-term safety of e-cigarettes as a way to quit smoking or as a healthier alternative is unknown.

Future prospective or retrospective studies should involve a bigger and more diversified group of smokers of various ages who use a wider range of e-cigarette brands with variable e-liquid compositions, notably nicotine doses. To measure e-cigarette risk, these studies should examine oral mucosal lesions in larger samples. The self-perceived impact must be considered while counselling these patients to ensure patient satisfaction.

CONCLUSION

This report summarises an extensive body of research on e-cigarettes and oral health. These studies lack enough evidence to conclude how e-cigarettes affect oral health. However, studies show that ECS is more likely to experience oral biological tissue changes than non-smokers or smokers.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.